GBA1 and Parkinson disease: GBA-PD patients exhibit an asymmetric onset with the classic triad of motor symptoms, bradykinesia, rigidity, and tremors (Goker-Alpan et al., 2008), although bradykinesia seems to be more common, as an initial symptom, than in iPD (Ziegler et al., 2007; Gan-Or et al., 2010; Lesage et al., 2011).