Snapshot A 30-year-old woman presents with a two year history of anxiety, gait instability, and progressively worsening tics. She has no family history of neurologic disease, but her father committed suicide at age 32. MRI scan of the brain shows atrophy of the cerebral cortex and caudate nucleus. Introduction Definition login to view 1 more bullet Epidemiology Usually begins between ages 30-50, but may begin as early as infancy (juvenile HD if age of onset < 20), or in older age Both sexes are affected equally Pathophysiology Autosomal dominant CAG triplet repeat expansion in one allele of the HD (huntingtin) gene on chromosome 4 Number of CAG repeats determines presence of disease login to view 4 more bullets Number of CAG repeats may increase with subsequent generations,(anticipation) particularly with paternal transmission HD mutation results in neuronal death, particularly in the caudate nucleus and putamen (basal ganglia) Age of onset and severity of disease is inversely correlated with number of CAG repeats Presentation Symptoms login to view 21 more bullets Evaluation Labs login to view 1 more bullet Imaging login to view 1 more bullet Differential Tourette's (Tic) disorder Syndenham chorea Schizophrenia Tardive dyskinesia Wilson's disease Spinocerebellar ataxia Treatment No curative treatment or treatment altering disease progression Supportive treatment can be highly effective login to view 4 more bullets Genetic counseling should be offered for patients, family members, and at-risk offspring Prognosis, Prevention, and Complications Condition is inevitably fatal Average prognosis is approximately 20 years from symptom onset