Explanation:

Explanation:

Explanation:

Chlamydiae are obligate intracellular pathogens. Their extreme biosynthetic defects in intermediary metabolism and energy generation make them absolutely dependent on the host cell to grow and replicate. Depending on the species, chlamydiae only replicate intracellularly in the macrophage or in columnar epithelial cells. Infection of a previously exposed host results in an accelerated and intensified inflammatory response, with tissue destruction directly proportional to the inflammatory response. Host cell tropisms are correlated with the type of inflammation elicited. For example, Chlamydiae trachomatis lymphogranuloma venereum, which infects macrophages, produces a granulomatous inflammation characteristic of delayed hypersensitivity reactions.

Explanation:

Meningococcal infection is not spread by any of the other routes

Explanation:

This is a hyperplastic polyp; these polyps comprise 90% of all colonic polyps and have no malignant potential.
Peutz-Jeghers polyps (choice B) also have no malignant potential, but tend to be larger and hive a complex branching pattern.
Tubular adenomas, tubulovillous adenomas, and villous adenomas (choices C, D, and E) are all true neoplastic polyps containing dysplastic epithelium; the malignant potential of these polyps increases with size and the percentage of the polyp that has a villous configuration.

Explanation:

The phrase “mosaic pattern” of newly formed woven bone is a specific tip-off for Paget disease of bone, and is not seen other bone conditions. The clinical and radiologic presentations are typical; an increased hat size may also be a clue. In its early stages, Paget disease is characterized by osteolysis, producing patchwork areas of bone resorption with bizarre, large osteoclasts. In the middle stage of the disease, secondary osteoblastic activity compensates with new bone formation producing the mosaic pattern. In late Paget, the bones are dense and osteosclerotic. Paget disease is suspected to be related to prior viral infection but the cause remains mysterious. Complications include myelophthisic anemia high output cardiac failure, pain secondary to nerve compression deformities secondary to skeletal changes and in about 1% of patient´s osteosarcoma or other sarcoma typically involving the jaw pelvis or femur. An increased incidence of astrocytomas is associated with tuberous sclerosis. Hodgkin lymphoma is usually a disease of young adults although older patients may have the lymphocyte depleted form. Meningiomas are mostly benign tumors that affect adults especially females. There may be an association with breast cancer possibly related to high estrogen states. Non-Hodgkin lymphoma is more common in AIDS and other immunodeficiency states although the incidence in the immunocompetent is increasing.

Explanation:

Maternal age is the greatest risk factor for Down´s syndrome, and the risk rises significantly in women over 35. None of the other conditions is associated with this syndrome.

Explanation:

Vitamin D deficiency is being recognized more frequently among the elderly, especially in the nursing home or other settings where inactivity, nutritional deficiency, and lack of sunlight exposure combine to Increase the propensity for deficiency. Vitamin D deficiency has been associated with abnormalities in bone metabolism, primarily osetomalacia. Clinically this can present as muscle weakness, limb pain, and impaired physical function. Bleeding gums and fatigue may be presenting symptoms of scurvy (vitamin C deficiency). High-output cardiac failure with vasodilation, dermatitis, and neuropathy is the clinical presentation of thiamine deficiency. The combination of diarrhea, scaly dermatitis, and dementia is one of the clinical presentations of niacin deficiency.

Explanation:

Breast cancer is the most common cancer in women of developed country, while lung cancer is the most lethal. Colorectal cancer is the third most common cancer

Explanation:

Rubella infects a fetus via uteroplacental transfer. Group B Streptococci, Chlamydia, Gonococci, and Mycoplasma all can infect the infant as it passes through the birth canal.

Explanation:

Anosmia is not associated with osteogenesis imperfecta, while osteopenia, blue sclerae, collagen mutations, and multiple fractures are all manifestations of osteogenisis imperfect.

Explanation:

Sepsis is a systemic response to a serious infection. Septic shock is a syndrome manifested either by the presence of hypotension unresponsive to fluid resuscitation or multisystem organ failure. Microbiologic cultures are often, but not invariably positive. The systemic inflammatory response syndrome implies that the body´s inflammatory response can be triggered by infectious as well as noninfectious conditions, such as pancreatitis or trauma. Toxic shock syndrome refers to a multisystem disease mediated by a toxin producing strain in nonimmune individuals. Streptococcal toxic shock syndrome is frequently preceded by a viral syndrome, minor trauma, or recent surgery.

Explanation:

This is an example of desmoplasia, which is excessive fibrous tissue formation in the stroma of a tumor. The abundant fibrous tissue growth is itself, benign. Desmoplasia is usually seen with malignant neoplasmas, although there are benign processes such as surgical scars that can also constitute a desmoplastic reaction.
Anaplasia is a term used for tumors that show severe loss of cell differentiation and tissue organization anaplastic tumors typically are much more clinically aggressive than their well differentiated counterparts. Dysplasia is atypical cellular proliferation (without being so severe as to qualify for the diagnosis of cancer); an example is the epithelium seen in tubular adenomas of the colon. In contrast, carcinoma in situ is a similar change that is severe enough to be classified as cancer but is confined to the epithelium with no invasion of underlying tissue.
Carcinoma in situ can be found throughout the epithelial surfaces of the body.
Metaplasia is the replacement of one type of differentiated cell or tissue by another not normally present at that site; an example is the replacement, in smokers, of the normal, ciliated, columnar epithelium of the respiratory tract with squamous epithelium.

Explanation:

The disease is tularemia, which may be spread by handling rabbits or rabbit skins, or by bites from ticks that feed on the blood of wild rabbits. The causative organism is Francisella tularensis, a gram negative coccobacillus. The disease begins as a rupturing pustule followed by an ulcer, with involvement of regional lymph nodes. More serious cases can be complicated by bacteremia, splenomegaly, rash, pneumonia, or endotoxemic shock. Borrelia causes relapsing fever (transmitted by ticks and lice) and Lyme disease (transmitted by ticks). Brucella causes brucellosis alters ingestion of contaminated milk or contact with infected livestock. Leptospira causes leptospirosis and Weil disease; the organism is acquired by ingestion of water contaminated with animal urine. Listeria causes listeriosis after contact with contaminated milk, vegetables, or with transplacental transmission.

Explanation:

The clinical findings describe DiGeorge syndrome. Patients clinically present with tetany (usually first noted in the facial muscles) due to hypocalcemia secondary to hypoparathyroidism. The thymus is absent, as are the parathyroid glands, due to failure of development of the 3rd and 4th pharyngeal pouches. Recurrent infections due to defective cellular immunity and abnormal facies are additional features. Since patients without a thymus are unable to complete normal T-lymphocyte development, these patients will have deficiencies in all immunologic reactions dependent on T cells. Type IV hypersensitivity, which is totally dependent on T lymphocytes and their cytokines, would be absent from these patients. Decreased alpha-fetoprotein is an amniotic fluid marker for Down syndrome. Down syndrome patients have abnormal immune responses that predispose them to serious infections (particularly of the lungs) and to thyroid autoimmune disease. However, there is no defect of the parathyroid glands. Elevated IgE levels are found in persons with atopic allergy. Since IgE isotype- switching depends on TH2 cytokines, patients with DiGeorge syndrome should be unable to develop allergy. Elevated IgM is seen in hyper-IgM syndrome. Patients have a high concentration of IgM and normal numbers of T and B cells, but low levels of IgG, IgA, and IgE. Helper T cells have a defect in the surface protein CD40 ligand that interacts with CD40 on the B-cell surface. This results in an inability of the B cell to switch from the production of IgM to other classes of antibodies. In patients with DiGeorge syndrome, the relative amount of IgM could be elevated because they would be unable to promote isotype switching and their B lymphocytes would therefore be “stuck” producing IgM. It is unlikely, however, that the total IgM concentration in the serum would be significantly altered. Prominent telangiectasias around the eyes are seen as part of the ataxia-telangiectasia syndrome. This is an autosomal recessive disorder, and is also referred to as a chromosomal breakage syndrome. Ataxia-telangiectasia is associated with increased numbers of translocations, especially involving the T-cell receptor loci; the gene for this disorder has been mapped to chromosome 11. Patient´s have an increased incidence of malignancy.

Explanation:

A morbidly obese (450 lb) male present with respiratory distress. ABG studies show a PCO2 of 55 mm Hg, and a pH of 7.28. CXR is unremarkable. Auscultation reveals a rapid and regular heartbeat, and the pulse is strong. What is the likely explanation of the patient´s arterial hypoxemia?

Explanation:

This patient has celiac disease, an autoimmune disease characterized by intolerance to gluten, a protein found in wheat, oats, and barley. This leads to villous atrophy in the proximal small intestine, with malabsorption. Patients display nausea, vomiting, and diarrhea. The sore tongue is part of oral allergy syndrome. Biopsy of the jejunum will confirm the villous atrophy. The ascending colon is adjacent to the abdominal wall, lateral to the descending duodenum and pancreatic head, and anterior to the right kidney. This structure is not affected in celiac disease. The aorta gives rise, anteriorly, to the superior mesenteric artery at this level. The aorta is not affected by celiac disease. The antrum of the stomach is not affected by celiac disease. The descending colon is adjacent to the left abdominal wall and lateral to the left kidney, and is not affected by celiac disease.

Explanation:

The most common bacterium implicated in community-acquired pneumonia is the pneumococcus Streptococcus pneumoniae. Other organ-isms frequently implicated in patients younger than 60 without comorbidity include Mycoplasma pneumoniae, respiratory viruses, Chlamydia pneumoniae, and Haemophilus influenzae. When community acquired pneumonia occurs in elderly patients or patients with comorbidity, aerobic gram-negative bacilli and Staphylococcus aureus are added to the list. The organisms listed in options A, B, and C are important causes of community-acquired pneumonia but are not the most frequent causes. Staphylococcus aureus is an important cause of community-acquired pneumonia (particularly in the elderly and in patients with comorbidity) but is not the most frequent cause.

Explanation:

The presence of sickle cell disease in a question stem is usually a significant clue. This question tests whether you know that patients with sickle cell anemia are more susceptible to osteomyelitis caused by Salmonella. (The patient´s fever, bone pain, and X-ray results indicate osteomyelitis). Staphylococcus aureus (gram positive coccus) is the most common cause of osteomyelitis overall, but 80% of osteomyelitis cases in sickle cell patients are caused by Salmonella. If Staphylococcus aureus had not been ruled out on bone culture, you should have looked for it in the answer choices. Notice that you were required to know more than just the organism´s name; you needed to know its distinguishing features. Option C describes Salmonella (a gram-negative rod) accurately. Salmonella exists in more than 1800 serotypes and is known to contaminate poultry. A comma-shaped organism that is sensitive to acidic pH is Vibrio cholerae, a gram-negative rod that causes severe enterotoxin-induced diarrhea, with “rice-water” stools and dehydration. The toxin acts by stimulating adenylyl cyclase to overproduce cAMP in the brush border of the small intestine. A facultative intracellular parasite could be any one of a number of organisms. Facultative intracellular organisms survive inside cells when endocytosed but are capable of being grown on cell-free media. Examples include Legionella and Listeria. A motile and oxidase positive organism is Pseudomonas, a gram-negative rod that produces a polysaccharide slime layer. P. aeruginosa is the prototype and commonly colonizes the lungs of patients with cystic fibrosis. It is associated with production of blue-green pus because of its production of blue green pigments. A nonmotile, facultative anaerobe could also be any of a number of organisms. The great majority of bacteria are facultative anaerobes, and of the gram-negative bacilli, Shigella and Yersinia would be examples of nonmotile genera.

Explanation:

Primary adrenal insufficiency would decrease the secretion of aldosterone, the hormone necessary for appropriate salt retention. When blood volume is low or sodium is depleted, renin is released from the juxtaglomerular cells in the kidney. Renin is an enzyme that cleaves the plasma protein angiotensinogen into angiotensin I. Angiotensin l circulates to the lungs where it is cleaved into angiotensin II by angiotensin converting enzyme. Angiotensin II acts to increase secretion of aldosterone from the adrenal cortex. Aldosterone acts to increase tubular reabsorption of sodium and excretion of potassium. Therefore the reduction in aldosterone in primary adrenal insufficiency would cause hyponatremia and hyperkalemia, making options B and D incorrect. ANP is released by the atrial cells following expansion of extracellular and intravascular fluid volumes. When the atria are distended ANP is released and acts to relax vascular smooth muscle and suppress the renin angiotensin aldosterone system resulting in a decrease in plasma volume vascular resistance arterial pressure and cardiac output. In this patient aldosterone is reduced resulting in salt wasting and a reduction in blood pressure. Therefore ANP levels and blood pressure would not be elevated in this patient making options A and C incorrect

Explanation:

The history of a recent severe sore throat in a young person is a classic clue suggesting rheumatic fever. The histologic description given is that of an Aschoff body, which classically occurs in the heart in rheumatic heart disease. Erythema marginatum (the expanding erythematous rash) and Sydenham chorea (rapid, purposeless movements) also accompany this disorder. The subcutaneous nodules characteristic of rheumatic fever are basically “giant” Aschoff bodies. Gaseous necrosis with epithelioid cells and Langhans giant cells are characteristic of the granulomas of tuberculosis. Hemosiderin laden macrophages may be found in chronic passive congestion of the liver. Burkitt lymphoma is characterized by dense collections of lymphoid cells with macrophages intermixed. The macrophages often have a clear space around them, giving the tissue a “starry sky” appearance. Reed Sternberg cells are characteristic of Hodgkin lymphoma. Occasional eosinophils are often admixed with the proliferating lymphocytes in this disorder.

Explanation:

The pulmonary wedge pressure (which is used as an estimate of left atrial pressure) is elevated to 30 mm Hg and the pulmonary artery pressure is elevated to 45/25 mm Hg. The left ventricular end diastolic pressure is normal but is not equal to the pulmonary wedge pressure. A pressure gradient of 25mm Hg (30 – 5) across the mitral valve is a clear indication of stenosis. The fatigue and shortness of breath result from mild pulmonary´ edema caused by the increase in pulmonary capillary pressure. One can surmise that the pulmonary capillary pressure is elevated because pressures are elevated at the arterial and venous ends of the pulmonary circulation. In aortic regurgitation, blood flows backward through the aortic valve during diastole when the valve is closed. Left ventricular end diastolic pressure (and pulmonary wedge pressure) may be elevated with chronic aortic regurgitation once the myocardium has failed, but aortic regurgitation itself will not result in a pressure gradient across the mitral valve. In aortic stenosis, the blood is ejected from the left ventricle into the aorta through a smaller than normal opening. Because the resistance to ejection of blood is high, the left ventricular pressure increases greatly with normal systolic pressure in the aorta. There is no evidence for myocardial infarction, i.e. peak systolic pressure and left ventricular end diastolic pressure are both normal.

Explanation:

Aneurysm of the posterior communicating artery is the second most common aneurysm of the circle of Willis (anterior communicating artery is most common) and can result in third cranial nerve palsy (paralysis). The oculomotor nerve (CN III) innervates the levator palpebrae muscle. CN III paralysis would therefore result in ptosis (drooping of the upper eyelid). CN III also innervates all of the extraocular muscles, except for the superior oblique (CN IV) and the lateral rectus muscles (CNVI). Thus, CN III palsy would result in unopposed action of the superior oblique and lateral rectus muscles, causing the affected eye to look down and out. CN III also supplies parasympathetic innervation to the sphincter muscle of the iris (which constricts the pupil) and to the ciliary muscle. Interruption of this pathway leads to a dilated and fixed pupil and to paralysis of accommodation. The symptoms described probably resulted from subarachnoid hemorrhage (SAH), in this case, due to rupture of a posterior communicating artery aneurysm. A classic clue to the diagnosis is a patient presenting with “the worst headache of his or her life.” When you are presented with a case of sudden severe headache, SAH should rank highly on your differential diagnosis list. The anterior cerebral artery supplies the medial surface of the cerebral hemisphere, from the frontal pole to the parieto-occipital sulcus. Occlusion may produce hypesthesia and paresis of the contralateral lower extremity. The anterior choroidal artery arises from the internal carotid artery and is not part of the circle of Willis. It perfuses the lateral ventricular choroid plexus, the hippocampus, parts of the globus pallidus, and the posterior limb of the internal capsule. The anterior communicating artery connects the two anterior cerebral arteries. It is the most common site of aneurysm in the circle of Willis and may cause aphasia, abulia (impaired initiative), and hemiparesis. The middle cerebral artery supplies the lateral convexity of the cerebral hemisphere, including Broca´s and Wernicke´s speech areas and the face and arm areas of the motor and sensory cortices. It also gives rise to the lateral striate arteries, which supply the internal capsule, caudate, putamen, and globus pallidus. The middle cerebral artery is the most common site of stroke.

Explanation:

Stage 2 sleep is characterized by low amplitude, mixed frequency EEG activity with more theta waves than Stage 1. In addition, vertex waves (sharply contoured potentials at the vertex), sleep spin-dies (short bursts of 12-16 Hz activity), and K complexes (high-amplitude waves with superimposed sleep spindles) occur intermittently. Muscle tone is slightly reduced, and eye movements are absent. REM sleep is characterized by low-amplitude, mixed frequency activity. Ponto-geniculo-occipital (PGO) spikes, which are transient, larger amplitude potentials, occur over the occipital arras There are also episodic bursts of rapid eye movements (BEMs), and skeletal muscle tone is decreased Stage 1 sleep, or drowsiness, is characterized by a transition from alpha rhythms (relaxed wakefulness) to theta rhythms. Electromyographic (EMG) activity is decreased, compared with relaxed wakefulness, and there are slow, roving eye movements. Stages 3 and 4 are also known as slow-wave sleep. They are characterized by high amplitude slow waves, especially delta waves. Eye movements are absent, and EMG activity is decreased compared with relaxed wakefulness.

Explanation:

Explanation:

This is a classic case of Goodpasture syndrome, which is autoimmune in origin and characterized by hemorrhagic pneumonitis leading to hemoptysis and glomerulonephritis progressing to renal failure. Most cases involve the presence of anti basement membrane antibodies. It occurs mostly in young men. Under immunofluorescence, there are linear deposits of IgG on alveolar and glomerular basement membranes. Electron dense humps are found with electron microscopy, not immunofluorescence. These humps are found in poststreptococcal glomerulonephritis; immunofluorescence in this case would show C3, IgM, and IgG granular deposits. Mesangial deposition of IgA occurs in Berger disease or IgA nephropathy. Spike and dome IgG deposits are found in membranous nephropathy, a cause of the nephrotic syndrome.

Explanation:

The clinical picture of confusion, ataxia, and variable disturbances of eye movements (e.g., nystagmus and ophthahnoplegia) is due to Wernicke encephalopathy, which results from thiamine deficiency. Hemorrhage and necrosis in the above mentioned areas are the underlying pathologic changes. Alcoholics are particularly prone to this condition. Axonal degeneration of posterior and lateral columns of spinal cord, or subacute combined degeneration, results from two different etiologies: vitamin B12 deficiency and HIV myelopathy. Ataxia, numbness, and spastic paresis of the lower extremities are the clinical manifestations. Demyelination affecting the central region of the basis pontis is known as central pontine myelinolysis. This complication is most commonly encountered in severely malnourished and dehydrated alcoholics. Rapid correction of hyponatremia triggers this condition. Demyelination involving the corpus callosum and anterior commissure, or Marchiafava Bignami disease, is a rare disorder associated with chronic alcoholism. It is probably related to some dietary deficiency. Loss of neurons in the neocortex, cerebellar Purkinje cells, and hippocampal pyramidal neurons results from hypoxia or hypoglycemia related necrosis. These neurons are the most vulnerable to hypoxic or hypoglycemic injury.

Explanation:

Explanation:

The patient has a macrocytic anemia with hypersegmented neutrophils. This picture is consistent with either folate or vitamin BI2 deficiency. The history of small bowel resections and the presence of neurologic signs on physical examination tip the diagnosis to B12 deficiency. Beta-thalassemia trait and iron deficiency cause a microcytic, not a macrocytic, anemia Folate deficiency causes a similar picture on peripheral blood smear but is not associated with neurologic signs and symptoms. Sickle cell trait does not cause anemia and is associated with a normal peripheral blood smear under usual physiologic conditions.

Explanation:

Affinity maturation in an ongoing immune response is a feature of the antibody response. There is no evidence that a similar process occurs in the T cell response. Major histocompatability complex (MHC) molecules present short antigen-derived peptides, not the intact antigen.
T cells recognise antigen only when presented by (self) M C molecules on an antigen presenting cell.
MMC class II molecules present antigen to CD4+, alpha/beta+ T cells. It is still not clear how gamma/delta+ T cells recognise antigen, however most gamma/delta+ T cells do not appear to be restricted by (self) MMC molecules.
Additional ´costimulatory´ signals are required to activate a resting T cell. Interaction of the T cell reactor (TcR) of a resting T cell with an appropriate Ag/M C complex in the absence of costimulatory signals may lead to the induction of anergy.

Explanation:

The greatest advance in prevention of hepatitis B has been the development of an effective vaccine which imparts immunity to close to 100% of those vaccinated. Following universal precautions and treatment with immune serum globulin enriched with anti-hepatitis B globulins can decrease the risk of hepatitis B transmission. Bleach is recommended as an irrigant following needle sticks. Unenriched immune serum globulin is only effective against hepatitis A.

Explanation:

Mycobacterium tuberculosis is so adapted to the human body that it has no natural reservoirs other than diseased or infected persons. It is transmitted almost exclusively by aerosolized respiratory secretions, although transmission has been reported during debridement of infected soft tissue abscesses and during autopsies. Intact respiratory mucous membranes of healthy exposed persons are typically quite resistant to invasion by M. tuberculosis. The organism has an obligate affinity for those tissues with high oxygen tensions, such as the lung apex. Fomites are not important in transmission.

Explanation:

This child has MHC class I deficiency, which causes detect in the development of CD8+cells in the thymus. Because there is no MHC class l, cytotoxic cells cannot be selected, although helper cells (CD4+), which recognize MHC class II molecules, are normally produced.
The gamma-delta T-cell receptor is present on a small proportion of T cells that do not undergo thymic selection. Their function in the body is not known, but they would not be affected by the absence of the class I MHC.
Intercellular adhesion molecule-1 is a molecule found on the surface of antigen- presenting cells in the body that reacts with LEA-1 on T cells for the purpose of cell-to-cell adhesion. Its absence would not affect the development of cells in the thymus. The killer inhibitory receptor is one of two receptors found on the surface of natural killer cells. It inhibits the killing of an attached cell if it is bound to MHC class I. Because this child has normal levels of CD16+ (natural killer) cells, it is unlikely he has a deficiency of this receptor. MHC class II is the molecule that presents peptides that have been processed in intracellular vesicles by antigen presenting cells to T-helper cells. If this molecule were absent from the child, he would be suffering from bare lymphocyte syndrome, which is associated with a failure of education of CD4+ helper cells, not CD8+ cells as described here.

Explanation:

Babesia microti is an intraerythrocytic parasite that causes a mild anemia and fever in affected humans. It is transmitted by the same tick that transmits Lyme disease Ixodes scapularis. Red blood cells are the only cells in the body that are devoid of MHC class I molecules so lysis of these cells by a cytotoxic cell would only be possible using NK cells.
NK cells are the cytotoxic cell that kills in the absence of MHC class I recognition. NK cells are actively inhibited if they recognize these antigens on a target cell. The most specific marker for the identification of NK cells is CD56, although CD16 is also found on their surface. CD4 cells are helper T cells. They assist in both antibody-mediated and cell-mediated immune responses, but by themselves, as stipulated in this question stem, they would not be capable of lysis of red blood cells. CD8 cells are cytotoxic T cells. These cells kill by identifying alterations in the MHC class I molecule. Since such molecules are absent from erythrocytes, cytotoxic T cells are not capable of lysing erythrocytes. CD14 is the endotoxin receptor that is found on macrophages. Macrophages are capable of ingesting and destroying infected erythrocytes in the spleen, but are not capable of causing their lysis in this system. CD16 is the receptor for the Fc component of immunoglobulin G. It is present on a variety of cells, including natural killers, macrophages, and neutrophils. Therefore, it is not the best marker for the NK cell uniquely but would label several populations of cells.

Explanation:

The liver can be divided into three zones. This division is based on the blood flow. Zone 1 is the closest to the blood supply known as the periportal zone; there is a zone 2, or intermediate (between 1 and 3); and zone 3 is called the pericentral vein zone due to its association with the terminal hepatic vein (historically thought to be in the center of the lobule). Zone 3 contains the P450 oxidase enzyme system, which is important in the chemical modification or degradation of chemicals, including drugs and endogenous compounds. Zone 3 is the most sensitive to injury because it is the farthest away from the blood supply. The P450 system is not located in the bile ducts. The intermediate zone, or zone 2, is the area that is the second most sensitive to ischemic injury. “Ito” cells are the fat-containing mesenchymal cells located in the space of Disse. This is the site of vitamin A storage. The periportal zone, or zone 1, is the area most sensitive to toxic injury. This is the area that shows infiltration with hepatitis.

Explanation:

The initial disease is varicella (chicken pox). The child then developed Reye syndrome, which is a postviral derangement of metabolism associated with enlarged, distorted mitochondria in many tissues. Most significant clinically are the effects on the liver and brain. In the liver, there is a reduction in the activity of many key biochemical pathways notably the citric acid cycle, urea cycle and beta oxidation of fatty, acids. The disruption of these pathways produces the very extensive microvesicular steatosis (fatty change) that is the characteristic liver finding. In the brain, edema is a prominent feature and the astrocytes show mitochondrial disruptions by electron microscopy. Many of the first described cases of Reye syndrome occurred in children treated with aspirin, but the role of salicylates in the pathogenesis of this condition has not been clearly established. Seventy five percent of patients have a mild clinical course; the remainders develop coma, liver failure, or permanent neurologic impairments. Death may result from either hepatic or CNS damage. Therapy is supportive. Hemosiderin is seen in hemochromatosis and other conditions with increased hepatic iron stores.
PAS-positive cytoplasmic granules are a feature of antitrypsin deficiency. Rhodamine-positive cytoplasmic granules reflect copper accumulation in patients with Wilson disease.

Explanation:

In this item, the clinical information is really just “window dressing” for the actual question. All you are being asked is, “What is the most common type of cancer seen in the bladder?” The answer is that 90% of primary bladder cancers are transitional cell carcinomas, derived from bladder urothelium (a transitional cell epithelium). Let´s take a moment to review the classic dues associated with bladder carcinoma: exposure to industrial chemicals, cigarette smoking, and infection with Schistosoma haematobium (predisposes to squamous cell type). Remember that a patient´s occupation is usually stated for a reason.
All of the other answer choices are quite rare by comparison.

Explanation:

The vignette illustrates a typical presentation for a tumor of the heart. Primary cardiac tumors are rare and usually require a intensive workup to pinpoint the diagnosis. Seventy five percent of primary cardiac tumors are benign; among these, myxoma is the most common. The tumors are usually single, and the most common location is the left atrium. They may cause syncopal episodes or even shock and death due to obstruction by a “ball valve” mechanism.
Angiosarcoma is a malignant tumor of vascular origin that can occur as a primary cardiac tumor. It is the most common malignant primary cardiac tumor, but it is still very raze. Angiosarcoma usually affects the right side of the heart. Mesothelioma is a benign tumor of mesothelial origin that can rarely present as a primary cardiac tumor. It is usually a small intramyocardial tumor that presents with disturbances of the conduction system of the heart. Rhabdomyoma is a benign tumor of muscle origin. It can occur as a primary cardiac tumor, typically in infants and children, in whom it may be associated with tuberous sclerosis. It usually occurs in the ventricles. Rhabdomyosarcoma is a malignant neoplasm that can also occur as a rare primary cardiac tumor. It is of muscle origin and usually affects the right heart.

Explanation:

Heinz bodies = oxidised denatured Hb. Post: splenectomy causes target cells, Pappenheimer bodies (siderotic granules) and Howell-Jolly bodies (DNA remnants).

Explanation:

Cortical thymocytes are immature forms, and either do not express CD4 or CD8 (double negative cells) or express both CD4 and CD8 (double positive cells). As the cells mature, they pass to the thymic medulla where they lose expression of either CD4 or CD8, to become single positive cells.
Negative selection occurs at the stage when thymocytes express both CD4 and CD8, but co-expression of these markers does not mediate negative selection. Negative selection occurs when a thymocyte expresses a TcR with high affinity for self-antigen: MHC complexes in the thymic micro-environment.
Once a thymocyte has successfully rearranged and expressed an -alpha/beta or gamma/delta TcR it is committed to that lineage.
Thymocytes whose TcR bind with high affinity to self Ag/MHC complexes are clonally deleted by a process of negative selection. B cells express IgM and IgD; T cells do not!

Explanation:

Oncogenes are endogenous human deoxyribonucleic acid (DNA) sequences that arise from normal genes called proto-oncogenes. Proto-oncogenes are normally expressed in many cells, particularly during fetal development, and are thought to play an important regulatory role in cell growth and development. Alterations in the proto-oncogene can activate an oncogene, which produces unregulated gene activity, contributing directly to tumourogenesis. Oncogene alterations are important causes of:

• Rhabdomyosarcomas (ras oncogene)

• Burkitt´s lymphoma (C-myc is translocated intact from its normal position on chromosome 8 to chromosome 14)

• Neuroblastoma (N-myc proto-oncogene is seen in a proportion of patients with poor prognosis).

They should be contrasted with tumour suppressor genes. In this situation, the genes normally down regulate cell growth, and require inactivation to allow malignant growth. Examples include retinoblastoma.

Explanation:

Turner´s syndrome is caused by a chromosomal abnormality that results in a 45, XO karyotype, producing loss of ovaries and somatic abnormalities. Klinefelter´s syndrome has a Karyotype of 47, XXY and results in congenital testicular damage. Testicular feminization syndrome is a syndrome of feminization due to androgen insensitivity, and the karyotype is a normal 46, XY. Down´s syndrome is caused by a trisomy of chromosome 21.

Explanation:

Rocky Mountain spotted fever is caused by Rickettsia Rickettsii. It is transmitted through tick bites (especially Dermacentor andersoni) in the western regions of the U.S.

Explanation:

Vascular endothelial growth factor (VEGF) is a heparin binding glycoprotein that increases endothelial cell proliferation in vitro and increases capillary growth (i.e., angiogenesis) in vivo. Unlike most other growth factors VEGF has unique target cell specificity for vascular endothelial cells. VEGF is overexpressed in solid tumors as well as in ischemic areas of the heart and retina. VEGF levels are also reversibly increased in a variety of normal and transformed cells exposed to a hypoxic environment. These characteristics of VEGF make it an ideal candidate as a regulator of angiogenesis in physiological and, pathophysiological situations in which vessel growth is preceded by deficient perfusion of the tissues. Angiostatin is an anti-angiogenic factor expressed by tumors that tends to inhibit angiogenesis. Growth hormone has a general effect that causes growth of almost all tissues of the body but does not appear to stimulate angiogenesis to a significant extent in solid tumors. Thrombospondin is a multifunctional glycoprotein that interferes with tumor growth, angiogenesis, and metastasis. An increase in tissue oxygen partial pressure is unlikely to be the stimulus for new vessel growth because (1) solid tumors are invariably hypoxic or ischemic, i.e. the partial pressure of oxygen is low; and (2) an increase in the partial pressure of oxygen in a tumor would tend to decrease the expression of VEGF, thereby decreasing the amount of angiogenesis in the tissues.

Explanation:

Elemental mercury is used in thermometers and sphyngomanometers. Accidental breakage with spillage into carpets may result in mercury poisoning. Bulk mercury used in dental amalgams has resulted in excess vapors in up to 10% of dental offices. Organomercurials found in fungicides may produce toxicity. Accidental ingestion of disk batteries with gastrointestinal decomposition has resulted in elevated mercury levels. Dialysis results in aluminum toxicity, probably from tap water used during the procedures.

Explanation:

Derangements of Starling forces explain edema formation. Increased capillary hydrostatic pressure, decreases in capillary oncotic pressure, or a combination of the two results in edema formation. Damage to the capillary endothelium increases permeability permitting transudation of protein and fluids into the interstitium. Elevated interstitial hydrostatic pressures tend to move fluid into the vasculature space.

Explanation:

Impetigo is caused by Group A beta-hemolytic streptococci or by Staphylococcus aureus. Tinea versicolor is a fungal disease. Lichen planus is an idiopathic condition unassociated with any infection. Psoriasis is an autoimmune form of skin rash. Seborrheic dermatitis is idiopathic and not associated with infection

Explanation:

Severe liver disease results in decreased glycogen supplies and decreased need for insulin in diabetic patients. Pancreatitis would be expected to lead to more hyperglycemia in this patient. Cessation of alcohol consumption would alter his caloric ingestion and produce unpredictable responses of his glucose. Wernicke Korsakoff psychosis is not associated with serum glucose levels. Gastroparesis would not be expected to predictably alter glucose levels.

Explanation:

Papillomavirus infection can be detected on Pap smears. Pap smears are not useful in the detection of the other conditions. Papanicolaou, or “Pap,” smear collects shed cells from the cervix for microscopic study and detects atypical cells or characteristic cytoplasmic vacuoles within squamous cells infected with papillomavirus. The virus is associated with benign warts or, in cases of infection with human papillomavirus types 16 and 18, carcinoma. The other conditions listed would not be detected.

Explanation:

Macrophages are long lived phagocytic cells important in the inflammatory response. Some of the many secretory products of macrophages include binding proteins such as fibronectin, enzyme inhibitors such as alpha-2 macroglobulins, pyrogens such as interleukin I, and tumor necrosis factor, also known as cachectin. Exotoxin is secreted by bacteria.

Explanation:

Atherosclerotic lesions develop within the intima of the blood vessel. The initial step is a proliferation of smooth muscle cells. This is associated with an accumulation of macrophages and lymphocytes. Subsequently, a connective tissue matrix which contains collagen, proteoglycans, and elastic fibers forms at the site of smooth muscle proliferation. Ultimately, in hyperlipidemic persons, lipid accumulates within the smooth muscle cells, macrophages, and connective tissue matrix.

Explanation:

Cyclophosphamide can cause hemorrhagic cystitis. Anticholinergics, tricyclic antidepressants, and MAO inhibitors have all been associated with various forms of bladder dysfunction. Penicillin can cause interstitial nephritis, but has been associated with bladder toxicity.

Explanation:

The streptococci are initially classified based on the degree to which their colonies cause hemolysis on blood agar. The reaction described is alpha hemolysis, due to alteration of hemoglobin to a green pigment. Beta hemolysis refers to a clearing around the colonies due to more complete destruction of hemoglobin. In gamma hemolysis (something of a misnomer) no hemolysis or color change occurs of the alpha hemolytic streptococci, only Streptococcus pneumoniae is inhibited by optochin or bile. Streptococcus agalactiae is common in normal vaginal and intestinal flora, and is a group B, beta hemolytic species that is resistant to bacitracin. Streptococcus mutans is part of the normal oral flora but can also cause dental caries and is an alpha hemolytic species that is not inhibited by optochin. Streptococcus pyogenes is a group A beta hemolytic species that causes a variety of sometimes severe infections, and is inhibited by bacitracin. Streptococcus sanguis is a cause of subacute endocarditis, and is an alpha hemolytic species that is not inhibited by optochin.

Explanation:

Enterotoxigenic E. coli (ETEC), an important cause of traveler´s diarrhea, produces a toxin that activates intestinal adenylate or guanylate cyclase. Consequently the intestinal mucosa overproduces cAMP, resulting in a mild and self-limited secretory diarrhea. Enteroaggregative E. coli (EAEC) does not express a toxin, but is seen to cluster over the colonic mucosa in some individuals. Although occasionally found in patients with chronic diarrhea, no clear mechanism for mucosal pathophysiology has been determined for EAEC. Enterohemorrhagic E. coli (EHEC) classically associated with strain O157:H7 and present in undercooked hamburgers, expresses a Shiga like toxin that causes bloody diarrhea and hemolytic-uremic syndrome. This toxin works by inhibiting the 60S ribosomal subunit. Enteroinvasive E. coli (EIEC) does not express a toxin, but rather is pathogenic through its capacity to invade the colonic mucosa and evoke an inflammatory response. The resulting dysentery like inflammatory diarrhea generally necessitates vigilant hydration but no antibiotics are indicated.
Enteropathogenic E. coli (EPEC) does not produce any known toxins but adheres tightly to the glycocalyx of the colonic mucosa and disrupts the microvilli. Villous atrophy mucosal thinning and inflammation in the lamina propria , are produced resulting in impaired absorption and diarrhea.

Explanation:

Sensitization to latex has become a major health-care problem. Local skin irritations are common but more severe allergic reactions occur, up to and including rare anaphylactic reactions that are occasionally fatal. The immune responses to latex are immediate-type hypersensitivity (type I) reactions, expressing themselves in minutes, and/or delayed-type hypersensitivity (type IV) reactions, which will express themselves in 48 to 72 hours. The type I reactions are due to IgE-mediated sensitivity to latex proteins, whereas type IV reactions are due to a cell-mediated response to the chemicals that are added in the processing of latex. The type IV response in this circumstance would be referred to as contact dermatitis. Irritant dermatitis can be observed in the early stages of sensitization and can be due to sweating, rubbing, and residual soap. In the present case, the timing of the reaction after 72 hours points to the type IV reaction rather than an irritant dermatitis. A type I reaction would have been apparent in minutes with characteristic rhinitis, conjunctivitis, urticaria, asthma, angioedema, or anaphylaxis after the technician put on her latex gloves. A type II reaction is a cytolytic response mediated by an antibody. The type II reaction is observed in the context of hemolytic anemias, thrombocytopenia, neutropenia, etc. A type III reaction is an immune complex response that sets into motion an inflammatory response.

Explanation:

This child has chronic granulomatous disease (CGD), which is a genetic detect in one or more of the subunits of NADPH oxidase. Activation of this membrane bound oxidase is the critical first step in the generation of toxic oxygen radicals with in the phagolysosome. One of the products of this reaction, hydrogen peroxide serves as the substrate for the second most important killing mechanism: myeloperoxidase acting to produce toxic halide radicals. It a person with CGD is infected with a catalase-positive organism, the substrate of the myeloperoxidase system is degraded, and thus the only remaining functional intracellular killing mechanism involves the other contents of the lysosomes (lysozyme, defensins, lactoferrin, and hydrolytic enzymes). Hydrogen peroxide is the substrate necessary for the function of the myeloperoxidase enzyme system. It would be destroyed by the catalase-positive organism in the abscess described. Hypochlorite is generated in the myeloperoxidase arm of the intracellular killing pathway. It would not be produced in this abscess because the catalase-positive organism would destroy the substrate for myeloperoxidase. Myeloperoxidase is an enzyme present in the lysosomes that acts on hydrogen peroxide to produce toxic halide radicals. Because the abscess in this case is caused by a catalase-positive organism, the substrate for myeloperoxidase would be destroyed. NADPH oxidase is the membrane bound oxidase that is genetically absent in a person with CGD.

Explanation:

Although many of the events that produce atherosclerotic plaques remain elusive, several steps in the process are known. The first gross findings associated with atherosclerotic plaque formation are fatty streaks. Fatly streaks are found in the vasculature of most people in the second decade of life. The fatty streak is a focal accumulation of serum lipoproteins within the intima of the blood vessel wall. As smooth muscle cells migrate to the lesion they produce a connective tissue matrix that overlies the lipid-laden foam cells. When this fibrous covering dislodges, the thrombogenic contents of the lesion are exposed to the circulation and the ensuing clot then occludes the vessels. Tissue ischemia and infarction then occur. The fibrous lesions that follow the fatty streak seldom produce infarction through direct extension of the lesion ischemia may occur with resulting angina, but because the lesion growth is slow, collateral vessels may grow and thus prevent infarction. The fatly streak precedes fibrous lesions found in coronary artery disease. Lipid-laden macrophages, called foam cells, contribute to the core of atherosclerotic lesions. They do not, however, release their lipids through exocytosis, forming a lipid-based occlusion.

Explanation:

Pregnancy is the most common cause of amenorrhea or abnormal uterine bleeding in an adolescent. Among girls aged 15-19 years the annual risk of pregnancy is 10%. Through adolescence, the cumulative risk is 40%. Normal symptoms that are seen in the majority of pregnancies include nausea, vomiting, fatigue (caused by the interaction of several factors such as elevated progesterone levels, low blood glucose levels, lower blood pressure, and increased RBC production), breast tenderness, frequent urination caused by the pressure the uterus exerts on the bladder and the effects of progesterone on the ureter´s smooth muscle. Additional progesterone mediated effects include elevated body temperature, constipation, “mood swings”, and irritability. It is also normal to have a progressive increase of the WBC count with a mean value of up to 16,000/mm^3 in the third trimester. Anorexia can produce hormonal imbalances and lead to amenorrhea, but the history should yield clues suspicious for an eating disorder.
Depression should not, by itself, cause amenorrhea or uterine bleeding. Systemic diseases such as hypothyroidism may be responsible for amenorrhea, but are relatively less common. Also, this girl previously had a normal menstrual cycle. The absence of characteristic manifestations of hypothyroidism such as sensitivity to cold temperatures, facial and periorbital edema, edema of the hands and feet, deep voice, dry and sparse hair, macroglossia, and cool, doughy skin, makes this disease unlikely. Infection would be a rare cause for amenorrhea symptoms, and would most likely need to involve the hypothalamus, pituitary, or gonadal axis. Also, frequent urination and leukocytosis are common manifestations of a normal pregnancy.

Explanation:

The key to answering this question is knowing the plasma concentration profile across the 40 weeks of pregnancy for each of the hormones mentioned. Plasma concentration of human chorionic gonadotropin (hCG) doubles every 2 days during the first 10 weeks of pregnancy and then declines to a level that is one-tenth of the peak for the remainder of the pregnancy. hCG is in the same hormone family as TSH, FSH, and LH. These are all glycoprotein hormones with identical a subunits but different β subunits. Hence, there is a similarity in receptors for these hormones as well. A mutation in the TSH receptor that also made it responsive to hCG would result in increased thyroid hormone secretion during pregnancy due to the increased circulating hCG. Under nonpregnant conditions, thyroid hormone secretion would be normal. This mutation was actually found in a woman who had experienced several early miscarriages. When she was treated for hyperthyroidism with propylthiouracil during her pregnancy, her child was carried to full term. Plasma concentrations of progesterone and estrogen increase throughout pregnancy. By 40 weeks the progesterone concentration may be 200 times greater than pre-pregnancy levels. Estradiol and estrone increase by about 50-told while estriol increases about 11000 fold. While the T3, estrogen and progesterone receptors all originate from the same superfamily, it is unlikely that the woman´s pregnancy associated hyperthyroidism is due to an action of progesterone or estrogen on the-T3 receptor. If this were the case plasma levels of thyroid hormone would be expected to rise throughout pregnancy, with the highest concentration occurring just prior to birth. Furthermore, in the nonpregnant state increases in estrogen during the follicular phase and increases in progesterone during the luteal phase would produce problems in thyroid hormone secretion. This patient has normal thyroid status when not pregnant. Human chorionic somatomammotropin (hCS) increases throughout pregnancy. It is related to the anterior pituita hormones prolactin and growth hormone. A mutation in either the TRH receptor or the TSH receptor would be unlikely to be responsive to hCS because this hormone is unrelated to either TRH or TSH. Furthermore, if such a mutation could occur it would produce maximal thyroid hormone concentration near the end of the pregnancy (not at 10 weeks).

Explanation:

This is the classic microscopic description of the pneumococcus Streptococcus pneumoniae, which is a common cause of lobar pneumonia. Most strains are still very sensitive to penicillins, although some drug resistant strains have been isolated. Haemophilus influenzae is a gram negative bacillus. Nontypeable strains may cause pneumonia in elderly patients with chronic respiratory disease. Neisseria gonorrhoeae is a gram negative diplococcus that is not typically associated with pneumonia. Pneumocystis carinii is a small, hat shaped fungus that is a common cause of pneumonia in HIV positive patients.
Staphylococcus aureus occurs as grapelike clusters of large, gram positive cocci. It may cause pneumonia after surgery or after a viral respiratory infection, such as influenza, and is associated with empyema formation.

Explanation:

In cases of proteinuria, hyaline (dark-staining) droplets can be found in the epithelium of the proximal convoluted tubule. These droplets are protein-containing, pinocytotic vesicles that have fused with lysosomes (to produce phagolysosomes). This change is a sensitive histologic indicator of proteinuria. Glomerular changes can cause proteinuria, but are not usually produced by it.

Explanation:

Systemic thromboembolism may develop in each of these patients. Vegetations associated with infective endocarditis may undergo fragmentation and result in systemic thromboembolism. Stasis develops in dilated ventricles, which predisposes to formation of thrombi attached to the ventricular walls (mural thrombi). Mural thrombi may also form within the left atrium in the presence of mitral valve prolapse. Thromboemboli may originate from mural thrombi. Decreased compliance is a pathophysiologic alteration present in a variety of cardiac disorders in which there is impediment to expansion or relaxation of ventricular walls, such as restrictive cardiomyopathy, hypertrophic cardiomyopathy, and constrictive pericarditis. This feature is not present in any of the conditions described in the question. Depressed myocardial contractility results from conditions that impair myocardial inotropism, such as dilated cardiomyopathy and ischemic heart disease. Depressed inotropism is not present in infective endocarditis or mitral valve prolapse. Of the three conditions in the question stem, only infective endocarditis is definitely related to an infectious etiology, usually bacteria. Recall that mitral valve prolapse is due to myxomatous degeneration of the mitral valve sometimes associated with Marfan syndrome. The etiology of dilated cardiomyopathy is heterogeneous, and most cases are idiopathic. Of the remaining cases, viral infections, toxic insults (especially alcohol), metabolic disorders (hemochromatosis), pregnancy, and genetic influences are the underlying causes. Mitral valve stenosis may develop as a result of vegetations forming on the mitral valve and occluding the valvular orifice. Endocarditis of the mitral valve more often leads to mitral insufficiency because of destruction of valve leaflets or rupture of chordae tendineae. On the contrary, both mitral valve prolapse (usually clinically silent) and dilated cardiomyopathy may lead to mitral valve insufficiency and regurgitation.

Explanation:

In a syndrome called cleidocranial dysostosis, absence of parry of the clavicles accompanies a broad skull, and facial and dental anomalies. Note that you could also have answered this question by noting that of the bones listed, only the clavicles form by intramembranous ossification. The femurs, metatarsals, phalanges, and tibias are cartilaginous (formed by endochondral ossification) rather than membranous bones.

Explanation:

This child probably has autosomal dominant von Willebrand disease. von Willebrand disease (WD) is the most common hereditary coagulation abnormality described in humans, although it can also be acquired as a` result of other medical conditions. It arises from a deficiency of von Willebrand factor (vWF), a multimeric protein that is required for platelet adhesion. An abnormal vWF (which also carries factor VIII in the blood) causes a defect in the initial adhesion of normal platelets to a damaged vessel wall. Since factor VIII levels are also consequently low, the partial thromboplastin time is also prolonged. Defects in platelet adhesion are also seen in Bernard-Soulier disease. Abnormal platelet morphology is not seen in von Willebrand disease, but may be observed with infiltration of the bone marrow by tumor or fibrosis or after splenectomy. Defects in primary platelet aggregation are seen in thrombasthenia, which is caused by a deficiency or defect in the glycoprotein GpIIb-IIIa complex.
Defects in release of platelet vesicles or secondary aggregation are seen in storage pool disease and aspirin use.

Explanation:

Breast cancer is the second leading cause of cancer deaths among women. While surgical excision with negative margins and no lymph node involvement has a relatively good prognosis for the patient, an adjunct therapy involving either chemotherapy or radiotherapy is strongly recommended for high grade cancers. In particular, tumors that express certain receptors such as estrogen progesterone and the HER2 type epidermal growth factor (EGF) receptors may make the lesion more susceptible to pharmacologic interventions, including the estrogen receptor antagonist tamoxifen and the HER2 EGFR blocker trastuzumab (Herceptin®). Since both estrogen and progesterone receptors are steroid hormone receptors they will mostly localize in the nucleus to act as transcription factors. These would appear as a nuclear pattern of straining. In contrast, EGFR receptors are tyrosine kinase receptors and will be largely localized to the cell membrane surface.

Explanation:

The patient has a left cervical rib. This anatomic variant, which is typically bilateral but can occur on only one side, is due to formation of an extra rib at the C7 level. Cervical ribs, while often asymptomatic, can cause thoracic outlet obstruction. This results in pain due to distortion of blood vessels; pain or paresthesias related to brachial plexus impingement (notably sensory disturbances in the distribution of the ulnar nerve); and palpable abnormalities in the greater supraclavicular fossa. Horner syndrome (ptosis, anhidrosis, and miosis) occurs with Pancoast tumors at the apex of the lung, as well as with certain brainstem or spinal cord lesions. Osteopetrosis is a hereditary disease characterized by increased density and thickening of bone cortex with narrowing of medullary cavities. Bones are brittle and fracture easily. Shoulder dislocation does not present with a supraclavicular bony structure

Explanation:

Cortisol levels are increased in pregnancy, conditions of physical and emotional stress and drug therapy (oestrogens, oral contraceptives, amphetamines, cortisone, and spironolactone). Treatment with other forms of steroid lead to decreased levels of cortisol.

Explanation:

Crohn´s disease commonly presents with diarrhoea, abdominal pain and weight loss. It can affect the whole gastrointestinal tract, the commonest being ileocolitis. Anemia is usually due to blood loss and less commonly B12 / folate malabsorption. An abdominal mass is often palpable in presence of small bowel disease, which can lead to Vitamin K malabsorption. Anal tags, fissures, perianal fistulae and abscesses are associated with crohn´s disease and not ulcerative colitis.

Explanation:

S. epidermidis causes biofilms to grow on plastic devices placed within the body. This occurs most commonly on intravenous catheters and on medical prostheses. Generally there are two identifiable modes of prosthetic valve endocarditis. The first occurs within the first year after surgery affecting 0.7-3% of cases and is often due to staphylococci.
Late endocarditis observed after two years post surgery is found in 0.5 – 1% of cases and is typically due to streptococci -typically alpha haemolytic otherwise known as Streptococcus viridans

Explanation:

Affinity maturation in an ongoing immune response is a feature of the antibody response. There is no evidence that a similar process occurs in the T cell response. Major histocompatability complex (MHC) molecules present short antigen-derived peptides, not the intact antigen.
T cells recognise antigen only when presented by (self) M C molecules on an antigen presenting cell.
MMC class II molecules present antigen to CD4+, alpha/beta+ T cells. It is still not clear how gamma/delta+ T cells recognise antigen, however most gamma/delta+ T cells do not appear to be restricted by (self) MMC molecules.
Additional ´costimulatory´ signals are required to activate a resting T cell. Interaction of the T cell reactor (TcR) of a resting T cell with an appropriate Ag/M C complex in the absence of costimulatory signals may lead to the induction of anergy.

Explanation:

Affinity maturation in an ongoing immune response is a feature of the antibody response. There is no evidence that a similar process occurs in the T cell response. Major histocompatability complex (MHC) molecules present short antigen-derived peptides, not the intact antigen.
T cells recognise antigen only when presented by (self) M C molecules on an antigen presenting cell.
MMC class II molecules present antigen to CD4+, alpha/beta+ T cells. It is still not clear how gamma/delta+ T cells recognise antigen, however most gamma/delta+ T cells do not appear to be restricted by (self) MMC molecules.
Additional ´costimulatory´ signals are required to activate a resting T cell. Interaction of the T cell reactor (TcR) of a resting T cell with an appropriate Ag/M C complex in the absence of costimulatory signals may lead to the induction of anergy.

Explanation:

Gardener´s syndrome or familial adenomatous polyposis is characterized by multiple small and large intestinal tumours and lipomas. Osteomata and fibromas are also seen.
It is a rare familial condition, when arising from mutations of the APC gene is inherited in an autosomal dominant fashion.
Gardener´s syndrome carries an increased risk of papillary carcinoma of the thyroid with preponderance for female patients.

Explanation:

Gardener´s syndrome or familial adenomatous polyposis is characterized by multiple small and large intestinal tumours and lipomas. Osteomata and fibromas are also seen.
It is a rare familial condition, when arising from mutations of the APC gene is inherited in an autosomal dominant fashion.
Gardener´s syndrome carries an increased risk of papillary carcinoma of the thyroid with preponderance for female patients.

Explanation:

Amyloid fibrils are uniquely stained in this fashion by Congo-red dye. The other answer choices are incorrect.

Explanation:

Fibrotic lesions resulting from asbestosis are not related either to the shape or the chemical composition of the fiber type. Asbestos is a generic term for several different mineral silicates, including chrysolite, amosite, anthophyllite, and crocidolite. All types of these mineral silicates produce disease. Asbestosis, a form of interstitial lung disease, is related both to the intensity and duration of exposure. Phagocytosis of the asbestos fiber is thought to damage the membrane of the macrophage, releasing lysosomes containing enzymes that damage the lung parenchyma. Cigarette smoking has a multiplicative effect on the risk of lung cancer, but does not increase the risk of mesothelioma.

Explanation:

All the other conditions are associated with a specific gene defect – CAH and Friedeich´s being autosomal recessive with Huntingdon being dominant. K1inefelter´s is due to a Chromosomal abnormality XXY. No specific defect has been detected thus far with ALS.

Explanation:

Xenotransplantation is the transfer of organs between species – particularly the transfer of animal organs to humans. Compare this with allotransplantation which is the transfer of organs within the same species.
There have already been several documented cases of xenotransplantation – baboon heart, chimpanzee kidneys.
A close human leukocyte antigen (HLA) match is not possible of course, unless a transgenic species is used that express human major histocompatability complexes (HLA).
Early immune response is humoral -immunoglobulin M (IgM).

Explanation:

Studies show that over 90% of vegans (those who ate the strictest vegetarian diet, which shuns all animal products, including milk and eggs) had vitamin B12 deficiency. Approximately 65% of vegetarians (diets that included milk and eggs) were also deficient. Only 5% of those who consumed meats had vitamin B12 deficiency. B12 is not found in any plant food other than fortified cereals. It is, however, abundant in many meats and fish, and in smaller amounts in milk and eggs. This makes it difficult for people following a strict vegetarian diet to get the necessary amount of vitamin B12. Vitamin B12 deficiency leads to anemia. Symptoms of vitamin B12 deficiency, which usually come on gradually, include fatigue, weakness, nausea, and constipation. Long-term and severe vitamin B12 deficiency can lead to nerve changes such as numbness, tingling in the hands and feet, balance and memory problems, and depression.

Explanation:

This is a typical presentation for fibromyalgia, an idiopathic painful condition characterized by multiple specific trigger points, the painful areas described in this individual. This presentation is not consistent with any of the other diagnoses.

Explanation:

The phrase “mosaic pattern” of newly formed woven bone is a specific tip-off for Paget disease of bone, and is not seen other bone conditions. The clinical and radiologic presentations are typical; an increased hat size may also be a clue. In its early stages, Paget disease is characterized by osteolysis, producing patchwork areas of bone resorption with bizarre, large osteoclasts. In the middle stage of the disease, secondary osteoblastic activity compensates with new bone formation producing the mosaic pattern. In late Paget, the bones are dense and osteosclerotic. Paget disease is suspected to be related to prior viral infection but the cause remains mysterious. Complications include myelophthisic anemia high output cardiac failure, pain secondary to nerve compression deformities secondary to skeletal changes and in about 1% of patient´s osteosarcoma or other sarcoma typically involving the jaw pelvis or femur. An increased incidence of astrocytomas is associated with tuberous sclerosis. Hodgkin lymphoma is usually a disease of young adults although older patients may have the lymphocyte depleted form. Meningiomas are mostly benign tumors that affect adults especially females. There may be an association with breast cancer possibly related to high estrogen states. Non-Hodgkin lymphoma is more common in AIDS and other immunodeficiency states although the incidence in the immunocompetent is increasing.

Explanation:

Kayser Fleischer rings, which represent deposits of copper in Descemet´s membrane of the cornea, are pathognomonic of Wilson´s disease. Hepatomegaly, renal insufficiency, anemia, and encephalopathy are all associated with Wilson´s disease, but are not specific for it.

Explanation:

Although 70% of compound fractures are contaminated with bacteria, less than 10% result in infection because of extensive operative debridement and perioperative antibiotic therapy. The anatomic location of hematogenous osteomyelitis depends on the age of the affected person. In children, hematogenous osteomyelitis usually affects the metaphysis of the long bones due to its large blood flow. In adults, the vertebrae are more vascular than other skeletal tissues. Therefore, bacteremias seed vertebral bodies preferentially at the more vascular anterior end plates. In up to two thirds of diabetics, osteomyelitis may develop by contiguous spread from an infected foot ulcer. Indwelling foreign bodies, such as prosthetic joints, decrease the quantity of bacteria necessary to establish a bone infection. These devices also permit pathogens to persist on their surface, protected from circulating immune factors and systemic antibiotics.

Explanation:

Glucose 6 phosphate dehydrogenase deficiency is an X linked disease present in approximately 15% of all black males in America. It is typically unsymptomatic until challenged with a drug agent which may cause hemolysis, such as primaquine, quinidine, or sulfonamides

Explanation:

Repair of radiation induced DNA and chromosomal damage is inversely related to the rate at which the radiation is absorbed. Damage to the genetic apparatus of the nucleus results from ionizing radiation. Low linear energy transfer (LET) radiation most commonly results in single strand breaks and base alterations, while high LET radiation produces double strand breaks. Free radicals generated by the ionizing radiation are primarily responsible for this DNA damage and the chromosomal alterations. Chromosomal breaks with rearrangements associated with loss of considerable amounts of chromosomal mass may lead to cell death at either the first or one of the first few postirradiation mitotic divisions. Large doses of radiation may produce direct cell death due to membrane or cytoplasmic structural damage.

Explanation:

A seminoma is the most common testicular tumor. The others are less common. Treatment involves orchiectomy and radiation.

Explanation:

Virchow´s criterion is a triad of stasis, endothelial damage, and hypercoagulability. Fibrinolysis is not included in the triad of Virchow.

Explanation:

Virulence of S. pneumoniae is, in part, determined by the presence of a high molecular weight capsular polysaccharide. In healthy persons, microaspiration occurs commonly. Pneumonia is rare due to pulmonary bacterial clearance and local host defense mechanisms. Any anatomic or physiologic derangement of these defense mechanisms predisposes to pneumonia. Bronchial embolization with infected mucinous secretions during the course of an upper respiratory infection probably is the initiating event in many cases of pneumonia. Initially, the bacteria are protected by the mucinous material. They multiply in infected alveoli, evoking an outpouring of proteinaceous fluid which serves as a nutrient and vehicle for spread to adjacent alveoli. Host defenses are produced to combat the infection. Antibody to capsular polysaccharide of the invading organism increases the efficiency of phagocytosis. It also causes agglutination of the organisms and causes them to adhere to the alveolar walls.

Explanation:

Fibromyalgia has not been demonstrated to be an autoimmune disorder. Autoimmune phenomena are well described in SLE), Hashimoto´s thyroiditis, vasculitis, and rheumatoid arthritis.

Explanation:

This is a case of immediate (type I) hypersensitivity mediated by IgE, mast cells, and basophils. The cytokine that mediates the isotype switch to IgE in B lymphocytes is interleukin 4, produced by T helper-2 cells. Interferon-gamma is a cytokine that activates macrophages and would not be involved in this response. Interleukin 1 is an endogenous pyrogen involved in the production of the acute phase reaction of systemic inflammation. Interleukin 2 is the cytokine that induces T-cell proliferation.
Interleukin 3 is a hematopoietic colony stimulating factor.

Explanation:

While most (85%) of renal stones are radiolucent and will be seen on plain film, the test of choice for detecting renal calculi is a high resolution CT scan. This may detect the stone, or it may reveal dilation of the ureter, if the stone hinders flow in the GU tract. This patient´s condition would not affect the psoas muscle or the vertebral body. Dilatation or aneurysm of aorta, when symptomatic, produces back pain and hemodynamic instability. This patient´s history is inconsistent with bowel obstruction, a condition that would produce colicky pain. Bowel obstruction would not produce hematuria and would typically produce some GI symptoms.

Explanation:

For the diagnosis of systemic lupus erythematosus (SLE), a patient must meet 4 of 11 criteria; these include malar rash photosensitivity, anemia, hematologic disorders, and arthritis. Libman-Sacks endocarditis can affect patients with SLE. Small, granular vegetations consisting of fibrin develop on the undersurface of the leaflets of mitral and aortic valves. Fragments of vegetations may detach, resulting in embolism. Eventually, vegetations heal by organization of fibrin and subsequent fibrosis, leading to distortion of valve leaflets and resultant insufficiency or stenosis. The pathogenesis is unclear but is probably related to thrombotic diathesis. Hemorrhagic pericarditis is usually a consequence of tuberculosis or metastatic spread of cancer to the pericardium. An exudate containing blood accumulates in the pericardial sac, producing pain and a characteristic auscultatory phenomenon known as a pericardial rub. SLE is associated instead with fibrinous pericarditis which also manifests with chest pain and pericardial rub infective endocarditis is prevalent inpatients with damaged or prosthetic valves and in intravenous drug abusers. It is associated with formation of bulky, friable vegetations that consist of masses of fibrin, neutrophils, and bacteria. Such vegetations cause extensive destruction of valve leaflets and may release fragments into the bloodstream, with resultant septic embolism. There is no association between SLE and mitral valve prolapse, which is a frequent, usually asymptomatic valvular abnormality that occurs in 2 to 3% of the general population. Mitral valve prolapse is also associated with Marfan syndrome. Complications include sudden death, thromboembolism, and mitral regurgitation.
Myocardial fibrosis does not occur in SLE. It develops in progressive systemic sclerosis, a collagenopathy characterized by extensive fibrosis in many organs, especially skin, lungs, and gastrointestinal tract. The heart is involved in 30% of cases. Myocardial fibrosis may cause arrhythmias.

Explanation:

This patient most likely has fetal alcohol syndrome, which is a combination of multiple abnormalities that are caused by maternal intake of alcohol during pregnancy. The craniofacial defects include epicanthal folds, short palpebral fissures, a smooth philtrum, a thin upper lip, small teeth, and poorly formed ears. The patients are often mentally retarded, have limitation of joint movement, and have microcephaly. Major cardiac manifestations include atrial and ventricular septal defects. Pregnant women should not drink any alcohol, because it is not known exactly when and how much alcohol causes this syndrome. Diethylstilbestrol is associated with clear cell adenocarcinoma of the vagina in female offspring of women taking this drug. Folate should be taken by all pregnant women and women planning on becoming pregnant to avoid neural tube defects. This patient´s findings are not caused by maternal intake of folate. Maternal lithium intake is associated with Ebstein anomaly and tricuspid atresia. Other noncardiac teratogenic manifestations are rare. Maternal thalidomide intake is associated with variable cardiac manifestations and phocomelia. It is rarely associated with the craniofacial findings in this patient.

Explanation:

This child most likely has β thalassemia, an autosomal recessive disease that, in the homozygous state, produces defects in the transcription, processing, or translation of β globin mRNA. The predominant hemoglobin switches from HbF (α2γ2) to HbA (α2β2) at about 6 months of age at which point these children become markedly anemic because of their inability to synthesize the β globin chain. Decreased β chain production leads to decreased HbA and increased HbF and A2 to compensate. The anemia of thalassemia is microcytic and hypochromic with anisocytosis. Amino acid substitutions in β globin lead to hemoglobinopathies, of which sickle-cell anemia is the arche type. Homozygotes with these hemoglobin variants do not produce any HbA but rather mutant types, such as HbS, HbC, and HbM. Antibodies against fetal blood cells are generally produced by a mother who has been sensitized to fetal blood antigens by transfusion or a previous pregnancy. Such immune mediated hemolysis leads to intrauterine anemia and hydrops fetalis. Cytoskeletal protein defects such as spectrin deficiency causing hereditary spherocytosis, produce anemia and jaundice that are apparent at birth. The RBCs contain the normal types of hemoglobin.
Alpha thalassemia is due to inadequate production of α-chains. The chains are coded for by four copies of the gene and α-thalassemia consequently varies in severity from silent carrier (one dysfunctional gene) to α-thalassemia trait (two dysfunctional genes) to hemoglobin H disease (three dysfunctional genes) to α-thalassemia major (fetal hydrops; four dysfunctional genes).

Explanation:

IL-1 is produced by macrophages and other antigen-presenting cells. It is frequently called the endogenous pyrogen because of its direct effect on the hypothalamus. Other actions include stimulation of T cells to secrete IL-2, chemotactic activity for neutrophils and monocytes, increased expression of intercellular adhesion molecules (ICAMs) on vascular endothelial cells, and activation of macrophages and natural killer (NK) cells. IL-2 is produced by activated T helper cells. It stimulates the proliferation of other T cells as well as activated B cells. It also activates NK cells and stimulates lymphokine secretion. IL-3 stimulates stem cells to produce hematopoietic cells; it is also known as multilineage colony stimulating factor (CSF). IL-4 is produced by T helper 2 (Th2) cells and mast cells. It has several functions, including inducing cells to express class II major histocompatibility complex (MHC) antigens and stimulation of B-cell proliferation. It is involved in the induction of atopic allergies by its mitogenic activity for mast cells and its enhancement of immunoglobulin class switching to lgG and IgE. (Note that IL-5 is involved in class switching to IgA.) IL-5 is secreted by activated T helper cells. It promotes B-cell proliferation and stimulates B-cell class switching to IgA.

Explanation:

Infectious mononucleosis is a benign infection caused by the Epstein Barr virus (EBV), a herpesvirus. Although B lymphocytes are infected by the virus, the characteristic atypical cells are activated cytotoxic and suppressor T cells-thus the paracortical location (T cell zone) in the lymph node. Lymph nodes in viral infections show expansion of germinal centers without loss of normal architecture. All lymphomas, including Burkitt, Hodgkin, and non Hodgkin lymphomas, destroy the normal architecture of the lymph node. AIDS is associated with a number of neoplastic and infectious processes that may alter the lymph node structure. The characteristic lymph node changes in AIDS are progressive transformation of the germinal centers, not paracortical hyperplasia. Burkitt lymphoma produces a sea of monotonous, mitotically active cells in a “starry sky” appearance. Hodgkin lymphoma also can show nodular or diffuse patterns but is characterized by the presence of Reed-Sternberg cells. Other non Hodgkin lymphomas show either a nodular appearance or diffuse sheets of cells that replace the germinal centers.

Explanation:

This woman presents with the classic signs and symptoms of multiple sclerosis (MS). A key to the diagnosis is different neurologic signs that are separated by space and time. (Another classic clue might have been oligoclonal bands on electrophoresis of the CSF.) MS is a demyelinating disease of the CNS, characterized by loss of oligodendroglial cells, which are responsible for producing myelin in the CNS. Diagnosis can be confirmed by an MRI revealing sharply delineated regions of demyelination (plaques) throughout the CNS white matter (especially in periventricular areas). Antibodies to acetylcholine receptors have been implicated in the etiology of myasthenia gravis, not MS. MS is generally characterized by axonal preservation, rather than degeneration. Demyelination of peripheral nerves occurs in a number of diseases (e.g., Guillain-Barre), but not in MS. Guillain Barre is characterized by ascending muscle weakness, areflexia, and paralysis. Oligodendrocytes are responsible for producing myelin in the CNS; Schwann cells are responsible for myelination in the peripheral nervous system and are not affected in MS.

Explanation:

The dashed curve is typical of obstructive lung diseases such as emphysema. The patient breathes at higher than normal lung volumes, as reflected by the left ward shift of the dashed MEFV curve shown in the diagram. Note that the total lung capacity (TLC) is 7 liters and the residual volume (RV) is about 3.5 liters in the patient (dashed curve). The vital capacity, which is the difference between TLC and RV is reduced to 3.5 liters with obstructive disease, compared to a normal value of 5 liters (solid curve). (You should know that absolute lung volumes cannot be determined from a MEFV test alone. An additional method is needed to measure residual volume. However the diagram above states that lung volumes are absolute indicating correct placement of the curves on the abscissa.) The maximum expiratory flow rate is reduced at any given lung volume in the patient with obstructive disease (dashed curve) because the airway diameter is reduced. One factor that can lead to decreased airway diameter in emphysematous lungs is the decrease in radial traction of the airways which occurs when lung elasticity is reduced.

Explanation:

Blood flow through the coronary circulation is regulated almost entirely by the metabolic requirements of the cardiac muscle. When the oxygen consumption of the heart increases, a larger than normal proportion of the adenosine triphosphate (ATP) in the heart muscle cells degrades to adenosine. The adenosine then dilates the coronary blood vessels, increasing oxygen delivery to an adequate level. In this way, the coronary blood flow increases in direct proportion to the oxygen consumption of the heart. In aortic stenosis, the left ventricular pressure becomes excessively high because the resistance of the aortic valve orifice is higher than normal. This increase in left ventricular pressure increases the work load on the left ventricle because the heart now pumps blood with an elevated left ventricular pressure. The increased work load on the heart requires a greater consumption of oxygen. Under these conditions of increased cardiac work and increased oxygen consumption, one expects the cardiac tissue oxygen concentration to be lower than normal.

Explanation:

ARDS, pathologically referred to as diffuse alveolar damage, is a clinical syndrome of acute respiratory failure resulting from diffuse injury to the alveolar/capillary barrier. Such injury may be caused by a great variety of initiating insults, the most frequent of which are shock, severe trauma, sepsis, and gastric aspiration. All these different forms of injury result in recruitment of neutrophils within the alveolar capillaries. Neutrophils release chemokines that attract histiocytes and produce oxygen radicals prostaglandins, and proteases that damage alveolar epithelium. Formation of hyaline membranes is due to a combination of plasma fluid extravasation and alveolar cell necrosis. CD4+ (helper) lymphocytes, CD8+ (cytotoxic) lymphocytes, eosinophils and mast cells have been implicated in a number of pulmonary diseases, but not in diffuse alveolar damage.

Explanation:

In this item, the clinical information is really just “window dressing” for the actual question. All you are being asked is, “What is the most common type of cancer seen in the bladder?” The answer is that 90% of primary bladder cancers are transitional cell carcinomas, derived from bladder urothelium (a transitional cell epithelium). Let´s take a moment to review the classic dues associated with bladder carcinoma: exposure to industrial chemicals, cigarette smoking, and infection with Schistosoma haematobium (predisposes to squamous cell type). Remember that a patient´s occupation is usually stated for a reason.
All of the other answer choices are quite rare by comparison.