Clinical and hematological features of beta(+)-thalassemia (IVS-1 nt 5, G-C mutation) in Thai patients.

Seventy-eight patients with IVS-1 nt 5, G-C, which is the common mutation of beta+-thalassemia found in the southern part of Thailand, were studied to determine whether it is possible to predict phenotypic severity from genetic factors. The clinical phenotype of homozygotes for IVS-1 nt 5, G-C and compound heterozygotes for IVS-1 nt 5, G-C and beta(0) - or beta(+)-thalassemia were variable and could not be accurately predicted. The associations between concomittant alpha-thalassemia or Hb CS or the presence of XmnI-Ggamma polymorphism and a mild clinical phenotype are not apparent, indicating the involvement of other ameliorating determinants or genetic modifications.