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Marfan's Syndrome

Marfan's syndrome is a genetic (inherited) disorder that affects the body's connective tissue. Connective tissue is the tough, fibrous, elastic tissue that connects structural body tissues. It is a major component of tendons, ligaments, bones, cartilage, and the walls of blood vessels. Marfan's syndrome was first noted in 1896 by Dr. Marfan, who described a young patient with severe features and symptoms which characterize the disease. Health experts estimate that about 40,000 Americans currently have Marfan’s syndrome, and the disorder probably affects one out of every 10,000 newborns.

In Marfan’s syndrome, a mutation (alteration) in a gene (segment of DNA that directs production of a body protein) causes a defect in the body’s production of fibrillin, an important building block of connective tissue. In many families with inherited Marfan’s syndrome, the mutation affects the FBN1 gene on chromosome 15, although a second gene on chromosome 5 may be involved in some cases.

Because of their inherited defect in fibrillin production, patients with Marfan’s syndrome suffer from many different problems related to weakness in connective tissue. These problems include:

· Skeletal abnormalities - Patients with Marfan’s syndrome are typically very tall, with long limbs and arachnodactyly (long, slender, spiderlike fingers). They may also have severe chest deformities, such as pectus excavatum (the chest wall "caves in" in front) or pectus carinatum (the chest wall protrudes in front). Some patients also have scoliosis (curvature of the spine). A high, arched palate is often noted on oral examination.

· Cardiovascular changes - Structural weakness of connective tissue affects the heart and blood vessels of those with Marfan’s syndrome, so that cardiovascular problems are the major cause of Marfan’s-related illness and death. In patients with Marfan’s syndrome, connective tissue weakness may cause mitral valve prolapse (a "floppy" mitral valve that doesn’t close properly) or mitral valve regurgitation (a severe problem in closing the mitral valve, which results in a significant backflow of blood into the left atrium). It may also lead to an aortic aneurysm (an abnormal swelling or "dilatation"), typically at the root of the aorta at the outlet of the heart. This dilatation can lead to aortic regurgitation (abnormal backflow of blood when the heart tries to pump blood forward), aortic dissection (a spreading tear in the inner wall of the aorta that causes a separation between the aorta’s inner and outer layers) and aortic rupture (a break in the wall of the aorta, with leakage of blood).

· Reduced vision - About 65 % of Marfan’s patients develop ectopia lentis. This is a dislocation of the lens of the eye, which is caused by a weakness in tiny eye ligaments that normally hold the lens in place. Marfan’s syndrome also seems to increase the risk for myopia (nearsightedness); cataracts at an unusually early age (age 40 to 50); glaucoma, retinal detachment and strabismus.

Subluxation of the lens is the most common ocular abnormality, which is bilateral and symetrical. The dislocation may be complete, with the lens floating free within the vitreous cavity. Iridodonesis (tremulousness of the iris) may occur from nonsupport of the overlying iris by the lens.

The axial length of the globe is increased in Marfan's patients leading to moderate to severe myopia as the most common refractive error. Retinal detachment is more common than in the normal population. Glaucoma may be the result of the angle anomaly or it may be associated with lens subluxation.

Children with Marfan's syndrome require regular ophtalmologic surveillance to correct visual acuity and thus prevent amblyopia. Patients of all ages require echocardiography annualy to monitor aortic diameter and mitral valve function, and should use standard endocarditis prophylaxis.

Diagnosis

The doctor may suspect Marfan’s syndrome based on the patient’s family history (Marfan’s-related cardiovascular problems or vision problems), the patient’s personal history of ectopia lentis and the patient’s physical appearance (tall, thin, with arachnodactyly). The diagnosis can be confirmed if the patient has a history of ectopia lentis and also has an aortic aneurysm visible on echocardiography (a painless test that uses sound waves to outline the structure of the heart and its major vessels). The presence of other skeletal abnormalities (chest wall deformities or scoliosis) will reinforce the diagnosis, as will the presence of heart murmurs due to aortic or mitral valve abnormalities. Genetic testing is also available in selected medical centers to check for specific chromosomal abnormalities related to abnormal fibrillin production.

Prevention

Presently, there is no way to avert or reverse the inherited abnormality in fibrillin that affects people with Marfan’s syndrome. Marfan’s patients and their relatives may wish to seek genetic counseling to clarify their risk of passing the disorder to future generations.

Treatment

There is no current medical treatment to prevent or reverse the inherited abnormality in fibrillin that affects people with Marfan’s syndrome. In the future, research on a strain of mice that are born with similar fibrillin problems may lead to a successful Marfan’s treatment. Until then, doctors try to prevent or delay the aortic changes seen in Marfan’s patients by prescribing beta blockers. These medications (such as propranolol, metoprolol and atenolol) decrease the strain on the aorta’s wall by slowing the heart rate and reducing the force of heart contractions, especially during exercise. The Marfan’s patient’s cardiovascular status is carefully monitored with frequent echocardiograms to check for developing problems in the aorta and mitral valve. If a serious problem is found, the patient may need surgical replacement of the aortic valve, mitral valve or part of the aorta. In general, if the patient’s aortic root has stretched to more than 6 centimeters in diameter or if the thoracic aorta has widened to greater than 5 centimeters in diameter, the affected portion of the aorta is replaced surgically. In terms of lifestyle modifications, patients with Marfan’s syndrome should follow non-strenuous exercise programs that involve non-competitive, non-contact sports (walking, bicycling, jogging) where patients are free to participate at their own pace.

Patients with Marfan’s-related scoliosis may be treated with bracing and physical therapy for scoliosis of 20° to 40° , or with surgery for scoliosis greater than 45° . To allow early diagnosis of Marfan’s-related eye problems, every patient should have an annual eye examination. Patients with ectopia lentis can often be treated with aphakic lenses and special eye drops (to widen the pupil) rather than surgery. Whenever eye surgery is necessary, it should be performed in an ophthalmology center that specializes in Marfan’s syndrome treatment.

References

*Jack J.Kansky. Clinical Ophtalmology - A Systemic Approach. Second edition

*Daniel H. Gold; Thomas A. Weingeist. The Eye in Systemic Disease