Time to development of ocular syphilis after syphilis infection

To provide an estimate of the incubation period of ocular syphilis based on serology using both clinical data and stored serum samples, we retrospectively reviewed patients with HIV-1 infection who presented with ocular syphilis between August 1997 and July 2015 in a tertiary hospital in Japan. The incubation period of ocular syphilis was defined as the time from syphilis infection to the development of ocular symptoms due to ocular syphilis. During the study period, 20 patients were diagnosed with ocular syphilis and 8 patients were enrolled in the present study. All patients were Japanese men who have sex with men with a median age of 46 years (IQR 41.5-53.5). The median CD4 count was 668.5/μL (IQR 567.8-734.3) and 5 of the 8 patients had HIV-1 viral load of less than 50 copies/mL. All study patients presented to our clinic because of the development of ocular symptoms, and they did not have any other symptoms compatible with primary, secondary, or tertiary syphilis. The median time between syphilis infection and development of ocular symptoms was 11 months (IQR 4-19, range 2.5-45). Seven out of eight (87.5%) cases developed ocular syphilis within 2 years of syphilis infection. Ocular syphilis should be suspected even in patients with early syphilis who present with ocular symptoms. Moreover, routine serologic screening for syphilis among patients with HIV-1 infection is critical for prevention of irreversible visual loss in ocular syphilis cases.