Abstract
Objective:Alpha thalassemia syndromes are caused by mutations on one or more of the four α-globin genes. Mutations could be either more commonly deletional or non-deletional. As some deletions (3.7 and 4.2) cause α+-thalassemia, some cause (-20.5, MED, THAI, FIL) α0 -thalassemia. The aim of this study was to determine alpha thalassemia mutations in patients with unsolved hypochromic microcytic anemia and to evaluate types of mutations.Material and Methods:Two hundred six patients with hypochromic microcytic anemia were evaluated for alpha thalassemia. A venous blood sample of 2 mL was drawn from each patient for DNA isolation. The samples were investigated for α-thalassemia mutations by using the Vienna Lab α-Globlin StripAssay TM commercial kit.Results:Fourteen different mutations were determined in 95 (46.1%) patients. The most common mutation was the 3.7 single gene deletion and was found in 37 patients (n=37/95, 39%). Others common mutations were the 20.5 kb double gene deletion (n=20 patients, 21%), MED double gene deletion (n=17 patients, 17.9%), α2 IVS1 (n=10 patients, 10.5%), α2 cd142 Hb Koya Dora (n=6 patients, 6.3%), α2 polyA1 (Saudi type) (n=6 patients, 6.3%), 4.2 single gene deletion (n=4 patients, 4.2%), α1 cd14 (n=2 patients, 2.1%), and -FIL mutation (n=2 patients 2.1%), respectively. Hb Adana, Hb Icaria, α2 init cd and α2 polyA2 (Turkish type) were found in 1% of the patients (n=1). Seven patients (7.4%) had α-thalassemia triplication. In our study, three mutations (Hb Icaria, α1 cd14, α2 init.cd) were determined firstly in Turkey. Seven mutations (-SEA, -THAI, Hb Constant Spring, α2 cd19, α2 cd59, α2 cd125, Hb Paksé) were not determined in this study.Conclusion:Alpha thalassemia should be considered in the differential diagnosis of hypochromic microcytic anemia especially in cases without iron deficiency and b-thalassemia carrier state. Genetic testing should be performed for the suspicious cases. We also recommend that a national database with all mutations in Turkey should be created to screen the alpha thalassemia cost-effectively.
Highlights
Alpha thalassemia syndromes are inherited autosomal recessively and caused by defects on one or more of the 4 α-globin genes, leading to reduced or absent production of the alpha-globin polypeptide chains [1,2]
Alpha thalassemia should be considered in the differential diagnosis of hypochromic microcytic anemia especially in cases without iron deficiency and b-thalassemia carrier state
We recommend that a national database with all mutations in Turkey should be created to screen the alpha thalassemia cost-effectively
Summary
Alpha thalassemia syndromes are inherited autosomal recessively and caused by defects on one or more of the 4 α-globin genes (αα/αα), leading to reduced or absent production of the alpha-globin polypeptide chains [1,2]. The α-globin gene mutations could be either the more common deletion (partial (α+) deletions or total (α0) deletions) or non-deletional types. There are reported to be more than 40 deletion mutations in various studies [2,3,4]. The most common alpha-thalassemia mutations in the world are the 3.7 single-gene deletions. Three-gene deletions (α+ with α0thalassemia) or a combination of two-gene deletions with a non-deletion mutation cause HbH disease. If there are deletion mutations on 4 α-genes, Hb Bart’s hydrops fetalis develops [5,6]. Non-deletion mutations may reduce α-globin chain synthesis more severely than most of the deletion mutations [1]. More than 70 non-deletion mutations have been reported [8]
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