Clinical features and gene analysis in Korean patients with early-onset Parkinson disease

Background: Systematic analysis of clinical features and gene mutations has not been performed in Korean patients with early-onset Parkinson disease (PD). Objective: To investigate the clinical characteristics and genetic background of Korean patients with early-onset PD. Design: Clinical and genetic study. Setting: University hospital. Patients: Ninety-four patients with early-onset PD (mean +/- SD age at onset, 39.8 +/- 7.3 years) of 1100 patients with PD. Interventions: Analysis of clinical characteristics and mutation analysis of the parkin and PTEN-induced kinase (PINK1) genes by direct sequencing and gene-dosage analysis using the multiplex ligation-dependent probe amplification technique. Main Outcome Measures: The correlation between age at onset and clinical characteristics and the clinical features of patients with onset before age 30 years vs patients with onset after age 30 years. Results: Because age at onset was younger, levodopa-induced dyskinesia and off-dystonia were more frequently observed (P=.008). Patients affected before age 30 years showed more frequent levodopa-induced dyskinesia and off-dystonia (P=.002). We identified 3 patients (5%) with parkin gene mutations but none with the PINK1 mutation. Conclusions: Earlier onset of levodopa-induced dyskinesia and off-dystonia were characteristic features of early-onset PD, especially before an onset age of 30 years. However, parkin gene mutations were less frequent in these patients than in Japanese groups reported elsewhere.