A case report of late-onset schizophrenia differentiated from a dementing disorder

Background With the increase in life expectancy and the subsequent increase in the older population, the clinical importance of late-onset psychosis also increases. Neuropathological findings play an important role in the differential diagnosis of dementing disorders in older adults. Herein, we report a case of late-onset schizophrenia that required differentiation from a dementing disorder. Case presentation: The patient was an 83-year-old woman who had experienced auditory hallucinations since she was 67 years old. She was hospitalized for treatment of her psychosis. Initially, various examinations were performed to consider the possibility that she had a dementing disorder such as dementia with Lewy bodies. 123I-meta-iodobenzylguanidine myocardial scintigraphy revealed no decrease in iodine accumulation in the myocardium, and 123I-ioflupane dopamine transporter imaging revealed no decrease in dopamine transporter accumulation in the striatum. The patient had an elevated concentration of total tau (488 pg/mL), a cerebrospinal fluid biomarker. After comprehensive testing, the patient was diagnosed with late-onset schizophrenia. Her psychiatric symptoms such as auditory hallucinations diminished after the administration of the recommended first-line drug risperidone (3 mg/day), and she was discharged on day 90. Conclusions This case was identified as late-onset schizophrenia. However, an elevated total tau concentration was observed, indicating that neurofibrillary tangles and neuronal death, which are characteristic of Alzheimer 's disease, may also have been present. Late-onset schizophrenia should be treated based on an appropriate differential diagnosis, including neuropathological consideration of dementing disorders.