A number of different genes come under the umbrella term of vascular leukoencephalopathies, including NOTCH3 (CADASIL), HTRA1 (cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL)), CTSA (CARASAL), COL4A1 and TREX1. The gene discussed is COL4A1; the disease is CARASIL.