Moreover, a mutation in immediate vicinity to the β‐secretase cleavage site in APP has recently been identified in the Icelandic population that protects against AD (Jonsson et al, 2012), while a double mutation at this site occurring in a Swedish family (swAPP) results in an exceptionally strong increase of Aβ generation (Citron et al, 1992). Here, APP is linked to Alzheimer disease.