COL4A1 and Leukoencephalopathy: In addition to Mendelian cases of cerebrovascular disease caused by rare COL4A1 and COL4A2 mutations, large-scale genetic studies identified associations between COL4A1 and intracranial aneurysms, deep ICHs, lacunar ischemic stroke, reduced white matter volume, arterial calcification, arterial stiffness and leukoencephalopathy (Adi et al., 2014; Ayrignac et al., 2015; Di Donato et al., 2014; Livingston et al., 2011; O'Donnell et al., 2011; Rannikmae et al., 2015; Ruigrok et al., 2006; Tarasov et al., 2009).