The clinical phenotype of two missense mutations in the presenilin I gene in Japanese patients

We report the clinical and neuropathologic phenotypes associated with two different missense mutations in the presenilin I (PS-I) gene in Japanese patients with early-onset familial Alzheimer's disease (FAD). In the AM/JPN1 pedigree a missense mutation (C-->T) was found at nucleotide 1102, which is predicted to cause an alanine-to-valine missense substitution at codon 260. In this family, the disease had a mean age of onset of 40.3 rears and an indolent course (range, 8-19 years). Neuropathologic studies in 3 members of this pedigree showed widespread senile plaques, neuro-fibrillary tangles, and neuronal loss, as well as abundant perivascular subpial amyloid deposits in the Virchow-Robin spaces and the presence of Pick-like intraneuronal inclusions in the dentate gyrus. In the second pedigree, transmitting a C-->T nucleotide substitution at position 1027, leading to the missense mutation of alanine to valine at codon 285, the disease had a later onset (mean, 51 years) but a more rapid course. Comparison of the disease phenotypes associated with other missense mutations in exon 9 of PS-I reveals no clinical or pathological phenotype, which uniquely distinguishes Alzheimer's disease associated with PS-I mutations from other forms of early-onset PAD, implying that direct mutation screening is required to identify these cases.