Loss of blood group A in acute leukemia. Morphologic and biochemical studies of red cells.

A patient with blood type A had acute myelomonocytic leukemia; his red cells (RBCs) typed as O and his serum had anti-B. RBC membranes were isolated from the patient as well as from controls with group A and O red cells. The membranes were incubated with uridine diphosphate (UDP)-N-acetyl-D-14C galactosamine in plasma from the patient and controls with group A and O red cells. RBC membranes from the patient behaved normally in that they incorporated the terminal carbohydrate responsible for blood group A activity. Scanning electron microscopy showed that the patient's RBCs had striking morphologic changes, with marked crenation and numerous knisocytes and dacryocytes. It was concluded that loss of the A antigen in this patient was not due to an abnormality of the enzyme required to convert H substance to A substance. It was postulated that weakening of the A antigen in some patients with leukemia may be related to a steric modification associated with abnormal red cell morphology.