GSTM1 and anemia (phenotype): Busulfan also caused thrombocytopenia, with average day 15 platelet numbers of 47 ± 13, 44 ± 17 and 43 ± 18 X103/dl (Fig 3A), and anemia, with Hb levels of 10.6 ± 0.6, 10.2 ± 1.8 and 10.2 ± 0.6 g/dl, (Fig 3B) in groups A, B and C, respectively.