Mutations in PARK2 (parkin) are the second most common genetic cause of parkinsonism after mutations in LRRK2. 17, 18 Across the consortium, we identified 184 homozygous carriers of PARK2 mutations who had a mean age of PD onset of 29·2 years (10·4 years). The gene discussed is LRRK2; the disease is Parkinson disease.