Hereditary hemorrhagic telangiectasia (HHT) is a disorder in which patients may possess multiple aneurysmal telangiectasias of the skin, mucous membranes, liver, brain, lung, spinal cord, and/or spleen. These abnormalities are hereditary with both male and female children being affected equally. Recent studies indicate that this disorder may have a greater prevalence in the general population than previously suspected.

The clinical manifestations of this disorder are the presence of multiple telangiectasias and bleeding, which may present as epistaxis (most common manifestation), hemoptysis, melena, hematochezia, or hematuria. Recurrent bleeding may result in anemia. When the lungs are affected, pulmonary arteriovenous malformations cause right-to-left shunting of blood. When the number of pulmonary lesions is excessive, dyspnea, fatigue, cyanosis, hypoxia, or erythrocytosis may result. Testing pulse-oximetry values with the patient supine and then standing is an easy and inexpensive method to screen for platypnea-orthodeoxia syndrome which is indicative of underlying right-to-left shunting of blood. A postitve test is characterized by an increase in the respiratory rate with a concomitant decrease in the oxygen saturation when the patient moves from the supine to standing position. Brain abscesses and strokes are more serious complications secondary to the right-to-left shunting of blood from pulmonary lesions. Other neurologic symptoms include headache, transient ischemic attacks, strokes, seizures, subarachnoid hemorrhage, and intracranial hemorrhage. It is of note that in most patients with neurologic symptoms, the underlying malformations are pulmonary in origin (secondary to right-to-left shunting of septic or bland emboli) with cerebral or spinal arteriovenous malformations being the underlying cause in fewer cases. Hepatic arteriovenous malformations cause left-to-right shunting of blood which may lead to high output heart failure. The diagnosis should be suspected in patients with cutaneous or membranous telangiectasias, a history of recurrent bleeding without an identifiable cause (usually epistaxis), and a family history.

Standard chest radiographs may display pulmonary lesions, but high-resolution helical computed tomography without contrast is often required to establish the diagnosis of pulmonary involvement. Contrast echocardiography and oxygen saturation measurement with pulse oximetry in both the supine and standing positions are also used by some physicians in screening for pulmonary lesions. When using pulse oximetry for screening, an oxygen saturation less than 96% in either position (supine or standing) indicates a need for more sensitive testing; however, an oxygen saturation greater than 96% in both positions does not rule out the possibility of pulmonary lesions. If pulmonary lesions are identified, serial scanning every 5 years to follow the growth of the lesion is recommended. When surgical intervention is indicated, pulmonary angiography is required. Pulmonary screening should occur in asymptomatic cases with a family history of pulmonary or cerebral hemorrhage Screening should begin at the time of puberty; however, if the family history includes prepubertal bleeding, then screening should begin earlier. Also, because there is an increased tendency for pulmonary hemorrhage in the third trimester of pregnancy, women of childbearing age should be screened prior to conception.

Therapy for pulmonary lesions includes ligation at the arterial side of the lesion, transcatheter embolization, or surgical wedge resection. Patients with pulmonary lesions also need antibiotic prophylaxis for surgical and dental procedures. Cerebral lesions may be treated with neurovascular surgery, embolization, or stereotactic radiosurgery. Esophagogastroduodenoscopy, colonoscopy and gastrointestinal angiography may be used to locate lesions of the gastrointestinal tract. Once localized, photocoagulation may be employed; however, bleeding may recur. Estrogen and progesterone therapy may decrease the need for transfusions in patients with gastrointestinal lesions. Laser ablation of cutaneous lesions may be useful when the lesions become a cosmetic concern. Severe, recurrent epistaxis may warrant referral to an otolaryngologist for septal dermoplasty.