THE MOLECULAR BASIS FOR β° THALASSAEMIA INTERMEDIA IN AN IRANIAN INDIVIDUAL

Summary. A symptomless Iranian patient homozygous for β thalassaemia has haematological changes similar to the β thalassaemia trait. This remarkably mild phenotype is probably the result of coexistent α thalassaemia and increased γ chain synthesis. Restriction endonuclease mapping analysis of the β globin genes indicates that the patient is homozygous for a single nucleotide substitution at the 5’donor splice junction in the second intervening sequence of the β globin gene. No other changes were observed in the non-α globin gene cluster. It seems unlikely that the augmented γ chain synthesis in this patient is related to the molecular defect responsible for his β° thalassaemia.