Primary syphilis in the lingual frenulum: a case report

Syphilis remains a globally prevalent sexually transmitted infection (STI) caused by Treponema pallidum. Although primary syphilis typically presents as a painless ulcer in the genital region, extragenital manifestations are uncommon. This case report describes an unusual presentation of primary syphilis in the lingual frenulum, emphasizing the importance of thorough oral cavity examinations in STI screening. A 57-year-old Brazilian man presented with 39°C fever and oral discomfort. He reported recent unprotected vaginal, anal, and oral intercourse. Clinical examination revealed a purulent and hyperemic lesion (1.5 × 1.5 cm) on the lingual frenulum. Diagnostic tests syphilis: reactive and non-reactive VDRL and HIV tests. The patient was treated with a single intramuscular dose of Benzathine Penicillin G (2.4 million IU). The lesion healed within seven days, and the patient was discharged without complications. Primary syphilis with an oral manifestation is rare and can be easily misdiagnosed. This case highlights the need for comprehensive STI screening, including oral cavity examination, especially in patients with high-risk sexual behaviour. Early diagnosis and appropriate antibiotic therapy are essential to prevent transmission and complications.