Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with long arms, legs, fingers, and toes. They also typically have exceptionally flexible joints and abnormally curved spines. The most serious complications involve the heart and aorta, with an increased risk of mitral valve prolapse and aortic aneurysm. The lungs, eyes, bones, and the covering of the spinal cord are also commonly affected. The severity of the symptoms is variable. MFS is caused by a mutation in FBN1, one of the genes that makes fibrillin, which results in abnormal connective tissue. It is an autosomal dominant disorder. In about 75% of cases, it is inherited from a parent with the condition, while in about 25% it is a new mutation. Diagnosis is often based on the Ghent criteria. There is no known cure for MFS. Many of those with the disorder have a normal life expectancy with proper treatment. Management often includes the use of beta blockers such as propranolol or atenolol or, if they are not tolerated, calcium channel blockers or ACE inhibitors. Surgery may be required to repair the aorta or replace a heart valve. Avoiding strenuous exercise is recommended for those with the condition. About 1 in 5,000 to 1 in 10,000 people have MFS. Rates of the condition are similar in different regions of the world. It is named after French pediatrician Antoine Marfan, who first described it in 1896. Signs and symptoms More than 30 signs and symptoms are variably associated with Marfan syndrome. The most prominent of these affect the skeletal, cardiovascular, and ocular systems, but all fibrous connective tissue throughout the body can be affected. Skeletal system Most of the readily visible signs are associated with the skeletal system. Many people with Marfan syndrome grow to above-average height, and some have disproportionately long, slender limbs with thin, weak wrists and long fingers and toes. The Steinberg sign, also known as the thumb sign, is one of the clinical examination tests for Marfan disease in the hands. It is a clinical test in which the tip of the thumb extends beyond the palm when the thumb is clasped in the clenched hand. Besides affecting height and limb proportions, people with Marfan syndrome may have abnormal lateral curvature of the spine scoliosis, thoracic lordosis, abnormal indentation (pectus excavatum) or protrusion (pectus carinatum)