A cycle of nelarabine therapy at the reduced schedule of 750 mg/m2 on days 1, 3, and 5 was administered, which led to a hematologic improvement for 1 year, when she presented at our hospital with neutropenia (neutrophils 840/cmm) and anemia (Hb 10 g/dL), with a re-expansion of the leukemic clone. The gene discussed is GSTM1; the disease is anemia (phenotype).