MS4A4E and Parkinson disease: These novel susceptibility genes encode proteins essentially involved in pathways related to PD, including neuroinflammation (MS4A4E and INPP5D) (Malik et al., 2015; O’Day, 2019), peripheral immune response (CLECL1, CLEC16A, IL7R, MS4A4E, and INPP5D) (Cukier et al., 2017; O’Day, 2019), apoptosis (AGAP2, DKKL1) (Wu et al., 2013; Workman et al., 2018), autophagy (CLEC16A) (Tam et al., 2017), endo-lysosomal system (AGAP2 and MS4A4E) (Wu et al., 2013), mitochondrial function/morphology (MPV17L2) (Dalla Rosa et al., 2014) and axon guidance (ZSWIM4) (Fink et al., 2017).