Genetic epidemiology of hemoglobinopathies among Iraqi Kurds

Hemoglobinopathies are major health problems among Iraqi Kurds, who are a distinct ethnic group inhabiting North and Northeastern Iraq. We reviewed published literature on these disorders in this part of the world, and it was revealed that the most prevalent is β-thalassemia with carrier rates of 3.7-6.9%. Alpha thalassemia is less prevalent with carrier rates of 0.03-1.22%, while the sickle cell gene is variably distributed with carrier rates of 0.06-1.2%. Other structural hemoglobinopathies and δβ-thalassemia are sporadic. Twenty-seven different β-thalassemia mutations were identified, with seven constituting 82% of 1039 chromosomes characterized, namely: IVS-II-1 (G>A), IVS-I-6 (T>C), IVS-I-I (G>A), codon 8 (-AA), codon 8/9 (+G), IVS-I-110 (G>A), and codon 5 (-CT). There were notable regional variations in the distribution of β-thalassemia mutations, with Cd44 being mainly prevalent in the North, while IVS-I-110 is mainly prevalent in the East. In relevance to α-thalassemia, ten different mutations were detected, with the four most frequent constituting 92.4% of 262 alleles characterized being: -α^3.7, --^MED, α^-5ntα, and α^PolyA1α. In relevance to sickle cell gene, it is seen in the northern part of the region bordering Turkey, with comparable prevalence rates, and is associated, similar to Turkey, mainly with the Benin haplotype, unlike that in Southern Iraq where it is associated with the Arab-Indian haplotype, similar to Eastern Arabian Peninsula. Given the high prevalence of hemoglobinopathies in the region, and the high rates of consanguineous marriages, a preventive program was initiated in 2008, and results of its first 5 years were promising, though there are still many outstanding challenges that require addressing.