Arjan Esmael

Ayşenur Öztürk

Nejat Akar

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235 Letter to the Editor  The incidence of alpha-thalassemia in Iraqi TurksIrak Türklerinde alfa-talasemi sıklığıArjan Esmael, Ayşenur Öztürk, Nejat AkarDepartment of Pediatric Genetics, Faculty of Medicine, Ankara University, Ankara, TurkeyAddress for Correspondence: Prof. Nejat Akar, Koru Mah 2621. Sok., Uyum Sitesi 18, Çayyolu, Ankara, Turkey Phone: +90 312 241 39 80 E-mail: akar@medicine.ankara.edu.trdoi:10.5152/tjh.2011.61To the EditorThalassemias  are  characterized  by  impaired quantitative  synthesis  of  globin  chains.  Several mutations have been identified in patients with thal-assemia, which are usually in alpha- or beta-globin genes.  Alpha-thalassemia  commonly  occurs  in Southeast Asian, Mediterranean, and Middle Eastern populations [1]. The gene responsible for the alpha-globin chain is located on the short arm of chromo-some 16 (16p13.3) and consists 2 zeta, 2 pseudo-alpha, and 2 alpha genes (α1 and α2) [2]. Each of the homologous chromosomes has 2 alpha genes; thus,  there  are  4  functional  alpha  genes  in  total. Molecular defects in alpha-thalassemia are usually gene deletions. Deletions of 1, 2, 3, or all 4 of the alpha genes may occur, and the severity of disease is directly proportional to the number of affected alpha genes. The most common of these are -α3.7 and  -α4.2  single  alpha-globin  gene  deletions,  and --MED and -α20.5 double gene deletions, which are widespread in the Mediterranean region [3]. The  most  common  genotypes  reported  in  the Dohuk region of Iraq were -α3.7/αα, --MED/αα, and -α3.7/-α3.7, which were observed in 84.3% of patients [4]. Another study reported that -α3.7 and --MED dele-tions  were  common  mutations  [5].  Additionally, -α3.7 deletion and alpha-globin triplication anti-3.7 kb type were observed in an Iraqi family with beta-thalassemia [6]. Nonetheless, there are no data on the frequency of alpha-thalassemia gene deletions in Iraqi Turks. As such, the present study aimed to determine  the  molecular  characterization  of  the alpha-thalassemia  gene  in  healthy  Iraqi  Turks,  in terms of -α3.7, -α4.2, --MED, and -α20.5 deletions.Iraqi Turkmens are the descendants of the Oghuz Turks that originated from Central Asia, an ethnic group that now primarily lives in northern Iraq. The study group included 83 unrelated individuals from northern  Iraq:  39  from  Kirkuk,  20  from  Mosul,  10 from Arbil, 10 from Baghdad, and 4 from the Diala and Tikrit regions. After all the participants provided informed  consent  blood  samples  were  collected into  tubes  containing  EDTA,  and  then  DNA  was extracted  from  peripheral  blood  leukocytes  using the  phenol-chloroform  method.  Multiplex  poly-merase  chain  reaction  (PCR)  was  performed  for mutation analysis, as previously described [7,8]. In all, 8 of the 83 participants were diagnosed with alpha-thalassemia an incidence rate of 9.6%. Multiplex  PCR  analysis  of  the  83  blood  samples showed  that  the  incidence  of  alpha-thalassemia, particularly  3.7  kb  deletion,  was  high  in  the  Iraqi Turk study population. In total, 3 alpha-globin geno-types  were  identified;  the  incidence  of  -α3.7/αα, -α3.7/-α3.7, and -α3.7/-α4.2 was 6.0%, 1.2%, and 2.4%, respectively,  whereas  --MED  and  -α20.5  deletions were not observed in the study group. The  frequency  of  alpha-thalassemia  was  3.6% among Turkish newborns in a study that employed globin  gene  mapping  analysis  of  DNA  [9]. Additionally,  the  alpha-thalassemia  trait  was observed in 0.63% of participants in a study con-ducted  in  the  Antalya  region  of  Turkey  [10].  The incidence of alpha-thalassemia was much higher in the Iraqi Turks in the present study than that report-ed in studies from Turkey; the difference could be due to geographic and ethnic differences.Conflict of interest statementThe  authors  of  this  paper  have  no  conflicts  of interest, including specific financial interests, rela-tionships, and/or affiliations relevant to the subject matter or materials included.References1.  Sengchanh S, Sanguansermsri T, Horst D, Horst J, Flatz G: High frequency of alphathalassemia in the So ethnic group of South Laos. Acta Haematol 2005;114:164-6.2.  Deisseroth A, Nienhuis A, Turner P , Velez R, Anderson WF, Ruddle F, Lawrence J, Creagan R, Kucherlapati R. Localization of the human α-globin structural gene to chromosome 16 in somatic cell hybrids by molecular hybridization assay. Cell 1977;12:205-18.3.  Kattamis AC, Camaschella C, Sivera P , Surrey S, Fortina P .  Human  alpha-thalassemia  syndromes:  detection  of molecular defects. Am J Hematol 1996;53:81-91.4.  Al-Allawi NA, Badi AI, Imanian H, Nikzat N, Jubrael JM, Najmabadi H. Molecular characterization of alpha-thal-assemia  in  the  Dohuk  region  of  Iraq.  Hemoglobin 2009;33:37-44.5.  Al-Allawi NA, Shamdeen MY, Rasheed NS. Homozygosity for the Mediterranean a-thalassemic deletion (hemoglo-bin Barts hydrops fetalis). Ann Saudi Med. 2010;30:153-5.6.  Deutsch S, Darbellay R, Offord R, Frutiger A, Kister J, Wajcman H, Beris P . Hb Iraq-Halabja beta10 (A7) Ala-->Val (GCC-->GTC): a new beta-chain silent variant in a family  with  multiple  Hb  disorders.  Am  J  Hematol. 1999;61:187-93.7.  Oron-Karni V, Filon D, Oppenheim A, Rund D. Rapid detection of the common Mediterranean alpha-globin deletions/rearrangements  using  PCR.  Am  J  Hematol 1998;58:306-10.8.  Tan AS, Quah TC, Low PS, Chong SS. A rapid and reli-able  7-deletion  multiplex  polymerase  chain  reaction assay for alpha-thalassemia. Blood. 2001;98:250-1.9.  Fei YJ, Kutlar F, Harris HF, Wilson MM, Milana A, Sciacca P , Schiliro G, Masala B, Manca L, Altay C, Gurgey A, Ma de  Pablos  J,  Villegas  A,  Huisman  THJ.  A  search  for anomalies in the zeta, alpha, beta, and gamma globin gene  arrangements  in  normal  black,  Italian,  Turkish, and Spanish newborns. Hemoglobin. 1989;13:45-65.10.  Canatan D, Oğuz N, Güvendik İ, Yıldırım S. The Incidence of Alpha-Thalassemia in Antalya-Turkey. Turk J Haematol 2002;19:433-4.Esmael et al.Alpha-thalassemia in Iraqi Turks Turk J Hematol 2011; 28: 235-6 236

The incidence of alpha-thalassemia in Iraqi Turks

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