Genetics Home > Causes of Marfan Syndrome
An inherited defect in the fibrillin-1 gene, or a new defect in the fibrillin-1 gene that occurs spontaneously, is what causes Marfan syndrome. About 75 percent of people with the condition inherit the mutation from one affected parent. The chance of two unaffected parents having a child with Marfan syndrome is about 1 in 10,000.
Marfan syndrome is caused by a defect (mutation) in the fibrillin-1 (FBN1) gene. The FBN1 gene produces a protein that is essential for formatting the elastic fibers found in connective tissue.
Although a Marfan syndrome diagnosis may not be made until later in life, people are born with the disease. People with Marfan syndrome have a defect in the same gene. However, the defect is specific to each family, and not everyone experiences the same characteristics of Marfan syndrome. This is called variable expression. Marfan syndrome research scientists do not yet understand why variable expression occurs in people with the condition.
As mentioned, mutations in the FBN1 gene are the Marfan syndrome cause. This gene produces a protein that is essential for formatting the elastic fibers found in connective tissue. A mutation can decrease the amount and quality of fibrillin-1 that is deposited in connective tissue, which can lead to weakened structural support.
Inheritance Versus Spontaneous Mutation
The defective gene can be inherited or it can be the result of a new gene defect that occurs during the formation of sperm or egg cells. Statistics related to the causes of Marfan syndrome include the following:
- About 75 percent of people with Marfan syndrome inherit the mutation from one affected parent
- A parent who has Marfan syndrome has a 50 percent chance of passing the disease on to his or her child
- Two unaffected parents have a 1 in 10,000 chance of having a child with Marfan syndrome
- About 25 percent of Marfan syndrome cases result from a new mutation in the gene.
(Click Genetic Testing for Marfan Syndrome for more information about the role of genetics in this disease.)