A case of secondary syphilis with mucous patches on the hard palate.

A rare case of secondary syphilis showing mucous patches on the hard palate is reported. A 31-year-old male had two erosive patches which were slightly raised on his hard palate. A linear lesion was also present on the inside of his right alveolar process. Many red-brown macules on his abdomen and bilateral inguinal lymphadenopathy accompanied these symptoms. The serological tests for syphilis were positive: VDRL test 1:512, TPHA test 1:20,480, and IgM-FTA-ABS test 1:40. Immunohistochemical staining with rabbit monoclonal antibody to Treponema pallidum by the biotin-streptoavidin system detected treponemal organisms in the paraffin-embedded specimen from his mucous patch. A diagnosis of secondary syphilis was made, and he was given amoxicillin (AMPC) at 750 mg per day for 4 weeks. His eruptions, including the mucous patch, healed in a week.