Marfan syndrome is a genetic condition caused by a mutations, or change, in one of your genes, called the fibrillin-1 (FBN1) gene. The FBN1 gene makes fibrillin-1, which is a protein that forms elastic fibers within connective tissue. Fibrillin-1 also affects levels of another protein that helps control how you grow.
Most people who have Marfan syndrome inherit it from their parents. Sometimes, the mutation that causes Marfan syndrome is not passed down from a parent but happens by chance while the unborn baby is developing in the womb.
When a parent has Marfan syndrome, there is a 50 percent chance that their child will have it. Every person inherits two FBN1 genes, one gene from each parent. Children who inherit an FBN1 gene with a mutation from one parent will have Marfan syndrome even if they have a normal FBN1 gene from the other parent.
What does fibrillin-1 do?
Fibrillin-1 makes elastic fibers that provide strength and flexibility so your skin, blood vessels, and ligaments can stretch and bounce back. These fibers also attach to another protein called transforming growth factor-beta (TGF-beta). TGF-beta helps control how the body grows and develops. If fibrillin-1 does not work properly, there is too much TGF-beta, which causes your bones to grow more than usual. The signs and symptoms of Marfan syndrome are caused by not having enough elastic fibers and having too much active TGF-beta in your body.