[Clinical and genetic studies of Alzheimer-type dementia].

The families of 128 probands with Alzheimer's disease (AD) and senile dementia (SD) were studied. Genetical and mathematical analyses were employed to estimate the clinico-genealogical findings. The genetic factors were found to be likely to make some contribution to the origin of Alzheimer-type dementia (ATD). The proportion of afflicted relatives considerably exceeded that of the above dementia patients. Two genetic models (monogenic and multifactorial) were tested. The limit estimations of genetic similarity between AD and SD manifestations both in the monogenic and multifactorial models denied the fact that there is a common major gene responsible for liability to Alzheimer-type dementias. The common gene modifiers were assumed to exist in AD and SD. In addition to the differences found between the types of inheritance in patients with these disease, the following features are: an oligogenic type of inheritance in SD and a quasi-dominant one with incomplete manifestations of homo- and heterozygotes in AD. Studies into the clinical polymorphism of Alzheimer-type dementias in hereditary cases enabled the authors to establish the genetically determined signs and the environmentally induced signs. The predisposing features (premorbid characteristic traits and specific features of mnemic and intelligence) were identified, which allowed the development of Alzheimer-type dementias to be predicted in 80% of women from hereditarily aggravated families.