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What is Feltys syndrome and explain in detail?
Feltys 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 Feltys 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, Feltys 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, Feltys syndrome may remain undiagnosed. In more rare instances, the development of Feltys syndrome may precede the development of the symptoms and physical findings associated with rheumatoid arthritis.Feltys 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 Sjögrens syndrome. Individuals with Feltys 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 Feltys 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 Feltys 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 bodys own immune system. In this condition, the white blood cells travel through the bloodstream to the synovial joints and release pro-inflammatory cytokines upon arrival. The result of this chemical release causes the synovial cells to release harmful chemicals in response as well as begin the growth of new blood vessels, forming a pannus. The pannus receives blood supply from the newly formed vessels and grows inward, invading the articular cartilage and bone within the joint. The damage to the once healthy tissue causes inflammation and ultimately fluid build-up in the joint. An accumulation of fluid results and the joints swell, slowly decreasing the space that keeps the bones from touching. If this condition is not treated, the joint space will completely narrow, causing ankylosis. At the advanced stage of ankylosis, joint mobility is completely occluded. Early presentation is commonly seen in the joints of hands and of the feet. As the disease progresses it can be seen in the knees, wrists, hips, and shoulders. This condition can affect and damage several other body systems such as the eyes, heart, lungs, and blood vessels.Rheumatoid arthritis is a condition that cannot be cured but symptoms can be treated using certain medications alone or in conjunction. Due to the increased inflammatory response of the bodys immune system, this condition can cause a reduction in red and white blood cells.

Neutropenia
In Feltys syndrome, chronic activation of neutrophils progresses to neutropenia and unabated infections. Neutropenia is a decreased concentration of neutrophils in the blood. Neutrophils are the most abundant cells among white blood cells and play an important role in the immune system by destroying bacteria via phagocytosis. Inflammatory chemicals draw neutrophils to the area where they congregate and fight infection. A decrease in the number of neutrophils stimulates an autoimmune response which leads to arthritis. The loss and destruction of neutrophils leading to neutropenia are, therefore, inflammation-driven due to the bodys need for an immune response.

Splenomegaly
Splenomegaly is a condition of the spleen causing it to be enlarged. The splenic condition involving Felty syndrome is more specifically noted as inflammatory splenomegaly. The spleen is an important lymphatic organ that is involved in filtration of the blood by discarding old and damaged red blood cells as well as maintaining platelet levels. The spleen is a lymphatic organ, which means it is largely involved in the immune system and immune responses. When the spleen becomes enlarged, it is a strong sign of infection somewhere in the body and can be caused by inflammatory conditions such as rheumatoid arthritis. The increased need for production assistance of white blood cells to affected areas causes hyperfunction of the spleen. This increase in defense activities ultimately causes hypertrophy of the spleen, leading to splenomegaly. The spleen is found in the left upper quadrant (LUQ) of the peritoneal cavity and due to its enlargement, can cause stress on neighboring organs.

Diagnosis
This condition affects less than 1% of patients with rheumatoid arthritis. The presence of three conditions: rheumatoid arthritis, an enlarged spleen (splenomegaly), and an abnormally low white blood cell count are indications that Feltys syndrome is possibly occurring. This condition as a whole is difficult to diagnose due to its complexity given a combination of disorders. It is commonly overlooked or misdiagnosed as other conditions (e.g., leukemia, systemic lupus erythrematosus) because of the rarity and lack of good understanding about it. An acronym can be used to make recognizing this disease somewhat easier:S: SplenomegalyA: AnemiaN: NeutropeniaT: ThrombocytopeniaA: Arthritis (rheumatoid)

Conditions of the blood
A complete blood count (CBC) can be done to diagnose anemia (normochromic, normocytic), thrombocytopenia, and neutropenia. Abnormal liver function tests are commonly used to help in diagnosis as the spleen and liver are strongly affected by one another.

Splenomegaly
If rheumatoid arthritis is present and other symptoms occur that are not commonly found within RA itself, such as a palpable spleen, further testing should be done. A palpable spleen is not always a clinical significance, therefore CT scan, MRI, or ultrasound can be administered in order to help diagnose the condition.  According to Poulin et al., dimensional guidelines for diagnosing splenomegaly are as follows:
Moderate if the largest dimension is 11–20 cm
Severe if the largest dimension is greater than 20 cm

Rheumatoid arthritis
RA in patients with Feltys syndrome is chronic (after 10–15 years), and presents with increased severity along with extra articular manifestations