Huntington’s disease of probable juvenile onset initially treated as schizophrenia: A case report, narrative review, and clinical guidance

<b>Objective:</b> We provide a case report, narrative literature review, and clinical guidance addressing the complexities of differential diagnosis of psychosis among young adults who present for neuropsychological evaluation. We highlight the potential for misdiagnosis of Huntington's Disease (HD) as schizophrenia or other neuropsychiatric conditions and describe implications for clinical neuropsychology practice. <b>Method:</b> We present the case of a 31-year-old male with eighth grade education initially diagnosed with schizophrenia who was ultimately found to have HD of probable juvenile onset via genetic testing following a neuropsychological evaluation. Family history of HD was not known to the patient until his late 20s due to being raised in an adoptive setting. <b>Results:</b> The patient had a history of apathy, anxiety, aggression, and academic challenges in childhood, with increasing need for assistance with activities of daily living and recent-onset gait instability, dysarthria, dysphagia, auditory hallucinations, compulsive behaviors, and depressive symptoms. Neuropsychological evaluation revealed difficulties with attention and set shifting, ideational dyspraxia, variable memory performance, slowed processing speed, blunted affect and impaired affect perception, shuffling unstable gait with reduced arm swing, and a subcortical pattern on language testing. Illness onset and course, neurocognitive, neuropsychiatric, and motor symptomatology, and genetic findings were suggestive of juvenile onset HD (JHD). <b>Conclusions:</b> This case exemplifies the complexities involved in diagnosing HD in young adults who present with neuropsychiatric symptoms. Valuable insights into the neuropsychological and neuropsychiatric profile of young adults with HD are shared, and clinical guidance regarding differential diagnosis is provided with an emphasis on HD and schizophrenia.