Autosomal dominant cerebellar ataxia with retinal degeneration: clinical, neuropathologic, and genetic analysis of a large kindred.

The autosomal dominant cerebellar ataxias (ADCA) comprise a heterogeneous group of neurologic disorders characterized by degeneration of the cerebellum, spinal cord, and brainstem. Genetic analysis has revealed two loci, SCA1 on chromosome 6p, and SCA2 on chromosome 12q, responsible for some ADCA. We present a four-generation kindred of 42 individuals, 12 of whom were clinically affected with ADCA and an associated cone dystrophy. Early loss of color discrimination with retinal and macular signs is followed by gradual progression of cerebellar dysfunction and development of pyramidal signs. Pathology shows degeneration of cerebellum, basis pontis, inferior olive, and retinal ganglion cells. For genetic analysis, we used polymorphic markers D6S89 and D12S79; linkage analysis gave negative results, excluding linkage to both SCA1 and SCA2. The data strongly support genetic heterogeneity consistent with the unique clinicopathologic features of the form of ADCA displayed in this large family.