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Indian J Hum Genet. 2010 Sep;16(3):154-8. doi: 10.4103/0971-6866.73410.

Clinical, hematologic and molecular variability of sickle cell-β thalassemia in western India.

Author information

1
Department of Hemato-Genetics, National Institute of Immunohaematology (ICMR), Mumbai, India.

Abstract

BACKGROUND:

Sickle cell-β thalassemia (HbS-β thalassemia) is a sickling disorder of varying severity, which results from compound heterozygosity for sickle cell trait and β thalassemia trait. The present study was undertaken to determine the genetic factors responsible for the clinical variability of HbS-β thalassemia patients from western India.

MATERIALS AND METHODS:

Twenty-one HbS-β thalassemia cases with variable clinical manifestations were investigated. The α and β globin gene clusters were studied by molecular analysis.

RESULTS:

Thirteen patients showed milder clinical presentation as against eight patients who had severe clinical manifestations. Four β thalassemia mutations were identified: IVS 1-5 (G→C), codon 15 (G→A), codon 30 (G→C) and codon 8/9 (+G). α thalassemia and XmnI polymorphism in homozygous condition (+/+) were found to be common among the milder cases. The β(S) chromosomes were linked to the typical Arab-Indian haplotype (#31). Framework (FW) linkage studies showed that four β thalassemia mutations were associated with different β globin gene frameworks. Linkage of codon 15 (G→A) mutation to FW2 is being observed for the first time.

CONCLUSION:

The phenotypic expression of HbS-β thalassemia is not uniformly mild and α thalassemia and XmnI polymorphism in homozygous condition (+/+) are additional genetic factors modulating the severity of the disease in the Indian subcontinent.

KEYWORDS:

HbS- β thalassemia; India; clinical; framework; mutations

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