RESUMO
OBJECTIVE: To examine molecular genetics and prenatal diagnosis of beta-thalassaemia. METHODS: The study was conducted at the COMSATS Institute of Information Technology, Sahiwal, Pakistan, from October 2012 to October 2013, and comprised families having children affected by thalassaemia and autosomal recessive b-thalassemia. Blood samples of thalassaemic children and their parents were collected from different areas of Pakistan. They were screened for reported mutations through amplification refractory mutation system-polymerase chain reaction. Once mutation was characterised, chorionicvilus sampling was carried out to provide the retrospective first trimester prenatal diagnosis. RESULTS: A total of five families were included in this study. Electropherogram showed that both mother and father were heterozygous (carrier) for intervening sequence I-5 mutation whereas the affected child was homozygous for this mutation. Five chorionic villus samples were examined to analyse the molecular defects which were responsible for beta-thalassaemia in the families. Prenatal diagnosis was performed for these families. They had at least one affected child (thalassaemia major) who was transfusion-dependant. Amplification refractory mutation system-polymerase chain reaction was found to be a very sensitive method to find the known point mutations present in beta-globin gene. Point mutations identified included intervening sequence I-5 (G-C), frameshift codon8/9 (+G) and frameshift codon-41/42 (-TTCT). CONCLUSIONS: It is the best preventive action to adopt the screening process to overcome the disease.
