GBA1 and Parkinson disease: Of PD cases, 10–15% are familial, and >20 gene mutations have been linked to PD development, including glucocerebrosidase (GBA), alpha-synuclein (SNCA), leucine-rich repeat kinase 2 (LRRK2), PTEN-induced kinase 1 (PINK1), parkin, and parkinsonism-associated deglycase (DJ-1, also known as PARK8)1,6–9.