NCAM2 and early-onset autosomal dominant Alzheimer disease: Although NCAM2 have so far not been associated with cognitive impairment, it has been involved in synaptic deficits in Alzheimer’s disease and was implicated in the intellectual disability phenotype in Down syndrome and autism spectrum disorders, as well as in other neurodevelopmental diseases (Molloy et al., 2005; Petit et al., 2015; Scholz et al., 2016).