GBA1 and Parkinson disease: GBA1, which encodes the enzyme glucocerebrosidase (GCase), a lysosomal enzyme involved in sphingolipid degradation, is the most common strong genetic risk factor for Parkinson’s disease.99 While homozygous mutations in this gene result in the lysosomal storage disorder Gaucher’s disease, heterozygous mutations are connected to increased risk for Parkinson’s disease.99 Exactly how GBA1 mutations increase risk and whether this can be attributed to loss- or gain-of-function mechanisms remains under debate.