Marfan's syndrome

Authors, Journal, Affiliations, Type, DOI

• Daniel P Judge MD, Harry C Dietz MD
• The Lancet 2005; 366: 1965–76
• Division of Cardiology, Department of Medicine (Judge); McKusick-Nathans Institute of Genetic Medicine (Dietz), Johns Hopkins University, Baltimore
• Review article (Seminar)
• DOI: https://doi.org/10.1016/S0140-6736(05)67789-6

Overview

Marfan syndrome is a systemic connective tissue disorder caused by mutations in FBN1 (fibrillin-1), with cardinal manifestations of proximal aortic aneurysm, ectopia lentis, and long-bone overgrowth. This landmark 2005 Lancet Seminar by two of the leading experts in the field reviews epidemiology, multisystem clinical manifestations, the revised Ghent diagnostic criteria, and management. A paradigm-shifting molecular insight is that fibrillin-1 deficiency leads to dysregulated TGF-β signalling — not merely structural tissue weakness — implicating TGF-β antagonists as potential therapeutic targets. Aortic dissection remains the leading cause of premature death, managed with beta-blockers and elective surgical root replacement at ≥5 cm diameter.

Keywords

Marfan syndrome, FBN1, fibrillin-1, aortic aneurysm, TGF-beta, connective tissue disorder, ectopia lentis, beta-blockers, Ghent criteria, Loeys-Dietz syndrome

Key Takeaways

Epidemiology

• Incidence ~2–3 per 10,000 individuals; worldwide distribution, no sex predilection
• ~25% of cases are sporadic (de novo FBN1 mutations); family history not always present
• Historical life expectancy was ~2/3 of normal (cardiovascular death in >90%); with modern surgery, nearly normal life expectancy is achievable
• Increased incidence in tall athletes (basketball, volleyball); echocardiographic screening warranted

Diagnostic Criteria (Revised Ghent 1996)

• Requires major criteria in ≥2 organ systems + involvement of a 3rd (index case without family history)
• Organ systems: skeletal, ocular, cardiovascular, pulmonary, skin/integument, dura, family/genetic history
• Skeletal major criterion: ≥4 of: pectus carinatum, pectus excavatum requiring surgery, arm span:height ratio >1.05, wrist/thumb signs, scoliosis ≥20°, reduced elbow extension, pes planus, protrusio acetabulae
• Ocular major criterion: ectopia lentis (present in ~60% of patients)
• Cardiovascular major criteria: dilatation of ascending aorta at sinuses of Valsalva ± AR; or dissection of ascending aorta
• Dural major criterion: lumbosacral dural ectasia (present in 63–92%)
• Family/genetic major criteria: FBN1 mutation known to cause MFS, or first-degree relative independently meeting criteria

Clinical Manifestations

Cardiovascular

• Mitral valve prolapse in >50% (mean age 11.9 years); 25% progress to mitral regurgitation; twice as many women progress as men
• Mitral insufficiency is the leading cause of morbidity/mortality in young children with severe MFS
• Aortic root aneurysm begins at sinuses of Valsalva; compare to age-dependent nomograms
• Two most important dissection risk determinants: maximal aortic diameter AND family history of dissection
• Aortic dissection almost invariably begins at aortic root (type A); can propagate to type I or remain type II (DeBakey)
• Dilated cardiomyopathy beyond valve regurgitation occurs at increased prevalence; may implicate fibrillin-1 role in cardiac ventricles
• Prolonged QT interval: increased prevalence in MFS (multiple ECG surveys)
• Ventricular dysrhythmia described in children

Skeletal

• Dolichostenomelia (long-bone overgrowth), arachnodactyly, Walker-Murdoch wrist sign, Steinberg thumb sign
• Scoliosis, pectus deformity (carinatum or excavatum), pes planus, protrusio acetabuli
• Dolicocephaly, high-arched palate, retrognathia, malar flattening, downward-slanting palpebral fissures

Ocular

• Ectopia lentis ~60%; also myopia, flat cornea, retinal detachment risk, early cataracts/glaucoma

Pulmonary

• Spontaneous pneumothorax in 4–15%
• Restrictive pattern from pectus/scoliosis; distal airspace widening/blebs

Skin

• Striae atrophicae in ~2/3 (at non-typical sites: anterior shoulder, lower back)
• Inguinal hernias; increased surgical/recurrent hernia risk

Dura

• Lumbosacral dural ectasia in 63–92%; often asymptomatic; assessed by CT or MRI; major criterion

Molecular Genetics and Pathophysiology

• FBN1 gene: chromosome 15q21.1; 65 exons spanning 235 kb; encodes 350 kDa glycoprotein
• Most mutations: within 47 tandemly repeated EGF-like domains; disrupt cysteine residues or calcium-binding → proteolytic degradation
• Dominance mechanism: initially thought to be dominant-negative; evidence now supports haploinsufficiency as critical threshold
  • Transgenic mutant FBN1 with 2 normal alleles insufficient to cause vascular phenotype
  • Null heterozygous mice show similar aortic architecture changes as missense heterozygotes
  • Adding wild-type allele rescued aortic phenotype in C1039G mice
• TGF-β dysregulation: fibrillin-1 microfibrils sequester TGF-β in the extracellular matrix; loss of fibrillin-1 → excess free TGF-β activity
  • Demonstrated in pulmonary (alveolar septation failure rescued by TGF-β neutralising antibody in Fbn1-deficient mice)
  • Myxomatous mitral valve disease in fibrillin-1-deficient mice prevented by TGF-β neutralising antibody
  • Aortic wall and dura also show elevated TGF-β activity
• Loeys-Dietz/TGFBR2 link: mutations in TGFBR1 or TGFBR2 paradoxically enhance aortic wall TGF-β signalling despite receptor loss-of-function — same downstream pathway as fibrillin-1 deficiency
• Over 500 FBN1 mutations catalogued; >90% private; significant phenotypic variation even within families with identical mutations

Differential Diagnosis

• MASS phenotype: MFS features not meeting diagnostic criteria (mitral, aortic, skin, skeletal); can be stable; vs emerging MFS in young individuals
• Loeys-Dietz syndrome: TGFBR1/TGFBR2 mutations; overlaps with MFS but adds hypertelorism, bifid uvula, arterial tortuosity, diffuse aneurysms at smaller sizes — more aggressive vascular disease; essential distinction for individualised management
• Homocystinuria: tall stature + ectopia lentis but NO aortic enlargement; autosomal recessive; mental retardation, thromboembolism; elevated plasma homocystine distinguishes
• Familial thoracic aortic aneurysm: dominant; aortic disease without systemic features; reduced penetrance; same management principles as MFS
• BAV with ascending aortic aneurysm: dilatation beyond sinotubular junction; no systemic CT features
• Shprintzen-Goldberg syndrome: FBN1 mutations (some); craniosynostosis + Marfanoid habitus; rare vascular disease
• Ehlers-Danlos type IV: MVP + aneurysm/rupture of medium/large arteries; joint hypermobility; atrophic scars

Management

Monitoring

• Yearly transthoracic echocardiography: serial aortic root measurements + sinotubular junction + ascending aorta
• CT angiography or MRI if limited TTE views (e.g., pectus deformity)
• Yearly comprehensive ophthalmological assessment

Medical Treatment

• Beta-blockers (standard of care): decrease dP/dT and reduce aortic shear stress; negative inotropic and chronotropic effects
  • Only randomised trial (Shores et al. 1994, n=70): propranolol → fewer primary endpoints (aortic regurgitation/dissection/surgery/CHF/death: 5 vs 9); normalised aortic dilatation rate 0.023 vs 0.084/yr (p<0.001)
  • Titrate to heart rate <100 bpm during exercise or 30% rise in systolic time interval
  • ~10–20% intolerant (asthma, depression, fatigue)
• ACE inhibitor (enalapril): non-randomised comparison (Yetman 2005, n=58); enalapril appeared superior to beta-blockers but significant methodological limitations (non-randomised; dose not titrated)
• Verapamil: alternative if beta-blocker intolerant; non-randomised evidence only
• Goal is to slow (not stop) aortic growth; annual imaging monitoring mandatory despite treatment

Surgery

• Elective aortic root replacement when maximum diameter reaches 5 cm (adult); earlier for >1 cm/yr growth or family history of early dissection
• Bentall procedure (1968): composite valve-graft replacement — elective mortality 1.5%; urgent 2.6%; emergency 11.7% (Gott 1999, n=675)
• Valve-sparing surgery (David procedure): preserves native aortic valve; avoids lifelong warfarin; excellent short-term results; preferred in eligible patients, especially women anticipating pregnancy
• No randomised trial of Bentall vs valve-sparing; long-term valve-sparing data pending (as of 2005)

Lifestyle

• Avoid contact sports, competitive athletics, isometric exercise (risk of acute dissection)
• Encourage moderate aerobic activity for skeletal/cardiovascular/psychosocial health
• Pregnancy: aortic root <4 cm = low risk; valve-sparing procedure preferred before pregnancy; warfarin contraindicated (fetal demise/embryopathy); LMWH safer but risk of prosthetic valve thrombosis; close obstetric + cardiac monitoring mandatory

New Developments (as of 2005)

• Paradigm shift: MFS is postnatal acquired tissue pathology from regulatory (TGF-β) not purely structural failure
• Most manifestations (except ectopia lentis) implicate dysregulated TGF-β activity
• Mouse models suggest postnatal modification possible with TGF-β antagonists

Limitations of the Document

• 2005 review — predates revised Ghent 2010 criteria (which added aortic Z-score thresholds and incorporated FBN1 testing more formally, eliminating FBN1-negative Marfan diagnoses)
• Predates losartan/TGF-β antagonist clinical trials (COMPARE trial published 2013 — losartan not superior to beta-blocker)
• Single RCT of beta-blockers (n=70, Shores 1994) is small and uses open-label design; no contemporary-GDMT era trial
• Valve-sparing surgical data were short-term only at time of writing
• Loeys-Dietz syndrome was only just being characterised (Loeys et al. 2005 published concurrently)
• Genotype-phenotype correlations limited; >90% private mutations make molecular prediction difficult

Key Concepts Mentioned

• concepts/Marfan-Syndrome — primary subject of this source
• entities/FBN1 — causative gene; molecular genetics
• entities/Loeys-Dietz-Syndrome — important differential diagnosis, shared TGF-β pathway

Key Entities Mentioned

• entities/FBN1 — primary mutant gene in MFS
• entities/Loeys-Dietz-Syndrome — new syndrome described concurrently (TGFBR1/TGFBR2)
• entities/Bicuspid-Aortic-Valve — differential diagnosis (BAV with aortic aneurysm)

Wiki Pages Updated

• wiki/sources/marfan-lancet-2005.md — created (this file)
• wiki/concepts/Marfan-Syndrome.md — created
• wiki/entities/FBN1.md — created
• wiki/entities/Loeys-Dietz-Syndrome.md — created
• wiki/sourceindex.md — updated
• wiki/wikiindex.md — updated