Congenital syphilis: A prospective study of 22 cases diagnosed by PCR

Congenital syphilis (CS) is caused by Treponema pallidum infection in utero. There is a need to develop new tools to diagnose CS: the diagnostic value of PCR is difficult to assess. The aim of this study was to describe the clinical and laboratory characteristics of mothers and infants with CS as diagnosed by PCR tests on various maternal and neonatal samples.

We included all infants epidemiologically linked to a mother diagnosed with syphilis whose samples were referred to the Syphilis Reference Center, and for whom at least one positive PCR result was obtained.

Twenty-two mother-infant pairs (8.3%) with assay performed on samples from one to four different anatomic sites were included between February 2011 and April 2018. Seven mothers (31.8%) were born abroad, fifteen (68.2%) presented psychological and/or social problems, eight (36.4%) had not been screened for syphilis prior to delivery, and eleven (50%) were referred from French overseas departments or territories, or from the Paris region. Six infants (27.3%) were stillborn and six were born preterm, while fifteen infants (68.2%) presented clinical features of CS. All infants born preterm were symptomatic. Infant VDRL/RPR titer was no greater than four times that in the mother's serum, except in two cases.

Lack of antenatal care, social disadvantage and psychological issues were common. There is a need for enhanced surveillance both in the French overseas departments/territories and in the Paris region. A larger study is required to assess the sensitivity and specificity of PCR. The best site for sampling has yet to be established. We recommend the collection of as many samples as possible to avoid underdiagnosis of CS.