The most common of these, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), is caused by NOTCH3 variants, and the second most frequent, CADASIL2, by autosomal dominant HTRA1 variants.1COL4A1/2 variants can cause small vessel stroke and intracerebral hemorrhage.2 Here, NOTCH3 is linked to CADASIL.