Monogenic Parkinsonisms and the genetics of Parkinson's disease.

The field of molecular genetics has recently provided important clues to further understanding of the etiopathogenesis of idiopathic Parkins o n ’s disease (PD). Different mendelian forms of PD have been identified, establishing the concept of etiological heterogeneity in degenerative parkinsonisms (Table I, see over) (1-3). The genes and loci so far identified are responsible for only a very small percentage of PD cases, and additional, as yet unknown, mendelian defects probably exist in other familial forms of the disease. In the vast majority of sporadic cases a monogenic etiology is unlikely, and PD results from a complex interplay of several genetic as well as non-genetic factors (3,4). However, molecular dissection of the rare monogenic forms is unraveling common pathogenic pathways that are probably involved in all the PD forms, including the sporadic ones.