A study of alpha thalassaemia families in western Saudi Arabia.

In Saudi Arabia there are three alpha globin chain alleles alpha alpha/, -alpha/, alpha alpha T/-producing six genotypes. In this study of 12 alpha thalassaemia families, the phenotypic expression of these six genotypes is determined. Globin chain biosynthesis gave five non overlapping ratios of 0.9 +/- 0.05, 0.69 +/- 0.06, 0.5 +/- 0.03, 0.38 +/- 0.04 and 0.23 +/- 0.06. The five groups are shown to be normal, alpha thal 2 trait with genotype -alpha/ alpha alpha, mild alpha thal 1 with -alpha/-alpha and alpha alpha/alpha alpha T as genotypes, severe alpha thal 1 with genotype -alpha/alpha alpha T and Hb H disease. The red cell indices MCV, MCH and MCHC of the groups show a step ladder fall. Hb H inclusions in red cells are slight in the mild alpha thal 1 and rises to gross in Hb H disease. The latter disease also shares typical red blood cell appearances with severe alpha thal 1. Hb H disease is relatively mild with no gross bony changes.