Dermatologically challenging syphilis presentation.

An atypical early primary syphilis case presentation with multiple umbilicated papular lesions on the penis and a nonreactive syphilis serology was misdiagnosed as molluscum contagiosum. Over a period of eight weeks, prior to dermatologic consultation, the papules enlarged, ulcerated, and healed. New plaque and patch formation on the penis and scrotum led to a differential diagnosis of inverse psoriasis vs. syphilis. Histological examination of a shave biopsy specimen revealed numerous Treponema pallidum organisms and repeat syphilis serological test results confirmed a syphilis diagnosis. Lesions responded to treatment with benzathine penicillin. One must keep a high index of suspicion for syphilis in light of its diverse presentation and increasing incidence.