Abstract

Tertiary syphilis is a rare entity which has increased in frequency over the past two decades, especially in patients with human immunodeficiency virus (HIV). Frequent loss of non-treponemal reactivity on laboratory evaluation and lack of identifiable spirochetes on histopathology often lead to a diagnostic challenge. A 52-year-old male with a history of HIV off antiretroviral therapy (ART) presented to the emergency department with a one-week history of painless ulcer on the back. Laboratory evaluation was remarkable for CD4+ T cell count of 237, HIV viral load of 111,951, and positive treponemal antibody screen with rapid plasma regain titer of 1:8. Broad shave biopsy was obtained which revealed an ulcer with dense lymphoplasmacytic infiltrate and focal suppurative and granulomatous inflammation. Spirochete immunostain showed round, dot-like structures. Given the unusual findings, the stain was repeated at the same laboratory and then sent to an additional laboratory for repeat testing. All three studies demonstrated identical features. The patient was diagnosed with cutaneous gumma of tertiary syphilis, administered intramuscular benzathine penicillin G, and was urged to resume ART. Unfortunately, he was lost to follow up. Literature review revealed in vitro studies which demonstrated the ability of spirochetes to assume a round, non-motile form in unfavorable circumstances such as starvation, alkaline environment, and antibiotic administration. This round configuration appeared to be reversible when favorable conditions were restored. Syphilis round bodies have previously been reported in the setting of electron microscopy and fluorography but to our knowledge have not been reported by light microscopy (LM) in a routine skin biopsy. While the clinical implications are unclear, the presence of round bodies visible with spirochete stain on LM may represent a helpful new paradigm for the diagnosis of tertiary syphilis.

Financial Disclosure: No current or relevant financial relationships exist.