What is the cause of this boy’s annular lesions?

This 15-year-old boy presented for evaluation of 3 similar-appearing lesions on his thigh and upper arm that were asymptomatic. There was no history of trauma or exposure. He was taking no medications and was otherwise healthy. He does not play any contact sports.

What is the cause of this boy’s annular lesions?

1. Cupping
2. Hickey (suction purpura)
3. Bite trauma
4. Benign pigmented purpura
5. Ringworm

Answer on next page.

Answer: Benign pigmented purpura

This patient had Majocchi purpura, or an annular variant of benign pigmented purpura that is not uncommon in young adults. This self-limited benign capillaritis is of unknown etiology and does not require treatment. Cupping lesions are usually not annular, and patients are usually willing to provide a history. The hickey and bite trauma histories are not as forthcoming but can usually be deduced based on anatomic site. Dermatophyte infections generally present with more scale, unlike what is seen here.