A case of hydrops fetalis, probably due to antibodies directed against antigenic determinants of GP.Mur (Miltenberger class III) cells.

The GP.Mur (Miltenberger class III) phenotype was found to occur in about 6.3 percent of Hong Kong (HK) Chinese blood donors. The incidence of antibodies directed against antigenic determinants of GP.Mur cells (anti-Mi) among patients was 0.34 percent, similar to that in Taiwan Chinese. A case of hydrops fetalis probably attributable to maternal anti-Mi was encountered in an HK Chinese woman during her sixth pregnancy. The anti-Mi was potent (titer 512, score 99). It fixed complement and was a mixture of IgG1 and IgG3. Two biological assays, the monocyte monolayer assay and the chemiluminescence test, were strongly positive. The father was found to be heterozygous for the GP.Mur gene.