[Comparative clinico-genetic studies of senile dementia and Alzheimer's disease].

The families of 128 probands with senile dementia (SD) and Alzheimer's disease (AD) were entered into the study. The correlation between the familial and sporadic cases of the disease was established. A geneticomathematic analysis was employed to estimate the clinicogenealogical findings. Two genetic models (monogenous and multifactorial) were tested. The contribution of the genetic factors to SD and AD liability was assessed. As a result of a comparative clinicogenetic study of SD and AD it was found that there is no doubt about the contribution made by the genetic factors to the origin of the Alzheimer type dementia (ATD). The rate of the afflicted relatives considerably exceeded the population rates of the investigated patterns of dementia. The limit estimations of the genetic similarity between the manifestations of AD and SD, both in the monogenous and multifactorial models, were obtained, which rejects the presence of the common major gene responsible for liability to these patterns of the ATD. It was assumed that AD and SD are characterized by the presence of the common genes modifiers. In addition, the difference was established between the types of inheritance in persons afflicted with these diseases: an oligogenic type of inheritance in SD, a quasidominant type with incomplete penetrance of homo- and heterozygotes in AD.