Serum and plasma levels of vascular endothelial growth factor (VEGF) are increased in HHT patients [17], and adult-onset AVMs in the brain and skin have been shown to require angiogenic stimulators such as VEGF in addition to ACVRL1 or ENG-deficiency [18, 19]. The gene discussed is ACVRL1; the disease is hereditary hemorrhagic telangiectasia.