Chromosome studies of four neurodegenerative diseases are described in current literature: Huntington disease cases in Finland show linkage disequilibrium of chromosome 4rflp haplotypes [1]. Hereditary Motor and Sensory Neuropathy Type I shows linkage to the pericentromeric region of chromosome 17 [2]. Friedreich’s ataxia gene has been assigned to chromosome 9q13-q21 [3]. The dystonia gene in Ashkenazi Jewish population has been located on chromosome 9q32-34 [4]. The same gene may be responsible for idiopathic torsion dystonia in non-Jewish kindred. Most familial forms of idiopathic torsion dystonia follow autosomal dominant transmission with reduced penetrance. The frequency in Ashkenazi Jewish population is 5-10 times greater than that in other groups.
