Congenital toxoplasmosis with delayed immune response in children. Diagnostic problems

: A newborn, delivered at term, developed a rapidly increasing hydrocephalus with intracranial calcifications and seizures during the first week of life. Clinical suspicion of congenital toxoplasmosis was at first not confirmed serologically (serum titer in the immunofluorescence test [IFT] of 1:1024 and complement-fixation reaction [CFR] of 1:40 equalling those of the mother; IgM-IFT being negative and the IFT and CFR titers significantly falling within two weeks). But in the further course of the disease the diagnosis of congenital toxoplasmosis was confirmed: 1. Microscopic tachyzoits in CSF when aged six weeks; 2. positive IgM-IFT in serum and CSF from the seventh weeks onwards; 3. steep IFT titer rise in serum and CSF from the 16th week onwards. This case demonstrates that with delayed immune response in the infected child only serial serological tests will exclude or confirm the diagnosis of congenital toxoplasmosis.