Evidence for genetic linkage in a family with autosomal dominant disease

In the early 1980s medical opinion favoured an environmental cause for Parkinson's disease. This viewpoint was founded partly on a small study of twins1 and the evidence that drug addicts inadvertently exposed to methylphenyltetrahydropyridine (MPTP) developed an illness very similar to the sporadic form of the disease. Ten years later, the pendulum had swung toward genetic factors. The twin data were reanalysed and deemed inconclusive,2 and several families were identified with apparent autosomal dominant inheritance.

The most convincing family is described by Golbe and others, who identified 41 affected people in four generations.3 The cases were slightly atypical, with young age of onset (mean 46.5 years), predominance of the rigid form of Parkinson's disease, and a rapid course (average 9.7 years to death). However, the …