Brain small vessel disease-1 is an autosomal dominant disorder with variable manifestations resulting from disruption of vascular basement membranes, particularly in the cerebral vasculature. The increased fragility of these vessels render them susceptible to hemorrhage, as early as in utero or by birth trauma, although the risk remains throughout life and some patients may present in adulthood. This genetic predisposition may extend beyond hemorrhagic stroke to include retinal and renal vascular defects. Clinical features thus reflect the location and severity of the vascular defect, including impaired neurologic development or function, hemiplegia, seizures, and variable ocular anomalies. The disturbed vasculature leads to cerebral degeneration, and brain imaging typically shows 'porencephaly,' hemosiderin deposition, calcifications, lacunar infarcts, enlarged ventricles, and leukoencephalopathy. Some patients may show 'schizencephaly' on brain imaging, which is also attributed to encephaloclastic processes, such as vascular injury. The disorder shows variable penetrance and expressivity. [From OMIM]