Marfan syndrome (MFS) is a genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with long arms, legs, fingers and toes. They also typically have flexible joints and scoliosis. The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm. The lungs, eyes, bones, and the covering of the spinal cord are also commonly affected. The severity of the symptoms of MFS is variable. MFS is caused by a mutation in FBN1, one of the genes that makes fibrillin, which results in abnormal connective tissue. It is an autosomal dominant disorder. About 75% of the time, the condition is inherited from a parent with the condition, while 25% of the time it is a new mutation. Diagnosis is often based on the Ghent criteria.