Marfan syndrome (or Marfan's syndrome) is a connective-tissue disorder that manifests through distinctive skeletal and ocular changes as well as congenital heart disease. A mutation in the gene (FBN1) that normally directs the body to make fibrillin-1 (an important connective-tissue protein) causes this condition. When functioning properly, fibrillin-1 is transported to the extracellular matrix and helps to form microfibrils and other elastic fibers in cells that allow blood vessels, ligaments, and the skin to stretch. These fibers also provide rigidity to bones and other supportive elements of the nervous system, muscular system, and eyes. When the FBN1 gene is defective, the body's levels of fibrillin-1 are dramatically low. Conversely, levels of activity for transforming growth factor beta (TGF-β), a protein that fibrillin-1 usually suppresses, become unusually high. This abnormality leads to major problems in the body's connective tissues. The excess TGF-β reduces the elasticity of many tissues, thereby weakening them, but also enabling them to grow excessively. The areas of the body most affected by Marfan syndrome are the heart, blood vessels, eyes, and skeleton. The nervous system, lungs, and skin may also be affected. See also: Connective tissue; Gene; Growth factor; Histology; Mutation; Protein

In approximately 75% of the cases, Marfan syndrome is transmitted genetically through autosomal (nonsex chromosome) dominant inheritance (that is, offspring inherit the disorder if only a single copy of the mutated gene is passed to them by a parent). Spontaneous mutations in the fibrillin-1 gene are responsible for the other cases. The appearance and progression of Marfan syndrome can vary tremendously. Many individuals display features of Marfan syndrome at birth or in infancy, whereas others do not develop any distinguishing signs until adulthood. Often, the symptoms of the disorder progressively worsen as the patient ages. See also: Dominance; Genetics; Human genetics

Manifestations of Marfan syndrome vary strongly, although individuals typically display a combination of the most prevalent signs of the disease. Outward signs include a tall, thin body; long limbs, fingers, and toes; flexible joints; a sunken or protruding sternum (breastbone); flat feet; curvature of the spine (scoliosis); and unusual stretch marks on the skin that cannot be explained by other conditions (for example, changes in weight). Many individuals develop severe eye problems, including extreme nearsightedness, early-onset glaucoma, cataracts (clouding of the lens), and retinal defects. Other conditions are less obvious, although they have more serious consequences. For example, defects in the heart and the aorta (the major artery carrying blood away from the heart to the rest of the body), especially enlargement and bulging of the aorta (aortic aneurysm), aortic rupture (aortic dissection), and malfunctioning heart valves, are apparent in many patients. Other life-threatening problems include sudden lung collapse and dural ectasia (an abnormally enlarged dura, the fibrous membrane forming the outermost covering of the brain and spinal cord). See also: Aneurysm; Cardiovascular system; Eye disorders; Heart (vertebrate); Heart disorders; Vascular disorders

There is no cure for Marfan syndrome. Patients often undergo corrective surgical procedures to repair defective heart valves and other damaged connective-tissue elements of the aorta and eyes. Other individuals use medications, including drugs that lower blood pressure and reduce the chances of aortic aneurysm and dissection. With routine monitoring and established treatment, individuals affected with Marfan syndrome can experience a near-normal and productive life. See also: Surgery