Trends in syphilis and syphilitic uveitis among South Korean adults in 2010–2019: a nationwide cohort study

Introduction This study aims to investigate the epidemiology, clinical manifestations, and diagnostic and management patterns of ocular syphilis in South Korea. Methods This retrospective nationwide cohort study analysed health claim data from 2010 to 2019 for individuals aged ≥20 years diagnosed with syphilis, with follow-up through 2021. Age- and sex-adjusted incidence and prevalence rates were calculated for ocular conditions including anterior uveitis, posterior uveitis, panuveitis and optic neuritis. Diagnostic and management trends were evaluated, and multivariate Cox regression analyses assessed the impact of demographic factors and comorbidities. Results From 2010 to 2019, the incidence rate of syphilis increased from 99.1 to 136.1 per 100 000. Among the 448 085 syphilis cases, 5118 developed anterior uveitis, 777 posterior uveitis, 551 panuveitis and 80 optic neuritis. While all types of uveitis showed increasing trends, anterior uveitis exhibited the steepest rise from 0.18 per 100 000 in 2010 to 1.40 per 100 000 in 2021. Diagnostic practices for ocular syphilis included 80.4% for dilated fundus examination, 73.7% for fundus photography and 11.0% for fluorescein angiography. Laser photocoagulation and vitrectomy were performed in 5.7% and 4.5% of patients with uveitis, respectively. Multivariate analyses showed that each additional year of age increased the risk for anterior and posterior uveitis by 4% and optic neuritis by 2%. Hypertension, diabetes mellitus and dyslipidaemia increased the risk of one or more ocular syphilis manifestations. Conclusion In 2010–2019, the incidence of syphilis in South Korea significantly increased, with rates higher than previous studies. Age, sex and metabolic comorbidities were associated with an increased risk of ocular syphilis. These results indicate the need for vigilance in screening for ocular syphilis, and the importance of comprehensive eye examinations in patients with syphilis.