Marfan syndrome !

Marfan syndrome is an inherited connective tissue disorder that makes people tall and loose-jointed and can dislocate the eye's lens and weaken the aorta.

Updated 2026-11-01

Structures involved

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Why it happens

What it is

An autosomal dominant connective tissue disorder caused by mutations in FBN1, the gene for fibrillin-1. It mainly affects the cardiovascular system (aortic root dilation, aneurysm and dissection; mitral valve prolapse), the eyes (lens dislocation) and the skeleton.

Who gets it

Affects about 1 in 5,000 people worldwide, equally in both sexes and all ethnic groups. About a quarter of cases arise from a new mutation with no family history. Features may appear at any age from infancy to adulthood.

Causes

Mutations in the FBN1 gene on chromosome 15, encoding fibrillin-1
Autosomal dominant inheritance with full penetrance but variable expression
At least a quarter of cases are de novo mutations

Risk factors

A parent with Marfan syndrome (50% chance for each child)
Advanced paternal age is linked to de novo mutations

Pathophysiology

Fibrillin-1 forms microfibrils that support elastic fibres and also hold TGF-beta in an inactive state. Defective fibrillin weakens elastic tissue and increases TGF-beta signalling, which degrades the aortic media (cystic medial degeneration). The aortic root dilates and can dissect, the ciliary zonules that hold the lens stretch, and bones overgrow in length with joint laxity.

Symptoms and signs

Tall, thin build with long limbs; arm span greater than height
Long, slender fingers and toes (arachnodactyly); positive thumb and wrist signs
Chest wall deformity: pectus excavatum or carinatum
Scoliosis, flat feet and joint hypermobility
Lens dislocation (ectopia lentis), usually upward, and severe myopia
Stretch marks without weight change; high-arched palate and dental crowding
Mitral valve prolapse: mid-systolic click, sometimes a murmur and palpitations

Diagnosis

Clinical: The revised Ghent criteria combine aortic root dilation (Z-score) and ectopia lentis, a systemic score of skeletal and other findings, family history and FBN1 testing. Examination includes height, arm span, thumb and wrist signs, chest wall, spine and slit-lamp eye examination.
Tests: Genetic testing for FBN1 mutations confirms the diagnosis and allows family testing; ECG for arrhythmias.
Imaging: Echocardiography measuring the aortic root at the sinuses of Valsalva, with serial follow-up; CT or MRI angiography of the whole aorta; slit-lamp examination for lens dislocation; spine X-rays for scoliosis.

Differential diagnosis

Loeys-Dietz syndrome
Vascular Ehlers-Danlos syndrome
Homocystinuria (downward lens dislocation, intellectual disability, thrombosis)
Familial thoracic aortic aneurysm syndromes
Constitutional tall stature and Klinefelter syndrome

Goal of treatment

Slow aortic dilation and prevent aortic dissection and rupture, protect vision and manage skeletal problems, with lifelong follow-up.

Treatment

Medical: Beta-blockers and/or angiotensin II receptor blockers to reduce stress on the aortic wall and slow root dilation.
Follow-up: Regular echocardiography and aortic imaging, eye examinations and spine checks; screening of first-degree relatives.
Surgical: Prophylactic aortic root replacement (valve-sparing when possible) when the diameter or growth rate reaches surgical thresholds; mitral valve repair, lens surgery or scoliosis surgery when needed.
Lifestyle: Activity guidance usually limits contact sports, isometric exercise and heavy lifting; pregnancy is planned with cardiology and high-risk obstetrics.

Complications

Aortic root aneurysm, aortic dissection and rupture (main cause of death)
Aortic regurgitation and mitral regurgitation with heart failure
Arrhythmias and infective endocarditis
Ectopia lentis, retinal detachment, glaucoma and early cataract
Spontaneous pneumothorax
Scoliosis and dural ectasia

Prognosis

Untreated, life expectancy was much shorter because of aortic dissection. With early diagnosis, medical therapy, imaging follow-up and timely aortic surgery, many people reach a near-normal lifespan.

Prevention

Genetic counselling for affected people and families
Screening of first-degree relatives with clinical examination, echocardiography and genetic testing
Regular surveillance to prevent dissection

Test yourself

Think of the answer, then tap the question to see it.

Which gene and protein are defective in Marfan syndrome?

The FBN1 gene, encoding fibrillin-1, a component of elastic microfibrils.

What is the inheritance pattern of Marfan syndrome?

Autosomal dominant, with about a quarter of cases arising from new mutations.

What is the main cause of death in Marfan syndrome?

Aortic root dilation leading to aortic dissection or rupture.

In which direction does the lens usually dislocate in Marfan syndrome, versus homocystinuria?

Upward (superotemporal) in Marfan; downward (inferonasal) in homocystinuria.

Which drug classes are used to slow aortic dilation in Marfan syndrome?

Beta-blockers and angiotensin II receptor blockers.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: Marfan syndrome (MedlinePlus Genetics (U.S. National Library of Medicine), 2024).

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Representative model, for educational purposes only.

Ascending aorta highlighted on the Durgical 3D model