GENOTYPE-PHENOTYPE CORRELATION OF HUNTINGTIN CAG REPEAT EXPANSION AND ASSOCIATED SYMPTOMS IN A LARGE INDIAN FAMILY CARRYING HUNTINGTON'S DISEASE MUTATION

Background We describe a 48 year-old man with a 20 year long history of behavioral changes, chorea and hallucinations. History and mental state examination were suggestive of Huntington disease (HD). Neurological examination revealed discrete, involuntary movements affecting his arms and trunk. Genotyping detected an expanded allele (43 CAG repeats, other allele 17 CAG). A detailed investigation revealed a three-generation-long family history of chorea and psychosis. There was a family history of HD in a sibship of 12 individuals, 9 older than him. The origin of the mutation was traced an ancestral paternal allele. This is a case study to look at an increased expansion in a family where the paternal allele of 43 CAG repeats expanded in the next generation to an allele with 47 repeats. Method To determine the CAG expansion, blood samples were obtained after informed consent and CAG repeat length was determined by PCR analysis. Till now samples of 5 family members including this patient are processed. To evaluate the impact of CAG repeat expansion on disease progression and symptoms, the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) and The Stroop Color and Word Test (SCWT) was carried out in these subjects. Result All the 5 family members were found to carry the HD mutation with the CAG repeat expansion in the affected allele ranging from 43–47. The comparison between age of onset and CAG repeat length and its correlation with motor, cognitive and behavioral analysis are underway. Conclusion In the current study, we have identified 12 living members of a large Indian family with symptoms of HD. Five patients were confirmed to carry the HD mutation by genetic testing and remaining members will also be tested and detailed genotype-phenotype analysis will be carried out.