Marfan Syndrome

Marfan Syndrome is a connective tissue disorder.

• Genetics: Autosomal dominant. FBN1 (Fibrillin-1) gene on chromosome 15.
• Incidence: 1 in 5,000-10,000.
• Pathophysiology: Defective fibrillin leads to abnormal elastic fibers and increased TGF-β signaling.
• Diagnosis: Ghent criteria (revised 2010).

Dural ectasia appears throughout this topic — in the must-know list, the Ghent criteria, investigations and as a surgical complication — but it is worth defining precisely because it is both a diagnostic criterion and an operative hazard.

What it is

• Dural ectasia is widening (ballooning) of the dural sac, most marked in the lumbosacral spine where CSF hydrostatic pressure is greatest. The chronically stretched, fibrillin-deficient dura expands, can scallop the posterior vertebral bodies, widen neural foramina, and form anterior sacral meningocoeles or nerve-root-sleeve (Tarlov) cysts.
• It is present in the large majority of adults with Marfan syndrome and may first appear or progress during adulthood, so a normal scan in childhood does not exclude it later.

How it is measured

• Diagnosis is radiological (MRI, or CT if MRI is contraindicated). The most-used quantitative measure is the dural sac ratio — the dural sac diameter divided by the vertebral body diameter at the same level; in ectasia the dural sac is wider relative to the vertebral body (a ratio above the threshold), the opposite of the normal taper.
• There is no single agreed cut-off, which is why reported prevalence varies; one validated proposal raises the S1 dural-sac-ratio threshold to about 0.64. Supportive qualitative signs include posterior vertebral scalloping, a widened sac and anterior meningocoele.

Why it matters clinically and surgically

• It can cause postural (low-pressure) headaches, low back pain and proximal leg pain, and rarely genitourinary symptoms from a large meningocoele.
• For the spine surgeon it is the key reason to image the lumbosacral dura before fusion: the thin, distended dura raises the risk of incidental durotomy and CSF leak, and it complicates pedicle-screw purchase where bone is scalloped.

Connective Tissue Abnormalities

• Fibrillin is a component of elastic fibers.
• Abnormal elastic fibers affect aorta, ligaments, lens zonules.
• Increased TGF-β signaling contributes to aortic disease.

Why Scoliosis Develops

• Ligamentous laxity + abnormal connective tissue.
• Curves may resemble idiopathic scoliosis but can be more severe.

Marfan-like Syndromes:

Key Distinguishing Features:

• Lens dislocation direction: Marfan UP, Homocystinuria DOWN
• Cognitive function: Normal in Marfan, impaired in Homocystinuria
• Uvula: Normal in Marfan, bifid in Loeys-Dietz
• Gene: FBN1 for Marfan, FBN2 for Beals

The self-assessment flags "pneumothorax from apical blebs" as an anaesthetic concern, but the pulmonary involvement deserves explicit treatment because it changes how these patients tolerate surgery and ventilation.

The lung in Marfan

• The same fibrillin-deficient connective tissue weakens the lung parenchyma, producing apical bullae and blebs. Their rupture causes spontaneous pneumothorax, which occurs in a meaningful minority of Marfan patients (far above the general-population rate) and is often recurrent.
• There is also a restrictive component: severe pectus excavatum and scoliosis reduce chest-wall compliance and lung volumes, lowering pulmonary reserve. Obstructive sleep apnoea is more common (craniofacial and airway laxity).

Why it matters perioperatively

• A patient presenting with sudden pleuritic chest pain and breathlessness has a pneumothorax until proven otherwise — and the same symptoms can herald aortic dissection, so both must be excluded.
• Under general anaesthesia, positive-pressure ventilation can convert a simple pneumothorax or rupture a bleb into a tension pneumothorax; combined with the chest-wall restriction of pectus/scoliosis, this reduces ventilatory margin during long prone spinal fusions.
• Recurrent pneumothorax may need pleurodesis; document baseline lung status before major surgery.

• Cardiac Monitoring: Blood pressure control.
• Standard Spine Protocol: Mobilization, physiotherapy.

• Life Expectancy: Reduced (median 40-50 years historically). Improved with aortic monitoring and surgery.
• Orthopaedic: Scoliosis surgery outcomes similar to idiopathic.

Global epidemiology. Prevalence is approximately 1 in 5,000 worldwide with no clear ethnic or geographic predilection. Inheritance is autosomal dominant with high penetrance but markedly variable expressivity; roughly 25 percent of cases arise from de novo FBN1 mutations and so present without a family history.

Side-by-side guidelines:

Surgical orthopaedic thresholds (broadly concordant globally). Brace curves of 25 to 40 degrees in the growing child; operate on curves over 40 to 50 degrees, which progress faster and respond less to bracing than idiopathic curves. Observe asymptomatic protrusio acetabuli.

Registry and resource notes. No dedicated Marfan implant registry exists; arthroplasty data are sparse because protrusio rarely requires replacement before late adulthood. National Marfan patient organisations (for example The Marfan Foundation in the US, the Marfan Trust in the UK, and equivalent bodies in many countries) coordinate multidisciplinary clinics.

High- vs limited-resource practice. In well-resourced settings, lifelong echocardiographic (and cross-sectional CT/MRI) aortic surveillance, FBN1 sequencing, valve-sparing root replacement, and neuromonitored spinal fusion are standard. Where genetic testing and advanced imaging are limited, diagnosis leans on the clinical Ghent features and echocardiography; the priority everywhere is recognising aortic risk, restricting high-intensity isometric and contact sport, and arranging cardiac assessment before any major orthopaedic surgery.

• Losartan vs beta-blockade. The Pediatric Heart Network trial (Lacro 2014) found no significant difference between losartan and atenolol for aortic-root growth, and subsequent meta-analyses suggest the two are broadly comparable. Whether combination therapy or angiotensin-receptor blockade adds benefit over beta-blockade alone remains unsettled.
• Optimal aortic-root replacement threshold. The 5.0 cm threshold is pragmatic, not absolute; family history of early dissection, rapid growth (over 3 to 5 mm/year), and planned pregnancy all argue for earlier surgery, while the relative merits of valve-sparing versus composite root replacement are debated.
• Prophylactic surgery for protrusio acetabuli. Older recommendations for triradiate closure in growing children are largely abandoned; Sponseller's data show most protrusio is well tolerated, so intervention is now reserved for genuinely symptomatic or rapidly progressive cases.
• Defining dural ectasia. There is no universally accepted radiographic cut-off; differing dural-sac-ratio thresholds affect reported prevalence and its weight within the Ghent systemic score.
• Fusion levels and approach in syndromic scoliosis. Curve length, kyphosis, pelvic obliquity, and bone fragility complicate level selection; the shift to posterior-only constructs is clear, but distal fusion levels and the role of pelvic fixation remain individualised.