ABSTRACT
An ABO discrepancy was observed in a 19-year-old man clinically diagnosed as congenital hypogammaglobulinemia. The patient's red cell was typed as group O, and his serum had no ABO isoagglutinins. Absence of A antigen and B antigen on patient's RBC was confirmed by adsorption- elution test and saliva test. A-transferase and B-transferase activities were not demonstrated in patient's serum. Patient's serum protein electrophoresis revealed hypogammaglobulinemia pattern, and immunoglobulin levels were markedly decreased. Complete absence of B lymphocytes was observed on patient's lymphocyte subset profile. Patient's father and mother were typed as blood group O and no abnormalities were recognized in their serum protein electrophoresis patterns and immunoglobulin concentration.