Huntington's disease (HD) is a debilitating autosomal-dominant disease. Its prevalence is ~ 3-7 / 100,000 persons (Table ). Presentation begins in approximately the 4 th -5 th decade of life, with chorea as the most common symptom. HD may also present with personality alterations, memory decline, and mood disturbance. Cognitive changes take place and culminate in dementia following onset of the movement disorder. Chorea may also develop into bradykinesia and rigidity late in the disease. The primary pathological hallmark is severe atrophy of the striatum, which is reduced to a fraction of its original size. HD is triggered by a CAG repeat expansion in the first exon of the huntingtin (htt) gene. Affected patients exhibit 36-250 repeats, compared to healthy individuals having 6-35 repeats. HD displays several features common to polyQ repeat diseases, including enhanced toxicity of a polyQ-containing fragment. Fulllength polyQ-htt is being cleaved in the cytosol, generating toxic fragments predominantly translocated to the nucleus and forming nuclear inclusions over time , with larger repeats inducing increased inclusion formation. Transcriptional dysregulation and aberrant chromatin remodeling are central features in HD pathology.