Abstract
Alpha thalassaemia is highly prevalent in the plural society of Malaysia and is a public health problem. Haematological and molecular data from 5016 unrelated patients referred from various hospitals to the Institute for Medical Research for α thalassaemia screening from 2007 to 2010 were retrieved. The aims of this retrospective analysis were to describe the distribution of various alpha thalassaemia alleles in different ethnic groups, along with their genotypic interactions, and to illustrate the haematological changes associated with each phenotype. Amongst the patients, 51.2% (n = 2567) were diagnosed with α thalassaemia. Of the 13 α thalassaemia determinants screened, eight different deletions and mutations were demonstrated: three double gene deletions, – – SEA, – – THAI, ––FIL; two single-gene deletions, α–3.7 and – α4.2; and three non-deletion mutations, Cd59G > A (haemoglobin [Hb] Adana), Cd125T > C (Hb Quong Sze) and Cd142 (Hb Constant Spring). A high incidence of α–3.7 deletion was observed in Malays, Indians, Sabahans, Sarawakians and Orang Asli people. However, the – – SEA deletion was the most common cause of alpha thalassaemia in Chinese, followed by the α–3.7 deletion. As many as 27 genotypic interactions showed 1023 α thalassaemia silent carriers, 196 homozygous α+ thalassaemia traits, 973 heterozygous α0 thalassaemia carriers and 375 patients with Hb H disease. Statistical analysis showed a significant difference in the distribution of α thalassaemia determinants amongst the various ethnic groups. Hence, the heterogeneous distribution of common determinants indicated that the introduction of an ethnicity-targeted hierarchical α thalassaemia screening approach in this multi-ethnic Malaysian population would be effective.
Highlights
Alpha thalassaemia is an inherited autosomal recessive disorder caused by a complete absence or decrease in the production of alpha globin peptides due to a deletion or mutation of one or more of the four alpha globin genes—two on each copy of chromosome 16
The present study aims to provide data on the incidence of the various forms of α globin gene deletions, mutations and their genotypes reflected in the diverse ethnic population of Malaysia in the context of their laboratory presentations, and to examine the data to elucidate the possibility of an ethnicity-based alpha thalassaemia screening programme
Peninsular Malaysia, lies Sabah and Sarawak, with the two major subpopulations of Sabahans and Haematological and molecular data from the patients who were referred to the Institute for Medical
Summary
Alpha thalassaemia is an inherited autosomal recessive disorder caused by a complete absence or decrease in the production of alpha globin peptides due to a deletion or mutation of one or more of the four alpha globin genes—two on each copy of chromosome 16. –α thalassaemia resulting from point mutations in either the α2 (αTα) or α1 (ααT) gene is commoner in Southeast Asia than any other part of the world These deletional and nondeletional forms of alpha thalassaemia can be broadly classified into four syndromes depending on the number of functional α globin gene inherited. Inheritance of just one functional α globin gene out of the four (– – /– α) results in Hb H disease, which is known as α thalassaemia intermedia. The present study aims to provide data on the incidence of the various forms of α globin gene deletions, mutations and their genotypes reflected in the diverse ethnic population of Malaysia in the context of their laboratory presentations, and to examine the data to elucidate the possibility of an ethnicity-based alpha thalassaemia screening programme
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