GBA1 and Parkinson disease: The frequency of GBA mutations ranged from 10.7 to 31.3% in the Ashkenazi Jewish population with PD (Aharon-Peretz et al., 2004; Clark et al., 2005) but ranged from 2.3%, the lowest frequency and reported in the Norwegian population with PD, to 9.8% for individuals of other ethnic origins (Toft et al., 2006; Seto-Salvia et al., 2012).