In recent years, heterozygous mutations in the ß-glucocerebrosidase (GBA1) gene, which encodes the lysosomal enzyme ß-glucocerebrosidase (GCase), have been associated with a higher risk of developing PD, thereby challenging the role of LRRK2 mutations as most common monogenic risk factors for PD [43–45]. Here, GBA1 is linked to Parkinson disease.