FIG4 and Parkinson disease: Inositol polyphosphate-5-phosphatase F (INPP5F), one of the polyphosphoinositide phosphatases, was first described as a PD risk factor in a meta-analysis carried out by Nalls et al. in 2014 (Nalls et al., 2014), which means that only one SNP was found to be associated with PD susceptibility so far.