Linkage analysis in spinopontine atrophy: correlation of HLA linkage with phenotypic findings in hereditary ataxia.

Because linkage has been reported between HLA and the locus for hereditary ataxia in some families, we studied a 3-generation kindred in which several individuals had dominantly inherited spinopontine atrophy. Affected family members had upper and lower limb ataxia, hypoactive reflexes, loss of proprioception, dysarthria, dysphagia, and pronounced extraocular movement abnormalities. Linkage analysis, based on 25 markers in 28 people, gave strongly negative results with both HLA (z less than -2.0 for theta less than 0.15) and GLO1 (z less than -2.0, theta less than or equal to 0.01). The highest LOD score was for linkage to GPT on chromosome 16 (z = 0.42, theta = 0.0). To assess the relationship between HLA linkage and phenotype, 4 published kindreds with adequate clinical and neuropathological descriptions were used for comparison to the present family. Persons in the 3 families showing evidence for HLA linkage had clinical and pathologic changes consistent with olivopontocerebellar atrophy, type 1. The conditions in the 2 "nonlinked" families were phenotypically distinct from the HLA-linked condition with respect to extraocular movement findings and peripheral sensory nervous system signs. They differed markedly from each other in neuropathologic changes.