Hereditary cerebellar ataxia and genetic linkage with HLA.

Five families with at least three generations of members affected with autosomal dominant spinocerebellar ataxia (SCA) were studied. HLA typing was carried out and the coded HLA haplotypes were used to calculate the likelihood of linkage using the LIPED computer program. The combined lod scores from these five families does not, by itself, support linkage. Negative lod scores were observed in all five families, however, when pooled with the previously published data significant lod scores were obtained [Z = 3.343 (theta = 0.20) and +4.286 (theta = 0.30)]. In four families, affected members had clinical features consistent with autosomal dominant cerebellar ataxia (ADCA) type I while in the fifth, ADCA type II was suggested. Clinical heterogeneity within ADCA raises doubts about the significance of summed lod scores. In view of the previous reports probably two genetically heterogeneous types of ADCA exist -- HLA linked and nonlinked.