Placental histopathology in syphilis.

Placental evaluation is important in congenital syphilis (CS) since clinical and serologic findings necessary to fulfill the diagnostic criteria of syphilis may be absent at birth, making early accurate diagnosis difficult. We examined 25 placentas from mothers with syphilis as confirmed by positive RPR rapid plasma reagin and fluorescent treponemal antibody absorption tests to determine which histopathologic features should raise the suspicion of CS. The 25 examined placentas were from 162 syphilitic mothers who delivered at our institution in 1990. Of the 27 infants delivered (including two pairs of twins), four were stillborn and three died at 1 day of age. Eleven of 23 liveborn infants fulfilled the Centers for Disease Control criteria of probable CS. Seven of the 25 placentas showed a well-defined constellation of histopathologic changes that included proliferative vascular changes, chronic villitis, relative villous immaturity, and, in six placentas, acute villitis. All seven of these placentas showed the presence of spirochetes by special stains. Six also had plasma cells in the basal decidua. Recognition of these placental changes, although nondiagnostic, should lead the pathologist to seek additional clinical history and ancillary tests. Placental histopathologic examination is an additional parameter to be considered in the diagnosis of CS.