Marfan syndrome is a genetic disorder. A mutation, or change, in the gene that controls how the body makes fibrillin causes Marfan syndrome. Fibrillin is a protein that plays a major role in your body's connective tissue.
Most people who have Marfan syndrome inherit it from their parents. If you have the condition, you have a 50 percent chance of passing the altered gene to each of your children.
Sometimes Marfan syndrome isn't inherited. The mutation in the fibrillin gene occurs in the egg or sperm cells. If a child is conceived, the altered gene may be passed on to the child. The risk of that child's brothers or sisters having Marfan syndrome is low.