Shahid Saba, Nadeem Muhammad, Zahid Danish, Hassan Jawad, Ansari Saqib, Shamsi Tahir
Saba Shahid, PhD. Department of Genomics, National Institute of Blood Disease & Bone Marrow Transplantation, Karachi, Pakistan.
Muhammad Nadeem, FCPS (Haem). Department of Hematology, National Institute of Blood Disease & Bone Marrow Transplantation, Karachi, Pakistan.
Pak J Med Sci. 2017 Mar-Apr;33(2):411-416. doi: 10.12669/pjms.332.11834.
BACKGROUND & OBJECTIVE: Alpha (α) thalassemia is a hereditary disorder and is caused by deletions or mutations in globin genes. It is present in two clinically significant forms: hemoglobin Bart hydrops fetalis (Hb Bart) syndrome and hemoglobin H (HbH) disease. It is highly prevalent in South-East Asia or Mediterranean countries. The most common deletion reported in alpha thalassemia in Pakistani population was -α with a frequency of 8.3%, and the rare forms were -α (0.2%) and ααα (0.9%). In our study, diagnosis of severe anemia cases without any α and β mutations or deletions were made by using extended alpha thalassemia deletions panel. The main objective of this study was to determine the prevalence and to study the spectra of alpha thalassemia gene deletions in beta thalassemia patients with the use of an extended panel including --, --, --, --, -- in addition to -α, -α & -ααα.
The samples were collected in ethylenediaminetetraacetic acid (EDTA) vacutainers. A total of 156 samples were analyzed for alpha thalassemia mutations. This cohort included 121 samples of beta thalassemia major, nine samples of beta thalassemia minor and 26 without any evidence of beta thalassemia mutations. DNA was extracted with Qiagen extraction kit. The primers for determination of different subsets of alpha thalassemia deletions were included. PCR amplification was performed and result interpreted on agarose gel.
Co-inheritance of alpha thalassemia (-α -α) with homozygous beta thalassemia was detected in 30% cases of studied cohort (37 out of 121). The most common found was -α deletion (35/37) as single/double deletions or in combination with -ααα. In undiagnosed cases screened for beta thalassemia major, we found Mediterranean (-α) deletion at specifically 875 bp on agarose gel. This is distinctive finding in case of detecting -α instead of any other deletion from Pakistan.
Alpha thalassemia deletions (-α -α) are the common co-inherited deletions found in beta thalassemia major patients. On the basis of results, we propose an extended alpha thalassemia genetic mutation panel should be used for screening of children presenting with anemia with suspicion of haemoglobinopathy.
α地中海贫血是一种遗传性疾病，由珠蛋白基因的缺失或突变引起。它有两种具有临床意义的形式：血红蛋白Bart水肿胎儿综合征（Hb Bart）和血红蛋白H（HbH）病。在东南亚或地中海国家极为常见。巴基斯坦人群中报道的α地中海贫血最常见的缺失类型是-α，频率为8.3%，罕见类型为--α（0.2%）和ααα（0.9%）。在我们的研究中，通过使用扩展的α地中海贫血缺失检测板对无任何α和β突变或缺失的严重贫血病例进行诊断。本研究的主要目的是利用包括--、--、--、--、--以及-α、-α和-ααα在内的扩展检测板，确定β地中海贫血患者中α地中海贫血基因缺失的患病率并研究其谱系。
样本采集于乙二胺四乙酸（EDTA）真空采血管中。共对156份样本进行α地中海贫血突变分析。该队列包括121份重型β地中海贫血样本、9份轻型β地中海贫血样本和26份无任何β地中海贫血突变证据的样本。用Qiagen提取试剂盒提取DNA。包含用于测定α地中海贫血缺失不同亚组的引物。进行聚合酶链反应（PCR）扩增，并在琼脂糖凝胶上解读结果。
在研究队列的30%病例（121例中的37例）中检测到α地中海贫血（-α -α）与纯合β地中海贫血的共同遗传。最常见的是-α缺失（35/37），为单/双缺失或与-ααα组合。在筛查的未确诊重型β地中海贫血病例中，我们在琼脂糖凝胶上于875 bp处特异性地发现了地中海型（-α）缺失。这是在检测来自巴基斯坦的-α而非任何其他缺失时的独特发现。
α地中海贫血缺失（-α -α）是重型β地中海贫血患者中常见的共同遗传缺失。基于这些结果，我们建议应使用扩展的α地中海贫血基因突变检测板对疑似血红蛋白病的贫血儿童进行筛查。
