However, the lysosomal enzyme genes HEXB, CTSD (Beyer et al., 2005, Papassotiropoulos et al., 2000, Paz et al., 2015, Sierksma et al., 2020), and more recently CTSH, CTSB, and IDUA (Bellenguez et al., 2020), also harbour associations with AD. The gene discussed is IDUA; the disease is Alzheimer disease.