Detection of Common Deletional Alpha-Thalassemia Spectrum by Molecular Technique in Kelantan, Northeastern Malaysia

Abstract

Thalassemia is a hereditary blood disorder that results from genetic defects causing deficient synthesis of hemoglobin polypeptide chains. Although thalassemia mostly affects developing countries, there is limited knowledge of its accurate frequency and distribution in these regions. Knowing the prevalence of thalassemia and the frequency of responsible mutations is therefore an important step in the prevention and control program as well as treatment strategies. This study was performed to determine the prevalence and to study the spectrum of gene deletions that are responsible in α-thalassemia in Kelantan, located in northeastern Malaysia. A total 400 first-time blood donors from multiple areas of donation centre were chosen randomly. The presence of three types of α-thalassemia gene deletion in southeast Asian population which were -SEAdeletion, -α 3.7 rightward deletion, and -α 4.2 leftward deletion was detected by using multiplex PCR method. 37 (9.25%) of blood donors were confirmed to have α-thalassemia deletion types. 34 (8%) were heterozygous for α3.7 deletion, 1 (0.25%) was heterozygous for α4.2 deletion, and 2 (0.5%) were heterozygous for SEA type deletion. Alpha-thalassemia-2 with 3.7 deletion was the most common determinant detected in Kelantan Malay compared to other ethnic groups. It has been noted that alpha-thalassemia-2 with 3.7 deletion is the most common type of α-thalassemia throughout the world.

Distribution of Alpha Thalassaemia Gene Variants in Diverse Ethnic Populations in Malaysia: Data from the Institute for Medical Research

“…This distinction in allele frequency observed amongst ethnic Chinese consolidates our previous finding [7] and is in accordance with the findings of other similar studies on the local population [11]. In general, the α – 3.7 single gene deletion has a global distribution among all ethnic groups, and is especially prevalent in most tropical and subtropical populations studied [12].…”

Alpha thalassemia allelic frequency in Lebanon

“…Although thalassemia in the Mediterranean and the Middle East countries are reportedly high , accurate epidemiological data on its frequency and distribution in these regions lack. In Lebanon, only one study conducted in 2000 by Qatanani et al , reported an incidence of 8.2% alpha gene mutations in patients with beta thalassemia intermedia.…”

A Novel Single Gene Deletion (−αMAL3.5) Giving Rise to Silent α Thalassemia Carrier Removing the Entire HBA2 Gene Observed in Two Chinese Patients with Hb H Disease: Case Report of Two Probands

“…Combined application of MLPA, gap-PCR and sequencing methods confirmed the molecular diagnosis in both the probands as compound heterozygotes for --SEA /-a MAL3.5 and the mother of proband 1 as having aa/-a MAL3. 5 . No discrepancy was observed in the primary genotyping result (--SEA /aa) from the father of proband 1.…”

“…The carrier is asymptomatic with normal to mild hematological change in red cell indices, 4 while the latter two may show mild to moderate microcytic hypochromic anemia during an incidental routine blood count and their HbA 2 may be normal or slightly depressed. [4][5][6] a-thalassemia intermedia or Hb H disease results from inheritance of just one functional a-globin gene (--/-a). Clinical presentation of Hb H due to non-deletional types is more severe than the deletional forms.…”