GBA1 and Parkinson disease: Extending the research into risk-modifying factors to rare predicted deleterious variants in lysosomal genes, the largest contribution to the development of PD in GBA1 mutation carriers was attributed to a second deleterious variant in GBA1 or a deleterious variant in genes associated with mucopolysaccharidoses, evidencing the importance of the overall lysosomal burden in the development of PD [12,17,314].