Explanation:

This boy probably has early disseminated Lyme disease, as indicated by:

• The history of rash
• The history of hiking in the woods 1 month ago

Migratory polyarthritis Since the patient does not have the rash right now, further workup must be done to confirm the diagnosis. In patients with Lyme disease suspected on the basis of historical and physical findings (other than patients with a classic erythema migrans [EM] lesion), the diagnosis of Lyme disease is made by a two-step approach that uses an enzyme-linked immunosorbent assay (ELISA) followed by a Western immunoblot.
Amoxicillin is incorrect because the diagnosis of Lyme disease has not yet been made. If the physician had seen the characteristic EM rash (erythematous, circular, expanding with central clearing), no further testing would have been necessary. The diagnosis of early Lyme disease can be made on clinical grounds alone in the presence of a classic EM lesion. When the rash is seen, a positive serology is not needed to make the diagnosis. And since this patient is younger than 8 years, amoxicillin would be indicated. But the physician did not see the rash; the mother only gave a history of it. The diagnosis of Lyme disease needs to be confirmed.
Arthrocentesis is incorrect because blood tests for ELISA followed by Western blot will be enough to make the diagnosis. An invasive test such as arthrocentesis is not needed.
Doxycycline is incorrect because the diagnosis of Lyme disease has not yet been made. Moreover, this child is younger than 8 years, which contraindicates the use of doxycycline. Doxycycline would be the treatment of choice if the diagnosis of Lyme disease was confirmed by the physician´s seeing the rash or by serologic testing in patients older than 8 years.
Prednisone is not used in the treatment of Lyme disease at all; it may be used in other cause of arthritis, such as rheumatoid arthritis, SLE, etc.

Explanation:

This girl has the typical clinical picture of impetigo contagiosa, a staphylococcal, streptococcal, or combined infection characterized by discrete, thin-walled vesicles that rapidly become pustular and then rupture, leaving a honey/straw-colored crust.
Impetigo occurs more frequently on the exposed parts of the body-face, hands, neck, and extremities- although it may appear at sites of friction as well. Over 50% of cases are due to Staphylococcus aureus, with the remainder being due to Streptococcus pyogenes or a combination of the two bacteria. Group B streptococci are associated with newborn impetigo. Impetigo is most commonly seen in early childhood and during hot, humid summers in temperate climates. A semisynthetic penicillin or first-generation cephalosporin is recommended for 7 to 10 days.
Bullous pemphigoid is a chronic, blistering autoimmune disease of unknown etiology that most commonly affects patients above the age of 60. Deposits of polyclonal autoantibodies and complement are found in a linear pattern at the basement membrane zone between dermis and epidermis. Thus, blisters are subepidermal, deep, and tense with intact skin.
Poison ivy presents with edema and erythema of the eyelids and linear, erythematous, or brownish streaks that are studded with tense vesicles. Erythematous patches with vesicles and scale-crust may be present on covered body parts as well, but are much less severe than on the exposed areas that were in direct contact with the plant Pruritus is usually excruciating.
Scabies presents with typical linear 2-to-5-mm-long burrows covered byline scale and with a tiny vesicle at the end. They can most commonly be found in the finger webs, on the flexor wrists, areolas, axilla, or glutei, or around the umbilicus. Incessant pruritus is typical and worsens at nighttime.
Tinea corporis typically presents as annular erythematous patches that have a scaly and sometimes vesiculated edge. The center usually clears as the lesion spreads centrifugally. In uncomplicated cases, there is no significant crusting apparent. A potassium hydroxide examination of skin scrapings is diagnostic.
Toxic epidermal necrolysis is a severe drug reaction where the entire or almost entire epidermis is sloughed off secondary to cytotoxic-induced necrosis of keratinocytes. Clinically, widespread erythema is present in a systemically severely ill patient and large sheets of skin slough off, leaving moist erosions. Mucosal involvement may lead to permanent sequelae.

Explanation:

Explanation:

This patient has developed rubella (German measles), a viral infection characterized by a maculopapular exanthem and tender lymphadenopathy of the post occipital, retroauricular, and cervical lymph nodes. The diagnosis is usually made clinically from the history and physical examination, but should be confirmed by serologic tests or a viral culture. Supportive treatment is given. The prognosis of rubella in children is excellent and complications are uncommon.
However, a pregnant woman who contracts rubella in the first trimester of pregnancy has a high probability that intrauterine transmission will give rise to the congenital rubella syndrome, and a urine pregnancy test should be performed to exclude the possibility of early pregnancy in this patient.
Anti- Borrelia antibody titer would be indicated if the patient had a history of a tick bite and/or clinical evidence of Lyme disease, such as erythema migrans. Otherwise, the titer would not be clinically useful, as it is positive in many patients who do not have a positive history or symptoms of Lyme disease.
Antinuclear antibody titer is indicated in patients suspected of having connective-tissue disease, such as lupus erythematosus. The clinical presentation of lupus in an adolescent female would not typically include a generalized maculopapular rash or a tender lymphadenopathy.
Rheumatoid factor titer would be useful if the patient were suspected of having rheumatoid arthritis (RA). RA typically starts with morning stiffness evolving over weeks or months and vague systemic symptoms.
A striated muscle biopsy would be indicated in a patient suspected of having dermatomyositis. Dermatomyositis presents with heliotrope erythema, Gottron papules, and proximal extremity weakness.

Explanation:

The most common cause of pneumonia in children older than 5 years of age is Mycoplasma pneumoniae. This child has a typical presentation for these organism-worsening upper respiratory symptoms, often with fever, mild tachypnea, and bilateral basilar rales. The further evaluation suggests the diagnosis. She has radiographic evidence of a significant bilateral lower lobe bronchopneumonia, which is what we would see with Mycoplasma infection. In addition, the x-ray findings usually appear to be out of proportion to the physical findings, i.e., they are worse than what you would expect to see based on the child´s appearance. These children are described by lay people as having “walking pneumonia.” The white blood cell count generally shows nothing characteristic; it is usually normal, perhaps with a lymphocytic predominance. Cold agglutinins might be positive in some cases, but these are nonspecific and generally are not clinically used.
The child also does not appear to be ill enough to warrant admission to the hospital, as long as there is good follow-up. She is mildly tachypneic, but without other signs of respiratory distress. She is moving air well and has good oxygenation in room air. Nothing is mentioned of dehydration or her inability to take fluids well. Therefore, she may be treated as an outpatient. The drug of choice is a macrolide-erythromycin, azithromycin, or clarithromycin. There is no evidence of hypoxemia, and the girl is moving air well without wheezing; therefore, she does not require oxygen or a bronchodilator. For the reasons stated above, hospitalization is not required and a third-generation cephalosporin is not the appropriate antibiotic for this organism.
The organism may be obtained by testing nasopharyngeal secretions with polymerase chain reaction, but this is not necessary at this point because the diagnosis can be made clinically and the child treated empirically. Growth on special cultures is rarely detected with Mycoplasma earlier than 1 week, and few laboratories maintain the capability of culturing this organism.
Oral amoxicillin would not effectively treat this organism.