ABSTRACT
BACKGROUND: Huntington's disease (HD) is an autosomal-dominant neurodegenerative disorder with an average age at onset of 40 years. It is a polyglutamine (polyQ) disorder that is caused by an increase in the number of CAG repeats in the huntingtin (HTT) gene. Genetic tests that accurately determine the number of CAG repeats are performed for confirmation of diagnosis, predictive testing of persons at genetic risk for inheriting HD, and prenatal testing. The aim of our study was to evaluate efficacy of triplet-primed polymerase chain reaction (TP-PCR) for routine diagnosis of HD in suspected cases from India. METHODS: We evaluated a combination of CAG flanking PCR and triplet-primed PCR for estimation of CAG repeats in 503 cases with clinical suspicion of HD. RESULTS: There were 250 cases (49.7%) that showed the presence of expanded alleles, with 241 (47.9%) being fully penetrant alleles and nine (1.8%) in the reduced penetrance category. There were seven juvenile cases with an age of onset of < 20 years, with the longest allele comprising 106 CAG repeats found in an 8-year-old male patient. The results demonstrated an inverse (R = - 0.67) relationship between CAG length and age at clinical onset. CONCLUSION: Our study on pan-Indian cases is one of the largest studies reported so far in India and focuses on the most accurate and comprehensive molecular diagnostic evaluation of HD.
Subject(s)
Huntingtin Protein/genetics , Huntington Disease/epidemiology , Huntington Disease/genetics , Peptides/genetics , Trinucleotide Repeats , Adolescent , Adult , Age of Onset , Aged , Aged, 80 and over , Alleles , Child , Codon , Cohort Studies , DNA Primers/chemistry , DNA Primers/metabolism , Female , Gene Expression , Genetic Testing , Humans , Huntington Disease/diagnosis , Huntington Disease/pathology , India/epidemiology , Male , Middle Aged , Penetrance , Polymerase Chain Reaction/methodsABSTRACT
CONTEXT: Hemoglobinopathies constitute the world's most common genetically inherited red blood cell disorder. Screening and accurate identification of hemoglobin (Hb) variants have become increasingly important in antenatal diagnosis and prevention of Hb disorders. AIM: The aim of this study was to screen and identify Hb fractions prevalent in the Central Reference Laboratory of India. MATERIALS AND METHODS: A total of 65,779 cases were screened for hemoglobinopathies on the bio-rad variant high-performance liquid chromatography (HPLC) system by beta-thalassemia short program. The retention times, proportion of the hemoglobin (%) and the peak characteristics for all hemoglobin fractions were recorded. Molecular analysis of the beta-globin gene was carried out by DNA sequencing on eight cases. RESULTS: Total number of abnormal Hb fractions on cation exchange-HPLC (CE-HPLC) was seen in 12,131 (18.44%) cases. Beta-thalassemia trait was the predominant genetic Hb disorder accounting for 7377 cases (11.21%) of the total cases. This was followed by sickle cell trait (2.01%), sickle cell disease (1.59%), beta-thalassemia syndrome (0.80%), HbE trait (0.79%), and borderline HbA2 (0.51%). Molecular characterization of eight rare cases of hemoglobin variants by beta-globin gene sequencing identified three cases of Hb Beth Israel, two cases of Hb Hofu trait, and one case each of Hb J Cambridge, Hb Mizunami, and Hb Sherwood Forest. CONCLUSION: Superior resolution, rapid assay time, and accurate quantification make CE-HPLC suitable for the routine investigation of hemoglobinopathies.
