Pathogenic variants in APP, PSEN1 and PSEN2 were thought to exclusively cause early onset familial AD (EOFAD) [5], but the screening of some late onset families and even sporadic cases, revealed that the contribution of familial genetic variants in APP, PSEN1 and PSEN2 in idiopathic cases cannot be neglected [6–8]. The gene discussed is PSEN1; the disease is early-onset autosomal dominant Alzheimer disease.