HIV Infection Modifies the Role of Prior Treponema pallidum Infection in the Clinical Presentation of Early Syphilis among Adult Patients from STI Clinics in Peru.

BACKGROUND:We aim to compare the clinical presentations (symptomatic vs asymptomatic) with prior Treponema pallidum infection status (first infection vs reinfection) among people with early syphilis. METHODS:We used data from PICASSO, a cohort study in Peru, that enrolled people with active syphilis from May 2019 to August 2021. Study participants had early syphilis and a prior syphilis serologic test result within the prior 12 months to determine prior T. pallidum infection status. We calculated prevalence ratios of symptomatic clinical presentation (primary or secondary syphilis) by prior T. pallidum infection status, stratified by HIV infection status. Additionally, we explored the association of prior T. pallidum infection status and lesion presentation, stratified by primary and secondary syphilis cases, using the Fisher's exact test. RESULTS:We include 84 T. pallidum reinfection cases and 61 first infection cases. We found increased frequency of symptomatic clinical presentation among first-infection cases (39% vs 20%, PR = 1.94, p = 0.014). This association was stronger among persons living without HIV infection (38% vs 7%, aPR = 6.63, p = 0.001) in comparison to those living with HIV infection (45% vs 34%, aPR = 1.38, p = 0.458). Among secondary syphilis cases, more participants from the reinfection group reported that their lesions improved one week after treatment (100% vs 29%, p = 0.045) compared to those with a first infection. Among the primary syphilis cases, all participants reported that their lesions improved one week after treatment. CONCLUSION:Prior syphilis was associated with decreased prevalence of symptomatic reinfection, especially among persons not living with HIV infection.