Introduction Syphilis is a systemic sexually transmitted infection caused by Treponema pallidum. NS can occur in any of its phases. Coinfection with HIV interferes with the clinical course of NS, leading to atypical diagnostic features. The aim of this study is to describe clinical and laboratory characteristics of inpatients treated for NS and to compare HIV-coinfected(HIV+) with HIV seronegative(HIV) subjects.

Methods Retrospective analysis of medical records of patients hospitalised for NS treatment at HCFMUSP (2010–2015) with reactive serum treponemal test and abnormal CSF analysis. Clinical and laboratory findings were compared between HIV+ and HIV- patients.

Results In our cohort of 47 patients with NS, 31 (66%) were HIV+. Median (M) age was 35 (Interquartile-IQR: 30–46) in the HIV+ group and 48(IQR: 40–58) among HIV- patients. Half of participants reported previous syphilis treatment. Serum VDRL was reactive in 44 patients. Mean time from symptoms onset to diagnosis was 30 days (IQR: 1–180). 23 patients were symptomatic: 5 neuropsychiatric disorders, 2 stroke, 11 ocular signs; 1 seizures and 4 brain stem/cranial nerve disorders. Among symptomatic individuals, 14 (61%) were HIV+. In the HIV+ group the M CD4 count was 326 cel/mm³(IQR: 204–546). CSF analysis was performed in 45 patients and yielded -M(IQR) values for HIV+ and HIV- groups, respectively: 8 (4–31) vs. 1.5 (1–5) cells/mm³; 87%(77-94) vs. 83%(68-92) lymphocytes and 8%(4-12) vs. 15%(6-27) monocytes/mm³; protein 47(35-69) vs. 35(30-38) mg/dL; and glucose 52(43-63) vs 58(53-66) mg/dL. 31% of patients had a reactive VDRL in CSF. HIV+ were shown to be of younger age (p=0.003) and to present significantly higher CSF cell counts (p=0.002) and protein (p=0.008).

Conclusion In our cohort most patients were HIV+, who developed the disease at an earlier age. CSF parameters showed significantly different cell counts and protein concentrations among HIV+. CSF VDRL presented a low sensitivity in both groups, with no significant difference between them. HIV+ patients were asymptomatic in more than half of cases