A promoter mutation, C → T at position -92, leading to silent /3-thalassaemia

Summary. This study describes the clinical phenotype of the C?→? T mutation at position – 92 of the β-globin gene. Excluding two cases with HbA2 levels within the range of the /3-thalassaemia carrier state, heterozygotes for this mutation showed normal or borderline red blood cells count, Hb levels, MCV, MCH and HbA2 values, and unbalanced globin chain synthesis. Compound heterozygotes for the - 92 C → T mutation and a β° thalassaemia mutation (β°39) (two cases) or severe β-thalassaemia (p⁺ IVSII nt 745) (two cases) developed thalassaemia intermedia. According to these characteristics, the –92 promoter mutation should be added to the list of silent β-thalassaemias.