The clinical and laboratory features of neurosyphilis in immunocompromised patients can be puzzling. This diagnostic challenge is well known in patients with acquired immunodeficiency syndrome but often overlooked in patients receiving immunosuppressive medications.

In this case a 38-year-old woman with rheumatoid arthritis on azathioprine, hydroxychloroquine, and rituximab, presented to the emergency department with 1 month of worsening vision of the left eye, bilateral eye pain, headache, photophobia, phonophobia, tinnitus, and a sensation of fullness in both ears. Neurological exam showed abnormalities limited to the left eye: optic disc edema and hemorrhages, 20/400 vision and afferent pupillary defect. MRI of the brain showed pachymeningeal enhancement. Blood and cerebrospinal fluid were unrevealing including treponemal and nontreponemal serologies. She received steroids for presumed rheumatoid pachymeningitis. Her symptoms worsened and she developed a diffuse maculopapular rash including the palms. A skin biopsy showed positive immunohistochemistry-staining spirochetes confirming secondary syphilis. Further blood tests showed hypogammaglobulinemia and a positive treponema pallidum particle agglutination test (TP-PA). She was treated with penicillin and some of her symptoms improved.