[The genetics of dementias, Part 3: a molecular basis for the multifactorial inheritance of sporadic Alzheimer's disease].

The majority of Alzheimer's disease cases, i.e. more than 85% of the whole population of patients, can be referred to as the sporadic form of the disease, with a negative family history and complex inheritance. As the genetic background of sporadic Alzheimer's disease is still largely unknown., strategies based on individual genetic risk profiling for either early prediction of the disease or its therapy and prevention are not possible. The APOE*4 allele of the gene for apolipoprotein E is still the only completely confirmed risk factor. Screening for new genetic risk factors with the use of genetic association analysis has many methodological difficulties and limitations. New combined approaches including genomics, proteogenomics, pharmacogenomics, epigenomics, and bioinformatics have to been applied in the future search for a molecular basis of AD. Genetic defects do not fully explain the complexity of the etiopathogenesis of this disease. It is rather certain that environmental factors (through epigenetic modifications in the patient' sepigenome) also have impact on the initiation of neurodegeneration processes. The identification of new genetic and environmental risk factors would make it possible to understand epistatic processes, for example interactions between genes and between genes and environmental factors, responsible for the complex etiology and multifactorial inheritance of sporadic Alzheimer's disease.