Variable clinical severity of Hb E beta-thalassemia among Indians.

ABSTRACT

OBJECTIVE: The aim of this preliminary report was to look at the effect of genetic variations in the alpha, beta and gamma globin genes in 7 cases of hemoglobin E/beta-thalassemia with diverse clinical expression of the disease. METHODS: beta-thalassemia mutations were characterized by PCR and dot blot hybridization. G gamma gene polymorphism (Xmnl) was determined by PCR followed by restriction enzyme digestion and polyacrylamide gel electrophoresis. alpha genotyping was done by Southern blot hybridization. RESULTS: Six cases had a severe beta+ mutation [IVS 1 nt 5 (G-->C)] and one case had a beta zero mutation [F/S 41/42 (-CTTT)]. Hence, the beta-thalassemia mutation does not seem to contribute towards the clinical diversity. alpha-genotyping showed a single alpha-gene deletion of the rightward type in three of the five milder cases. The -158 G gamma (C-->T) substitution was present at least in heterozygous state (+/-) in all the milder cases. CONCLUSIONS: Deletional alpha thalassemia and presence of the -158 G gamma (C->T) substitution are the two factors which appear to be more important in decreasing the severity of the disease rather than the nature of the beta thalassemia mutation.