This is consistent with the more benign phenotype previously reported in other PD patients with p.R1441G.24, 25 The reason for the unusually early age at onset of the proband is not clear.21 He was negative for both point and dosage mutations in the PARK2 gene (data not shown), the most frequent genetic cause of early-onset PD, as well as for mutations in GBA which not only increase risk for PD but also lower the age at onset by at least 4 years.26 It is possible that environmental exposures or other genetic factors not tested might influence the age at onset in this instance. This evidence concerns the gene PRKN and Parkinson disease.