Besides genetic forms related to GBA polymorphisms, retromers (protein complex used in the recycling of transmembrane endosomal receptors to the trans-Golgi network) could be altered in some forms of idiopatic PD (iPD) and in the absence of a functional retromer network, sphingolipids in excess are diverted to lysosomes, leading to a dramatic increase in the production of ceramides [170]. This evidence concerns the gene GBA1 and Parkinson disease.