Amyloid‐beta pathology in a case with dementia with Lewy bodies with a rapidly progressive clinical course similar to Creutzfeldt–Jacob disease

Most cases of dementia with Lewy bodies (DLB) follow a chronic course. However, some cases of rapidly progressive dementia (RPD) are difficult to distinguish from other diseases. Herein, we report how to differentiate DLB presenting with RPD from other diseases and its pathological features, with examples from our own experience. A 70-year-old man with RPD and psychiatric symptoms, including hallucinations and delusions, was transferred to our hospital. We suspected Creutzfeldt-Jakob disease (CJD), but disease-specific tests were all negative. The patient was treated with corticosteroids on the suspicion of an autoimmune condition; however, his symptoms did not improve. Based on the results of nuclear medicine and other tests, we suspected DLB and administered anti-Parkinsonian drugs; however, they were ineffective, and the patient died. Brain autopsy revealed extensive deposits of Lewy bodies, which were pathologically diagnosed as DLB. Additionally, extensive deposition of senile plaques was observed; however, neurofibrillary tangles (NFTs) were not prominent. DLB generally presents as a chronic disease. However, some patients with DLB present with RPD; therefore, the differential diagnosis of other diseases, such as CJD, is very important. In addition, although this case was not diagnosed with Alzheimer's disease (AD) due to the lack of NFTs, extensive amyloid deposition was observed in the brain tissue. Previous reports have described cases of RPD with amyloid deposition alone, and in this case too, it is suggested that amyloid deposition might have had a strong influence on the clinical course of RPD.