Congenital rubella syndrome after maternal reinfection

This report concerns a case of congenital rubella syndrome (CRS) with atypical immune response affecting an infant whose mother had repeated evidence of immunity before pregnancy. Laboratory diagnosis of CRS could only clearly be achieved by virus isolation after the second month of life despite typical clinical features of CRS and multiple organ involvement. After the first month of age, low concentrations of specific IgM antibodies were revealed by ELISA and confirmed by a reference test system (IgM-specific haemagglutination inhibition assay). Persistent and increasing high levels of IgM antibodies were detected only after the 6th month of life. Later on IgG antibody levels decreased. Immunological investigations showed an IgG1-hypoglobulinaemia. The unusual feature of the present case report is not only the failure of the maternal rubella immunity to prevent CRS, but the defect of the child's immune system, probably attributable to congenital infection. As a consequence, laboratory diagnosis of CRS could not be achieved initially by the proved serological methods.