Congenital toxoplasmosis associated with transient monoclonal IgGl-lambda gammopathy.

A congenital toxoplasmosis infection was diagnosed in a newborn child with severe oculo-central nervous system involvement. Antibodies to toxoplasma became detectable in the mother's serum during pregnancy, and at delivery both mother and child had high titers of IgG toxoplasma antibody. A normal protein profile was found in the serum of the mother, but transient monoclonal gammopathy (IgG1- lambda ) was found in the child. A specific antiidiotype serum raised against this monoclonal immunoglobulin failed to react with the serum of the mother and with other sera positive for toxoplasma antibody. The toxoplasma antibody in the serum of the newborn child was restricted to IgG-lambda, but no evidence was found that the monoclonal fraction was responsible for the antibody activity.