ABO hemolytic disease of the newborn: A unique constellation of findings in siblings and review of protective mechanisms in the fetal-maternal system

Two siblings born 6 years apart presented with similar findings of hepatosp lenomegaly, dermal hematopoiesis, hemoglobinuria, and increased platelet co nsumption, but only moderate anemia and normal serum bilirubin. ABO incompa tibility was identified, and other causes were excluded. A review of the cu rrent understanding of mechanisms that promote and prevent antibody-mediate d hemolysis in the fetus is reviewed. Due to the low ratio of observed to e xpected significant clinical events among ABO incompatible mother-infant pa irs, and the multiplicity of mechanisms that diminish hemolysis, we specula te that severe ABO hemolytic disease of the newborn occurs when there is a specific failure in one of these preventive mechanisms.