Marfan syndrome affects different people in different ways. Some people have only mild symptoms, while others are more severely affected. In most cases, the symptoms progress as the person ages. The body systems most often affected by the syndrome are:

1. Skeleton. People with the syndrome are typically very tall, slender, and loose-jointed. Because Marfan syndrome affects the long bones of the skeleton, a person's arms, legs, fingers, and toes may be disproportionately long in relation to the rest of the body. A person with the syndrome often has a long, narrow face, and the roof of the mouth may be arched, causing the teeth to be crowded. Other skeletal problems include a sternum (breastbone) that is either protruding or indented, curvature of the spine (scoliosis), and flat feet.

Eyes. More than half of all people with the condition experience dislocation of one or both lenses of the eye. The lens may be slightly higher or lower than normal, and may be shifted off to one side. The dislocation may be minimal, or it may be pronounced and obvious. One serious complication that may occur with this disorder is retinal detachment. Many people with the condition are also nearsighted (myopic), and some can develop early glaucoma (high pressure within the eye) or cataracts (the eye's lens loses its clearness).

2. Heart and blood vessels (cardiovascular system). Marfan syndrome patients have problems associated with the heart and blood vessels. Because of faulty connective tissue, the wall of the aorta (the large artery that carries blood from the heart to the rest of the body) may be weakened and stretch, a process called aortic dilatation. Aortic dilatation increases the risk that the aorta will tear (aortic dissection) or rupture, causing serious heart problems or sometimes sudden death. Sometimes, defects in heart valves can also cause problems. In some cases, certain valves may leak, creating a "heart murmur," which a doctor can hear with a stethoscope. Small leaks may not result in any symptoms, but larger ones may cause shortness of breath, fatigue, and palpitations (a very fast or irregular heart rate).

3. Nervous system. The brain and spinal cord are surrounded by fluid contained by a membrane called the dura, which is composed of connective tissue. Marfan syndrome patients grow older, the dura often weakens and stretches, then begins to weigh on the vertebrae in the lower spine and wear away the bone surrounding the spinal cord. This is called dural ectasia. These changes may cause only mild discomfort; or they may lead to radiated pain in the abdomen; or to pain, numbness, or weakness in the legs.

4. Skin. Many people with Marfan syndrome develop stretch marks on their skin, even without any weight change. These stretch marks can occur at any age and pose no health risk. However, people with Marfan syndrome are also at increased risk for developing an abdominal or inguinal hernia, in which a bulge develops that contains part of the intestines.

5. Lungs. Although connective tissue problems make the tiny air sacs within the lungs less elastic, people with Marfan syndrome generally do not experience noticeable problems with their lungs. If, however, these tiny air sacs become stretched or swollen, the risk of lung collapse may increase. Rarely, people with Marfan syndrome may have sleep-related breathing disorders such as snoring, or sleep apnea (which is characterized by brief periods when breathing stops).