The cause of Marfan syndrome is a mutation on a gene that tells the body how to make fibrillin, a protein that is a critical part of connective tissue.
Three out of four people with Marfan syndrome inherited it from a parent. A parent with Marfan syndrome has a 50-50 chance of passing the defective gene along to his or her children. In about one-quarter of cases, Marfan syndrome is not inherited, but appears because of a spontaneous gene mutation.
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