It is sometimes inherited as a dominant trait. It is carried by a gene called FBN1, which encodes a connective protein called fibrillin-1.People have a pair of FBN1 genes. Because it is dominant, people who have inherited one affected FBN1 gene from either parent will have Marfan's. This syndrome can run from mild to severe.
People with Marfan's are typically tall, with long limbs and long thin fingers.
In addition to being a connective protein that forms the structural support for tissues outside the cell, the normal fibrillin-1 protein binds to another protein, transforming growth factor beta (TGF-β). TGF-β has deleterious effects on vascular smooth muscle development and the integrity of the extracellular matrix. Researchers now believe that secondary to mutated fibrillin there is excessive TGF-β at the lungs, heart valves, and aorta, and this weakens the tissues and causes the features of Marfan syndrome. Since angiotensin II receptor blockers (ARBs) also reduce TGF-β, they have tested this by giving ARBs (losartan, etc.) to a small sample of young, severely affected Marfan syndrome patients. In some patients, the growth of the aorta was indeed reduced.
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