Abstract: Objective: To investigate the occurrence of neurosyphilis in patients whose RPR without sero-conversion after syphilis treatment. Methods: The data of syphilis patients who underwent lumbar puncture in our department from January 2020 to December 2021 were retrospectively analyzed. Patients in this study met the criteria that serum RPR titer declined ≥4-fold but did not convert to negative after syphilis treatment, RPR titer fluctuated at 1 dilution persist ≥12 months without visual, auditory, or neurological symptoms. Results: A total of 36 patients were enrolled, including 4 confirmed case of neurosyphilis and 9 suspected case. The incidence of asymptomatic neurosyphilis was 36.1%. Conclusion: Lumbar puncture is recommended to exclude the possibility of neurosyphilis in patients whose RPR decreased ≥4-fold but did not convert to negative for at least 12 months after syphilis treatment.

Key words: syphilis, lumbar puncture, neurosyphilis