Given that most FAD-linked PS mutations cause a partial loss of γ-secretase function (Szaruga et al., 2015), especially carboxyl-peptidase activity, leading to an accumulation of toxic longer Aβ42 and Aβ43, the effect of FAD-linked PS mutations is more complicated in the course of AD pathogenesis, not the case of simple absence of γ-secretase activity. The gene discussed is PSEN1; the disease is Alzheimer disease.