Descending Maculopapular Rash in a Child

A 10-year-old girl presented with a two-day history of headache. A fever, dry cough, and maculopapular rash developed one day after the headache began. The rash first appeared on the face and spread to her entire body. The patient had no pruritus or pain. She had loss of appetite but no nausea, vomiting, diarrhea, constipation, or recent travel. She had been taking trimetho-prim/sulfamethoxazole for nine days to treat a urinary tract infection. She was taking clonidine and risperidone (Risperdal) for attention-deficit/hyperactivity disorder. She had no known drug allergies and was up to date on immunizations.

[Figure omitted. See PDF]

[Figure omitted. See PDF]

Question

Based on the patient’s history and physical examination findings, which one of the following is the most likely diagnosis?

1. A. Chickenpox.

2. B. Drug eruption.

3. C. Erythema infectiosum.

4. D. Measles.

5. E. Rubella.

Discussion

The answer is B: drug eruption. The morbilliform rash is characteristic of a drug eruption and consistent with use of a sulfonamide medication. Morbilliform rash is the most common drug eruption and appears as an erythematous, maculopapular rash that begins on the trunk and spreads to the limbs. Urticaria may occur with a drug eruption. In most patients, the clinical presentation of a drug eruption is dependent on prior sensitization. In patients with no previous exposure, a drug-induced rash...