Huntington's disease (HD) is an autosomal, dominantly inherited neurodegenerative disorder that is caused by an expansion of cytosine–adenine–guanine (CAG) repeats in the first exon of the huntingtin gene IT15, which encodes the huntingtin protein.1 The expansion of CAG repeats in huntingtin leads to the formation of neuronal intracellular and intranuclear aggregates.2 HD is characterized by severe motor and cognitive symptoms due to brain atrophy with loss of neurons especially in the striatum and cerebral cortex. The gene discussed is HTT; the disease is Huntington disease.