Various aspects of alpha-thalassemia

Molecular characteristics of a non-deletion alpha-thalassaemia of the Po River Delta

The form of alpha-thalassaemia of the Po river delta presents haematological and globin biosynthetic characteristics similar to alpha-thalassaemia-1 but never gives rise to HB H disease nor to hydrops foetalis. In alpha-thalassaemic subjects originally from this region globin mRNA translation and alpha-globin gene arrangement have been investigated. The data obtained indicate that alpha-globin synthesis and reticulocyte alpha-globin mRNA are reduced by one fourth; in addition, since the defect in alpha-globin synthesis does not change with cell ageing, a possible instability of alpha-globin mRNA is excluded. Restriction enzyme analysis of the DNA shows a normal alpha-globin gene organization. This form of alpha-thalassaemia is therefore of the non-deletion type; its molecular lesion is either at the level of alpha-globin mRNA transcription or processing. The fact that this, as well as other forms of non-deletion alpha-thalassaemia, have a phenotypic expression similar to alpha-thalassaemia 1 is discussed.

Diagnosis of alpha-thalassemia trait from Coulter Counter 'S' indices

A number of patients of Mediterranean and Asian origins were found to have unexplained microcytic hypochromic red blood cells. Iron deficiency and beta-thalassaemia trait were both satisfactorily excluded in all of them. The haematological indices of these patients, obtained on a Coulter Model 'S' Counter, were found to be very similar to those seen in obligatory heterozygotes for alpha-thalassaemia. It is postulated that these patients were also carriers for alpha-thalassaemia. Subsequent investigation of some of these patients showed the characteristically reduced rates of alpha-chain synthesis seen in this condition. The discriminant function of England and Fraser (1973) may be of help in diagnosing this state. alpha-Thalassaemia trait should be considered in all patients of 'high-risk' ethnic origins with a blood picture suggestive of beta-thalassaemia trait but in whom the levels of Hb A2 and Hb F are within normal limits.