This is the defect of connective tissue characterized by faulty scaffolding, caused by mutations of FBN1 gene leading to abnormal fibrillin(which is a structural protein). This cause absence of normal microfibrils in the extracellular matrix hence no scaffolding on which tropoelastin is deposited to form elastic fibers as the result Marfan’s syndrome.
Microfibrils are normally abundant in the aorta, ligaments, and ciliary zonules of the lens where they support the lens. Hence, Marfan syndrome (in which there is deficiency of normal fibrillin and microfibrils) mainly involves these tissues.
The syndrome is characterized by defects in skeletal, visual, and cardiovascular structures:
- Patients are tall and thin with abnormally long legs and arms, spider like fingers (arachnodactyly), hyperextensible joints.
- Dislocation of the ocular lens (Ectopialentis) is frequent.
- Cardiovascular changes include: (A) Mitral valve prolapse due to loss of connective tissue support in themitral valve leaflets. (B). Dilatation of the ascending aorta due to cystic medionecrosis (lead to lack ofmedial support).Dilatation of the aortic valve ring and the root of the aorta leading to Aortic regurgitation. (C) Dissecting aneurysm of the aorta due to medial necrosis and intimal tear.