The Role of Alleles with Intermediate Numbers of Trinucleotide Repeats in Parkinson’s Disease and Other Neurodegenerative Diseases

Genetic factors underlie the pathological processes responsible for the manifestations of a wide range of neurodegenerative diseases. The expansion of unstable trinucleotide repeats forms pathological alleles that lead to the development of monogenic neurological diseases (Huntington’s disease, Kennedy’s disease, spinocerebellar ataxia, etc.). However, data have recently appeared on the role of alleles with intermediate numbers of these repeats in the formation of the clinical features of multifactorial neurological phenotypes (Parkinson’s disease, Alzheimer’s disease). This article summarizes data on current concepts of the role of the “intermediate” allele, mainly of the huntingtin gene ( HTT ), in the pathogenesis and clinical picture of neurodegenerative diseases, primarily Parkinson’s disease. The issue of the need to develop a special tactic for managing individual carriers of the “intermediate” allele by teams of highly qualified specialists in neurology and genetics is also discussed, as this would allow neurodegenerative diseases to be diagnosed early and medical genetic counseling of families to be improved.