Rare β-Globin Gene Mutations in Pakistan.

The aim of this study was to analyze the rare β-thalassemia (β-thal) mutations in the Pakistani population. A total of 8716 unrelated Pakistani individuals having children with transfusion-dependent thalassemia were investigated by amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) for the previously reported common and rare β-thal mutations. Genomic sequencing of the β-globin gene and its immediate 5' and 3' flanking regions was done where no known mutation was found. Out of the 8716 individuals studied, 88 (1.0%) were not characterized by ARMS-PCR. Genomic sequencing revealed that 67 (0.82%) individuals had 19 different β-thal mutations including one novel mutation (HBB: c.136delT). The remaining 21 (0.26%) individuals did not show any mutation on the β-globin gene and its immediate flanking regions. The characterized alleles included seven (0.09%) in the 5' untranslated region (5'UTR), 29 (0.35%) in the coding regions, and 31 (0.38%) in the splice junction regions. HBB: c.92+1G>A and HBB: c.113G>A were the most frequently seen rare mutations. The spectrum of β-thal mutations in the Pakistani population is very diverse. In addition to the already reported mutations, another 19 different types of mutations were found. Interestingly, 21 individuals who had children with transfusion-dependent thalassemia and one known β-thal mutation, did not show any mutation on the β-globin gene. HBB: c.92+1G>A and HBB: c.113G>A are the most frequently seen rare mutations in Pakistan.