What is the cause of this woman’s rash?

This 57-year-old woman presented with a bilateral inguinal rash of 3 months’ duration. It extended onto the anterior thigh, and she described it as both itchy and tender. She denied any new exposure history (eg, detergent, softener, clothes, etc) or new medications. She was otherwise healthy.

What is the cause of this woman’s rash?

A. Intertrigo
B. Seborrheic dermatitis
C. Tinea cruris
D. Psoriasis
E. Candidiasis
F. Erythrasma

Answer on next page

Answer: Psoriasis

The results of a potassium hydroxide (KOH) examination were negative, and biopsy confirmed the diagnosis of psoriasis—or in this case sebopsoriasis. Late-onset psoriasis is common and should be considered in the differential diagnosis for patients who do not respond to appropriate treatments for conditions that produce intertriginous rashes. She did not have classic psoriasis changes on her elbows, knees, scalp, or nails.