Increases in serum sphingomyelin and plasma ceramide have also been investigated in PD (Alimov et al., 1990; Mielke et al., 2013), and glucocerebrosidase (GBA) mutations, a genetic risk factor for PD, implicated in ceramide metabolism (Sidransky et al., 2009). This evidence concerns the gene GBA1 and Parkinson disease.