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. Signs and symptoms 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). Complications Recurrent infection Enlargement of the spleen causing too few red blood cells and platelets in the bloodstream Enlarged lymph nodes Skin hyperpigmentation Cutaneous ulceration Causes The cause of Felty's syndrome is unknown, but it has been found to be more common in those with chronic rheumatoid arthritis. Some patients share the HLA-DR4 serotype. This syndrome is mostly present in people having extra articular manifestations of rheumatoid arthritis. People with this syndrome are at risk of infection because they have a low white blood cell count. Mechanism The underlying pathogenesis of Felty's syndrome is not clear. Rheumatoid Arthritis Rheumatoid arthritis is an autoimmune disease that is characterized by inflammation of the synovial joints due to attack by the body's