Secondary syphilis mimicking tinea cruris in an HIV infected patient: a case report.

Syphilis is known as the great imitator with various clinical presentations which often lead to confusion and misdiagnosis. A 28-year-old male presented with non-pruritic and painless erythematous patches around the anus and scrotum. Initial differential diagnosis with tinea cruris. Fungal examination was negative. Serological tests for syphilis were positive and anti-HIV screening was reactive. A diagnosis of secondary syphilis was established and the patient was given intramuscular injection of 2.4 million unit of benzathine penicillin. The skin lesions improved significantly 1 week after treatment, confirming a diagnosis of secondary syphilis with HIV. Annular skin lesions in secondary syphilis are uncommon and often misleading. This case emphasizes the importance of considering secondary syphilis in the differential diagnosis of annular lesions.