PRKN and Parkinson disease: The patient's age at onset (61 years) was typical for sporadic PD, and it is possible the parkin phenotype had not yet become clinically established; we note that there exist occasional reports of parkin cases that did not manifest any signs of parkinsonism at ages well above that expected (>55 years),8,21 but those cases were compound heterozygous, and the possibility of reduced penetrance of 1 mutant allele would not apply in the homozygous situation.