GBA1 and Parkinson disease: Further, current estimates predict that ∼5–10% of PD patients carry a GBA1 mutation (PD‐GBA1), although this figure is much greater in PD patients of Ashkenazi origin (Bultron et al., 2010; Migdalska‐Richards and Schapira, 2016; Sidransky et al., 2009).