Secondary syphilis resembling erythema multiforme.

Background: Secondary syphilis, which typically begins 4-10 weeks after initial exposure to Treponema pallidum, manifests with a range of cutaneous patterns. One unusual variation features oval, targetoid plaques that may resemble erythema multiforme (EM).
Methods: We describe a 23-year-old woman with an EM-like eruption, a mucous patch, and a prominent alopecia somewhat moth-eaten in appearance. She had positive rapid plasma reagin and fluorescent treponemal antibody absorption (FTA-ABS) tests, and a skin biopsy revealed swollen endothelial cells with a superficial perivascular infiltrate containing plasma cells. Response to intramuscular penicillin therapy was consistent with the empiric diagnosis of secondary syphilis.
Conclusions: One should consider secondary syphilis in the differential diagnosis of an eruption resembling EM.
(© 2010 The International Society of Dermatology.)