In utero development of a warm-reactive autoantibody in a severely jaundiced neonate

The fetus and neonate are widely considered to be immunologically immature. However, there are rare case reports of RBC alloantibody and autoantibody development.

This report describes the case of a severely jaundiced full-term boy neonate presenting at birth with an IgG warm-reactive autoantibody.

Mother and neonate were both blood group A, D+. The mother had a negative antibody screen at 18 weeks' gestation and a negative DAT and antibody screen at the time of delivery. The neonate was born with a strongly reactive DAT (IgG) and a panreactive eluate. The serum also contained a panreactive antibody, and all crossmatches were incompatible. The neonate had a bilirubin of 12.5 mg per dL at birth, which peaked at 22.5 mg per dL. However, there was no overt evidence of hemolysis, as evidenced by normal serial Hct levels and reticulocyte counts. The neonate responded well to phototherapy and did not require either simple or exchange transfusion. The neonate's warm-reactive autoantibody maintained its original strength of reactivity on follow-up testing performed at 2 weeks and 2 months of age.

This report describes a rare case of apparent in utero RBC autoantibody development. The fetal/neonatal immune response to blood group antigens is reviewed.