GBA1 and Parkinson disease: 2009; Horowitz et al. 2011; Duran et al. 2013). Similarly, the p.T369M substitution has previously been identified in PD cases (Clark et al. 2007; Nichols et al. 2009; Benitez et al. 2016). Whilst it is known that severe GD‐associated GBA substitutions increase the risk of cognitive decline (Alcalay et al. 2012; Winder‐Rhodes et al. 2013), recent evidence indicated that the p.E326K substitution also increases the risk of working memory/executive function decline and visuospatial memory impairment in PD (Mata et al. 2015).