Why has this rash resisted topical antifungals?

After 1 month of scratching this slightly pruritic rash on his trunk, a 12-year-old boy was referred for consultation. Another physician had prescribed topical terbinafine for a presumed fungal infection, but no improvement was noted.

What condition caused this eruption?

A. Pityriasis alba.

B. Pityriasis rosea.

C. Pityriasis lichenoides et varioliformis acuta (PLEVA).

D. Pityriasis amiantacea. 

E. Pityriasis (tinea) versicolor.

(Answer on next page)

Answer: Pityriasis rosea

A careful search of the patient’s skin revealed a herald patch—a large, solitary lesion that precedes the eruption of pityriasis rosea, B—on the boy’s shoulder. None of the other conditions in the differential feature a herald patch.

Pityriasis alba appears as a temporary, poorly defined area of hypopigmentation in atopic persons. PLEVA presents as crusted papules—not macules. Pityriasis amiantacea is confined to the scalp. A negative potassium hydroxide evaluation ruled out tinea versicolor.