Familial alloimmune neutropenia of NA-2 specificity.

Three siblings with alloimmune neonatal neutropenia are presented. An immunoglobulin G (IgG) antineutrophil antibody specific for NA-2 antigen was demonstrated in maternal serum and in both of the three affected infants who were studied as neonates. The mother's neutrophils were negative for NA-2 antigen. The father and all four children, including the three known to be affected, had neutrophils that expressed NA-2 antigen. One patient studied sequentially demonstrated an inverse relationship between the antineutrophil antibody titer and the absolute neutrophil count. Exchange transfusions did not appear to benefit two of the infants.