Parkinson's disease in Ireland: Clinical presentation and genetic heterogeneity in patients with parkin mutations

Early-onset autosomal recessive parkinsonism is associated with parkin gene mutations. Different parkin mutations occur in many ethnic backgrounds; however, the phenotype may vary. We studied 102 young-onset (age at onset <60 years) Parkinson's disease (PD) patients. From 102 patients, 40 with early-onset PD (<45 years at symptomatic onset) were selected for clinical assessment and parkin gene molecular analysis for duplications/deletions and point mutations. We identified parkin mutations in 7 of 40 early-onset patients; including novel compound heterozygotes and potential splice site changes. The mean age at onset in the 7 parkin mutation-positive patients was 33 +/- 9 years (age range, 18-42 years), marginally lower than that of the 33 parkin-negative early-onset patients, 38 +/- 7 years (age range, 17-45 years). A family history of PD was present in 4 of 7 patients with parkin mutations, compared with 6 of 33 early-onset parkin-negative patients. Overall, parkin mutations were found in 4 of 10 patients with a positive family history and 3 of 30 patients without a family history of PD. Patients with parkin mutations had more dystonia, dyskinesia, and sleep benefit compared with parkin-negative patients. We subsequently identified a single point mutation among the 62 young-onset (age at onset 45 to <60 years). Mutations in the parkin gene may account for similar to17% of early-onset (age at onset <45 years) parkinsonism in Ireland, in agreement with previous European studies. (C) 2004 Movement Disorder Society.