GBA1 and Parkinson disease: Using SAA in CSF, it was shown that people with PD and DLB carrying severe mutations in the gene glucocerebrosidase (GBA) manifest a higher prevalence of α-Syn seeding (93% and 100%) compared to other genetic forms with known variable (LRRK2, 78% positive seeding) or even sparse Lewy body pathology (bi-allelic Parkin, PINK1, 0% positive seeding)10–12.