The recent article by Chen et al1 caught our attention as a third study associating mutations in the myofibrillogenesis regulator 1 gene with paroxysmal nonkinesigenic dyskinesia (PNKD). Currently, a total of 12 kindreds with only 2 missense mutations (A7V and A9V) have been reported.1-3 Family records were collected in various centers across the United States; their origins, if mentioned, are European. Hence, it appears that the spectrum of mutations responsible for PNKD is limited, and Chen et al suggest that this may have implications for genetic testing approaches.