Recently, mutations in the glucocerebrosidase gene (GBA), which encodes the lysosomal hydrolase glucosylceramidase deficient in Gaucher disease, have been identified as a risk factor for the development of Parkinson’s disease (Sidransky et al., 2009; Sidransky and Lopez, 2012), dementia with Lewy bodies (Nalls et al., 2013) and a subtype of Alzheimer’s disease (Tsuang et al., 2012). Here, GBA1 is linked to early-onset autosomal dominant Alzheimer disease.