Alterations of the genes encoding amyloid precursor protein (APP), presenilin-1 or 2 (PS1 or PS2), Adamalysin 10 or Apolipoprotein E4 (APOE4) are frequent in familial AD [12], but the large majority of AD patients show increased brain levels of neurotoxic Aβ without changes of the gene aforementioned. The gene discussed is PSEN1; the disease is Alzheimer disease.