Thus, mutation of single genes (i.e. parkin, LRRK-2, DJ-1, synuclein) can lead to DA neuronal loss (with or without Lewy body aggregates), glucocerebrosidase (GBA) expression correlates not only with the risk of developing PD (Beavan and Schapira, 2013) but also with its progression (Brockmann et al., 2015). This evidence concerns the gene GBA1 and Parkinson disease.