A 36-year-old, male has a family h/o suicide with abnormal movements with dementia. The investigation of choice is

(A) Trinucleotide repeats Harrison18-3330]> Huntington's disease is one of the Trinucleotide repeat disorders which can explained above mentioned patient condition.# Huntington's Disease (HD)> HD is a progressive, fatal, highly penetrant autosomal dominant disorder characterized by motor, behavioral, and cognitive dysfunction> HD is characterized by rapid, nonpatterned, semipurposeful, involuntary choreiform movements. In the early stages, the chorea tends to be focal or segmental, but progresses over time to involve multiple body regions. Dysarthria, gait disturbance, and oculomotor abnormalities are common features. With advancing disease, there may be a reduction in chorea and emergence of dystonia, rigidity, bradykinesia, myoclonus, and spasticity. Functional decline is often predicted by progressive weight loss despite adequate calorie intake. In younger patients (about 10% of cases), HD can present as an akinetic-rigid or parkinsonian syndrome (Westphal variant). HD patients eventually develop behavioral and cognitive disturbances, and the majority progress to dementia. Depression with suicidal tendencies, aggressive behavior, and psychosis can be prominent features. HD patients may also develop non-insulin-dependent diabetes mellitus and neuroendocrine abnormalities, e.g., hypothalamic dysfunction. A clinical diagnosis of HD can be strongly suspected in cases of chorea with a positive family history. The disease predominantly strikes the striatum. Progressive atrophy of the caudate nuclei, which form the lateral margins of the lateral ventricles, can be visualized by MRI. More diffuse cortical atrophy is seen in the middle and late stages of the disease.