A case of congenital toxoplasmosis whose mother demonstrated serum low IgG avidity and positive tests for multiplex-nested PCR in the amniotic fluid.

We encountered a woman whose infant developed congenital toxoplasmosis. Serum Toxoplasma gondii antibody titers (320x) at 12 weeks of gestation increased to 5120x at 25 weeks. Toxoplasma immunoglobulin M was 2.8 index, and immunoglobulin G avidity index was 23%. Cyclic administration of acetylspiramycin was maintained from 22 weeks until delivery. Multiplex-nested polymerase chain reaction of maternal blood and amniotic fluid at 28 weeks both tested positive for Toxoplasma DNA. A male neonate weighing 2916 g was born at 38 weeks via cesarean section. No abnormalities were detected by physical and funduscopic examinations, whereas a head computed tomography of the neonate revealed three independent intracranial calcifications. The infant underwent therapy with pyrimethamine and sulfadiazine for one year. Serum titers of Toxoplasma gondii antibodies were all less than cut-off values between 5 and 12 months after birth, but all increased up to positive levels 18 months after birth.