Marfan syndrome is an autosomal dominant disorder affecting connective tissues caused by mutation in the gene encoding fibrillin 1 (FBN1). The disorder has an incidence of at least 1 in 10.000. It arises by new mutation in 25–30% of cases. In some familial cases, the diagnosis may have gone unrecognised in previously affected relatives because of mild presentation and the absence of complications.
The main features of Marfan syndrome involve the SKELETAL, OCULAR and CARDIOVASCULAR systems.
Skeletal features of Marfan syndrome
- Thumb sign (thumb nail protrudes beyond ulnar border of hand when adducted across palm)
- Wrist sign (thumb and 5th finger overlap when encircling wrist)
- Reduced upper : lower segment ratio (<0.85)
- Increased span : height ratio ( > 1.05)
- Pectus carinatum
- Pectus excavatum requiring surgery
- Scoliosis >20 or spondylolisthesis
- Reduced elbow extension
- Pes planus with medical displacement of medial maleolus
- Protrusio acetabulae
- Moderate pectus excavatum
- Joint hypermobility
- High arched palate with dental crowding
- Characteristic facial appearance
Clinical diagnosis is based on the Gent criteria, which require the presence of major diagnostic criteria in two systems, with involvement of a third system. Major criteria include any combination of four of the skeletal features, ectopia lentis, dilatation of the ascending aorta involving at least the sinus of Valsalva, lumbospinal dural ectasia detected by MRI scan, and a first degree relative with confirmed Marfan syndrome. Minor features indicating involvement of other symptoms include striae, recurrent or incisional herniae, and spontaneous pneumothorax.
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