Primary syphilis lesion characteristics, serological response and management in HIV-positive and HIV-negative men who have sex with men.

The characteristics and serological responses of primary syphilis are not completely understood. We aimed to describe the characteristics, the serological responses and presumptive treatment of primary syphilis in HIV-positive and -negative men who have sex with men (MSM). We conducted a retrospective review of microbiological and demographic information from MSM presenting with primary syphilis. There were 111 cases of primary syphilis in MSM, the median age was 46 (IQR = 37-53years) and 40 (36%) were living with HIV. Fifty percent of MSM presented with painful lesions and 14% with extra-genital lesions. Extra-genital lesions were significantly more likely to be painful than non-genital lesions (OR 4.72; 95%CI = 1.25-17.83, p = 0.02). Overall, a reactive serological response demonstrated a sensitivity of 80% (57/71) compared with Treponema pallidum PCR. Serology was more sensitive in MSM with no previous syphilis (OR = 3.38, 95%CI = 1.00-11.43, p < 0.05). MSM presenting with painless lesions were more likely to be treated presumptively (OR = 3.39, 95%CI = 1.38-8.33, p < 0.002). There were no differences in the characteristics, serological responses or management according to HIV status. Fifty percent of MSM with primary syphilis presented with painful lesions; extra-genital lesions are more likely to be painful than genital lesions, serology is positive in 80% and there were no differences between HIV-positive and -negative MSM. Understanding the characteristics of primary syphilis will underpin public health campaigns.