Deposition of amyloid (A4) protein within the brains of persons with dementing disorders other than Alzheimer's disease and Down's syndrome.

Deposition of amyloid (A4) protein was assessed in the cerebral cortex of 26 patients dying with various neurodegenerative disorders, other than Alzheimer's disease. Amyloid deposits were (variably) present in 2/3 (66%) elderly (i.e. over 65 years of age) patients with progressive supranuclear palsy, 4/7 (57%) with Parkinson's disease, 2/5 (40%) with Huntington's chorea and in both elderly patients with frontal lobe dementia but were only rarely seen in any patient before this age. The A4 protein deposits were nearly always of a diffuse type with only an occasional 'cored' neuritic plaque being present. Amyloid deposition in elderly persons may thus relate more to certain aspects of ageing and genetics than to AD, per se. Only in this latter condition are the cerebral cortical amyloid deposits widely associated with a neuritic change and a neurofibrillary degeneration of nerve cells.