Since other common disorders of Hb that appear to provide relative protection against severe malaria, notably carriers of beta thalassaemia and homozygous Hb E, also have relatively high microerythrocyte counts [1,45], this haematological mechanism of protection may have broader implications for our understanding of the selection of these host erythrocyte polymorphisms by malaria. Here, GSTM1 is linked to beta thalassemia.