Primary Oral Syphilis Presenting With Tongue Ulcers: A Case Report

Syphilis has historically been called "The Great Mimicker" because of its various stages and clinical signs. It typically occurs in one of three stages: primary, secondary, or tertiary. Primary syphilis often shows painless genital ulcers (syphilitic chancre), which can be hard to detect in women or men who have sex with men (MSM). Oral presentation of syphilis is extremely rare and can be a diagnostic challenge. Here, we present a rare case of primary oral syphilis in a healthy young MSM presenting with painless tongue ulcers for 7 days, 6 weeks after an oral sexual encounter. His rapid plasma reagin (RPR) titer was 1:16, and his Treponema pallidum hemagglutination assay (TPHA) titer was 1:10240. He was treated with benzathine penicillin G 2.4 million units intramuscularly once. Six weeks later, his symptoms completely resolved, and at 1-year follow-up he remained well with no recurrence, and his RPR titer dropped fourfold. The case highlights the diagnostic challenge of such a rare presentation of syphilis. Detailed sexual history in similar presenting patients is crucial to help include syphilis within the differential diagnosis.