Cerebellar ataxia, dystonia, and tremor within a family: variable phenotypes of a single genetic disorder?

We report a non-Jewish, Anglo-Saxon, American family, in which one sibling has dystonia, a second has cerebellar ataxia, and a third has a combination of dystonia and ataxia. All three siblings have pyramidal signs. Their mother and maternal uncle have tremor, and their maternal grandmother may have had a neurodegenerative disorder. Although the inheritance pattern is uncertain, this may represent phenotypic variability resulting from a single gene mutation. The multiple phenotypes within this family do not fit any known inherited neurodegenerative or metabolic disorder.