What genes are usually tested for HHT?

ENG, ACVRL1, and SMAD4 are the core genes on many clinical panels. Some panels also include additional vascular-malformation genes or deletion/duplication analysis.

Does a negative result rule out HHT?

No. If the clinical picture is strong, HHT can still be present even when a panel is negative or inconclusive.

Why does SMAD4 matter?

SMAD4 can overlap with juvenile polyposis, so the result may change colon and GI surveillance questions in addition to HHT screening.

What screening may follow a positive result?

Clinicians often consider AVM screening in the lungs and brain, plus anemia and iron evaluation if bleeding is ongoing.

Should children or siblings be tested?

If there is a known familial pathogenic variant, cascade testing can identify relatives who should be screened earlier.

Is HHT just nosebleeds?

No. Nosebleeds are common, but the bigger issue is whether silent AVMs or chronic bleeding are present and need follow-up.

HHT genetic testing | AVMs, anemia, and family follow-up

Short answer

Hereditary hemorrhagic telangiectasia, or HHT, is an autosomal dominant vascular disorder that can cause recurrent nosebleeds, telangiectasias, iron deficiency anemia, and arteriovenous malformations in the lungs, brain, liver, or gastrointestinal tract. Genetic testing can confirm a familial cause in genes such as ENG, ACVRL1, or SMAD4, but it works best when it is paired with Curaçao clinical criteria and a plan for AVM screening.

What testing can clarify

Question	How testing helps	Limit
Is this likely HHT?	A pathogenic variant can support a clinical diagnosis when the family pattern fits.	A negative result does not fully exclude HHT if the clinical picture is strong.
Which relatives need targeted testing?	A known familial variant makes cascade testing straightforward.	Relatives may still need age-appropriate clinical screening and counseling.
Does SMAD4 change the plan?	SMAD4 can point to overlap with juvenile polyposis and colon surveillance questions.	That interpretation is best handled with a genetics or HHT specialist.
What else should be checked?	Testing helps decide who needs AVM screening, CBC, and iron studies.	It does not replace imaging or bleeding management.

When testing helps

HHT testing is most useful when the result will change what happens next. That usually means a person has recurrent epistaxis plus telangiectasias, a visceral AVM, or a known family variant. In those settings, a positive result can speed up screening and make family follow-up more precise.

Testing can also help when clinical signs are incomplete. Younger relatives may not yet have obvious nosebleeds or telangiectasias, but a targeted familial variant can still identify who should be monitored more closely.

When a negative result does not settle the diagnosis

HHT remains a clinical diagnosis as well as a genetic one. If someone has recurrent nosebleeds, visible telangiectasias, an AVM, or a strong family history, a negative panel does not automatically rule out HHT. Some families have variants that are hard to detect, and some people meet clinical criteria before a gene result is found.

That is why the strongest interpretation pairs genetics with the Curaçao criteria, family history, and organ-specific screening. A VUS is also not a diagnosis by itself.

Why screening matters

The main reason HHT testing matters is prevention. AVMs can be silent until they cause stroke, brain abscess, hypoxemia, or bleeding. If HHT is confirmed or strongly suspected, clinicians often consider lung, brain, and liver screening, plus iron deficiency evaluation if bleeding is ongoing.

SMAD4 results can also change GI follow-up because of juvenile polyposis overlap. That is a good example of why HHT testing is not just about a yes-or-no label.

What follow-up may include

Follow-up for HHT often includes genetic counseling, AVM screening, and a plan for CBC and ferritin or iron studies if bleeding is causing anemia. If a familial variant is known, cascade testing can help relatives get the right screening sooner.

Questions to ask

Which genes are included, and does the test cover deletion/duplication analysis?
Is there a known family variant that makes targeted testing better than a broad panel?
What AVM screening is recommended if the result is positive or the clinical picture is strong?
Should I also get a CBC and ferritin/iron studies for possible chronic blood loss?
Does a SMAD4 result change colon or GI surveillance planning?

Bottom line: HHT testing is most useful when it helps protect the person and relatives with the right screening plan, not when it is treated like a stand-alone answer.

FAQ

What genes are usually tested for HHT?: ENG, ACVRL1, and SMAD4 are the core genes on many clinical panels. Some panels also include additional vascular-malformation genes or deletion/duplication analysis.
Does a negative result rule out HHT?: No. If the clinical picture is strong, HHT can still be present even when a panel is negative or inconclusive.
Why does SMAD4 matter?: SMAD4 can overlap with juvenile polyposis, so the result may change colon and GI surveillance questions in addition to HHT screening.
What screening may follow a positive result?: Clinicians often consider AVM screening in the lungs and brain, plus anemia and iron evaluation if bleeding is ongoing.
Should children or siblings be tested?: If there is a known familial pathogenic variant, cascade testing can identify relatives who should be screened earlier.
Is HHT just nosebleeds?: No. Nosebleeds are common, but the bigger issue is whether silent AVMs or chronic bleeding are present and need follow-up.

Bottom line: HHT testing matters most when it turns a vague bleeding story into a concrete screening and family-follow-up plan.

HHT genetic testing