Lower Gastrointestinal Syphilis: Case Series and Literature Review

Background Syphilis infections are increasing globally. Lower gastrointestinal syphilis (LGIS) is a rare manifestation of early syphilis transmitted through anal sexual contact. Misdiagnosis of LGIS as inflammatory bowel disease may result from clinician under-awareness. Methods We searched the literature for articles describing cases of LGIS, and identified additional cases diagnosed within our institution. Data were extracted from the articles and medical records and analyzed to provide a summative account. Results 54 cases of LGIS were identified in 39 articles published between 1958 and 2020. 8 additional cases were diagnosed at our institution between 2011 and 2020, totaling 62 cases. All cases were described in men and transwomen aged 15 to 73 years. 50 (93%) individuals endorsed having sex with men. In 26 cases (52%) individuals were HIV co-infected. LGIS presented most commonly with hematochezia (67%) and anal pain (46%). The most common physical exam findings were rectal mass (38%), lymphadenopathy (31%), and rash (26%). Non-treponemal titers ranged from 1:2-1:1024. Of the 52 cases in which endoscopy was reported, 22 (42%) showed anorectal mass and 18 (35%) showed anorectal ulcer. In 44 cases (75%), histopathology revealed a chronic inflammatory infiltrate with a prominent lymphocyte component (45%) and/or plasma cells (36%). 78% of specimens to which a tissue stain was applied were positive for spirochetes. Conclusions LGIS should be suspected in men and transwomen presenting with a lower gastrointestinal symptom or mucosal abnormality. A sexual history must be elicited and guide testing. Misdiagnosis can delay treatment and threatens patient and public health.