Diagnosis is the beginning of safer, more informed care.
HHT can be diagnosed using clinical features or genetic testing. Once HHT is known or suspected, screening looks for problems that may not cause symptoms until they become serious. The goal is not to make care feel complicated—it is to make sure the right questions are asked early.
How HHT is diagnosed
Four findings, counted together
Most HHT diagnoses are made clinically, using the Curaçao Criteria. A clinician counts how many of these four findings are present.
1
Nosebleeds
Spontaneous and recurrent, not explained by injury or dry air alone.
2
Telangiectases
Multiple, at characteristic sites such as the lips, mouth, fingers, and nose.
3
Internal involvement
A malformation in the lungs, brain, liver, spine, or gastrointestinal tract.
4
Family history
A first-degree relative diagnosed with HHT by these same criteria.
0 to 1
Unlikely
Not the same as ruled out. A young person may not yet show findings that appear later.
2
Possible or suspected
Worth pursuing further, often with genetic testing or screening.
3 or 4
Definite HHT
A clinical diagnosis. Screening should follow.
That last point matters for families. A child who does not meet the criteria today has not been ruled out, which is why genetic testing carries so much weight when the family’s genetic change is already known.
The path from here
How screening usually goes
The order rarely changes, even though the specific tests and intervals differ from person to person.
1
HHT is diagnosed or suspected
Through the Curaçao Criteria, a genetic test result, or a diagnosis in a close relative.
2
Baseline screening
Lungs, brain, and often liver screens are done upon diagnosis to look for internal arteriovenous malformations that can often be treated.
3
Treat what is found
Many findings are treatable, and some need only monitoring. Either way, you now have a baseline to compare against.
4
Recheck on a schedule
Intervals depend on what was found and on life events such as pregnancy. Your clinician sets them with you.
Screening is not a search for trouble. It establishes your baseline, so that anything that changes later has something to be compared against.
What screening looks for
The tests, explained
Filter by what is being checked or by who it applies to. Open a test to see what it is looking for, what happens on the day, and what the result changes. Your exact tests and intervals come from the International HHT Guidelines and from the clinician who knows your history.
10 tests
The bubble study (contrast echocardiogram)
What it is looking for. Malformed blood vessels in your lungs, called pulmonary arteriovenous malformations, or pulmonary AVMs. These are the single most important thing screening finds, because they usually cause no symptoms at all and because they can be treated once they are found.
What happens. This is an ultrasound of your heart. A technician puts a small amount of salt water, shaken until it is full of tiny bubbles, into a vein in your arm while the ultrasound is running. Normally the bubbles stop at the lungs. If they show up on the other side of the heart, that points to a shunt in the lungs. It takes under an hour, there is no radiation, and nothing about it hurts beyond the initial needle.
What the result changes. A clear study is reassuring and means you do not need a CT scan. A positive study leads to a CT scan of the chest to see where the malformations are and whether they are large enough to treat. Screening is repeated at intervals, because pulmonary AVMs can develop later.
CT scan of the chest
What it is looking for. The exact position and size of pulmonary AVMs, once a bubble study has suggested they are there.
What happens. You lie on a table that moves through a ring-shaped scanner and hold your breath for a few seconds. It takes minutes. For this particular scan you do not need contrast dye injected, which means no drip and no reaction risk.
What the result changes. It determines whether a malformation can be closed off with a procedure called embolization, which is done through a catheter rather than open surgery. If a malformation is too small to treat, you will be advised to take antibiotics before dental work and other procedures instead.
Pulse oximetry and chest X-ray in children
What it is looking for. Signs that a child’s lungs are affected. This is the usual first step for a child with no symptoms, because it avoids both radiation exposure beyond a single film and the need for a drip.
What happens. A clip on the finger measures oxygen levels, and a standard chest X-ray takes seconds.
What the result changes. A reading of 97% or higher usually means rechecking every three to five years. Below that, or if your child is short of breath or cannot keep up in sports, further tests follow. A child with symptoms is usually sent straight for a bubble study, which is more sensitive. In adults, oxygen levels and a chest X-ray are not enough on their own, and a bubble study is used instead.
MRI of the brain
What it is looking for. Malformed blood vessels in the brain. Most people with HHT do not have them, and most that exist never cause a problem, but finding one changes what your clinicians watch for.
What happens. You lie still inside a tube-shaped scanner for 30 to 45 minutes. It is loud, and you will be given earplugs or headphones. There is no radiation. Contrast dye is usually given through a vein, though it is left out during pregnancy. Tell the team in advance if enclosed spaces are difficult for you, because this can be planned for.
What the result changes. Most people have this scan once, around the time of diagnosis, and for a child with an affected parent it is recommended early in life. A clear scan generally does not need repeating unless new symptoms appear, though many centers repeat it once in adulthood after a clear childhood scan.
Blood tests for iron and anemia
What it is looking for. Whether repeated bleeding has depleted your iron. This is the simplest and most useful test in HHT care, and the one most often left undone.
What happens. One blood draw. Ask for a complete blood count, an iron panel, and a ferritin level together, because a normal hemoglobin can hide low iron stores, and low iron causes exhaustion and breathlessness well before anemia shows up.
What the result changes. Every adult with HHT should have this at least once a year, and more often with frequent nosebleeds. Low iron is treated with tablets first and with iron given through a vein when tablets cannot keep pace. If you are tired in a way that sleep does not fix, this is the first thing to check.
Ultrasound of the liver
What it is looking for. Malformed vessels in the liver. These are common in HHT and almost always silent, so this is not a test everyone needs.
What happens. Gel on the abdomen and a handheld probe, the same as any other ultrasound. No radiation, no dye, usually 20 to 30 minutes.
What the result changes. It is usually ordered because of symptoms rather than as routine screening: breathlessness, swelling, abnormal liver blood tests, or abdominal pain. If something is found, an echocardiogram follows to check how hard your heart is working. Treatment is rarely needed, and a liver biopsy should not be done in someone with HHT.
Endoscopy and capsule endoscopy
What it is looking for. Telangiectases in the stomach and intestine that bleed slowly and invisibly. This is investigated when anemia is worse than your nosebleeds account for.
What happens. For upper endoscopy, a thin camera passes through the mouth into the stomach while you are sedated. For capsule endoscopy, you swallow a camera the size of a large vitamin and go about your day while it photographs the small bowel and passes naturally.
What the result changes. Bleeding points can often be treated during the procedure. A separate note: people with HHT caused by a change in the SMAD4 gene also need regular colonoscopies starting in the teenage years, because that gene carries a bowel polyp condition alongside HHT.
Genetic testing
What it is looking for. A change in one of the genes that cause HHT, usually ENG, ACVRL1, or SMAD4.
What happens. A blood draw or a saliva sample. Results usually take several weeks. Meeting with a genetic counselor before and after is standard, and worth taking up.
What the result changes. This is the test that can settle the question for a whole family. Once the change is identified in one relative, everyone else can be tested for that specific change: those who have it start screening, and those who do not can stop worrying about HHT altogether. If no change is found, that does not undo a clinical diagnosis, because in 10% to 15% of families no change is identified with current testing.
Screening before and during pregnancy
What it is looking for. Pulmonary AVMs, mainly. Pregnancy increases blood volume and cardiac output, which can cause an untreated malformation in the lungs to grow or bleed.
What happens. Ideally screening happens before conception. If it did not, tell your obstetric team about HHT as soon as the pregnancy is confirmed. Screening during pregnancy uses either a bubble study or a low-dose chest CT, usually early in the second trimester. Brain imaging is not routine in pregnancy unless you have symptoms or a previous bleed, and is done without contrast dye.
What the result changes. Pulmonary AVMs found during pregnancy are usually treated from the second trimester onward. With screening done and a delivery planned by a team that knows about HHT, most people with HHT have a normal pregnancy and birth. If you have been screened recently and nothing was found, no additional screening is needed during the pregnancy unless symptoms develop.
Questions worth asking about any of these tests
- What is this test looking for, and what happens if it finds it?
- When should I have this again, and who will remind me?
- Will you send the result to my other clinicians, and can I have a copy?
- Which of my relatives should be screened, and who tells them?
- Is there anything I should not do until this test is done, such as dental work?
That last question matters more than it sounds. Until pulmonary AVMs have been ruled out, anyone over the age of ten with known or suspected HHT should take antibiotics before dental cleanings and other procedures that can introduce bacteria into the bloodstream.
Genetic testing
One test can settle the question for a whole family
Genetic testing can confirm a diagnosis when clinical findings are unclear, and it can identify relatives who need screening before anything has gone wrong. About 90% of cases involve a change in the ENG or ACVRL1 gene, and a further 3% to 5% involve SMAD4.
Testing usually starts with the family member who most clearly has HHT. Once their genetic change is identified, relatives can be tested for that specific change, which is faster, cheaper, and far easier to interpret than testing each person from scratch.
In 10% to 15% of people, no change is found in a known HHT gene. That does not undo a clinical diagnosis, and it does not mean the testing failed. It means the diagnosis continues to rest on clinical findings.
What to do with results
Positive
Screening can begin on schedule, before symptoms appear
Negative
When the family change is known, a relative who tests negative can stop HHT screening
Abnormal
Review any abnormal screening result with a clinician experienced in HHT, ideally at a Center of Excellence
Specific tests and intervals come from the International HHT Guidelines.