Molecular genetics of Alzheimer disease amyloid

Alzheimer disease is a late onset neurodegenerative disorder characterized by global cognitive decline. Definitive diagnosis of Alzheimer disease requires either the autopsy or biopsy confirmation of specific lesions formed by insoluble proteinaceous fibers in the brain: extracellular deposits of amyloid in senile plaques and cerebral blood vessels, and intracellular neurofibrillary tangles in the cytoplasm of neurons. The etiology of Alzheimer disease is unknown. Although most cases appear sporadic, epidemiological surveys have demonstrated an increased risk in first- and second-degree relatives of Alzheimer disease patients. A small proportion of Alzheimer disease cases occur in families displaying autosomal dominant inheritance of the disorder. In these instances, termed familial Alzheimer disease, the disease seems to be triggered by a genetic defect.