Marfan syndrome is a rare genetic disorder that affects the body's connective tissue. This is the material that holds together the various parts of the body and plays a role in how the body grows. The syndrome affects the formation and functioning of the heart, blood vessels, lungs, kidneys, eyes and skeleton. Named for the French pediatrician who first described it in 1896, Marfan syndrome may affect males or females of any ethnic origin.

The condition is caused by a defect in a gene that controls the production of fibrillin (a protein found in connective tissue), causing the tissue to weaken or stretch. About three quarters of Marfan syndrome cases occur through an autosomal dominant mode of inheritance. This means that only one parent need have Marfan syndrome to pass the disorder onto a child. For example, if one parent (male or female) has Marfan syndrome, there is a 50 percent chance that each pregnancy will produce offspring inheriting the syndrome, and a 75 percent chance if both parents have Marfan syndrome. About one third of Marfan cases arise spontaneously, from two unaffected parents, due to a mutation in either the egg or sperm. These spontaneous cases are typically associated with a more severe form of the syndrome.

The estimated incidence of Marfan syndrome is roughly 1 in 5,000 people, according to the National Marfan Foundation. Approximately 40,000 Americans are diagnosed with the condition each year.

Although many individuals with Marfan do not exhibit symptoms until later, the form of the disorder that manifests itself during childhood tends to be more severe. Among these children, the aorta, which is responsible for carrying blood from the heart to the rest of the body, may have structural abnormalities. The most common defect is a dilated aortic root, or an expanded section where the aorta connects to the heart. This condition tends to get worse over time and may result in a number of complications, including:

• Aortic regurgitation. A condition in which the aortic valve (located between the left ventricle and the aorta) cannot close properly. This defect allows blood to leak backward instead of flowing forward.
  
  
• Mitral valve prolapse. A condition in which the flaps of the mitral valve (located between the left atrium and left ventricle) cannot close properly. As a result, blood may leak back through the valve (regurgitation), when it should only move forward.
  
  
• Arrhythmias. Abnormal heart rhythms that could result if other heart conditions are left untreated.

In recent years, physicians have made great strides in the treatment of Marfan patients. Although there is no cure for the underlying genetic defect, Marfan patients are closely monitored to see if their condition is deteriorating. Heart problems in people with Marfan syndrome increase their risk of heart attack and sudden cardiac death. If the aorta becomes too enlarged, preventive surgery may be recommended. Other aggressive treatment options have helped to push the average lifespan of Marfan patients over 60 years. Life expectancy is longer among women than men.