The prevalence of syphilis has increased in Japan since 2010. Its rapid increase among women in their 20s is of particular concern because it is associated with an increase in the prevalence of congenital syphilis. We report a case of primary syphilis diagnosed from a tongue ulcer in a pregnant woman who did not receive antenatal care. A 29-year-old pregnant woman, who did not receive antenatal care, presented with a tongue ulcer at our hospital. She had a history of being a commercial sex worker. Laboratory tests revealed elevated C-reactive protein levels (5.56 mg/dL) and positive TPLA and RPR. We referred the patient to the department of infectious diseases as well as to the department of obstetrics and gynecology. She was treated with benzylpenicillin potassium (24 MU/day) for 14 days. Later, the tongue ulcer disappeared and RPR showed negative results. She gave birth to a boy who did not have congenital syphilis. The number of patients with syphilis presenting with oral symptoms is increasing, and it is expected that more of such cases will be examined by dentists. Therefore, it is crucial to consider syphilis as a differential diagnosis of oral mucosal disease and establish coordination among specialists who can be consulted and referred to when syphilis is initially suspected.
