Genetic studies in Parkinson's disease.

In a previous paper (2), we had demonstrated the existence of familial cases of Parkinson's disease. We have now identified two main patterns to these familial cases within our own clinical material. The total familial subgroup of 50 kinships that we report represents 13% of our 342 kinships personally examined in detail. Only 2 of these familial cases turn out to be phenocopies of Parkinson's disease. A further 34 kinships (10% of all Parkinson's disease) are classified within the essential-tremor related Parkinsonism subgroup that we have previously described and 10 kinships (3% of all Parkinson's disease) form what we now call the recessive akineto-rigid syndrome. A further 4 kinships (called pseudodominant) are probably examples of this same entity. These subgroups have quite distinct inheritance patterns and deserve more thorough metabolic investigations and clinical characterization. On the basis of these studies, we propose that a genetic type of Parkinson's disease be included in any classification of the disorder.