Heritable and Genetic Aortic Disease: Marfan, Loeys-Dietz, Bicuspid Aortopathy and Familial Aneurysm

Most aortic aneurysms are degenerative: they develop late in life in people with high blood pressure, a smoking history and atherosclerosis. A smaller but important group is heritable. In these families the aortic wall is weakened by a change in a single gene affecting its connective tissue or smooth muscle, aneurysms appear earlier and often in the ascending aorta or arch, and dissection can occur at diameters that would be considered safe in a degenerative aneurysm. Recognising heritable disease changes how a patient is monitored, when and how they are operated on, and whether their relatives need to be checked.

Who should suspect a heritable aortic condition

• An aortic aneurysm or dissection before the age of about 60, or at any age without the usual risk factors.
• A parent, sibling or child who has had an aortic aneurysm, dissection or sudden unexplained death.
• Aneurysm of the aortic root or ascending aorta, rather than the abdominal aorta, particularly in a younger person.
• A bicuspid aortic valve, which is present in about 1 to 2 per cent of the population and is associated with dilatation of the ascending aorta.
• Physical features associated with connective-tissue syndromes: tall stature with long limbs and fingers, chest wall deformity, lens dislocation or severe short-sightedness, joint hypermobility, stretch marks in unusual places, a bifid uvula or widely spaced eyes, easy bruising or thin translucent skin, or a history of arterial aneurysms or dissections elsewhere in the body.
• Aneurysms or tortuosity of other arteries (carotid, vertebral, iliac, visceral) found on imaging.

Any one of these is a reason to ask the question. Several together make a genetic cause likely.

The main conditions

Marfan syndrome

Caused by changes in the FBN1 gene, which encodes fibrillin-1. Characteristic features include tall stature, long limbs and fingers, lens dislocation and aortic root dilatation. Aortic dissection is the main threat to life, and prophylactic replacement of the aortic root at a defined diameter, together with blood-pressure medication, has transformed life expectancy over the past forty years.

Loeys-Dietz syndrome

Caused by changes in genes of the TGF-beta signalling pathway (TGFBR1, TGFBR2, SMAD3, TGFB2, TGFB3). Features overlap with Marfan syndrome but may include widely spaced eyes, a bifid uvula or cleft palate, and marked tortuosity of arteries. Dissection can occur at smaller aortic diameters and in arteries throughout the body, so surveillance covers the whole arterial tree and surgical thresholds are lower.

Vascular Ehlers-Danlos syndrome

Caused by changes in COL3A1, affecting type III collagen. Tissues are fragile: arteries, bowel and uterus can rupture, and surgery itself carries higher risk, so the approach to intervention is more conservative and reserved for clear indications, with particular care around vascular access.

Familial thoracic aortic aneurysm and dissection

Many families have thoracic aortic disease without any syndromic features. A growing list of genes is implicated (ACTA2, MYH11, MYLK, PRKG1, LOX and others), each with its own pattern of risk; some, such as ACTA2, are also linked to early stroke and coronary disease. In a substantial proportion of families no gene is yet identified, and the diagnosis rests on the family history alone.

Bicuspid aortic valve aortopathy

The commonest heritable aortic condition. The abnormal valve is often accompanied by dilatation of the ascending aorta, independent of how well the valve is working. First-degree relatives have a higher chance of a bicuspid valve themselves and are usually offered an echocardiogram.

Turner syndrome and other associations

Women with Turner syndrome have a raised risk of aortic dissection, and size thresholds are adjusted to body size. Other rarer syndromes and some inflammatory conditions also affect the aorta and are considered when the picture does not fit.

Genetic testing and counselling

Genetic testing is usually done on a blood or saliva sample using a panel of aortic-disease genes, after discussion with a clinical geneticist or genetic counsellor about what a result would and would not mean. A positive result confirms the diagnosis, guides thresholds and allows targeted testing of relatives. A negative result does not exclude heritable disease: if the family history is strong, relatives are screened anyway. Variants of uncertain significance are common and are interpreted with care rather than acted on in isolation. In Singapore, clinical genetics services are available through the public hospitals and selected private providers, and Dr Choong refers for testing and counselling where the clinical picture suggests it.

Surveillance: what is scanned and how often

The aortic root and ascending aorta are measured by echocardiography, with CT or MR angiography used to see the whole aorta and its branches and to confirm measurements. Because the body's measurements matter, diameters are often indexed to height or body surface area, particularly in women and smaller people. After diagnosis, scans are repeated at six months to confirm stability and then usually yearly, more often if the aorta is enlarging or close to a threshold, and the interval is set for the individual rather than from a table. In Loeys-Dietz syndrome and vascular Ehlers-Danlos syndrome the imaging extends from head to pelvis because other arteries are at risk. Surveillance is lifelong, including after surgery, since the remaining aorta stays at risk.

When surgery is considered

For a degenerative ascending aortic aneurysm, repair is usually considered at around 5.5 cm. In heritable disease the thresholds are lower and depend on the condition, the gene, the rate of growth, family history of dissection at small sizes, and plans for pregnancy. Broadly, current international guidance suggests considering root or ascending aortic replacement at about 5 cm in Marfan syndrome, lower (4 to 4.5 cm) in Loeys-Dietz syndrome depending on the gene and family history, and in the range of 5 to 5.5 cm in bicuspid aortopathy, with surgery at smaller diameters when growth exceeds about 3 mm a year, when there are high-risk features, or when a woman is planning a pregnancy. These figures are a starting point for a conversation, not a rule, and they are revised as evidence accumulates. For the descending and thoracoabdominal aorta, thresholds are similarly lowered and open repair is generally preferred.

How treatment differs

Three principles shape treatment in heritable aortic disease. First, medication: beta-blockers and angiotensin receptor blockers slow aortic growth in Marfan syndrome and are used widely across the heritable conditions, together with strict blood-pressure control and avoidance of fluoroquinolone antibiotics and of heavy isometric exertion. Second, open rather than endovascular repair: stent-grafts rely on sealing against healthy aortic wall, and in connective-tissue disease the wall continues to dilate around the device, so open surgical replacement is the standard for elective repair, with endovascular techniques reserved for emergencies, for bridging, or for landing in previously placed surgical grafts. Third, planning for the whole aorta over a lifetime: a person who has a root replacement at 35 may need arch or thoracoabdominal surgery decades later, so each operation is designed with the next in mind. Valve-sparing root replacement, which preserves the patient's own aortic valve and avoids lifelong anticoagulation, is preferred where the valve is suitable. Arch and thoracoabdominal repair follow the principles described on our aortic arch repair and thoracoabdominal aneurysm pages, with cardiothoracic and vascular surgeons working together.

Screening the family

When a heritable condition is diagnosed, first-degree relatives (parents, siblings and children) should be offered assessment. Where a causative gene has been found, relatives can have a targeted genetic test; those who carry the variant enter surveillance and those who do not can usually be reassured. Where no gene has been found, relatives are offered imaging of the aorta, typically an echocardiogram and, depending on the condition, a CT or MR scan, repeated at intervals. Children are screened from an age appropriate to the condition. Screening is one of the most effective things that can be done in heritable aortic disease, because dissection in a relative who did not know they were at risk is the outcome everyone is trying to prevent.

Watch: Aortic Aneurysm Screening and Surveillance · Read: Aortic aneurysm screening for men in Singapore

Living with a heritable aortic condition

Most people with a heritable aortic condition live full lives with surveillance, medication and timely surgery. Practical advice usually covers exercise (moderate aerobic activity is encouraged; heavy weightlifting, competitive contact sport and activities with sudden straining are generally avoided), pregnancy planning (which needs pre-conception assessment, specialist obstetric care and sometimes surgery beforehand), keeping a card or note of the diagnosis for emergency services, and knowing the symptoms of dissection: sudden severe tearing chest or back pain, which needs an immediate 995 call. Family members often find genetic counselling helpful in understanding inheritance, which for most of these conditions is autosomal dominant: each child of an affected parent has a one in two chance of inheriting the variant.

The Montalcino Aortic Consortium

Sudden severe chest, back or abdominal pain, collapse, or a new neurological deficit in someone with a known or suspected aortic condition is an emergency: call 995 in Singapore.

Common questions about heritable aortic disease

My father had an aortic aneurysm. Should I be scanned?

If his aneurysm was in the chest, occurred before about 60, or there is any other family history, yes: an echocardiogram and a discussion of whether genetic testing is appropriate are reasonable. If it was an abdominal aneurysm late in life, a one-off ultrasound of your abdominal aorta from your mid-sixties is the usual advice, earlier if you smoke.

Can a heritable aneurysm be treated with a stent-graft?

Usually not for planned repair. The aortic wall around a stent-graft keeps dilating in connective-tissue disease, so open replacement is preferred. Stent-grafts have a role in emergencies and in specific situations such as sealing within an existing surgical graft.

Does a normal genetic test mean I am safe?

No. Current gene panels explain only a proportion of familial aortic disease. If the family history is convincing, surveillance continues regardless of the test result.

I have a bicuspid aortic valve. Does my family need checking?

Current guidance supports offering first-degree relatives an echocardiogram to look for a bicuspid valve and ascending aortic dilatation, because both run in families.

Can I exercise?

Yes, and you should. Regular moderate aerobic exercise is encouraged. The activities to avoid are those involving heavy straining or sudden surges in blood pressure, such as maximal weightlifting, and collision sports. Your own limits depend on your aortic size and condition, and are worth agreeing explicitly with your specialist.