Hereditary Hemorrhagic Telangiectasia (HHT), also known as Olser-Weber-Rendu, is a
genetic disorder that affects blood vessels in many parts of the body.
It is uncommon, but not rare. About 1 out of 10,000 people in the United States are
affected, and as many as 6 million people worldwide have HHT.
Telangiectases and arteriovenous malformations (AVMs) are the characteristic lesions
of this condition. These represent abnormal connections between arteries and veins
in which the small capillaries that normally join the arteries and veins are missing.
HHT has extremely variable expression in terms of both location of lesions and severity
of symptoms, even between close relatives.
It is frequently misdiagnosed in affected individuals.
The most commonly affected organs are the nose, skin, lungs, gastrointestinal tract
and brain—in that order.
HHT is an autosomal dominant genetic disorder, which means that it can be passed onto
children from one parent; on average, about half of children will be affected.
90-95% of individuals with HHT will develop nose bleeds by adulthood, but severity
varies from infrequent and minor to daily and severe.
90-95% develop at least a few telangiectasia on the skin of the face and/or hands
by middle age; these typically appear as purple spots 1/16 to 1/8" in diameter, but
they can be pin point in size.
30% have lung or pulmonary arteriovenous malformation (PAVM)
20% develop significant stomach or intestinal bleeding, but not usually before age
50.
10-15% have at least one brain or cerebral AVM (CAVM).
An unknown percentage have liver AVM.
The severity of epistaxis or telangiectases of the skin does not correlate with the
likelihood to have internal AVM (i.e. brain or PAVM)
Without treatment, PAVM are a common cause of stoke and brain abscess in HHT families.
Without treatment, brain AVM are a common cause of hemorrhagic stroke in HHT families.
Treatments are available for almost all symptoms of HHT and have evolved significantly
in the last decade.