Marfan syndrome produces a wide range of symptoms across the body, most notably in the skeleton, heart, and eyes. Because it affects connective tissue, the protein-rich material that holds your body’s structures together, the signs can show up almost anywhere. The condition affects roughly 1 in 3,000 to 5,000 people, and symptoms vary so much from person to person that some cases go undiagnosed for years.
About 75% of people with Marfan syndrome inherit it from a parent. The remaining 25% develop it from a new, spontaneous gene change. In both cases, the culprit is a mutation in the gene responsible for producing fibrillin-1, a protein that gives connective tissue its strength and elasticity. When fibrillin-1 is defective, connective tissue throughout the body becomes weaker and more stretchy than it should be, and a cascade of chemical signaling problems makes the damage worse over time.
Skeletal Signs
The most visible symptoms of Marfan syndrome involve the skeleton. People with the condition tend to be unusually tall and thin, with long arms, legs, fingers, and toes. The arm span often exceeds the person’s height, and the lower body is disproportionately long compared to the upper body. These features can be subtle in childhood and become more obvious during growth spurts.
Two simple physical tests help identify Marfan-related hand and wrist features. The “thumb sign” is positive when the tip of the thumb extends well beyond the edge of the hand when folded across the palm. The “wrist sign” is positive when the thumb and pinky finger overlap when wrapped around the opposite wrist. Neither test alone confirms the diagnosis, but together they carry significant weight in the diagnostic scoring system.
Chest wall deformities are common. The breastbone may push outward (called pectus carinatum) or sink inward (pectus excavatum). Scoliosis, or curvature of the spine, affects many people with Marfan syndrome and can range from mild to severe. Flat feet, reduced ability to fully straighten the elbows, and an overall loose-jointed flexibility are also typical. Certain facial features appear more frequently too: a long, narrow face, deeply set eyes, a small jaw, and downward-slanting eyes.
Heart and Blood Vessel Problems
The most serious symptoms of Marfan syndrome involve the cardiovascular system, particularly the aorta. The aorta is the body’s largest artery, carrying blood from the heart to the rest of the body, and weakened connective tissue makes its walls vulnerable to stretching and bulging.
Aortic root dilation is the hallmark cardiovascular feature. The aorta tends to widen at the point where it exits the heart, like a weak spot in a tire slowly expanding under pressure. This widening, or aneurysm, often produces no symptoms at all in its early stages. That’s what makes it dangerous. As the aorta enlarges, the risk of aortic dissection increases. A dissection occurs when a small tear in the inner wall of the aorta lets blood force its way between the layers of the artery wall. This is a life-threatening emergency that causes sudden, severe chest or back pain.
Mitral valve prolapse is another common finding. The mitral valve, which controls blood flow between two chambers of the heart, can become floppy and leak. This sometimes causes palpitations, shortness of breath, or fatigue, though many people have no symptoms from it at all.
Because aortic problems can develop silently, regular monitoring with echocardiograms (ultrasound imaging of the heart) is essential. Current guidelines recommend yearly heart imaging for children with Marfan syndrome, with more frequent checks if the aorta is already enlarged beyond 45 mm or growing faster than 5 mm per year.
Eye and Vision Symptoms
More than half of people with Marfan syndrome develop a dislocated lens, a condition called ectopia lentis. The tiny fibers that hold the eye’s lens in place are made of the same connective tissue affected by the condition, so the lens can shift out of its normal position. This displacement causes blurred or distorted vision and is one of the strongest clinical indicators of Marfan syndrome.
Nearsightedness and astigmatism are extremely common, often appearing in childhood and progressing more quickly than typical vision changes. The degree of nearsightedness is frequently severe, beyond what’s considered routine.
Marfan syndrome also raises the risk of several other eye conditions: early cataracts, glaucoma (increased pressure inside the eye), misaligned eyes, and retinal detachment. Retinal detachment is the most urgent of these. Warning signs include a sudden burst of floaters (small specks or lines drifting across your vision), flashes of light, or a dark shadow creeping into your peripheral vision. These symptoms require immediate attention because a detached retina can lead to permanent vision loss if not treated quickly.
Skin and Lung Involvement
Unexplained stretch marks are a surprisingly common Marfan symptom. These marks, called striae, appear without the usual triggers like rapid weight gain or pregnancy. They often show up on the shoulders, lower back, and thighs, and result from the skin’s connective tissue being unable to handle normal mechanical stress.
Spontaneous pneumothorax, a sudden collapse of part of the lung, occurs when small air-filled blisters on the lung surface rupture. This causes sharp chest pain and sudden shortness of breath. While pneumothorax can happen to anyone, it’s more common in people with Marfan syndrome due to the underlying tissue weakness. It carries notable weight in the diagnostic scoring system used to confirm the condition.
How Symptoms Vary by Age
Marfan syndrome is present from birth, but many features don’t become apparent until later in childhood or adolescence. Young children might show only subtle skeletal differences, like unusually long fingers or flexible joints, that are easy to overlook. The more serious cardiovascular and eye findings often emerge or worsen during periods of rapid growth.
In adults, the skeletal signs are usually well established, and monitoring shifts toward tracking aortic size and eye health. Some features, like scoliosis and lens dislocation, can progress over time, while others, like chest wall deformities, tend to stabilize after growth is complete. The wide variability means that even within the same family carrying the same mutation, one person may have severe symptoms while a sibling has mild ones.
How Diagnosis Works
No single symptom confirms Marfan syndrome. Diagnosis relies on a formal scoring system called the revised Ghent criteria, which assigns points to different physical findings. A wrist and thumb sign together scores 3 points. A protruding breastbone scores 2. Flat feet, pneumothorax, stretch marks, nearsightedness, and mitral valve prolapse each contribute 1 or 2 points. A total score of 7 or higher, combined with aortic enlargement or lens dislocation, generally confirms the diagnosis.
Genetic testing for fibrillin-1 mutations can support the diagnosis, especially when physical signs are borderline or when there’s no known family history. The test is particularly useful in children, who may not yet show the full range of features. For people with a family history of confirmed Marfan syndrome, fewer physical findings are needed to make the diagnosis, since even mild features carry more significance when the genetic context is already established.