Psychosis, Treatment Emergent Extrapyramidal Events, and Subsequent Onset of Huntington's Disease: A Case Report and Review of the Literature.

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease characterized by a triad of progressive motor dysfunction, cognitive decline and psychiatric disturbances. The hallmark of HD is the distinctive choreiform movement disorder that typically has a subtle, insidious onset in the fourth to fifth decade of life and gradually worsens over 10 to 20 years until death. Notably, two-thirds of HD patients present with chorea and one third with mental changes. The prevalence of psychiatric symptoms is significantly higher than in the general population, and is estimated to be around 66-73%. Here, we report a unique case of subsequent onset of HD in a patient previously treated for schizophrenia and complicated by the extrapyramidal side effects to antipsychotics.