Pathology of the umbilical cord in congenital syphilis: analysis of 25 specimens using histochemistry and immunofluorescent antibody to Treponema pallidum.

Identification of Treponema pallidum in the placenta is important for diagnosis of congenital syphilis; however, spirochetes are difficult to observe in chorionic villi. To determine the sensitivity of umbilical cord examination for T pallidum, and the association of spirochetes with cord pathology, placentas were prospectively obtained from 25 women with untreated syphilis. The most common finding using hematoxylin-eosin staining was a normal-appearing umbilical cord (48%); necrotizing funisitis was the most frequent pathological lesion (36%). Spirochetes were detected using silver and immunofluorescent staining in 89% of cords, including 92% of histologically normal and 84% of abnormal cords. Three specimens showed subamnionic aggregates of spirochetes, consistent with amniotic fluid infection. Necrotizing funisitis was strongly associated with umbilical artery infection by spirochetes (P = .008). There was a 100% correlation between results of silver and immunofluorescent staining. The umbilical cord is a sensitive site for morphological confirmation of T pallidum; it is significant for the pathologist that spirochetes may often be detected in the absence of overt tissue inflammation or necrosis.