Unexpected Reason for Non-healing Oral Ulcers: Syphilis.

Syphilis is a sexually transmitted infectious disease caused by Treponema pallidum and characterized by a complex and variable clinical presentation. Cases of unexpected oral syphilis presenting as non-healing ulcers are uncommonly reported. We report 3 cases (one female and two males, aged 35, 35, and 56 years, respectively) in which patients presented with non-healing oral ulcers. Biopsies revealed surface ulceration and a significant neutrophilic infiltrate rather than the more conventional plasma cell infiltrate seen with most reported syphilis infections, potentially leading to an inaccurate diagnosis. Treponema pallidum immunohistochemistry highlighted spirochetes within the epithelium, with additional diagnostic confirmation by serum T. pallidum particle agglutination assay. Sexual history documentation by the clinician with nonspecific oral ulcers is paramount to aiding diagnosis and leading to proper management. Further, it is important to perform immunohistochemistry for T. pallidum in oral biopsies from non-healing ulcers, especially when clinical history raises the differential diagnosis or when other clinical manifestations may support this consideration.