The Spectrum of β-Thalassemia Mutations in Siirt Province, Southeastern Turkey

Global distribution of β-thalassemia mutations: An update

One excellent illustration of how a single gene abnormality may result in a spectrum of disease incidence is the incredible phenotypic variety of β-thalassemia, which spans from severe anemia and transfusion needs to an utterly asymptomatic sickness. However, genetic causes of β-thalassemia and how the anemia's severity might be altered at various stages in its pathophysiology have been well investigated. There are currently known to be more than 350 mutations that cause genetic disease. However only 20 β thalassemia mutations account for more than 80% of the β thalassemia mutation across the globe due to phenomenon of geographical clustering where each population has a few common mutations together with a varying number of rare ones. Due to migration of the population, the spectrum of thalassemia mutation in changing from time to time. In this review, efforts are made to collate β globin gene mutations in different countries and populations.

Spectrum of β-Thalassemia Mutations in Some Areas of Guangxi Zhuang Autonomous Region of Southern China: A Study on a Pediatric Population Aged 0-15 Years

β-Thalassemia (β-thal), one of the most common form of single-gene inheritable blood diseases in the world, is highly prevalent in southern China, especially in the Guangxi Zhuang Autonomous Region. To update the β-thal mutation spectrum in this region, we performed hematological and genetic analyses on 888 β-thal major (β-TM), β-thal intermedia (β-TI) and β-thal carrier patients, aged 0-15 years old, from different parts of Guangxi Province. We identified 55 genotypes and 18 β-thal mutations. The codons 41/42 (-TTCT) (HBB: c.126_129delCTTT) (43.97%), codon 17 (A>T) (HBB: c.52A>T) (25.43%), -28(A>G) (HBB: c.-78A>G) (8.18%), IVS-II-654 (C>T) (HBB: c.316-197C>T) (7.85%) and codon 26 (G>A) (HBB: c.79G>A) (5.02%) were the five most common, accounting for more than 90.0%. The results of our study are providing an up-to-date β-thal mutation spectrum in the 0-15-year-old pediatric population, which will help genetic counseling and prevention of β-TM in mainland China's most endemic region, Guangxi Zhuang Autonomous Region.

Genetic investigation of haemoglobinopathies in a large cohort of asymptomatic individuals reveals a higher carrier rate for β-thalassaemia in Sichuan Province (Southwestern China)

The incidence of haemoglobinopathy is high in China, especially south of the Yangtze River. However, the exact status of haemoglobinopathy in Sichuan is unknown. To carry out a detailed research of haemoglobinopathy in individuals living in Sichuan, 13,298 subjects without clinical symptoms who were living in Sichuan Province, with an age distribution of 5–73 years, were included in this study. Between March 2014 and July 2017, these subjects received examinations at the Medical Lab of Chengdu Women's & Children's Central Hospital. Mean corpuscular volume (MCV) < 82 fL or mean corpuscular haemoglobin (MCH) < 27 pg was used to indicate haemoglobinopathy carriers. Abnormal haemoglobin was screened by electrophoresis, and genes were sequenced to identify genotypes. Genotype diagnosis of alpha- and beta-thalassaemia was carried out by using PCR and shunt hybridization. There were 638 suspected haemoglobinopathy carriers (4.80%, 638/13,298). DNA sequencing identified 6 subjects with abnormal haemoglobin genotypes and 15 subjects with Hb E. The frequency of heterozygosity for thalassaemia was 4.12% (1.48% for α-thalassaemia and 2.61% for β-thalassaemia) in Sichuan Province. The mutation spectrum of α-thalassaemia consisted of the five most common mutations: --^SEA, -α^3.7, -α^4.2, α^CS, and α^QS. Seven types of β-thalassaemia mutation were found in this study: CD41-42 (-TTCT) was the most frequent (28.47%), followed by 17 (A > T), −28 (A > G), and IVS-II-654 (C > T). The main abnormal haemoglobin genotype (HbE) and thalassaemia genotype (--^SEA, CD41-42 (-TTCT)) were consistent with those in other regions of China, but the carrier rate of β-thalassaemia in Sichuan was higher than that of α-thalassaemia.