Characterization of Two Novel Deletions Involving the 5' Region of the β-Globin Gene.

We report two novel β-thalassemia (β-thal) deletions involving the 5' region of the β-globin gene (HBB). The first deletion spans 538 bp and removes the β-globin promoter, 5' untranslated region (5'UTR) and most of exon 1. This deletion was identified in a 3-year-old Vietnamese boy with non transfusion dependent Hb E (HBB: c.79G>A)/β0 -thal. The second deletion spans 1517 bp and removes the β-globin gene promoter, 5'UTR, and exons 1 and 2. This deletion was identified in two unrelated adults of European descent who had β-thal trait with unusually high Hb A2 levels. Deletions such as these are generally associated with higher levels of Hb A2 and Hb F than typical β-thal alleles, which may ameliorate the severity of the disease.