HCHWA-D is an autosomal dominant disease that predominantly occurs in a limited number of families in the villages of Katwijk and Scheveningen in the Netherlands.8 A point mutation (E693Q) of the amyloid precursor protein (APP) gene9 leads to extensive Aβ deposition in the cortical and leptomeningeal arterioles and arteries. Here, APP is linked to autosomal dominant disease.