“…This deficiency is also discovered in blood banks in ∼4% of cases of ABO blood group discrepancy reflected by missing or weak ABO isoantibodies during reverse grouping. 6 Hypogammaglobulinemia in adults may be seen in hematological malignancies, particularly chronic lymphocytic leukemia (CLL) and multiple myeloma (MM). 7 In CLL, 27%-52% of patients have hypogammaglobulinemia 8 and transiently in 38.5% of patients after anti-CD20 therapy.…”