GSTM1 and anemia (phenotype): Although the subjects with homozygous Hb O-Arab typically had mild to moderate anemia with a lower hemoglobin levels, most of them were asymptomatic, and only a few of them exhibited mild clinical symptoms such as lassitude, jaundice and splenomegaly (Dror, 2013; Nagel et al., 1999; Efremov et al., 1977; Heard et al., 1991).