| Abstract: | Over fifty missense mutations in the presenilin‐1 (PSEN1) gene have been reported in families with presenile familial Alzheimer's disease (FAD). We describe a novel missense mutation (G209R) within the predicted fourth transmembrane domain of the PSEN1 in a Japanese family with presenile FAD. The affected cases showed similar disease histories with the mean age at onset of 49.6 ± 3.1 years and rapid progressive dementia characterized by memory impairment, amnestic aphasia, disorientation and personality change, but lacking parietal focal symptoms such as apraxia or agnosia. Compared with the previously reported cases of same Gly209 mutation (G209V), the clinical features of the G209R‐FAD cases appear to be less critical than those of G209V‐FAD cases, although the Gly to Arg mutation is considered to be less conservative than the Gly to Val mutation. These findings may suggest the possible existence of other genetic and/or environmental factors or the possibility that these two different Gly209 mutations may underlie different pathomechanisms in the development of presenile FAD. Hum Mutat 14:90, 1999. © 1999 Wiley‐Liss, Inc. |
