GBA1 and Parkinson disease: Recent genome-wide association studies have found that more than a dozen loci (including PARK1/4, PARK2, PARK5, PARK6, PARK7, PARK8, PARK9, PARK15, and glucocerebrosidase (GBA)) have been linked with familial Parkinson’s disease, and currently, upwards of 10 % of all cases of Parkinson’s disease are estimated to be associated with Parkinson’s disease gene family [3–5].