A 7-year-old girl is urgently referred to dermatology for a rash of several weeks’ duration. It is the rash itself, rather than any related symptoms, that frightens the family; the possibility of measles (raised by their primary care provider) compounded their concern. Antifungal cream (clotrimazole) has been of no help.
Physically, the child feels fine, without fever or malaise. But further questioning reveals that she was diagnosed with and treated for strep throat “about a month before” the rash developed.
The child was recently adopted by her aunt and uncle after her parents were killed in an automobile accident. This, understandably, has caused her to fall behind in school. She has no pets, no siblings, and no family history of skin disease.
Numerous discrete, round papules and plaques are distributed very evenly on the trunk. They are uniformly scaly and pink, measuring 2 to 3 cm each. In addition, several areas of thick, white, tenacious scaling are seen in the scalp.
The patient’s elbows, knees, and nails are free of any notable change.
What is the diagnosis?