MOLECULAR DIAGNOSIS OF β -THALASSEMIA IN INDIAN POPULATION

Abstract

β-thalassemia is the most prevalent single gene disorder in India. The thalassemia is a heterogeneous group of genetic disorders characterized by decreased or absent production of one or more globin chain that make hemoglobin molecule. β- globin gene is responsible for β- thalassemia. It is caused by the mutation in the HBB gene located on chromosome 11. It is inherited in an autosomal recessive manner. The common symptoms of the diseases are growth retardation, pallor, jaundice, poor musculature, hepatosplenomegaly, leg ulcers and extramedullary hematopoiesis. The amplification refractory mutation system – polymerase chain reaction (ARMS-PCR) technique was used for molecular diagnosis of β- thalassemia mutations. The five common mutations IVS 1-5 G → C, IVS 1-1 G → T, codon 41/42 (-TCTT), codon 8/9 and the 619 bp deletion account for approximately 90% of the mutations in β-thalassemia patients. Among this mutation, IVS 1-5 is the commonest and its prevalence varies from 22.2 to 81.4% in different regions of India, being the highest in Tamilnadu in South-eastern India. In North-Western part of India, 619 bp deletion is the most common mutation found in Sindhis and Lohanas community. β- thalassemia has improved substantially in the last 20 years following recent medical advance in transfusion, iron chelation and bone marrow transplantation therapy. This study would help in molecular screening and in prenatal diagnosis by direct detection of mutation in β-globin gene along with genotype-phenotype correlation. This will also help in carrier testing for relatives at risk and in providing genetic counseling to the affected individual.