GSTM1 and anemia: The patient received a total of seven phenotype-matched (not for Lewis) RBC units during hospitalization, each justified by signs of symptomatic anemia or very low Hb levels (usually <5.0g/dL), with a brief post-transfusion increase in Hb level, further hemolysis, and return to the pre-transfusion Hb level within 48 to 72 hours.