Osler-Weber-Rendu syndrome is an inherited disorder of the blood vessels, which can cause excessive bleeding. The syndrome is also called hereditary hemorrhagic telangiectasia, or HHT.

Osler-Weber-Rendu syndrome is inherited as an autosomal dominant trait. The condition can affect males or females of any ethnic or racial group.

Children with this syndrome develop red or reddish-purple collections of abnormal blood vessels called telangiectases.

The syndrome is genetic, which means it results from a broken or missing gene. Scientists have identified some of the genes involved, but do not know exactly how the gene defects lead to the abnormal blood vessels seen in persons with this syndrome.

Frequent nosebleeds in children may be an early symptom.

Telangiectases may not appear until puberty. They can bleed easily and may be seen on the tongue, lips, nasal mucosa, face, ears, fingertips, nails, whites of the eyes, and skin.

There may be GI bleeding, including loss of blood in stool or dark black stools.

Bleeding into the brain may cause symptoms such as seizures or unexplained, small strokes. Severe bleeding can be deadly.

Some patients only discover that they have this condition when they cough up blood and a chest x-ray shows a spot on the lung called an arteriovenous malformation (AVM). Large or multiple AVMs can cause shortness of breath.

A port wine stain is occasionally present.

An experienced health care provider can detect telangiectases during a physical examination. There is often a family history of hereditary hemorrhagic telangiectasia.

Other signs include:

• Chest x-ray may show a "spot on the lung" (arteriovenous malformation).
• Echocardiogram may show heart failure.
• Blood tests may reveal iron deficiency anemia.
• Special blood gas tests may show decreased levels of oxygen in blood.
• Endoscopy may show abnormal blood vessels that bleed easily in the throat, bowels, or airways.
• Hepatomegaly may occur if there are abnormal blood vessels in the liver.

Genetic testing may be available for mutations in the endoglin or ALK1 genes.