A 58-year-old woman presented with a 6-week history of intermittent passage of bright red blood from the rectum, as well as progressive fatigue and dyspnea. Her medical history included recurrent episodes of spontaneous epistaxis since childhood. Physical examination revealed telangiectasias on the labial mucosa (Panel A) and nail folds (Panel B). In addition, her mother was reported to have frequent epistaxis and similar skin lesions. Laboratory test results showed severe iron-deficiency anemia and lower gastrointestinal endoscopy revealed arteriovenous malformations and telangiectasias of the colon (Panel C). Radiologic evaluation revealed no pulmonary or cerebral vascular malformations. On the basis of these findings, a clinical diagnosis of hereditary hemorrhagic telangiectasia, or the Osler–Weber–Rendu syndrome was made. Genetic testing was performed, and the results were positive for an endoglin gene mutation; this confirmed the molecular diagnosis in the patient and her mother.