Anti-Diego a red blood cell alloantibody as a possible cause of anemia in a 3-week-old infant.

Our aim in this case report was to describe anemia caused by anti-Diego(a) red blood cell (RBC) antibody in a 3-week-old infant derived during pregnancy to low-frequency Diego(a) RBC antigen. Pre- and postnatal maternal serum screening for unexpected RBC antibodies and determination of RBC antibody specificity in the sera of the mother and child and in the elute of the child were performed by use of microcards (Diamed, Basel, Switzerland; BioVue, Ortho Clinical Diagnosis, Raritan, NJ, USA) with commercially prepared test RBCs (Diamed, Ortho Clinical Diagnosis, and Gamma Biologicals, Houston, TX, USA) at 37 degrees C and indirect antiglobulin test (IAT) according to manufacturer instructions. Direct antiglobulin test (DAT) was performed by use of microcards (Diamed, Ortho Clinical Diagnosis) with both polyspecific and monospecific IgG anti-human globulin. Di(a) antigen was determined on maternal, paternal, and infant's red cells by commercial reagent (Gamma Biologicals). Determination of RBC antibody specificities in maternal and child sera and in the child's RBC eluate showed 2+ positive reactions only with two Di(a+) test RBCs. Father and baby were positive and mother was negative for Di(a) antigen. When a newborn has positive DAT and there are no clinical reasons for this, the possibility of positive DAT resulting from alloimmunization to low-frequency RBC antigens should be considered.