GBA1 and Parkinson disease: In previous studies, we42 and others43,44 have observed increased plasma concentrations of ceramides and glucosylceramides or glucosylsphingosines in patients with idiopathic PD who were not carrying GBA1 mutations that are associated with mal-folding or dysfunction of the GBA1 gene product, lysosomal glucocerebrosidase alpha (GCase).