Introduction:
Syphilis is an infectious disease caused by Treponema pallidum(TP), a member of the Spirochaetaceae family. It is one of the most common sexually transmitted diseases. According to the World Health Organization (WHO) estimates, approximately 17.7 million people all over the world between the ages of 15 and 49 years had syphilis in the year 2012, and this number reportedly increases by an estimated 5.6 million every year (1). The estimated prevalence and incidence of syphilis varies with region and country. The highest prevalence of syphilis has been reported in Africa, with more than 60% of new cases occur in developing countries (1). Gestational syphilis reportedly occurs most frequently in Africa, accounting for more than 60% of the global estimates (2). Syphilis is a Category 5 infectious disease in Japan according to the Infectious Diseases Law, and the number of syphilis cases has been gradually increasing since 2013 (3). Syphilis, especially among young people, has become a concern in the recent years. Syphilis in pregnant women and congenital syphilis have become public health issues worldwide (4). In Japan, the haematology test for syphilis is performed at public expense as a screening test in the first trimester of pregnancy during antenatal health examination. In some foreign countries, syphilis screening tests are also conducted in the second and third trimesters of pregnancy (5). However, in Japan, screening tests for syphilis are not conducted after the initial examination.
Herein, we report a case in which a vulvar ulcer at 37 weeks of gestation led to the diagnosis of syphilis after a negative screening test during early pregnancy.