An unusually frequent beta-thalassemia mutation in an Iranian Province.

Iran, a country located on the "thalassemia belt", is an area with an unusually high prevalence of beta-thalassemia (thal). The gene frequency of thalassemia shows great variation within Iran from one area to another. The purpose of this study was to determine the spectrum of beta-thal mutations in Sistan-Baluchestan (S-B), a southeastern province of Iran which has a high mutation frequency of about 10%, and to compare this with neighboring provinces and countries. A total of 400 carriers (200 pre-marriage young couples selected at centers conducting prenatal diagnosis programs) with an established diagnosis of beta-thal minor, were enrolled into the study. Mutations in the beta-globin gene were detected using amplification refractory mutation system (ARMS) and restriction fraction length polymorphism (RFLP). Three hundred and sixty mutant chromosomes (13 different mutations) were detected with the two most common mutations accounting for about 80% of all detected beta-thal alleles in this region. The most common mutation by far was IVS-I-5 (G>C) (72.3%), followed by frameshift codons (FSC) 8/9 (+G) (5.8%) and codon 44 (-C) (2.5%). In conclusion, IVS-I-5 and FSC 8/9 (+G) account for about 80% of all mutations in S-B. Sistan-Baluchestan may be regarded as the 'hot zone' for the IVS-I-5 mutation.