APP and Alzheimer disease: For example, mutations of the Amyloid Precursor Protein (APP) gene that increase the ratio of the longer Aβ42 to the shorter Aβ40 species (such as the London Val717Ile mutation), cause primarily AD pathology, whereas several APP missense mutations within the Aβ-coding sequence (such as the Dutch Glu693Gln mutation) strongly favor CAA [4].