GSTM1 and G6PD deficiency: To determine the impact of the IL7 variants (genotypes and haplotypes) on susceptibility to SMA and inefficient erythropoiesis, we performed binary logistic regression analyses in a model controlling for the potential confounding effects of age, gender, HIV-1 and bacteremia status, G6PD deficiency, Hb phenotypes, and α-thalassemia status.