Diagnosis: Secondary syphilis
Our patient’s punch biopsy showed an unremarkable epidermis but a superficial perivascular infiltrate. On higher magnification, the infiltrate proved to be predominately plasma cells. After further investigation and interview, the patient revealed a history of unprotected sex with multiple women; his rapid plasma reagin (RPR) was elevated with a titer of 1:256. Specific treponemal antibody tests confirmed the diagnosis of syphilis. The patient’s human immunodeficiency virus (HIV) test was negative.
Syphilis, a systemic disease with varied dermatological findings, has been described as “the great imitator.” Although it is on the list of differential diagnoses for multiple conditions, it is rarely the culprit—especially given how uncommon it has become in 20th century medicine. With the worldwide HIV epidemic, safe sex programs effectively dropped the incidence of primary and secondary syphilis in the United States to the lowest in recorded history in the year 2001 at 2.17/100,000.1
More recently, however, this infection appears to be making a comeback. Beginning in 2002, its incidence started to rise, reaching 4.6/100,000 in 2009.1
Secondary syphilis usually appears 6 to 8 weeks after the appearance of the primary chancre. As the pathogen spreads into the bloodstream, a host of systemic symptoms may occur, including an influenza-like illness of body aches, fever, fatigue, and headache. While the exanthem of secondary syphilis is traditionally described as a nonpruritic, papular eruption involving the trunk, extremities, face, palms, and soles, a number of cutaneous manifestations are possible, including localized alopecia and syphilids.2 In addition, a number of atypical cases are described in the literature, although none has described an urticarial variant, as seen in our case.