Felty's syndrome (FS), also called Felty syndrome, is rare autoimmune disease characterized by the triad of rheumatoid arthritis, enlargement of the spleen and low neutrophil count. The condition is more common in those aged 50–70 years, specifically more prevalent in females than males, and more so in Caucasians than those of African descent. It is a deforming disease that causes many complications for the individual. The symptoms of Felty's syndrome are similar to those of rheumatoid arthritis. Affected individuals have painful, stiff, and swollen joints, most commonly in the joints of the hands, feet, and arms. In some affected individuals, Felty's syndrome may develop during a period when the symptoms and physical findings associated with rheumatoid arthritis have subsided or are not present; in this case, Felty's syndrome may remain undiagnosed. In more rare instances, the development of Felty's syndrome may precede the development of the symptoms and physical findings associated with rheumatoid arthritis. Felty's syndrome is also characterized by an abnormally enlarged spleen (splenomegaly) and abnormally low levels of certain white blood cells (neutropenia). As a result of neutropenia, affected individuals are increasingly susceptible to certain infections. Keratoconjunctivitis sicca may occur due to secondary Sjögren's syndrome. Individuals with Felty's syndrome may also experience fever, weight loss, and/or fatigue. In some cases, affected individuals may have discoloration (abnormal brown pigmentation) of the skin, particularly of the leg, sores (ulcers) on the lower leg, and/or an abnormally large liver (hepatomegaly). In addition, affected individuals may have abnormally low levels of circulating red blood cells (anemia), a decrease in circulating blood platelets that assist in blood clotting functions (thrombocytopenia), abnormal liver function tests and/or inflammation of the blood vessels (vasculitis).
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