GBA1 and Parkinson disease: The mechanism by which GBA1 mutations increase PD risk is currently unknown, but given that pathological manifestations are identical in PD‐GBA1 and idiopathic PD patients, it is predicted that, as in idiopathic PD, accumulation of alpha‐synuclein and dopaminergic neuron loss in the substantia nigra are the key components for PD‐GBA1 (Migdalska‐Richards and Schapira, 2016; Wang et al., 2015).