Osler-Weber-Rendu syndrome (OWR) is also known as hereditary hemorrhagic telangiectasia (HHT). It is a genetic blood vessel disorder that often leads to excessive bleeding. According to the HHT Foundation International, the syndrome affects about one in 5,000 people (HHT Foundation).
The name Osler-Weber-Rendu syndrome is named for the doctors comes who worked together researching this condition in the 1890s. They discovered that this bleeding problem was not caused by issues with blood clotting, as had been previously assumed. Instead, it was caused by problems with the blood vessels themselves.
The distinguishing feature of OWR is the occurrence of arteriovenous malformations (AVM). These are abnormal blood vessels in which blood flows directly from an artery into a vein without going through the capillaries. Small AVMs can occur in the skin and organs are are called telangiectasias. When large AVMs occur in critical organs like the brain, lung, liver, and gastrointestinal tract, hemorrhage in these areas can become life threatening. It is estimated that approximately 10 percent of patients with OWR require blood transfusions because of excessive bleeding (HHT Foundation).
People with OWR inherit an abnormal gene that causes their blood vessels to form incorrectly. OWR is a dominant disorder. This means that only one parent needs to have the abnormal gene to pass it on. If you have the syndrome, there’s a 50 percent chance you’ll pass it to your child. If you don’t, your grandchildren should be safe from the syndrome. OWR does not skip a generation.
In very rare cases, a child can be born with OWR even when neither parent was affected by the syndrome. This happens when one of the genes that cause OWR mutates in an egg or sperm cell.
Symptoms of OWR and their severity vary widely, even among family members.
The most obvious common symptom is a large red birthmark sometimes called a port wine stain. This is one example of an AVM.
Small red marks called telangiectasias are another common symptom of OWR. These are caused by AVM that have formed in the skin, and they are prone to bleeding. The marks may appear on young children or not until after puberty. Telangiectasias can appear on the:
- whites of the eyes
AVMs can also occur internally. The most common sites, in order, are:
- gastrointestinal tract
According to the HHT Foundation, 95 percent of people with OWR suffer from an AVM in the nose, leading to nosebleeds (HHT Foundation). In children, this is one of the most prevalent symptoms. Nosebleeds may happen daily or as rarely as twice a year.
When AVMs form in the lungs, they can affect lung function. A person with a lung AVM will probably notice shortness of breath. They may cough up blood. Lung damage from AVM may lead to strokes or bacterial infection of the brain.
A person with a gastrointestinal AVM may be prone to digestive problems, such as bloody stools. According to the HHT Foundation, almost a quarter of people with OWR have an AVM somewhere in their digestive tracts (HHT Foundation). These are not generally painful. However, loss of blood often leads to anemia. Gastrointestinal AVM can occur in the stomach, intestines, or esophagus.
AVMs can be particularly dangerous when they occur in the brain. When one bleeds, it can cause seizures and minor strokes.
The presence of telangiectasias is one indication of OWR. Other symptoms that might lead to a diagnosis include:
- frequent nosebleeds
- bloody stools
- a parent with the syndrome
If you have OWR, your doctor might want to do additional tests. For example:
- A blood test can check for anemia, or iron deficiency in the blood.
- A chest X-ray can show any AVMs on the lungs.
- Your doctor can insert a small camera down your throat to check for AVMs in your esophagus. This is called an endoscopy.
- An echocardiogram uses sound waves to check blood flow in and out of your heart.
People with OWR should be screened for AVMs in the lungs and brain. This can help doctors detect a potentially dangerous problem before something goes wrong. An MRI can screen for problems in the brain. Echocardiograms can detect lung AVMs.
A knowledgeable doctor can monitor the ongoing symptoms of this syndrome through regular checkups.
Genetic testing is not usually needed to diagnose OWR. These tests are expensive, and may not be available in all circumstances. People with a family history of OWR, who are interested in genetic testing, should discuss their options with a genetic counselor.
The various symptoms of OWR each require their own types of treatment.
Nosebleeds are one of the most common manifestations of OWR. Fortunately, there are several types of treatments which may help. Noninvasive treatments include:
- using a humidifier to keep the air in your home or workplace moist
- keeping the inside of your nose lubricated with ointment
- taking estrogen might be helpful in decreasing bleeding episodes.
If noninvasive remedies fail, there are other options. Laser therapy heats and seals the edges of each telangiectasia. However, you may need to have repeated sessions for lasting symptom relief. Septal dermoplasty is also an option for people with severe nosebleeds. This procedure replaces the mucous membrane, the thin lining inside the nose, with a skin graft that provides a thicker lining. This cuts down on nosebleeds.
More serious surgery may be required for AVMs in the lungs or brain. The goal is to take preemptive action before there are problems. Embolization is a surgical process that treats lung AVMs by stopping blood flow. It can be done in a few hours as outpatient surgery. This procedure involves the injection of glue or other non-reactive liquid adhesive material into the AVM in order to block it off. For this purpose, a small catheter is passed through a groin vessel all the way up into the blood vessels supplying the AVM. Surgery for brain AVMs depends on their size and location.
Embolization is much trickier to perform on the liver. It can cause serious complications. Therefore, liver AVMs are usually left alone unless the person shows signs of trouble.
If intestinal bleeding causes anemia, your doctor will recommend iron replacement therapy. This will be in pill form, unless you’re not absorbing enough iron. In that case, you may have to take iron intravenously. In serious cases, your doctor might order hormonal treatment or a blood transfusion.
Dermatologists can treat port wine marks with laser therapy if they bleed a lot or you dislike the way they look.
Other Complications of ORW Syndrome
When mouth bacteria enter the bloodstream and pass through a lung AVM, it can cause a brain abscess (a collection of infected material containing immune cells and pus) If you have lung AVMs, talk to your doctor about whether you should take antibiotics before getting any dental work. The routine preventive use of antibiotics is not universally accepted.
People with a family history of OWR may want to consider genetic counseling before having children.
Most people with OWR lead perfectly normal lives. The syndrome is only life threatening when an internal AVM begins to bleed uncontrollably.
If you need support, the HHT Foundation International is a strong advocate for people with OWR. They keep up with all the research on the syndrome. They can also refer you to specialists in the diagnosis, care and treatment of OWR.