Three new beta-thalassemia mutations with varying degrees of severity.

We report the identification of three, new beta-thalassemia (beta-thal) mutations with varying degrees of severity. The most severe mutation, a frameshift mutation in exon 3 of the beta-globin gene [codon 120 (-A)], was associated with a dominant beta-thal phenotype. A second frameshift mutation, codon 50 (-T), resulted in a phenotype of typical high Hb A(2) beta-thal trait. The mildest mutation was IVS-II-2 (T > C), which changes the splice donor sequence of IVS-II from GT to GC. This transition mutation resulted in a slight reduction in beta-globin gene expression and could be considered a mild beta(+)-thal allele.