The homozygous deletion of GSTM1 often referred to as “null genotype” was associated with SOS after allogeneic HSCT with a busulfan-based conditioning regimen in pediatric beta-thalassemia patients (OR 4.3, CI 1.5–12.5, p = 0.008) published by Srivastava et al. [42]. The gene discussed is GSTM1; the disease is Beta-thalassemia.