GBA1 and Parkinson disease: Heterozygous mutations in the GBA1 gene, a gene causing the well-known autosomal-recessive lysosomal storage disorder Gaucher’s disease when mutated in a homozygous or compound-heterozygous state, have been identified as a strong risk factor for late-onset PD, increasing the risk for PD, depending on the severity of the mutation, by 3–15-fold (Sidransky et al. 2009).