Are Aneurysms Hereditary? Causes and Risk Factors

Aneurysms do run in families, but the inheritance pattern is not as straightforward as inheriting eye color or blood type. Having a first-degree relative with an aneurysm roughly doubles to triples your own risk compared to someone with no family history, depending on the type of aneurysm and how many relatives are affected. Still, most aneurysms arise from a tangle of genetic susceptibility, lifestyle habits, and sheer mechanical wear on blood vessel walls. The hereditary piece is real and clinically meaningful, but it is only part of the story.

How Much Does Family History Actually Matter?

For brain aneurysms (also called intracranial aneurysms), family history is the single strongest known risk factor. Compared with the general population, first-degree relatives of someone who has had a ruptured brain aneurysm face a three- to seven-fold higher risk of the same event. The background prevalence of brain aneurysms in the general population sits around 2 to 3 percent. That number climbs to about 4 percent in people with one affected first-degree relative and roughly 8 percent in those with two affected relatives.¹ In a dedicated screening study of families with multiple affected members, nearly one in five participants turned out to harbor at least one aneurysm on imaging, and women were roughly twice as likely as men to be affected.²

The pattern is similar for aortic aneurysms. A study using whole-aorta imaging in relatives of patients with abdominal aortic aneurysm found a 28-fold increase in thoracic aortic aneurysms among relatives compared with the age-adjusted general population. Thoracic dilations showed up in about 18 percent of the relatives screened. Many of these showed up even when the original patient had no idea that other family members were affected.³ That finding is striking because it suggests aneurysm risk can cluster in families even without anyone being aware of it.

Single-Gene Conditions That Cause Aneurysms

A minority of aneurysms trace to a single identifiable genetic mutation. These cases tend to be the most dramatic and often show up at younger ages. About 20 percent of patients who develop a thoracic aortic dissection have an underlying genetic cause that can be identified through genetic testing.⁴ The best-known of these conditions include Marfan syndrome, vascular Ehlers-Danlos syndrome, Loeys-Dietz syndrome, and autosomal dominant polycystic kidney disease.

Marfan syndrome is caused by mutations in the gene for fibrillin-1, a protein that acts as scaffolding in connective tissue. When that scaffolding is defective, the aortic wall progressively weakens and dilates. Aortic aneurysm is the leading cause of early death in untreated Marfan patients.⁵ Research has shown that the altered fibrillin-1 protein makes the tiny fibers in the aortic wall less stiff than they should be, predisposing the vessel to gradual ballooning over time.⁶

Vascular Ehlers-Danlos syndrome stems from mutations in a different gene, COL3A1, which encodes a type of collagen. This condition carries a higher rate of arterial events than Marfan syndrome. In one comparative study, arterial events occurred in roughly 21 percent of individuals with COL3A1 mutations, compared with about 1.5 percent of those with fibrillin-1 mutations. Vascular Ehlers-Danlos also tends to produce these events earlier in life.⁷ The same study examined several genes in the Loeys-Dietz family of mutations, which involve the TGF-beta signaling pathway and cause aneurysms along with skeletal abnormalities and blood vessel tortuosity. The arterial event rates for these genes fell between the extremes of Ehlers-Danlos and Marfan.

Autosomal dominant polycystic kidney disease is a condition most people associate with kidney problems, but it also substantially raises the risk of brain aneurysms. Patients with this condition develop aneurysms much more frequently than the general population, and the risk climbs further in those who also have a family history of brain aneurysm.⁸ One older estimate put the prevalence of brain aneurysms in polycystic kidney disease patients as high as 40 percent among those with a positive family history for cerebral aneurysm, though that number likely reflects a selected population.⁹ The link appears to involve dysfunction of the cells lining blood vessels, triggered by the same genetic defect that causes the kidney cysts.¹⁰

When No Single Gene Is Responsible

The single-gene conditions get a lot of attention, but they account for only a fraction of all aneurysms. Most brain aneurysms, for instance, arise in people who do not have Marfan syndrome, Ehlers-Danlos, or polycystic kidney disease. For these people, the genetic contribution appears to come from many common gene variants, each nudging risk up by a small amount.

A large genome-wide study comparing over 10,000 brain-aneurysm cases with more than 300,000 controls identified 17 regions of the genome associated with risk, 11 of them newly discovered. That study confirmed a polygenic architecture, meaning the disease involves many small genetic effects rather than one big one, and the identified variants explained more than half of the estimated heritability of brain aneurysms.¹¹ An earlier meta-analysis covering more than 116,000 individuals pinpointed variants near genes involved in cell-cycle regulation and blood-vessel signaling, including the CDKN2B region on chromosome 9, the SOX17 region on chromosome 8, and the endothelin receptor gene on chromosome 4.¹² These same regions have turned up in Japanese populations, reinforcing that the genetic architecture crosses ethnic boundaries.¹³

Here is the practical upshot: inheriting a handful of these common variants makes your blood vessel walls slightly more vulnerable, but it does not guarantee you will develop an aneurysm. Most people who carry these variants never do. The risk variants matter most when they pile up alongside environmental triggers.

The Heritability Gap and Epigenetics

Even after accounting for all the gene variants discovered so far, there is a sizable chunk of familial risk that remains unexplained. Genetic variations account for an estimated 41 percent of the heritability of brain aneurysms, which leaves the majority of the risk unaccounted for by DNA sequence alone.¹⁴ That same review noted that individuals with hereditary connective-tissue disorders have brain-aneurysm rates of 10 to 20 percent and rupture rates of 8 to 25 percent, far exceeding the general population. But for people without those specific diagnoses, environmental exposures may alter how genes are read and expressed, a process called epigenetic modification. Changes in DNA methylation and in small RNA molecules that regulate gene activity have been linked to the behavior of cells lining blood vessels, including their ability to proliferate, migrate, and resist damage.

What this means in plain terms is that a family’s shared aneurysm risk might not be entirely in the DNA they pass down. Shared exposures, shared habits like smoking, and even shared metabolic tendencies can leave chemical marks on genes that influence vascular health across generations. This is an active area of research and one reason why genetic testing alone cannot yet fully predict who will or will not develop an aneurysm.

Smoking, Alcohol, and Other Modifiable Risk Factors

Smoking is the most potent modifiable risk factor for brain aneurysm rupture. Current smokers have roughly double the odds of presenting with a ruptured aneurysm compared with people who have never smoked, and even former smokers carry an elevated risk. The association scales with dose: more years of smoking and more packs per day both independently increase the likelihood of rupture.¹⁵ For aortic aneurysms, smoking is also a major initiating factor, promoting chronic inflammation and weakening the vessel wall.¹⁶

Heavy alcohol use compounds the problem. Risky alcohol consumption has been independently associated with about double the odds of a brain aneurysm rupturing and a roughly threefold increase in the odds of clinically severe hemorrhagic stroke, even after adjusting for other risk factors. Interestingly, the same study found no significant association between cannabis use and aneurysm rupture.¹⁷

High blood pressure, the other major player, wears down artery walls over time and is a well-established contributor to both the formation and rupture of aneurysms. Hypertension is somewhat heritable itself, which adds another layer to the question of whether family clustering of aneurysms reflects shared genes, shared lifestyle, or both.

When Genes and Smoking Combine

One of the more revealing findings in aneurysm research is evidence that genetic predisposition and smoking interact in a way that is worse than you would expect from simply adding the two risks together. A study compared the odds of hemorrhagic stroke from a ruptured brain aneurysm across four groups: nonsmokers with no family history, nonsmokers with family history, smokers without family history, and smokers with family history. Having a family history alone roughly two-and-a-half-fold increased the odds. Smoking alone tripled them. But the combination of both pushed the odds to about six-fold, more than the sum of the two individual risks.¹⁸

This type of interaction, where the combined risk exceeds what you would predict by just stacking up separate risk factors, is sometimes described as synergistic. For someone with a family history of aneurysms, it means that smoking is an especially dangerous gamble compared with the general population. Quitting smoking does not erase genetic risk, but it removes the factor that appears to amplify it most sharply.

Why Women Are More Affected

Brain aneurysms are more common in women than in men, and ruptured brain aneurysms strike women disproportionately, especially after menopause. The reasons appear to involve estrogen. A shorter reproductive lifespan (fewer years between first menstruation and menopause) was linked to a two-fold higher risk of aneurysm rupture. Early menopause, specifically before age 45, was associated with a similarly elevated risk.¹⁹

Animal research helps explain why. In mice, estrogen deficiency promoted aneurysm rupture at dramatically higher rates: 47 percent of estrogen-deficient mice experienced rupture, compared with only 7 percent of controls. When those estrogen-deficient mice received estrogen supplementation, the rupture rate dropped back to about 6 percent. The mechanism involves an immune pathway where the loss of estrogen triggers certain inflammatory cells that weaken vessel walls.²⁰ This is not a genetic factor in the traditional hereditary sense, but it is a biological one that affects half the population and is worth considering alongside purely genetic risk.

How Vessel Anatomy Plays a Role

Not all aneurysm risk is about what is in your blood or your genes. The physical shape and geometry of your blood vessels contribute too, and that geometry is partly inherited. Research has shown that the angles and dimensions of cerebral artery branch points in people with brain aneurysms do not follow the optimal patterns seen in people without aneurysms. In particular, the angle at major branching points tends to be significantly larger in aneurysm patients, which creates areas of abnormal mechanical stress on the vessel wall.²¹

Think of it like water flowing through plumbing. If a pipe bends at a wide angle, the water hits the bend differently, concentrating force on certain spots. Over decades, that concentrated force can weaken the vessel wall at the branch point. Because basic vascular geometry is partially determined by genetics, this is another subtle way heredity influences aneurysm risk without involving a “disease gene” per se.

What Happens Inside the Vessel Wall

Regardless of whether the initial vulnerability is genetic, environmental, or structural, the downstream damage to the vessel wall involves a common set of biological players. Enzymes called matrix metalloproteinases chew through the structural proteins that give artery walls their strength and elasticity. In both abdominal aortic aneurysms and aortic dissections, two of these enzymes are consistently found at elevated levels in diseased tissue.¹⁶ Inflammation, oxidative stress, and high blood pressure all ramp up the activity of these enzymes, creating a feedback loop: damage attracts inflammatory cells, which release more of the enzymes, which causes more damage.²²

This shared destruction pathway is why so many different risk factors, from genetic mutations to smoking to high blood pressure, can all lead to the same end result. The initial trigger differs, but the final common path is a weakened vessel wall that gradually bulges outward.

Who Should Be Screened

Given the hereditary component, a practical question arises: should people with a family history of aneurysms get imaging to look for them? The answer depends on how strong the family history is and what type of aneurysm is involved.

For brain aneurysms, modeling studies support screening for people with two or more first-degree relatives who have had a ruptured brain aneurysm. Some evidence also suggests screening is worthwhile when only one first-degree relative is affected. Patients with polycystic kidney disease are also considered screening candidates given their elevated risk.²³ Screening typically involves a non-invasive brain MRI, and a screening study estimated an aneurysm prevalence of about 10 percent in the at-risk screened population.²⁴

For abdominal aortic aneurysms, professional guidelines have traditionally focused on men aged 65 and older with a smoking history. But research increasingly supports broadening those criteria to include anyone with a family history of aortic aneurysm, along with women and older adults who fall outside the standard guidelines but carry other risk factors.²⁵ Abdominal aortic screening uses a simple ultrasound, and finding an aneurysm before it ruptures can be lifesaving because rupture carries a very high mortality rate.

Screening does come with trade-offs. Discovering a small, stable aneurysm means living with the knowledge of it, undergoing follow-up imaging, and sometimes facing a decision about whether to intervene surgically on something that may never cause a problem. But for people in the higher-risk categories, the benefit of catching a dangerous aneurysm early generally outweighs these downsides.

Genetic Testing and Its Limits

Genetic testing can identify mutations in the single-gene conditions discussed earlier. If you have a known family history of Marfan syndrome, vascular Ehlers-Danlos syndrome, Loeys-Dietz syndrome, or polycystic kidney disease, genetic testing can confirm whether you carry the mutation and guide clinical surveillance. For thoracic aortic aneurysms in particular, roughly one in five cases has an identifiable genetic cause.⁴

For the more common, polygenic forms of aneurysm risk, genetic testing is far less useful at this stage. The common variants identified so far each carry a very small individual effect, and no validated polygenic risk score exists yet that would be accurate enough to guide clinical decisions for brain or abdominal aortic aneurysms. Genes associated with abdominal aortic aneurysm have been identified, but they have not yet been incorporated into clinical recommendations. A family history conversation with your doctor remains a better practical predictor than any commercially available genetic test for the majority of aneurysm types.

Abdominal Versus Brain Versus Thoracic Aneurysms

It is worth noting that “aneurysm” is a broad term covering bulges in different blood vessels, and the genetic and environmental contributions are not identical across types. Brain aneurysms tend to form at branch points in the arteries of the brain, where blood flow dynamics and vessel geometry matter a great deal. Abdominal aortic aneurysms are strongly linked to smoking, atherosclerosis, and age, and occur overwhelmingly in men over 65. Thoracic aortic aneurysms are the most likely to have a clear genetic cause, especially in younger patients.

The family-history signal is strongest for brain aneurysms and thoracic aortic aneurysms. For abdominal aortic aneurysms, the genetic contribution is real but harder to untangle from shared lifestyle factors like smoking. What ties them together is the shared biology of arterial wall degradation, but the relative importance of genes versus environment shifts depending on which vessel is involved and how old the person is when the aneurysm develops. Younger patients with aneurysms deserve particularly close attention for possible hereditary causes, since the usual wear-and-tear explanations are less plausible when someone develops a bulging artery in their 30s or 40s.