GSTM1 and malaria: Previous studies in India and the Democratic Republic of Congo have shown that α+thalassemia is associated with a dose-dependent decrease in the proportion of total Hb that is represented by HbS in the RBCs of HbAS individuals (Brittenham et al., 1977; Mouele et al., 2000), a phenomenon that might play a part in the loss of malaria protection in HbAS subjects with co-inherited α+thalassemia (Hood et al., 1996).