GSTM1 and beta-thalassemia intermedia: Genotypes attributable to thalassemia intermedia included homozygosity for IVS1.6 T > C and compound heterozygosity for a mild −101 C > T mutation or the haemoglobin variant Hb C. Among individuals with thalassemia major, the genotype most frequent is represented by compound heterozygosity β0/β+ codon39/IVS1.110 G > A (1.2%).