Molecular analysis of β-thalassemia patients: first identification of mutations HBB:c.93-2A>G and HBB:c.114G>A in Brazil.

The various clinical phenotypes in β-thalassemias have stimulated the study of genetic factors that could modify the manifestations of these diseases. We examined 21 patients with β-thalassemia (β-thal) in order to identify some genetic modifying factors: β-thalassemia mutations, HBG2:g.-158C>T polymorphism, α-globin gene deletions and (AT)xNz(AT)y motif within the hypersensitive site 2-locus control region (HS2-LCR). In the 42 alleles analyzed, the most frequent mutations observed were HBB:c.92+6T>C (30.9%), HBB:c.118C>T (16.7%), HBB:c.93-21G>A (11.9%) and HBB:c.92+1G>A (4.8%); this finding is in accordance with previous data of the Brazilian population. The other genetic factors analyzed showed no relation with the severity of the disease. For the first time in Brazil, we report HBB:c.93-2A>G and HBB:c.114G>A mutations on the β-globin gene, both in a heterozygous state. This is also the first study to analyze the HS2-LCR in β-thalassemic individuals in the Brazilian population.