OBJECTIVES: To assess the molecular basis of phenotypic heterogeneity in north Indian patients with thalassemia major (TM). METHODS: To determine the clinical severity, 130 patients of TM were studied for the age of first presentation and frequency of blood transfusion. The type of beta mutations, Xmn-1(G)gamma polymorphism and G6PD Mediterranean mutation was characterized. Analysis of the phenotypic presentation and the genotype was performed. RESULTS: Majority (83.8%) presented before 1 year of age (mean 8.8 months). The caste distribution showed 41.6% were Aroras and 32.3% were migrants from Pakistan. IVS1-5(G-->C) was commonest (32.7%) and the common five Indian mutations comprised of 88.4% of alleles. The mean age of presentation with IVS1-5(G-->C), Fr 8/9, (+G) 619-bp del and IVS1-1(G-->T) homozygosity was 4.3, 6, 3.4 and 9.1 months respectively. Xmn-1(G)gamma status showed -/- in 66.9%, +/- in 26.1% and +/+ in 6.9% patients. Xmn-1(G)gamma-/- presented before 1 year of age. The mean age of presentation with +/+ was 18.3 months. Six hemizygous boys and one heterozygous girl with G6PD Mediterranean were found (prevalence 5.3%). Eight patients could be reclassified as thalassemia intermedia on follow up. CONCLUSIONS: This study showed that majority of TM in north India present before 1 year of age and homozygous 619-bp deletion presents the earliest. The presence of Xmn-1(G)gamma polymorphism delays the presentation, is associated with the IVS 1-1 (G-->T) and shows variable improvement with hydroxyurea therapy. Based on the results of genotyping, reevaluation of patients can improve the outcome in a few patients.
OBJECTIVES: To assess the molecular basis of phenotypic heterogeneity in north Indian patients with thalassemia major (TM). METHODS: To determine the clinical severity, 130 patients of TM were studied for the age of first presentation and frequency of blood transfusion. The type of beta mutations, Xmn-1(G)gamma polymorphism and G6PD Mediterranean mutation was characterized. Analysis of the phenotypic presentation and the genotype was performed. RESULTS: Majority (83.8%) presented before 1 year of age (mean 8.8 months). The caste distribution showed 41.6% were Aroras and 32.3% were migrants from Pakistan. IVS1-5(G-->C) was commonest (32.7%) and the common five Indian mutations comprised of 88.4% of alleles. The mean age of presentation with IVS1-5(G-->C), Fr 8/9, (+G) 619-bp del and IVS1-1(G-->T) homozygosity was 4.3, 6, 3.4 and 9.1 months respectively. Xmn-1(G)gamma status showed -/- in 66.9%, +/- in 26.1% and +/+ in 6.9% patients. Xmn-1(G)gamma-/- presented before 1 year of age. The mean age of presentation with +/+ was 18.3 months. Six hemizygous boys and one heterozygous girl with G6PD Mediterranean were found (prevalence 5.3%). Eight patients could be reclassified as thalassemia intermedia on follow up. CONCLUSIONS: This study showed that majority of TM in north India present before 1 year of age and homozygous 619-bp deletion presents the earliest. The presence of Xmn-1(G)gamma polymorphism delays the presentation, is associated with the IVS 1-1 (G-->T) and shows variable improvement with hydroxyurea therapy. Based on the results of genotyping, reevaluation of patients can improve the outcome in a few patients.