Marfan syndrome affects different parts of the body differently. No two people have the exact same combination or severity of features – some people have mild changes, others have more pronounced ones. Here is what to look out for, system by system:
*Body build and skeleton: People with Marfan syndrome are often unusually tall and slender, with long arms, legs, fingers, and toes (this finger appearance is called arachnodactyly, meaning “spider fingers”). The arm span may be greater than the person’s height. Joints are often more flexible (“loose-jointed”) than average.
*Chest wall: The breastbone or the sternum, located in the center of the chest, may either sink inward (pectus excavatum) or push outward (pectus carinatum), giving the chest an unusual shape. This can sometimes affect breathing comfort or heart positioning.
*Spine: A sideways curve of the spine, called scoliosis, is common and tends to progress during the fast-growth years of childhood and adolescence.
*Feet: Flat feet are frequently seen.
*Face and mouth: A long, narrow face, a high-arched roof of the mouth (palate), and crowded teeth are common features.
*Eyes: This is an important area to monitor. The lens of the eye can shift out of its normal position (called lens dislocation or ectopia lentis), which is one of the most specific signs of Marfan syndrome. People are often also significantly nearsighted (myopic) from a young age, and are at higher risk of retinal detachment, cataracts, and glaucoma later in life.
*Heart and blood vessels: This is the most medically significant area. The walls of the aorta (the large blood vessel carrying blood from the heart to the rest of the body) can weaken and gradually widen over time causing a condition called aortic root dilation. The heart valves, especially the mitral valve, can also become “floppy” (mitral valve prolapse), sometimes causing an irregular heartbeat or a feeling of the heart skipping.
*Skin and lungs: Stretch marks (unrelated to weight changes) can appear on the skin. Some people are more prone to a collapsed lung (pneumothorax).

Because these features can appear gradually and vary so much, some people are only diagnosed as adults, especially if their case is mild or if no one in the family was previously diagnosed.