What could be causing this man’s dermatitis?

This 77-year-old man presented for evaluation of painful erosive dermatitis on his penis (Top). He initially was believed to have an infection and was given cephalexin. When he was seen for a follow-up visit 2 weeks later, the rash had worsened (Bottom). He had been taking the same antihypertensive and cholesterol-lowering medications for years. He denied having any rash elsewhere on his body, and he had no eye or mouth lesions.

What could be causing this man’s dermatitis?

A. Impetigo
B. Pemphigus vulgaris
C. Bullous pemphigoid
D. Candidiasis
E. Contact dermatitis

What would be the best approach to evaluation?

A. Bacterial culture
B. Fungal culture
C. Skin biopsy
D. Change antibiotic to cover methicillin-resistant Staphylococcus aureus
E. Add an oral antifungal for Candida

Answer on next page.

Answer: Bullous pemphigoid

A biopsy confirmed the diagnosis of bullous pemphigoid. All of the listed diagnoses (impetigo, pemphigus vulgaris, candidiasis, and contact dermatitis) are reasonable to consider. Treatment options are determined by biopsy results, although it would not be unreasonable to cover all of the bases until the results of the biopsy are in.