Prenatal screening for β-thalassemia major reveals new and rare mutations in the Pakistani population.

β-Thalassemia is the most common genetic disorder in Pakistan, where more than 6000 affected children are born annually, and the carrier population is around 10 million. The objective was to study β-globin gene mutations in chorionic villous biopsy samples. Prenatal screening of 383 pregnant women between 2003 and 2010 was carried out using a panel of 13 mutation primers and amplification refractory mutations system (ARMS)-PCR. In addition, DNA sequencing was used to confirm uncharacterized mutations and in some cases fetal disease status was confirmed by linkage analysis. Families enrolled in this study represented major ethnic groups in Pakistan. Of the 13 mutations tested, three mutations accounted 71% of the total, including IVS1-5(G-C)[HBB:c.92+5G>C], codon 8/9(+G) [HBB:c.27_28insG] and del 619[NG_000007.3:g71609-72227del619]. Mutations in four uncharacterized samples were later confirmed by DNA sequencing as -88(C-T)[HBB:c.-138C>G], -90(C-T)[HBB:c.-140C>T] and codon 59(+T)[HBB:c.178_179insT]. To our knowledge, this is the first report of these mutations in Pakistan. Moreover, 19.2% fetal samples were normal and 52.3% heterozygous, whereas 26.4% were affected with thalassemia major. IVS1-5:IVS1-5 was the most common genotype in fetal samples. Prenatal diagnosis of β-thalassemia using ARMS PCR is an efficient approach for reducing the burden of this disease in Pakistan. In addition, rare mutations reported in this study should be incorporated in the diagnostic strategy.