Adult onset spinocerebellar ataxia in a Canadian movement disorders clinic.

Background: The spinocerebellar ataxias (SCAs) are a genetically and clinically heterogeneous group of neurodegenerative disorders. Relative frequencies vary within different ethnic groups and geographical locations.

Objectives: 1) To determine the frequencies of hereditary and sporadic adult onset SCAs in the Movement Disorders population; 2) to assess if the fragile X mental retardation gene 1 (FMR1) premutation is found in this population.

Presenilin 1 Glu318Gly polymorphism: interpret with caution.

Background: The significance of the presenilin 1 (PSEN1) Glu318Gly polymorphism has been described as either a causal mutation with reduced penetrance or a benign polymorphism. When this polymorphism is found in a symptomatic person with a family history of dementia, counseling on recurrence risk becomes very problematic.

Objective: To demonstrate that the PSEN1 Glu318Gly polymorphism should be interpreted cautiously.