In many countries in sub-Saharan Africa, in stark contrast to other areas of the world, children are the main recipients of blood transfusions, where severe anaemia [haemoglobin (Hb) <60 g/l] remains a leading cause of both admission to hospital and of direct mortality.1–4 Owing to limited supplies of donated blood, the World Health Organization (WHO) guidelines encourage restrictive transfusion approaches. The gene discussed is GSTM1; the disease is anemia (phenotype).