An otherwise-healthy 12-year-old boy presented with a 1-month history of perianal irritation and discharge. Previous therapy included topical antifungal agents. Physical examination revealed sharply demarcated perianal erythema with pustules, edema rimmed with hyperpigmentation, and mucopurulent exudation (Figure 1). There was no palpable inguinal lymphadenopathy. The pharynx was normal. None of his family members had similar lesions.