Family shares a new nystagmus locus

A genetic study of one family may improve our understanding of early eye stabilisation and squint because it suggests that their control may lie in single gene. Linkage analysis for nystagmus showed linkage with markers between 13q31–q33, not previously reported. This defines the dominantly inherited familial disorder as dominant acquired vestibulocerebellar disorder, not a benign form of cerebellar ataxia.

In four generations of the family affected members had gaze evoked nystagmus developing at 1 to 2 years of age. It was non-progressive and ataxia, if present, was minimal; there were no abnormalities on neuroimaging. Squint was also present and more common in family members with nystagmus, and much more so than in the general population. Vision was preserved except for family members with amblyopia related to squint. No corresponding structural anomalies have been identified that would explain the functional disorder. The researchers speculate that a failure in function of the flocculus may be involved

The study included 30 family members examined by an ophthalmologist, orthoptist, and eye movement specialist. DNA from each was used in a genomic screen against 400 polymorphic repeat microsatellite markers and 17 other markers in pairwise linkage analysis.

This form of early acquired nystagmus, which is not congenital, has nor been investigated before.