Primary syphilitic chancre on the upper arm in an HIV-1-infected patient.

A 32-year-old HIV-infected man presented with an ulcerating skin lesion with indurated borders on the upper right arm. Both dark-field microscopy and syphilis serology confirmed the diagnosis of primary syphilis. Extragenital syphilitic chancres are uncommon but nevertheless have to be kept in mind as they often delay diagnosis.