What are these flat-topped, purplish papules?

A 44-year-old woman presents with slightly pruritic, purplish papules near the elbows and shins of several weeks’ duration. She has no history of trauma and takes no medication.

What does this look like to you?

A. Lichen spinulosus.
B. Lichen amyloidosis.
C. Lichen simplex chronicus.
D. Lichen planus.
E. Lichen nitidus.

(Answer on next page.) 

Answer: Lichen planus

The flat-topped, purplish, polygonal papules are typical of lichen planus, D. Lichen spinulosus lesions are well-circumscribed plaques that contain follicular keratoses. Lichen amyloidosis presents with highly pruritic, hyperpigmented papules and plaques. The pruritic, hyperpigmented papules and plaques of lichen simplex chronicus are often scaly. Lichen nitidus features pinpoint lichenoid papules. 

Agents that have been used to treat lichen planus include systemic corticosteroids, class II topical corticosteroids, topical tretinoin, griseofulvin, and dapsone. ■