Familial vestibulocerebellar disorder maps to chromosome 13q31-q33: a new nystagmus locus.

PURPOSE To determine a gene locus for a family with a dominantly inherited vestibulocerebellar disorder characterised by early onset, but not congenital nystagmus. DESIGN Observational and experimental study. METHODS We carried out a phenotypic study of a unique four generation family with nystagmus. We performed genetic linkage studies including a genome wide search. RESULTS Affected family members developed vestibulocerebellar type nystagmus in the first two years of life. A higher incidence of strabismus was noted in affected members. Haplotype construction and analysis of recombination events linked the disorder to a locus (NYS4) on chromosome 13q31-q33 with a lod score of 6.322 at theta=0 for D13S159 and narrowed the region to a 13.8 cM region between markers D13S1300 and D13S158. CONCLUSIONS This study suggests that the early onset acquired nystagmus seen in this family is caused by a single gene defect. Identification of the gene may hold the key to understanding pathways for early eye stabilisation and strabismus.