Early-onset Alzheimer dementia superimposed on schizophrenia: a rare case report.

Disorganized behavior is a primary sign of schizophrenia. Yet it is not unique to schizophrenia. Recently, there has been a growing understanding that endogenous mental disorders could be a prodromal stage of neurodegenerative dementia. As a result, the connection between endogenous mental disorders and dementia has become a subject of significant interest. In the present study, a 49-year-old female with schizophrenia since the age of 17 was diagnosed with early-onset Alzheimer's disease after a detailed examination with PET and cerebrospinal fluid, despite suspicion of organic disease due to progressive forgetfulness, abnormal behavior and delusions. Schizophrenia is not the only disorder in which disorganized behavior is seen. When such a clinical phenomenon develops, other possible causes should be considered. Dementia is one of the most important of these causes. In a psychiatric disorder with disorganized behavior, other possible causes, especially dementia, should be considered.