A prospective study of 50 cases of familial Parkinson's disease.

In a recent paper (Barbeau and Pourcher, 1982) we demonstrated that so-called "idiopathic" Parkinson's disease is not a homogeneous entity, and defined the existence of a sub-group of patients with genetic parkinsonism. To investigate this last possibility, and to uncover possible metabolic clues as to the etiology of such cases, we carried out a prospective study of 50 kindreds with "familial" parkinsonism. Two control groups were similarly studied: 50 kindreds with essential tremor (neurological control group) and 50 kindreds originating from spouses of the previous patients (non neurological control group). We uncovered two main patterns of genetic transmission within the parkinsonian patients: a parkinsonism related to dominant essential tremor (34 kindreds; 10% of all Parkinsonians) and a recessive "akineto-rigid syndrome" (10 kindreds; 3-4% of all Parkinsonians). A further 4 kindreds assumed a pseudo-dominant pattern but were probably recessive. Finally 2 kindreds were obviously other entities presenting as "phenocopies" of Parkinson's disease. Metabolically, hyperthyroidism appeared to be more frequent in essential tremor and "essential-tremor related parkinsonism" kindreds, while hypothyroidism and possibly hypoparathyroidism (post surgery) seemed more frequent in the recessive akineto-rigid syndrome kindreds.