GSTM1 and anemia: Usually, the compound heterozygous Hb D-Punjab and β-thalassemia caused mild microcytic and hypochromic anemia with reductions in MCV and MCH and elevated Hb A2, but showed no clinical changes (el-Kalla and Mathews, 1997; Perea et al., 1999; Panyasai et al., 2017; Fucharoen et al., 2002).