GBA1 and Parkinson disease: The cause of PD is unknown, however, large-scale sequencing studies have compellingly identified several risk genes that have a lipid-related function, including GBA1, GALC, SMPD1, SREBF1, ELOVL7, DGKQ, ASAH1 and PLA2G61–10, with GBA1 mutations being the strongest genetic risk factor for PD.