Molecular epidemiology of ß-thalassemia in Pakistan: Far reaching implications.

BACKGROUND: ß -Thalassaemia, an autosomal recessive hemoglobinopathy, is one of the commonest genetically transmitted disorders throughout the world. Collective measures including carrier identification, genetic counseling and prenatal diagnosis are required for preventing ß-thalassemia. AIM: To achieve this objective, Identification of the spectrum of genetic mutations, especially for various ethnic backgrounds in Pakistan. Therefore, we designed a cross sectional prospective study to identify the frequency of various gene mutations in different ethnic groups of Pakistan. MATERIALS AND METHODS: Over a 5-year period, DNA from 648 blood samples {including specimens of chorionic villus sampling (CVS)} were analyzed for the twelve most common ß-thalassemia mutations found in the Pakistani population by a Multiplex amplification refractory mutation system (ARMS). Each sample was analyzed for the mutation as well as the normal gene, appropriate with negative and positive controls, and reagent blanks. RESULTS: Out of 648 samples mutations were identified in 640 (98.75%) samples by multiplex ARMS. 8 common ß-thalassemia mutations were identified in 8 different ethnic groups accounting for 93.9% of the ß-thalasemia alleles. CONCLUSIONS: Based on the outcome of this study a cost effective proposal is formulated for detection of ß-thalassemia mutations.

Molecular epidemiology of ß-thalassemia in Pakistan: far reaching implications.

ß-thalassaemia, an autosomal recessive hemoglobinopathy, is one of the commonest genetically transmitted disorders throughout the world. Collective measures including carrier identification, genetic counseling and prenatal diagnosis are required for preventing ß-thalassemia. To achieve this objective, Identification of the spectrum of genetic mutations, especially for various ethnic backgrounds in Pakistan is necessary. Therefore, we designed a cross sectional prospective study to identify the frequency of various gene mutations in different ethnic groups of Pakistan. Over a 5-year period, DNA from 648 blood samples [including specimens of chorionic villus sampling (CVS)] were analyzed for the twelve most common ß-thalassemia mutations found in the Pakistani population by a Multiplex amplification refractory mutation system (ARMS). The most common mutation identified was Intervening Sequence 1-5 (IVS 1-5 (G-C)); accounting for 40.89% mutated alleles, and was represented in all ethnic groups. 15.7 % of the ß-thalassemia alleles were found to have Frameshift 8-9 (Fr 8-9) as the second most common mutation Other common genetic defects responsible for ß-thalassemia: IVS 1-1 (G-T) was found in 8.17%, Codon-30 (Cd-30 (G-C)) 8.02%, Codon-5(Cd-5 (-CT)) contributed 2.16% and Deletion 619 base pair (Del 619bp) affected 11.11% were found in Pakistan. This large study adds to the pre-existing data in Pakistan. Knowledge of the predominant mutation in a given ethnic group will not only help in developing a short panel of (population-specific) primers of mutations thereby providing a cost-effective method for prenatal diagnosis and also help the clinicians to counsel regarding blood transfusion regimen/ pregnancy termination.

Efficacy of hydroxyurea in providing transfusion independence in ß-thalassemia.

BACKGROUND: Packed red blood cell (PRC) transfusion with iron chelation is the mainstay of treatment for ß-thalassemia major. This prospective interventional trial serves as a follow up to our similar earlier study that evaluated the efficacy and safety of hydroxyurea (HU) in minimizing PRC transfusions in patients with ß-thalassemia major. METHODS: One hundred fifty-two patients with ß-thalassemia major received HU at a mean dose of 16 mg/kg/d. The results were analyzed at the end of 24 months. Transfusion requirement during the 6 months preceding the study was considered as the control. RESULTS: One hundred forty-six of 152 patients were evaluated after 24 months of follow up; 6 patients were either lost to follow-up or withdrew consent. Grade 1 myelosuppression was observed in 4 patients and diarrhea in 2 patients. Sixty children (41%) did not require any transfusion after using HU; 57 patients (39%) showed partial response with greater than 50% reduction in PRC transfusion; and 29 patients (20%) were nonresponders with less than 50% reduction in PRC transfusion. The mean volume of PRC transfused was reduced for all patients. CONCLUSIONS: HU was found to be safe in patients with ß-thalassemia major, and resulted in the reduction of transfusion requirement and in an increase in the interval between transfusions.