Clinical manifestations and serological rebound in HIV and syphilis co-infection: a case report and literature review

Co-infection with human immunodeficiency virus (HIV) and syphilis creates a clinical and diagnostic challenge due to overlapping transmission routes and immunosuppression secondary to HIV. We describe a case concerning possible serological rebound in syphilis, which may be attributed to delayed initiation of antiretroviral therapy (ART), although this was not confirmed by a repeat non-treponemal test. A 40-year-old man with HIV and symptomatic secondary syphilis delayed ART initiation in the setting of poor treatment adherence for three months after syphilis diagnosis. During that three-month delay, his toluidine red unheated serum test (TRUST) titer was noted to rebound from 1:32 to 1:128. After ART initiation, he achieved sustained viral suppression (< 20 cp/mL) and immune recovery (CD4 + T cell count: 577/µL) within eight months of ART initiation; however, his syphilis titer did stabilize at 1:32. There is a need for caution in evaluating whenever possible when two diseases share a diagnosis. Our case highlights may highlight possible effects of deferral of ART initiation on immunologic recovery and the serological response for syphilis, and a need for ongoing comprehensive follow-up and circumspection in evaluation of serological change overall. Interpretation was limited by the absence of parallel repeat TRUST testing and being unable to entirely rule out possible reinfection.