Marfan Syndrome

Definition

Marfan syndrome (MFS) is an autosomal dominant systemic disorder of connective tissue caused by heterozygous loss-of-function mutations in FBN1 (fibrillin-1 gene, chromosome 15q21.1). Cardinal features are proximal aortic aneurysm/dissection, ectopia lentis, and long-bone overgrowth. The molecular mechanism involves both haploinsufficiency of fibrillin-1 and dysregulated TGF-β signalling as a downstream consequence.

Key Concepts

Epidemiology

• Incidence ~2–3 per 10,000 (or 1:5,000–1:10,000 by broader estimates); no sex predilection; worldwide distribution sources/marfan-lancet-2005 (high) sources/marfan-naturerc-2010 (medium)
• Actual population prevalence (6 studies): 1.5–17.2 per 100,000 — all far below the widely cited 1:5,000 estimate and below 1:2,000 (European rare disease threshold); studies include Northern Ireland 1.5/100,000 (Lynas), China schoolchildren 17.2/100,000 (Sun), Scotland 6.8/100,000 (Gray), Denmark 4.6/100,000 (Fuchs), Hamburg adults 7/100,000 (Rybczynski), Taiwan 10.2/100,000 (Chiu 2014); wide range reflects different diagnostic criteria used + substantial under-diagnosis sources/marfan-ghent-aclingene-2015 (high)
• ~25% are de novo mutations; family history absent in 1 in 4 cases sources/marfan-lancet-2005 (high)
• High penetrance (nearly all carriers develop the disease); marked phenotypic heterogeneity between and within families sources/marfan-naturerc-2010 (medium)
• Before surgical aortic root replacement era: life expectancy ~2/3 normal; cardiovascular death >90%; after: nearly normal life expectancy sources/marfan-lancet-2005 (high)
• Tall stature → increased incidence in basketball and volleyball athletes; echocardiographic screening recommended sources/marfan-lancet-2005 (high)
• Diagnostic delay — major clinical problem (EURORDIS survey, 682 MFS families, 18 European countries): median 2 years from first symptoms to diagnosis; 25% wait ≥4.5 years; 38% consulted >5 physicians before diagnosis; 25% received an incorrect diagnosis before MFS; delay led to inappropriate treatment in 81%; 72% reported the delay responsible for detrimental consequences sources/marfan-ghent-aclingene-2015 (high)

Pathogenesis

• FBN1: 65 exons, 235 kb; encodes 350 kDa glycoprotein fibrillin-1; >1,500 mutations now described (as of 2015; was >1,000 in 2010, ~500 in 2005); most in EGF-like domains disrupting cysteine residues or Ca²⁺ binding → proteolytic degradation sources/marfan-lancet-2005 (high) sources/marfan-naturerc-2010 (medium) sources/marfan-ghent-aclingene-2015 (high)
• Exon 24–32 genotype correlation: mutations in exons 24–32 tend to predict more severe phenotype; neonatal Marfan syndrome (most severe form) almost always maps here sources/marfan-naturerc-2010 (medium)
• Haploinsufficiency (not dominant-negative) is the critical threshold mechanism: transgenic mutant FBN1 with 2 normal alleles insufficient for vascular phenotype; wild-type allele addition rescues aortic phenotype sources/marfan-lancet-2005 (high)
• TGF-β dysregulation (central mechanism): fibrillin-1-rich microfibrils sequester latent TGF-β (as large latent complex: TGF-β + LAP + LTBP) in ECM; mechanical/pH/cytokine stimuli → protease-mediated TGF-β release → receptor activation; deficiency → failed sequestration → excess TGF-β signalling sources/marfan-lancet-2005 (high) sources/marfan-naturerc-2010 (medium)
• TGF-β dysregulation demonstrated in: lungs (alveolar septation failure — Neptune 2003), mitral valves (myxomatous change — Ng 2004), aortic wall (Habashi 2006 — see below), dura sources/marfan-lancet-2005 (high)
• Losartan in mouse models (Habashi 2006, Science): losartan (AT1 receptor antagonist) prevents aortic aneurysm in fibrillin-1-deficient mice — reduced elastic fibre fragmentation + slower aortic root growth; provided preclinical rationale for human trials sources/marfan-naturerc-2010 (medium)
• Canonical vs non-canonical TGFβ pathways: TGFβ signals through TGFβRI/II to activate either the canonical (R-Smad/Smad2/3) or non-canonical (MAPK/ERK) pathway; non-canonical ERK pathway is the major contributor to aortic disease (Holm 2011 Science — ERK inhibitor reduces TAA in C1039G/+ mice) sources/marfan-cv-clingene-2015 (high)
• AT1R/AT2R balance: AT1R drives harmful ERK1/2 signalling; AT2R inhibits AT1R-mediated ERK1/2 (protective); AT2R deletion in C1039G/+ mice exacerbates TAA with increased ERK1/2 but unchanged R-Smad sources/marfan-cv-clingene-2015 (high)
• DCM as primary cardiomyopathy (Cook 2014 JCI): DCM in fibrillin-1-deficient mice is a primary cardiac disorder due to impaired cardiomyocyte mechanosignaling from fibrillin-1-deficient ECM; fibrillin-1 functions as force-transmitting molecule; DCM is an exception to broad anti-TGFβ therapy sources/marfan-cv-clingene-2015 (high)
• Two-pathway TAA model: (1) hemodynamic load on structurally impaired tissue → AT1R/integrin mechanosensor activation → MMP + TGFβ gene upregulation; (2) adaptive remodelling → excessive latent TGFβ activation from microfibril-deficient ECM → unopposed feed-forward maladaptive remodelling loop; both pathways converge; secondary immune-inflammatory response further exacerbates TAA sources/marfan-cv-clingene-2015 (high)
• GxxPG fibrillin-1 fragment: proteolytic product of fibrillin-1 containing GXXPG elastin-binding protein fragment; stimulates macrophage chemotaxis + MMP upregulation; neutralising antibodies reduced inflammation and TAA in mgR/mgR mice sources/marfan-cv-clingene-2015 (high)
• Cystic medial necrosis: fragmentation/disorganisation of elastic lamina → basophilic glucosaminoglycan material (Erdheim 1920s); nonspecific — seen in all thoracic aortic aneurysms, not pathognomonic sources/marfan-naturerc-2010 (medium)
• Apoptosis of vascular smooth muscle cells (via angiotensin II type 2 receptor) may contribute to remodelling process sources/marfan-naturerc-2010 (medium)
• Microfibrils required for postnatal maintenance of elastic fibres (not initial assembly); loss → abnormal vascular smooth-muscle cell synthetic repertoire → MMP-2/9 upregulation → exaggerated elastolysis + increased hyaluronan content sources/marfan-lancet-2005 (high) sources/marfan-naturerc-2010 (medium)

Clinical Manifestations

Cardiovascular Manifestations

• Aortic root aneurysm (sinuses of Valsalva): most life-threatening manifestation; growth from utero; age-dependent nomograms required for interpretation sources/marfan-lancet-2005 (high)
• Two key dissection risk determinants: maximal aortic diameter + family history of dissection at small size sources/marfan-lancet-2005 (high)
• Aortic stiffness as independent risk factor: relative increase in vascular elastance is an independent risk factor for dissection, beyond diameter alone (Nollen 2004 Eur Heart J) sources/marfan-cv-clingene-2015 (high)
• Elastic fiber fragmentation before dilation: significant elastic lamellae fragmentation occurs throughout all aortic segments (including descending and infra-renal aorta) before detectable vessel dilation in mgR/mgR mice; implies structural disease precedes dimensional changes sources/marfan-cv-clingene-2015 (high)
• AAA risk after TAA repair: prior TAA surgery is an independent risk factor for abdominal aortic aneurysm; careful surveillance distal to repair site is essential sources/marfan-cv-clingene-2015 (high)
• Aortic dissection nearly always type A (originates at root); DeBakey type I (propagates) or type II (isolated) sources/marfan-lancet-2005 (high)
• Mitral valve prolapse in ~75% (updated: Pyeritz 1983; vs 1.3% in general population); 25% progress to mitral regurgitation by adulthood; 2× more women than men progress; leading cause of morbidity/mortality in children with severe MFS sources/marfan-lancet-2005 (high) sources/marfan-cv-clingene-2015 (high)
• Dilated cardiomyopathy beyond valve regurgitation occurs with increased prevalence (may reflect fibrillin-1 role in cardiac ventricles) sources/marfan-lancet-2005 (high)
• Prolonged QT interval and ventricular dysrhythmia reported in children; supraventricular arrhythmias (AF) in association with mitral disease sources/marfan-lancet-2005 (high)
• Pulmonary artery dilatation (minor criterion if age <40); descending/abdominal aortic dilatation/dissection (minor criterion if age <50) sources/marfan-lancet-2005 (high)

Skeletal Manifestations

• Dolichostenomelia (arm span:height >1.05), arachnodactyly, Walker-Murdoch wrist sign, Steinberg thumb sign sources/marfan-lancet-2005 (high)
• Scoliosis ≥20°, pectus carinatum/excavatum, pes planus, protrusio acetabuli sources/marfan-lancet-2005 (high)
• Craniofacial: dolicocephaly, high-arched palate, retrognathia, malar flattening, downward-slanting palpebral fissures sources/marfan-lancet-2005 (high)

Ocular Manifestations

• Ectopia lentis in ~60%; prompts further MFS evaluation sources/marfan-lancet-2005 (high)
• Also: early severe myopia, flat cornea, retinal detachment, early cataracts/glaucoma sources/marfan-lancet-2005 (high)

Pulmonary and Other Manifestations

• Spontaneous pneumothorax in 4–15% (apical blebs); restrictive lung disease from pectus/scoliosis sources/marfan-lancet-2005 (high)
• Striae atrophicae in ~2/3 (at non-typical sites); inguinal hernias sources/marfan-lancet-2005 (high)
• Lumbosacral dural ectasia in 63–92%; often asymptomatic; major diagnostic criterion; assessed by CT/MRI sources/marfan-lancet-2005 (high)

Diagnosis

Revised Ghent Nosology (2010)

Historical context: The Berlin 1988 nosology (Beighton) was the first international consensus; Ghent-1 (De Paepe 1996) introduced genetic data and assessed major/minor criteria across 6 organ systems (skeletal, ocular, cardiovascular, pulmonary, skin/integument, dura). The current Ghent-2 nosology (Loeys 2010) supersedes both — ~90% concordance with Ghent-1 retrospectively, with beneficial 10% discordance (earlier diagnosis in children; avoids overdiagnosis in adults without CV risk) sources/marfan-lancet-2005 (high) sources/marfan-ghent-aclingene-2015 (high)

International landmark consensus (Loeys et al., J Med Genet 2010). Two cardinal features anchor the nosology: aortic root aneurysm (Z-score ≥2) and ectopia lentis. sources/marfan-ghent-jmg-2010 (very high)

Without family history — 4 diagnostic routes to MFS:

1. Ao (Z≥2) + ectopia lentis = MFS
2. Ao (Z≥2) + bona fide FBN1 mutation = MFS
3. Ao (Z≥2) + systemic score ≥7 = MFS (after excluding SGS/LDS/vEDS features)
4. EL + FBN1 mutation previously associated with aortic disease in a proband = MFS

• EL + FBN1 not linked to aortic disease = Ectopia Lentis Syndrome (ELS)
• Ao Z<2 + systemic score ≥5 (≥1 skeletal feature) without EL = MASS phenotype
• MVP + Ao Z<2 + systemic score <5 without EL = MVPS

With family history of MFS — 3 diagnostic routes:

• EL + family history = MFS
• Systemic score ≥7 + family history = MFS
• Ao Z≥2 (if ≥20 years) or Z≥3 (if <20 years) + family history = MFS

Systemic score (max 20 pts; ≥7 = systemic involvement): sources/marfan-ghent-jmg-2010 (very high)

• Wrist + thumb sign: 3 pts (wrist or thumb only: 1 pt); pectus carinatum: 2 pts (excavatum/asymmetry: 1 pt); hindfoot deformity: 2 pts (pes planus: 1 pt)
• Spontaneous pneumothorax: 2 pts; dural ectasia: 2 pts; protrusio acetabuli: 2 pts
• Reduced US/LS ratio + increased arm/height ratio (no severe scoliosis): 1 pt; scoliosis or thoracolumbar kyphosis: 1 pt; reduced elbow extension (≤170°): 1 pt
• Facial features (3 of 5: dolichocephaly, enophthalmos, downslanting palpebral fissures, malar hypoplasia, retrognathia): 1 pt; skin striae: 1 pt; myopia >3 diopters: 1 pt; MVP: 1 pt
• Removed from 1996 criteria due to lack of specificity: joint hypermobility, highly arched palate, herniae

Children (<20 years): sources/marfan-ghent-jmg-2010 (very high)

• Insufficient systemic features (<7) + borderline aortic root (Z<3) + no FBN1 mutation: "non-specific connective tissue disorder" until follow-up shows Z≥3
• FBN1 confirmed but aortic root still below Z=3: "potential MFS"
• Aortic threshold with family history in children: Z≥3 (vs Z≥2 for adults)
• ELS cannot be formally diagnosed before age 20

Evidence base and limitations:

• FBN1 detectable in up to 97% of patients meeting criteria; greater reliance on aortic Z-scores and FBN1 mutation status compared with 1996 nosology sources/marfan-cv-clingene-2015 (high)
• No external reference standard: No single clinical or genetic feature proves or excludes MFS with LR >10 or LR <0.1; formal sensitivity, specificity, and accuracy cannot be calculated for any version of the Ghent nosology — diagnosis requires clinical judgement sources/marfan-ghent-aclingene-2015 (high)
• Diagnostic triggers and confirmation rates (n=329 adults referred for suspected MFS): Highest MFS confirmation rates: childhood MFS diagnosis (88%), eye manifestations (83%), family history of Marfan features (52%), aortic aneurysm/dissection (50%). Lowest: pneumothorax (43%), skeletal features (30%), tissue weakness/hypermobility (14%), nonaortic cardiovascular findings (0%); tall stature and scoliosis are common referral reasons but rarely confirm MFS sources/marfan-ghent-aclingene-2015 (high)
• Seven-signs adult screening tool (Sheikhzadeh 2012): Pre-test probability tool for MFS in general population adults; ectopia lentis = 4 pts; family history of MFS = 2 pts; 1 pt each for: previous thoracic aortic surgery, pectus excavatum, wrist and thumb sign, previous pneumothorax, skin striae; Low risk (≤1 pt), Moderate (>1–3.5 pts), High (>3.5 pts) sources/marfan-ghent-aclingene-2015 (high)

Echocardiographic Assessment

• Long-axis parasternal projection; measurements at end-diastole, leading-edge technique (ASE standard) sources/marfan-naturerc-2010 (medium)
• Four levels: aortic annulus (hinge points), sinuses of Valsalva, sinotubular junction, tubular ascending aorta; measurements strictly perpendicular to aortic long axis sources/marfan-naturerc-2010 (medium)
• Compare to age- and BSA-adjusted nomograms (Roman 1989); z-score >2 = dilation sources/marfan-naturerc-2010 (medium)
• BSA calibration issue: Z-scores calculated using Roman 1989 nomograms underestimate aortic root dilatation in patients with large body surface area — directly relevant since MFS patients tend to be tall with large BSA; improved normograms (Devereux and others) subsequently published; clinicians should verify which normograms are used and whether validated for tall patients sources/marfan-ghent-aclingene-2015 (high)
• Caveat: nomograms poorly validated in patients >95th percentile height (most MFS patients); non-linear relationship → assuming linearity overestimates upper normal limit sources/marfan-naturerc-2010 (medium)
• Pediatric screening: sinus of Valsalva:aortic annulus ratio ≥1.45 → sensitivity 0.82, specificity 1.00 for aortic dilation; loses utility if annulus is also dilated sources/marfan-naturerc-2010 (medium)
• CT/MRI if poor TTE window or for complete aortic assessment

Dural Ectasia Assessment

• CT or MRI lumbosacral column required
• Qualitative: S1 dural sac diameter > L4 = not tapering → suggestive
• Quantitative (Oosterhof): dural sac ratio (dural sac diameter ÷ AP vertebral diameter) at each level L1–S1
  • L3 ratio >0.47 or S1 ratio >0.57 → 95% sensitivity, 98% specificity for dural ectasia sources/marfan-naturerc-2010 (medium)
  • Most useful criterion combination: S1 > L4 AND abnormal ratio at L5 + S1 sources/marfan-naturerc-2010 (medium)
  • Validated in pediatric and adolescent populations

Genetic Testing

• FBN1 mutations detectable in 90–95% of patients meeting Ghent 1996 criteria sources/marfan-naturerc-2010 (medium)
• Clinical utility limited: >90% private mutations; no rapid/efficient molecular test; ~10% of classic MFS mutations missed by conventional screening sources/marfan-lancet-2005 (high)
• Best uses: (1) insufficient clinical criteria at initial exam; (2) presymptomatic diagnosis in families with known mutation; (3) atypical phenotype to rule out LDS or other CT disorders sources/marfan-naturerc-2010 (medium)
• Diagnosis remains largely clinical; molecular diagnosis is an appendix to clinical evaluation sources/marfan-lancet-2005 (high) sources/marfan-naturerc-2010 (medium)

Differential Diagnosis

• entities/Loeys-Dietz-Syndrome: TGFBR1/TGFBR2 mutations; overlaps MFS but adds hypertelorism, bifid uvula, arterial tortuosity, diffuse aneurysms dissecting at smaller diameters; distinction essential for management sources/marfan-lancet-2005 (high)
  • LDS Type I: craniofacial involvement (cleft palate, hypertelorism, craniosynostosis) — linked to more severe arterial disease sources/marfan-naturerc-2010 (medium)
  • LDS Type II: isolated bifid uvula, no craniofacial involvement — relatively less aggressive but still more aggressive than MFS sources/marfan-naturerc-2010 (medium)
  • Arteriopathy not confined to ascending aorta: abdominal aorta, pelvic, intracranial vessels may all be affected sources/marfan-naturerc-2010 (medium)
  • Surgery recommended at smaller aortic dimensions than MFS thresholds; strict follow-up essential sources/marfan-naturerc-2010 (medium)
  • Valvular disease in ~20–30% of LDS patients (Attias 2009 Circulation); cerebral artery involvement further complicates surgical planning sources/marfan-cv-clingene-2015 (high)
• MASS phenotype: MVP + mild non-progressive aortic dilation + skin/skeletal; ≥2 systems required; may carry FBN1 mutation (fibrillinopathy); aortic dilation always mild and non-progressive sources/marfan-lancet-2005 (high) sources/marfan-naturerc-2010 (medium)
• Homocystinuria: ectopia lentis + tall stature but NO aortic enlargement; autosomal recessive; elevated plasma homocystine diagnostic sources/marfan-lancet-2005 (high)
• Familial non-syndromic TAAD: 11–19% of surgical aortic aneurysm patients have direct relatives with aneurysms; autosomal dominant with reduced penetrance; 4 causative genes identified: TGFBR2 (TAAD2), TGFBR1 (TAAD5), ACTA2/smooth muscle α2-actin (TAAD4 — possibly most common), MYH11/smooth muscle βMHC (TAAD-PDA); family screening indicated sources/marfan-naturerc-2010 (medium)
• BAV with ascending aortic aneurysm: dilatation beyond sinotubular junction; no systemic CT disorder features sources/marfan-lancet-2005 (high)
• Shprintzen-Goldberg syndrome (SGS): craniosynostosis + Marfanoid habitus + intellectual disability; now known to be caused by heterozygous SKI mutations (TGFβ repressor) — NOT FBN1 as originally reported (Doyle 2012 Nat Genet); augmented Smad2/3 + ERK1 baseline activity; consistent with gain-of-function TGFβ upregulation sources/marfan-lancet-2005 (high) sources/marfan-cv-clingene-2015 (high)
• entities/Aneurysm-Osteoarthritis-Syndrome (AOS): SMAD3 inactivating mutations; aortic aneurysms + arterial tortuosity + early-onset osteoarthritis + LDS-like craniofacial features; paradoxical TGFβ upregulation despite LOF; van de Laar 2011 Nat Genet sources/marfan-cv-clingene-2015 (high)
• Syndromic TAA (sTAA): TGFB2 mutations → paradoxical TGFβ1 upregulation + increased R-Smad; medial degeneration + fibrosis; Lindsay 2012 Nat Genet sources/marfan-cv-clingene-2015 (high)

Management

Medical Management

• Beta-blockers (standard of care): reduce aortic dP/dT; negative inotropic + chronotropic effects sources/marfan-lancet-2005 (high)
  • Only RCT (Shores 1994, n=70, open-label): propranolol → fewer primary endpoints (5 vs 9); normalised aortic dilatation 0.023 vs 0.084/yr (p<0.001) sources/marfan-lancet-2005 (high)
  • Titrate to HR <100 bpm during exercise; dose is variable, not predicted by bodyweight
  • 10–20% intolerant; calcium channel blockers (verapamil) as second-line alternative sources/marfan-lancet-2005 (high) sources/marfan-cv-clingene-2015 (high)
  • No benefit of propranolol on aortic diameter or tissue architecture in mgR/mgR mice at hypotensive doses sources/marfan-cv-clingene-2015 (high)
• Losartan (ARB) — human data: Groenink 2013 (Eur Heart J) RCT: losartan vs no additional treatment (control 70% on beta-blocker); significantly reduced aortic root diameter and rate of dilation over 3 years; no significant difference in ascending aorta diameter or surgical endpoints; modest benefit post-proximal aortic reconstruction sources/marfan-cv-clingene-2015 (high)
• Atenolol vs losartan — definitive trial (Lacro 2014, NEJM): Randomised double-blind trial (Pediatric Heart Network) in children and young adults with MFS: atenolol vs losartan — equally beneficial effects; no significant differences in aortic root growth rate or side effects; choice between the two agents based on individual patient factors and tolerability; definitively refutes prior suggestion of losartan superiority from mouse model data and earlier small trials sources/marfan-ghent-aclingene-2015 (high)
• Fibrillin-1 fragment biomarkers: circulating fibrillin-1 fragment concentrations associated with TAA frequency and dissection risk; under development to complement aortic diameter measurements (Marshall 2013 Circ Res) sources/marfan-cv-clingene-2015 (high)

Surgical Management

• Elective aortic root replacement at 5 cm diameter (adult); earlier for >1 cm/yr growth or family history of early dissection sources/marfan-lancet-2005 (high) sources/marfan-ghent-jmg-2010 (very high)
• Other factors informing surgical timing: severity of AR, MVP disease, ventricular dysfunction, pregnancy planning, desire for valve-sparing procedure sources/marfan-ghent-jmg-2010 (very high)
• Bentall procedure (composite valve-graft): elective mortality 1.5%; urgent 2.6%; emergency 11.7% sources/marfan-lancet-2005 (high)
• Valve-sparing surgery (David procedure): preserves native valve; avoids lifelong warfarin; now preferred in eligible patients, especially pre-pregnancy women sources/marfan-lancet-2005 (high)
• No randomised trial Bentall vs valve-sparing (as of 2005) sources/marfan-lancet-2005 (high)
• Type B dissection (~10% of all MFS dissections): originating in descending thoracic aorta; surgical indications — intractable pain, limb/organ ischaemia, diameter >5.5 cm, rapid aortic growth; open surgery preferred over endovascular stenting (weakened connective tissue may not tolerate stent radial pressure; adjacent aorta may also be diseased) sources/marfan-ghent-jmg-2010 (very high)
• Pregnancy: increased CV risk; majority of aortic complications in 3rd trimester or early postpartum; risk markedly increased if aortic root >4.0 cm at conception sources/marfan-ghent-jmg-2010 (very high)

Surveillance

• Annual echocardiogram standard; twice yearly for pediatric patients or those with accelerated aortic root growth sources/marfan-cv-clingene-2015 (high)
• MRI preferred over CT for serial surveillance to minimise cumulative radiation from serial scans sources/marfan-cv-clingene-2015 (high)
• Aortic growth slowed but not stopped by medical therapy; imaging mandatory despite treatment sources/marfan-lancet-2005 (high)

Lifestyle

• Avoid contact sports, competitive athletics, isometric exercise sources/marfan-lancet-2005 (high)
• Moderate aerobic activity encouraged for overall health sources/marfan-lancet-2005 (high)
• Pregnancy: safe if aortic root <4 cm; valve-sparing procedure before pregnancy preferred; warfarin contraindicated (fetal demise/embryopathy); LMWH preferred over warfarin sources/marfan-lancet-2005 (high)

Contradictions / Open Questions

• 1996 vs 2010 Ghent criteria: Sources predating the 2010 revision (marfan-lancet-2005; marfan-naturerc-2010) use the 1996 criteria (major/minor across 6 organ systems). The 2010 revision sources/marfan-ghent-jmg-2010 (very high) incorporates aortic Z-scores, systemic score (max 20 pts), and FBN1 mutation status as anchors; ~90% concordance on retrospective analysis with beneficial 10% discordance. 1996 criteria considered overdiagnose some patients and inadequately handle children.
• Haploinsufficiency vs dominant-negative: The authors favour haploinsufficiency as the critical mechanism, with dominant-negative as a contributory factor. This remains debated; the interaction between these mechanisms is not fully resolved.
• Losartan vs atenolol — RESOLVED (Lacro 2014, NEJM): Habashi 2006 (Science) showed losartan prevents aortic aneurysm in fibrillin-1-deficient mice sources/marfan-naturerc-2010 (medium); the COMPARE trial (2013) showed modest but non-superior benefit. The definitive Lacro 2014 NEJM trial (Pediatric Heart Network) established atenolol and losartan as equally effective in children and young adults with MFS — no clinically significant advantage of losartan over atenolol sources/marfan-ghent-aclingene-2015 (high). Either drug may be chosen based on patient factors. The broader translational gap between TGF-β mouse models and human MFS aortic disease remains.
• Valve-sparing vs Bentall: Long-term outcomes of valve-sparing surgery were unavailable at time of writing; subsequent data are generally favourable but without RCT.
• ACE inhibitor vs beta-blocker: The Yetman 2005 non-randomised comparison (enalapril apparently superior) cited in this review has not been confirmed by RCT. No head-to-head RCT evidence exists.
• DCM and anti-TGFβ therapy: DCM in MFS mice is driven by fibrillin-1 mechanosignaling — an exception to broad anti-TGFβ therapy (Cook 2014 JCI); broad TGFβ blockade could theoretically worsen primary cardiomyopathy, requiring organ-specific therapeutic approaches.
• Non-canonical vs canonical pathway primacy: Holm 2011 (Science) identified non-canonical ERK pathway as major aortic disease contributor in mild MFS mice; however losartan treatment of severe mgR/mgR mice normalised ERK1/2 but NOT R-Smad, suggesting the relative importance of each pathway may vary with disease severity — the correct treatment target may be stage- and tissue-specific.
• SGS genetic reclassification: Originally attributed to FBN1 mutations; now known to be SKI mutations (Doyle 2012 Nat Genet) — prior literature citing FBN1-linked SGS should be re-interpreted.

Connections

• Related to entities/FBN1 — causative gene
• Related to entities/Loeys-Dietz-Syndrome — critical differential with shared TGF-β pathway
• Related to entities/Aneurysm-Osteoarthritis-Syndrome — related aortopathy; SMAD3 mutations; grouped by dysregulated TGFβ signalling
• Related to entities/Bicuspid-Aortic-Valve — differential diagnosis
• Related to concepts/Aortic-Regurgitation — complication of aortic root aneurysm

Sources

• sources/marfan-ghent-jmg-2010 (very high)
• sources/marfan-lancet-2005 (high)
• sources/marfan-cv-clingene-2015 (high)
• sources/marfan-ghent-aclingene-2015 (high)
• sources/marfan-naturerc-2010 (medium)