Use of a PCR-based assay for fetal Cw antigen genotyping in a patient with a history of moderately severe hemolytic disease of the newborn due to anti-Cw.

Anti-Cw is an uncommon cause of clinically significant hemolytic disease of the newborn (HDN). We report an unusually severe case of HDN due to anti-Cw that required phototherapy and exchange transfusion. We also describe a novel PCR-RFLP method for Cw typing of fetal genomic DNA that was used for prenatal diagnosis in a subsequent pregnancy. Following PCR amplification of a 163 bp segment of the RHCE gene containing the nucleotide 122 G to A substitution that corresponds to the Cw allele, Cw types were distinguished by TaqI digestion. PCR-RFLP analysis confirmed that the father and previously affected child were Cw-positive. The fetus was Cw-negative, thus excluding HDN in the current pregnancy and obviating the need for further invasive or noninvasive diagnostic procedures for the remainder of the pregnancy. This case illustrates the utility of PCR-based fetal genotype determination in pregnancies at risk of HDN due to uncommon red cell antibodies such as anti-Cw.