The phenotypic and molecular diversity of hemoglobinopathies in India: A review of 15 years at a referral center.

Introduction: The hemoglobinopathies pose a significant health burden in India. Apart from the β thalassemias and sickle cell disorders, α thalassemias and structural hemoglobin variants are also common. Here we have reviewed the phenotypic and molecular diversity of hemoglobinopathies encountered at a referral center in western India over a period of 15 years.

Materials And Methods: Screening for hemoglobinopathies was done using HPLC and cellulose acetate electrophoresis. Molecular characterization was done using Covalent Reverse Dot Blot Hybridization (CRDB), Amplification Refractory Mutation System (ARMS), GAP PCR and direct DNA sequencing.

Results: The study includes 31 075 individuals who were referred for diagnosis of hemoglobinopathies and prenatal diagnosis. Of these 14 423 individuals showed various hemoglobin abnormalities. Beta genotyping in 5615 individuals showed the presence of 49 β thalassemia mutations. 143 β thalassemia heterozygotes had normal or borderline HbA levels. We identified three δ gene mutations (HbA Pellendri, HbA St.George, HbA Saurashtra) in β thalassemia heterozygotes leading to normal HbA levels. The commonest defects among the raised Hb F determinants were Gγ(Αγδβ) Indian inversion and the HPFH-3 Indian deletion. A total of 312 individuals showed the presence of α thalassemia, of which 12.0% had a single α gene deletion (-α/αα). HbH disease was identified in 29 cases with 10 different genotypes. Alpha globin gene triplication was seen in 2.1% of β thalassemia heterozygotes with a thalassemia intermedia phenotype. Seven unusual α chain variants and eight uncommon β chain variants were identified.

Conclusion: The repertoire of molecular defects seen in the different globin genes will be valuable for management and control of these disorders both in India as well as in other countries where there is a huge influx of migrant populations from India.