Inheritance of mutant GBA1 from both parents results in Gaucher disease, the most common of the lysosomal storage diseases.[27] Carriers of GBA1 mutations are found fivefold more frequently among PD patients than in non-PD controls,[28] and GCase has become an important therapeutic target for PD, as lowered activity has been linked to elevated α-syn levels.[29,30] The GCase enzyme is more ancient and widely expressed than α-syn. Here, GBA1 is linked to lysosomal storage disease.