Genetic Complexity and Parkinson's Disease

Mihael H. Polymeropoulos et al. describe the genetic linkage of a large Parkinson's disease (PD) pedigree to chromosome 4q21-q23 (1). In this study, which affirms a long hypothesized genetic component to the disease, linkage was detected in a single large family with the use of an autosomal dominant model with 99% penetrance of the disease trait. The clinical presentation in this family, however, may differ from typical idiopathic PD because of the apparent autosomal dominant transmisson, early onset, rapid course, and less frequent occurrence of tremor as a significant sign (2). Thus, it is unclear whether the putative PD locus identified by Polymeropoulos et al. (which they termed PD1) is responsible for the majority of familial idiopathic PD cases.