Marfan syndrome affects the body’s connective tissue, which means it can cause problems in the heart and blood vessels, eyes, skeleton, lungs, and the tissue surrounding the spinal cord. It occurs in roughly 1 in 5,000 people. Because connective tissue acts like scaffolding throughout the body, a single genetic mutation ripples outward into many different organ systems, some with life-threatening consequences and others that are manageable with monitoring.
How One Gene Disrupts the Whole Body
Marfan syndrome is caused by a mutation in the gene that produces a protein called fibrillin-1. This protein is a building block of connective tissue, the flexible material that holds organs, blood vessels, bones, and other structures together. When fibrillin-1 is defective, the connective tissue throughout the body is weaker and less able to do its job.
The mutation also triggers a chain reaction involving a growth-signaling molecule called TGF-beta. Normally, fibrillin-1 helps keep TGF-beta locked in an inactive form within the tissue. When fibrillin-1 is faulty, TGF-beta escapes and becomes overactive. This excess signaling drives many of the specific problems seen in Marfan syndrome, from aortic enlargement to lung and heart valve changes. The condition is inherited in an autosomal dominant pattern, meaning only one copy of the mutated gene (from one parent) is enough to cause it.
The Heart and Aorta
Cardiovascular complications are the most dangerous aspect of Marfan syndrome. The aorta, the large artery that carries blood from the heart to the rest of the body, is especially vulnerable. Weakened connective tissue in the aortic wall allows it to gradually stretch and widen, a process called aortic root dilation. This widening typically concentrates at the base of the aorta, near the point where it connects to the heart.
As the aortic root enlarges, two serious risks increase. First, the aortic valve can stop closing properly, allowing blood to leak backward into the heart. Second, the stretched aortic wall can tear, a condition known as aortic dissection. Dissection remains the leading cause of death and serious illness in people with Marfan syndrome. Even after surgical repair of the aortic root, the risk of a repeat dissection further down the aorta is significantly elevated. One large study found that Marfan syndrome increased the odds of recurrent aortic dissection more than eightfold compared to other patients.
Regular imaging of the aorta is a cornerstone of managing the condition. Blood pressure medications that reduce stress on the aortic wall are commonly used, and preventive surgery to replace the weakened section of the aorta is often recommended once the root reaches a certain diameter threshold.
The Eyes
The lens of the eye is held in place by tiny fibers made largely of fibrillin. When those fibers are weakened, the lens can shift out of its normal position, a condition called ectopia lentis, or lens subluxation. This is one of the hallmark features of Marfan syndrome and occurs in an estimated 30% to 72% of affected individuals. The lens typically drifts upward and to the side, though in some cases it can fall into the back of the eye or shift forward.
A displaced lens causes blurred vision and can lead to complications like glaucoma or retinal detachment if left unmanaged. Beyond lens displacement, nearsightedness is far more common in people with Marfan syndrome than in the general population. Between 34% and 44% of patients are nearsighted, and more than half have moderate to high degrees of it due to an elongated eyeball. Regular eye exams starting in childhood are important for catching these changes early.
The Skeleton
Marfan syndrome often produces a recognizable body shape. People tend to be tall and slender with disproportionately long arms, legs, and fingers. The long, thin fingers are sometimes called arachnodactyly. Several other skeletal features are common:
- Pectus excavatum: a sunken or caved-in breastbone, sometimes severe enough to compress the heart and lungs and require surgery.
- Pectus carinatum: a breastbone that protrudes outward.
- Scoliosis: a sideways curvature of the spine, considered clinically significant in Marfan syndrome when it exceeds 20 degrees. Severe scoliosis can affect breathing and posture.
- Flat feet and joint hypermobility: loose, flexible joints that are prone to dislocations and chronic pain.
These skeletal changes are often the first visible signs that prompt a diagnosis, particularly in children and teenagers who are growing rapidly.
The Spine and Nervous System
One of the most overlooked effects of Marfan syndrome is dural ectasia, an enlargement of the membrane (the dura) that surrounds the spinal cord. It occurs in over 90% of people with the condition, primarily in the lower back and sacral area. The expanding dura can thin the surrounding vertebrae and widen the spaces where spinal nerves exit.
Symptoms vary widely. Some people have no noticeable problems, while others experience chronic lower back pain, leg pain, abdominal discomfort, or headaches that worsen when standing. In older patients, dural ectasia can compress nerve roots, leading to numbness, weakness, or even bladder and bowel dysfunction. Because back pain is so common in the general population, dural ectasia in Marfan patients is frequently overlooked or attributed to other causes.
The Lungs
Weakened connective tissue in the lungs raises the risk of spontaneous pneumothorax, where air leaks out of the lung and into the chest cavity, causing part or all of the lung to collapse. This typically happens without any injury or obvious trigger. Symptoms include sudden sharp chest pain and difficulty breathing. Activities that involve rapid pressure changes, like scuba diving or flying in unpressurized aircraft, further increase this risk and are generally advised against.
Pregnancy Risks
Pregnancy places significant extra strain on the cardiovascular system, and for women with Marfan syndrome, this translates to a meaningfully higher risk of aortic dissection. The aorta naturally accommodates increased blood volume during pregnancy, but a weakened aortic wall may not handle the added stress safely.
An aortic root diameter above 40 millimeters before pregnancy is considered a high-risk threshold. In one study of 31 pregnancies in women with Marfan syndrome, two resulted in postpartum aortic dissection (about 6.5%). Among the eight pregnancies where the aortic root was already dilated to 40 millimeters or more, one in eight ended in dissection. Women whose aortic root grew by more than 1 millimeter during pregnancy were significantly more likely to experience dissection later. Close cardiac monitoring throughout pregnancy and the postpartum period is essential.
Exercise and Physical Activity
People with Marfan syndrome are generally advised to avoid activities that spike blood pressure or put sudden mechanical stress on the aorta. Heavy weightlifting, powerlifting, competitive sprinting, and high-intensity interval training all fall into this category. Contact sports like football, rugby, ice hockey, and boxing carry the added danger of direct chest trauma to an already vulnerable aortic wall.
Scuba diving poses a unique risk because of the pressure changes involved and the predisposition to collapsed lungs. Activities with a high fall risk, such as competitive rock climbing, horseback riding, and skateboarding, are also discouraged, especially for patients on blood thinners after aortic surgery.
That said, moderate physical activity is not off the table. Low to moderate intensity aerobic exercise, such as walking, easy cycling, or light swimming, is generally considered safe when heart rate and blood pressure stay within recommended ranges. The goal is to stay active while avoiding the kinds of exertion that create dangerous surges of pressure inside the aorta.
Life Expectancy Today
Seventy years ago, the average life expectancy for someone with Marfan syndrome was around 45. Today, with regular monitoring, medications to protect the aorta, and timely preventive surgery, patients can expect to live into their late 70s. That dramatic improvement is driven almost entirely by better cardiac care, including the ability to surgically replace weakened sections of the aorta before dissection occurs. Early diagnosis and consistent follow-up remain the most important factors in achieving a normal lifespan.