The essentials

Marfan syndrome is an inherited condition of the connective tissue that mainly affects the aorta, the eyes and the skeleton. It is diagnosed with a physical exam, a heart ultrasound (echocardiogram) and an eye exam, often confirmed by an FBN1 genetic test. Ordinary blood tests cannot show it. With regular aortic scans, medicines and planned surgery, most people now reach a near-normal lifespan.

What is Marfan syndrome, at a glance?

Connective tissue holds the body together. In Marfan syndrome, a change in the FBN1 gene weakens a protein called fibrillin-1, so tissues stretch too easily, especially the wall of the aorta, the main artery leaving the heart[1]. Intelligence is not affected[3].

Marfan syndrome in brief
TopicKey facts
Other namesMFS, Marfan's syndrome[1]
How commonAbout 1 in 5,000 people, in all ethnic groups and both sexes[1][3]
CauseA variant in the FBN1 gene; inherited from a parent in about 3 out of 4 cases, new in the child in about 1 out of 4[2]
Key testsEchocardiogram with an aortic root Z-score, eye exam with dilated pupils, FBN1 genetic test; a homocysteine blood test only to rule out a look-alike[4][9]
Main dangerWidening of the aortic root (an aortic aneurysm) that can lead to a tear (aortic dissection)[6]
OutlookWith proper treatment, many people have a normal lifespan[1]

What are the signs and symptoms of Marfan syndrome?

No one has every feature, and the signs can differ even within one family[3]. Some are present at birth, others appear in the teenage years or in adulthood[2].

  • Common Heart and aorta: about 9 in 10 people diagnosed have heart or blood vessel problems, most often a widened aortic root[3]. It usually causes no symptoms, which is why scans matter. A floppy mitral valve (prolapse) can cause palpitations or breathlessness[1].
  • Common Body build: tall and slender, long arms, legs and fingers, an arm span longer than height, loose joints, a sunken or protruding chest, a curved spine (scoliosis), flat feet, crowded teeth[1].
  • Common Eyes: most people are nearsighted[1]. A lens that has slipped out of place (ectopia lentis) is one of the two key signs of the syndrome[4].
  • Possible Stretch marks without weight change, back or leg pain from a widened sac around the spinal cord (dural ectasia), early cataract and glaucoma[1].
  • Rare but serious: aortic dissection or a collapsed lung (spontaneous pneumothorax)[1][3]; a detached retina is also more frequent than usual.

Being tall and thin is not enough to suspect it. What matters is a combination of features, or a relative with the syndrome or with an aortic tear at a young age.

When should I see a doctor?

When to see a doctor

  • Emergency: call 911 for sudden, severe pain in the chest, back or belly, often described as tearing or ripping, even if it moves or eases; fainting; sudden chest pain with shortness of breath (possible collapsed lung)[3]. Say that you have Marfan syndrome.
  • Within 24 to 48 hours for new flashes of light, a shower of floaters or a shadow over part of your vision, which can mean a detached retina, or a sudden drop in vision. If your vision is going fast, go the same day.
  • At your next appointment if you notice several of the body features above, if a relative has Marfan syndrome or had an aortic dissection, or if you plan a pregnancy[6].

What causes Marfan syndrome, and is it inherited?

Fibrillin-1 forms thin fibres that give tissues strength and stretch, and it also holds back a growth signal called TGF-beta. When FBN1 does not work properly, both functions fail: tissues become weaker and some bones grow too long[1][3].

The syndrome is autosomal dominant: one changed copy of the gene is enough. A person with Marfan syndrome has a 1 in 2 chance of passing it on with each pregnancy[2]. About 1 in 4 people are the first in their family, because the change appeared in an egg or sperm cell[2]. Nothing the parents did caused it.

Several conditions look similar and also weaken the aorta. Telling them apart changes the follow-up, so doctors keep them in mind:

  • Loeys-Dietz syndrome (genes TGFBR1, TGFBR2, SMAD3, TGFB2, TGFB3): widely spaced eyes, a split uvula, twisted arteries and aneurysms beyond the aorta[8].
  • Vascular Ehlers-Danlos syndrome (mostly gene COL3A1): easy bruising and unpredictable tearing of blood vessels and organs[11].
  • Classic homocystinuria (gene CBS): tall build and a dislocated lens as in Marfan syndrome, but also blood clots, brittle bones and sometimes learning difficulties[9].

How is Marfan syndrome diagnosed, and which tests are used?

Doctors use the revised Ghent criteria (2010). They rely on two key features, a widened aortic root and a dislocated lens, plus the FBN1 result, a "systemic score" and the family history[4]. Without a family history, both key features together are enough; if one is missing, a proven FBN1 variant or a systemic score of 7 points or more is needed[4][5].

The tests behind a Marfan diagnosis and what each one shows
TestWhat it looks forHow to read it
Echocardiogram (heart ultrasound)Diameter of the aortic root at the sinuses of Valsalva, heart valvesConverted to a Z-score for age and body size; 2 or more means widened[5]
Eye exam with dilated pupils (slit lamp)Position of the lens, nearsightedness, retinaAny lens dislocation counts as a key feature[4]
Physical exam (systemic score)Wrist and thumb signs, chest shape, flat feet, arm span, scoliosis, stretch marks and othersPoints out of 20; 7 or more supports the diagnosis[4]
FBN1 genetic test (blood or saliva)A disease-causing change in the geneConfirms the diagnosis in more than 95% of people with the syndrome[4]
Gene panel for aortic diseaseFBN1 plus Loeys-Dietz and vascular Ehlers-Danlos genesReasonable when the picture is unclear or there is no lens dislocation[6]
CT or MRI of the aortaThe whole aorta, when ultrasound does not see it wellAlso used after aortic surgery[6]
Total homocysteine blood testHomocystinuria, when a lens is dislocatedNormal: usually below 10 to 15 µmol/L; untreated homocystinuria: often above 100 µmol/L[9]

So, apart from homocysteine in selected cases, routine blood work plays no role in making the diagnosis. A normal blood count or cholesterol panel says nothing either way. The genetic test uses a blood sample, but it reads DNA, not a level in the blood.

How do you read an echocardiogram and genetic test report for Marfan syndrome?

Fictitious example of an echocardiogram and genetic test summary (United States format), man aged 24, 6 ft 4 in
TestResultReferenceFlag
Aortic root, sinuses of Valsalva (TTE)4.3 cm; Z-score +3.4Z-score below +2H
Sinotubular junction3.0 cm; Z-score +1.4Z-score below +2
Aortic valveTrace regurgitationNone or trace
Mitral valveMild prolapse, mild regurgitationNo prolapseAbnormal
FBN1 sequencing and deletion analysisHeterozygous pathogenic variantNo pathogenic variantAbnormal
Total homocysteine, plasma9 µmol/LBelow 15 µmol/L
  1. Z-score +3.4: the aortic root is 3.4 standard deviations above the average for a person of this age and body size. The same 4.3 cm can be within normal limits for an older, larger person, which is why the Z-score, not the centimeters, says "widened"[5].
  2. Sinotubular junction normal: in Marfan syndrome the widening usually starts at the root, the segment closest to the heart[3].
  3. Mitral prolapse: common in the syndrome; a small leak usually needs only follow-up[3].
  4. FBN1 "pathogenic variant": with a Z-score of 2 or more, this is enough for the diagnosis, even without a lens problem[5]. A "variant of uncertain significance" (VUS) is not a diagnosis: ask whether testing relatives could clarify it.
  5. Homocysteine normal: homocystinuria is unlikely. The H flag is a letter, not just a color; genetic results are written in words.

"Z-score", "sinotubular junction", "pathogenic variant"? BloodSense explains each line of your report in plain words, so you arrive at the cardiology or genetics visit with the right questions.

Get my report explained

How is Marfan syndrome monitored over time?

Follow-up is mostly imaging, not blood tests[6]:

  • Echocardiogram at diagnosis, again 6 months later to measure the growth rate, then every year if the aorta is stable[6].
  • CT or MRI if the ultrasound does not show the aorta well; after aortic root surgery, yearly at first, then every other year if stable[6].
  • Eye exams with an ophthalmologist, for the lens, retina, eye pressure and cataract[1][2].
  • Spine checks, especially in growing children, for scoliosis[2].
  • Blood pressure at every visit; compare with a blood pressure chart by age and treat high blood pressure, which strains the aorta[6].
  • Blood tests only for a specific reason, such as troponin and D-dimer in the emergency room, when chest pain could be a dissection or a heart attack[6].

How is Marfan syndrome treated?

There is no cure, but treatment prevents the main complication. No doses are given here.

  • Medicines to slow the aorta: a beta blocker or an angiotensin receptor blocker (ARB) at the highest tolerated dose is recommended, and both together are reasonable[6]. In a pooled analysis of 7 trials (1,442 patients), ARBs roughly halved the yearly growth of the aortic root Z-score, and beta blockers did about as well[7].
  • Planned surgery: replacing the aortic root is recommended at 5.0 cm, and reasonable from 4.5 cm when the risk is higher: growth of 0.3 cm a year or more, a family history of dissection, severe valve leak or a wish for pregnancy[6]. Planned surgery prevents dissection and improves survival[6].
  • Spine and chest: close monitoring of scoliosis, a back brace in growing children, surgery for curves of 40 degrees or more or for a sunken chest that presses on the lungs[2].
  • Medicines to discuss: fluoroquinolone antibiotics have been linked to aortic aneurysm and dissection; tell every prescriber about your diagnosis[6].

Can you live a normal life with Marfan syndrome?

Yes, for most people. Many have a normal lifespan with treatment[1], and nearly half of people with the syndrome may not yet know they have it[3], which is why screening relatives matters.

  • Exercise: regular light to moderate aerobic activity is encouraged once blood pressure is controlled; avoid heavy weightlifting, straining with held breath, burst efforts and collision sports[6].
  • Family: parents, brothers, sisters and children should have an echocardiogram and, if the variant is known, a targeted genetic test[6].
  • Pregnancy: see a cardiologist and a genetic counselor before conceiving. Dissection risk is about 1% when the root is below 4.0 cm and much higher above 4.5 cm, where surgery before pregnancy is recommended[6].
  • Emergencies: carry a card or phone note that says "Marfan syndrome, risk of aortic dissection"[3].

Questions to ask your doctor

  1. What is my aortic root Z-score, and how fast has it changed since the last scan?
  2. At what size would you advise surgery for me?
  3. Was my genetic result "pathogenic" or "uncertain", and which relatives should be tested?
  4. Which sports and medicines should I avoid?

Frequently asked questions

Can a blood test detect Marfan syndrome?

Not a routine one. The only blood-based test that can confirm it is the FBN1 genetic test, which reads DNA from the sample[4]. A homocysteine test can rule out homocystinuria, a look-alike[9].

Can you have Marfan syndrome with a normal genetic test?

Yes, rarely. A small share of people who meet the clinical criteria have no FBN1 variant found, and the diagnosis then rests on the aorta, the eyes, the systemic score and the family history[4].

Can a baby be tested before birth?

When the family variant is known, yes: a sample from the placenta (CVS) can be tested during pregnancy, and embryos can be tested in IVF (preimplantation genetic diagnosis)[2]. Genetic counseling before pregnancy is recommended[6].

  1. MedlinePlus Genetics. Marfan syndrome. US National Library of Medicine. medlineplus.gov (accessed November 13, 2026)
  2. NHS. Marfan syndrome (overview, diagnosis and treatment pages). nhs.uk (accessed November 13, 2026)
  3. The Marfan Foundation. Marfan syndrome. marfan.org (accessed November 13, 2026)
  4. Loeys BL, Dietz HC, Braverman AC, et al. The revised Ghent nosology for the Marfan syndrome. J Med Genet. 2010;47(7):476-485. doi:10.1136/jmg.2009.072785 (accessed November 13, 2026)
  5. The Marfan Foundation. Diagnostic criteria: the 2010 revised Ghent nosology. marfan.org (accessed November 13, 2026)
  6. Isselbacher EM, Preventza O, Hamilton Black J, et al. 2022 ACC/AHA Guideline for the Diagnosis and Management of Aortic Disease. Circulation. 2022;146(24):e334-e482. doi:10.1161/CIR.0000000000001106 (accessed November 13, 2026)
  7. Pitcher A, Spata E, Emberson J, et al. Angiotensin receptor blockers and β blockers in Marfan syndrome: an individual patient data meta-analysis of randomised trials. Lancet. 2022;400(10355):822-831. doi:10.1016/S0140-6736(22)01534-3 (accessed November 13, 2026)
  8. MedlinePlus Genetics. Loeys-Dietz syndrome. US National Library of Medicine. medlineplus.gov (accessed November 13, 2026)
  9. Morris AAM, Kožich V, Santra S, et al. Guidelines for the diagnosis and management of cystathionine beta-synthase deficiency. J Inherit Metab Dis. 2017;40(1):49-74. doi:10.1007/s10545-016-9979-0 (accessed November 13, 2026)
  10. MedlinePlus. Homocysteine test. US National Library of Medicine. medlineplus.gov (accessed November 13, 2026)
  11. MedlinePlus Genetics. Ehlers-Danlos syndrome. US National Library of Medicine. medlineplus.gov (accessed November 13, 2026)
  12. MedlinePlus Genetics. What is genetic discrimination? US National Library of Medicine. medlineplus.gov (accessed November 13, 2026)

This page is general information. It does not replace the advice of a cardiologist or a genetics team, who interpret aortic measurements and genetic results together with your examination and family history.