In humans, heterozygous mutations of either endoglin or alk1 cause hereditary hemorrhagic telangiectasia (HHT)-1 or HHT-2, respectively, both characterized by vascular anomalies such as dilated vessels, edema, arterio-venous malformations, and pulmonary, liver and neurological problems due to vascular defects [16]. The gene discussed is ENG; the disease is hereditary hemorrhagic telangiectasia.