Marfan Syndrome vs Ehlers-Danlos Syndrome: Telling the Connective Tissue Disorders Apart
Marfan syndrome and Ehlers-Danlos syndrome (EDS) are both heritable disorders of the connective tissue scaffold, and both can present with joint laxity and skin abnormalities. The core axis that separates them is the defective protein and the dominant clinical footprint: Marfan is a fibrillin-1 disorder dominated by skeletal, ocular, and aortic-root disease, whereas EDS is a group of collagen disorders dominated by skin fragility and joint hypermobility. Identifying which protein and which organ system is driving the picture points to the diagnosis and the life-threatening complication to fear.
How to tell them apart
| Feature | Marfan Syndrome | Ehlers-Danlos Syndrome |
|---|---|---|
| Gene/Protein | FBN1 mutation → deficient fibrillin-1 | Collagen defects: COL5A1/COL5A2 (type V collagen) in classical EDS, COL3A1 (type III collagen) in vascular EDS; gene unknown in hypermobile EDS |
| Dominant clinical footprint | Skeletal, ocular, and cardiovascular triad | Skin fragility and joint hypermobility |
| Skeletal/habitus | Tall stature, long limbs (arm span > height), arachnodactyly, pectus deformity, scoliosis, high-arched palate | Habitus not characteristically tall or arachnodactylic; disease centers on skin and joints |
| Ocular findings | Lens dislocation (ectopia lentis, upward and temporal) and myopia | No characteristic lens dislocation |
| Skin findings | Striae | Velvety, hyperextensible skin with 'cigarette paper' scars (classical); thin, translucent skin (vascular); soft, mildly hyperextensible skin (hypermobile) |
| Joint findings | Joint laxity is mild | Prominent joint hypermobility—generalized in classical/hypermobile types, small-joint hypermobility in vascular type |
| Major danger / cause of death | Aortic root dilation and aortic dissection | Depends on subtype: poor wound healing (classical); arterial, bowel, and uterine rupture with shortened lifespan (vascular); chronic pain and disability (hypermobile) |
The reasoning
Anchor first on the dominant organ system. A tall patient with arachnodactyly, ectopia lentis, and an aortic root problem is Marfan until proven otherwise—the fibrillin-1 defect. When the presentation is dominated by stretchy, fragile skin, atrophic 'cigarette paper' scars, easy bruising, and marked joint hypermobility, think EDS and its collagen defects. Next, subtype the EDS by the feared complication: velvety hyperextensible skin with poor wound healing suggests classical (type V collagen); thin translucent skin with a history or risk of arterial, bowel, or uterine rupture flags vascular EDS (COL3A1)—the most dangerous form; and generalized hypermobility with chronic pain but only mild skin change points to hypermobile EDS. The arbitrating question is: is the patient dying from aortic dissection (Marfan) or from skin/wound and hollow-organ/arterial fragility (EDS)?
Key tests
- Genetic testing: FBN1 mutation confirms Marfan; COL5A1/COL5A2 confirms classical EDS and COL3A1 confirms vascular EDS (hypermobile EDS has no identified gene).
- Echocardiography (aortic root imaging): reveals aortic root dilation in Marfan, mandating serial monitoring; not the defining lesion in EDS, though vascular EDS threatens arterial rupture requiring vascular imaging.
- Slit-lamp ophthalmologic examination: detects ectopia lentis (upward and temporal lens dislocation) supporting Marfan; lens dislocation is not a feature of EDS.
- Clinical diagnostic criteria: Marfan is diagnosed using the Ghent criteria integrating skeletal, ocular, and cardiovascular findings, whereas EDS diagnosis rests on subtype-specific skin and joint findings.
What they share
- Inherited connective tissue disorders affecting the body's structural scaffold
- Joint laxity/hypermobility (mild in Marfan, prominent in EDS)
- Skin findings are present in both (striae in Marfan; hyperextensible or translucent skin in EDS)
- Risk of catastrophic vascular events depending on subtype
Pitfalls
- Both cause joint laxity—remember it is mild in Marfan but a defining, prominent feature in EDS, so laxity alone does not diagnose EDS.
- Both cause skin changes; do not equate them—Marfan's striae are distinct from the hyperextensible, scarring, or translucent skin of EDS.
- Vascular EDS and Marfan both carry lethal vascular risk, but the vessels and mechanism differ: Marfan threatens the aortic root with dissection, while vascular EDS threatens arterial, bowel, and uterine rupture.
- Missing the eye exam: ectopia lentis is a strong pointer to Marfan and is absent in EDS, so failing to examine the lens can blur the distinction.
- Hypermobile EDS has no identified gene—expecting a positive genetic test can lead you to wrongly exclude it.
Practice this the way the exam tests it — on branching cases where your decisions shape the patient.