GBA1 and Parkinson disease: Interestingly, homozygous mutations in glucocerebrosidase (GBA), a lysosomal enzyme breaking down glucosylceramide (GlcCer) into glucose and Cer, cause a LSD known as Gaucher disease (GD), while the same mutations in heterozygosis increase by five folds the lifetime risk of Parkinson’s disease (PD) (Sidransky et al., 2009).