[Phenotype of familial forms of early-onset Alzheimer's disease linked to chromosome 14. Clinical and neuropsychological characteristics of a large group]

We report the clinical features and neuropsychological data of chromosome-14 linked early-onset Alzheimer's disease in a large family (FAD-RO1). Information available in the literature from eight additional chromosome 14-linked Alzheimer's disease kindreds was compared with the data obtained from six kindreds with amyloid precursor protein gene mutations (APP). In the chromosome 14-linked families the disease has an earlier onset and a shorter duration than in families with APP mutations, with an age at death lower than sixty years of age. Seizures, myoclonus and extra pyramidal signs were frequently present in the cases of FAD-RO1 as in six chromosome 14-linked kindreds, but these features were absent in two other ones. The high frequency of seizures (80%) in FAD-RO1 and two other chromosome 14-linked kindreds is remarkable. Seizures and myoclonus were encountered at a lower prevalence in APP kindreds. This review suggests that some clinical features are more prevalent in chromosome 14-linked than in APP kindreds but a phenotypic heterogeneity does exist within and between families. The profile of deterioration of the neuropsychological performances, as illustrated by the FAD-RO1 members, shows that chromosome 14-linked kindreds do not demonstrate a specific expression in comparison to APP kindreds. Memory was first impaired. Deficits in visuo-spatial and visuopractic abilities were then noted. Finally the verbal performance deteriorated.