ABO Discrepancy in a Patient With Plasma Cell Myeloma.

ABO discrepancies in plasma cell myeloma (PCM) present unique challenges in blood typing tests and transfusion management. We present the case of a 51-year-old male with PCM who exhibited discrepancies between forward and reverse blood grouping. Further investigation revealed that the patient's blood type was a variant of blood group B. While type III discrepancies, typically characterized by elevated globulin levels causing false-positive reactions in both forward and reverse blood grouping, are common in multiple myeloma, our case differed due to the loss of B antigens secondary to the malignant condition. This caused a discrepancy in forward blood grouping. The rarity of ABO discrepancies in multiple myeloma underscores the importance of thorough evaluation. Awareness of potential antigen alterations in such patients is crucial to ensure safe transfusion practices.