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Several mutations in the amyloid precursor protein (APP) gene may lead to either Alzheimer's disease or cerebral haemorrhage due to congophilic amyloid angiopathy (CAA). A single family is known in which both types of pathology are expressed because of a missense mutation at codon 692 of the APP gene (APP692). Here we describe the clinical and pathological expression of APP692 in eight patients with the mutation. Furthermore, 21 first-degree relatives with an a priori risk of 50% of being a carrier were tested for the APP692 mutation and studied for presymptomatic signs by neurological examination, neuropsychological testing and brain MRI. Patients with APP692 presented with haemorrhage, dementia or both. The dementia in patients with the APP692 mutation was compatible with Alzheimer's disease both clinically and neuropathologically. Of the 21 healthy relatives at 50% risk, five carried the APP692 mutation. The presymptomatic carriers showed a subtle, non-significant impairment of cognitive function compared with relatives without APP692. A significant increase in the number of periventricular and subcortical white matter lesions at young age was seen in presymptomatic carriers (mean age 26.4 years). The findings of this study suggest that a single (genetic) mechanism may underlie the pathology of Alzheimer's disease and CAA. These diseases are manifested subclinically by white matter pathology. Further insight into the relationship between CAA and Alzheimer's disease may provide clues about the aetiology of Alzheimer's disease.

Original publication

DOI

10.1093/brain/123.10.2130

Type

Journal article

Journal

Brain : a journal of neurology

Publication Date

10/2000

Volume

123 ( Pt 10)

Pages

2130 - 2140

Addresses

Department of Epidemiology and Biostatistics, Erasmus Medical Centre, Rotterdam, The Netherlands.

Keywords

Humans, Alzheimer Disease, Amyloidosis, Genetic Predisposition to Disease, Amyloid beta-Protein Precursor, Pedigree, Neuropsychological Tests, Age of Onset, Heterozygote, Mutation, Missense, Adult, Middle Aged, Family Health, Female, Male