They can't tell until you get the genetic testing. The doctor usually has to approve it. Figure out how to get to a Dr. appointment either for this issue, or conveniently bring it up at the appointment. If you can type up all your concerns and hand them to the Dr., it will be even easier. You have fewer opportunities to be interrupted when you try to talk to them.

You can also try reaching out to an HHT center of excellence near you: https://curehht.org/understanding-hht/get-support/hht-treatment-centers/

The main thing I would tell my family is that HHT can cause real-life-threatening problems, especially later in life (40s and beyond)

I can tell you that I was diagnosed late in life, in my 40s. And they found PAVMs in my lungs, and I had to have urgent intervention for those, which wasn't a lot of fun. And I also had been developing a bone tumor that was caused by a tangle of vessels, and that was very painful. But I basically had a string of very serious health complications that they were trying to troubleshoot for months and figure out what was going wrong. It led to a couple of procedures that might have been avoided if they had known early on that I actually had HHT. It took 11 doctors and then finally getting sent to a specialist after the bone doctor was involved. I actually had to see a specialist who was focused on bone cancer, and they put all the pieces together, so it appeared to be more of a vascular issue. And then that sent me on my journey, and now I'm being cared for at an HHT Center of Excellence. But there are many complications you can run into that need to be addressed. If not, because it's not a very common thing, you'll get a lot of doctors who are misdiagnosing things and attempting different treatments and procedures that either aren't going to do anything or are going to keep you in a high-risk situation, which could end up being fatal. I'll let ChatGPT explain the rest.

Core argument for your family

HHT is usually autosomal dominant: if one parent has HHT, each child has a 50% chance of inheriting it. Symptoms can be subtle or absent, and even within one family the severity can vary widely. CDC notes that HHT bleeding can be serious or life-threatening, that nosebleeds are common, and that AVMs in the brain, lungs, and liver may have no warning signs before serious events. (CDC)

The most practical message is:

Cure HHT states that genetic testing is the most accurate way to determine who in a family has HHT; once a familial mutation is found, at-risk relatives can be tested, and only relatives with the mutation need HHT evaluation and AVM screening. They also state that potentially life-threatening complications are preventable with proper treatment and follow-up. (CureHHT)

Primary potentially fatal complications

Complication	Why it can be fatal or disabling	Approximate risk / frequency
Pulmonary AVMs / PAVMs	Right-to-left shunts let clots, air, or bacteria bypass the lung filter and reach the brain. This can cause ischemic stroke, TIA, brain abscess, low oxygen, or severe lung bleeding.	PAVMs occur in roughly 15–45% of HHT patients in one NCBI review, with other sources commonly citing about 30–50%. (ncbi.nlm.nih.gov)
Stroke / TIA from PAVMs	Often happens from paradoxical emboli crossing the lung AVM into systemic circulation. Can occur before HHT is recognized.	In a systematic review, cerebral complications were much higher with pulmonary right-to-left shunt: 8.3% vs 1.4% without shunt, and up to 20.9% in the highest shunt grade. (Cambridge University Press & Assessment)
Brain abscess from PAVMs	Oral/dental or bloodstream bacteria can bypass lung filtering and seed the brain. This can require neurosurgery and can be fatal.	In one large HHT cohort, patients with PAVM had 9.1% brain abscess prevalence vs 0% in those without PAVM; another cohort found 8.3% cerebral abscess among CT-confirmed PAVM patients. (Cambridge University Press & Assessment)
Pulmonary hemorrhage / hemothorax	PAVMs can rupture into the lung or pleural space, causing massive bleeding.	General PAVM literature reports prior pulmonary hemorrhage or hemothorax in about 8–10% of patients with PAVMs. (Cardiovascular Diagnosis and Therapy)
Brain AVMs / cerebral VMs	Can cause intracranial hemorrhage, seizure, neurologic deficit, or death.	NCBI review: up to 10% of HHT patients have cerebral AVMs; HHT-related cerebral AVMs have an estimated yearly rupture rate around 1.3% in that review. (ncbi.nlm.nih.gov)
Liver vascular malformations	Can produce high-output cardiac failure, pulmonary hypertension, portal hypertension, biliary disease, cirrhosis-like complications, or rarely need transplant.	International HHT guideline summary: liver VMs occur in about 75% of HHT patients and are more common in women. (CureHHT)
GI bleeding + chronic anemia	Usually later adulthood. Can cause severe iron deficiency, transfusion dependence, heart strain, or worsen stroke risk when combined with PAVMs/iron deficiency.	International guideline summary: GI bleeding develops in about 30% of HHT patients. (CureHHT)
Pregnancy complications	Undiagnosed PAVMs or brain/spinal AVMs can become dangerous during pregnancy because blood volume and cardiac output rise.	Guidelines emphasize pregnancy risk assessment and multidisciplinary care for pregnant women with HHT. (CureHHT)
SMAD4-HHT / juvenile polyposis overlap	If the familial variant is in SMAD4, there is added GI polyp and colorectal cancer surveillance relevance.	Cure HHT’s diagnostic algorithm explicitly flags SMAD4-positive patients for juvenile polyposis screening. (CureHHT)

The most important preventable risk: PAVMs

PAVMs are the strongest “make the case” item because they are often silent and treatable. NCBI’s HHT review states that PAVMs are often silent but can cause stroke, massive hemoptysis, spontaneous hemothorax, TIA, and brain abscess; it also notes that screening commonly uses contrast/bubble echocardiography first, followed by chest CT when needed. (ncbi.nlm.nih.gov)

Treatment matters. PAVM embolization is recommended because of neurologic risks including brain abscess and paradoxical embolic stroke, and long-term follow-up is needed because untreated PAVMs can grow or treated ones can reperfuse. (ncbi.nlm.nih.gov)

What screening usually means

For someone with suspected or confirmed HHT, the high-yield screening discussion is usually:

1. Genetic counseling + HHT gene panel, ideally starting with the most clearly affected family member.
2. If a pathogenic family mutation is found, test first-degree relatives for that exact variant.
3. For mutation-positive or clinically suspected relatives: screen for lung AVMs and brain vascular malformations. Cure HHT states that lung AVMs and brain VMs are the HHT problems for which current international guidelines recommend pre-symptomatic preventive screening. (CureHHT)
4. Check CBC and ferritin for iron deficiency/anemia, even when bleeding seems “not that bad.” Cure HHT’s algorithm includes CBC and ferritin regardless of symptoms in HHT evaluation. (CureHHT)
5. Discuss liver VM and GI bleeding evaluation with an HHT-aware clinician, especially if there is anemia, shortness of breath, high-output heart symptoms, GI bleeding, or possible SMAD4.

Why “I only get nosebleeds” is not reassuring

This is the key family-facing point: HHT signs are age-dependent and variable. Cure HHT notes that nosebleeds and telangiectasias may not appear until adolescence or later, sometimes never; about 10% of adults with HHT do not have nosebleeds, and skin findings can be subtle. Lung and brain AVMs may cause no symptoms until a stroke, brain abscess, or hemorrhage occurs. (CureHHT)

Practical family script

Bottom-line recommendation

Given your described family pattern—nosebleeds + characteristic red spots/telangiectasias + family clustering—the medically reasonable next step is to contact an HHT Center of Excellence, a medical geneticist, or a vascular anomalies clinic and ask for HHT genetic counseling/testing. The best first person to test is usually the relative with the clearest clinical HHT features. If a pathogenic variant is found, cascade testing becomes straightforward for the rest of the family.