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22-Year-Old Female with Rash on Legs

Can you diagnose this case?

David L. Kaplan, MD-Series Editor

Signs and Symptoms

This 22-year-old woman presented with 1-month history of an asymptomatic rash on her legs. A few months prior, another physician had treated her for psoriasis, which had cleared after application of a topical corticosteroid. She was otherwise healthy, and she had been taking oral contraceptives for the past 4 years. She had no history of any exposures.

How would you diagnose this lesion?

Choose one to reveal diagnosis and discussion

Psoriasis
Benign pigmented purpura
Insect bite reaction
Erythema nodosum
Folliculitis

Answer: Benign pigmented purpura

See the full case at Consultant360

This was an example of Majocchi purpura, one of the benign pigmented purpuras, in a patient who also had psoriasis.

Psoriasis would have more scale than this woman’s lesions. Insect bites would be pruritic, erythema nodosum would be indurated and tender, and folliculitis would be raised and symptomatic.

Fortunately, benign pigmented purpura is benign and self-limited, given that no treatments have yet been proven effective. Prevention remains a challenge, since the etiology remains elusive.

David L. Kaplan, MD, is a clinical assistant professor of dermatology at the University of Missouri–Kansas City School of Medicine in Kansas City, Missouri, and at the University of Kansas School of Medicine in Kansas City, Kansas. He practices adult and pediatric dermatology in Overland Park, Kansas.