Felty Syndrome definition
Felty syndrome is a condition that includes rheumatoid arthritis, splenomegaly (enlargement of the spleen) and granulocytopenia (decreased level of certain type of white blood cells). In Felty syndrome rheumatoid arthritis is seropositive, which means that rheumatoid factor can be found in the blood. This syndrome is sometimes seen as a complication of rheumatoid arthritis [1,5].
The exact cause of Felty syndrome is not known. It is usually found in people who have had rheumatoid arthritis for a long time. Besides the mentioned, other etiological factors are:
- Erosive synovitis
- Extra-articular manifestations of rheumatoid arthritis
- Patients, who have a positive HLA-DR4- human leukocyte antigen.
Scientists believe that Felty syndrome belongs to the autoimmune disease group (also see Lambert-Eaton syndrome, Antiphospholypid-antibody syndrome). Some cases have been proven to be genetically determined, but the specific mechanism is still unknown .
The pathogenesis of Felty syndrome is not clear. It has been suspected that there is an autoimmune reaction against neutrophil antigens. When infections occur, neutrophils respond to it by producing biologically active agents that bind together with active substances from the bacteria. These newly created complexes trigger the autoimmune response .
Most commonly patients complain about:
- Discomfort, fatigue
- Appetite loss, weight loss
- Swelling, stiffness, pain and deformation of the joints
- Discomfort in the eyes- itching, redness, burning sensation (Dry eye syndrome)
Patients usually have existing rheumatoid arthritis. In some cases arthritis develops at the same time as Felty syndrome. Many patients also have extra articular manifestations of rheumatoid arthritis- nodules, vasculitis, skin ulcers, pleuropericarditis, eye involvement (episcleritis), Sjogren syndrome.
Usually patients present with long history of active disease.
Some patients initially have bacterial infections of skin and respiratory system
In case there is splenic infarcts, patients complain about pain in the upper left quadrant of the abdomen.
When examining the patient, doctor might find:
- Enlarged spleen
- Mild enlargement of the liver
- Enlarged and painful lymph nodes
- Rheumatoid nodules
- Sjogren syndrome
- Swollen, tender, painful and/or deformed joints
- Signs of vasculitis- skin ulcers, pigment changes, purpura on the lower extremities
- In case systemic vasculitis is present, patient might have ischemia of extremities or neuropathy.
- Signs of portal hypertension- ascitis, gastrointestinal bleeding, nausea, vomiting, changes in blood analyses.
- Episcleritis 
One of the key laboratory findings in Felty syndrome is granulocytopenia. Granulocytes are a type of white blood cells that contain little granules. These cells are a part of immune system. Granules contain enzymes that can digest bacteria. Granulocytopenia occurs due to frequent infections. In case of Felty syndrome, patients with granulocyte levels lower than 1000/µL have a high risk for infection.
Due to enlargement of spleen, anemia and thrombocytopenia can occur. Anemia can also be caused by chronic inflammation of the joints.
Other laboratory findings include:
- Increased levels of rheumatoid factor in the blood
- Antinuclear antibodies
- Erythrocyte sedimentation rate can be increased
- Serum immunoglobulin levels can be increased
- In some cases cryoglobulins are present
- Hemolytic-uremic syndrome can occur [2,4]
- X-ray, MRI and CT imaging of the joints shows soft tissue swelling, osteoporosis, narrowing of the joint space, erosions of the bone and cartilage
- Ultrasonography and CT imaging can reveal enlarged spleen 
First approach to treating Felty syndrome is to treat the underlying rheumatoid arthritis. Since rheumatoid arthritis is an autoimmune disease, the therapy requires suppression of immune system. Medications used to treat patients with Felty syndrome are:
- Non-steroid anti inflammatory drugs, for example ibuprofen can reduce pain and swelling in the joints
- Methotrexate- in love doses this drug is immunosuppressive, but the exact mechanism of action is not known. It decreases swelling, pain and stiffness of the joints.
- Folic acid is used in combination with methotraxate to decrease the adverse effects of this drug, like nausea, vomiting, headaches, fatigue. It also reduces the risk of gastrointestinal bleeding.
- Gold salts reduce inflammation. The exact mechanism of how they work is unknown
- Some patients respond to cyclophosphamide treatment, which has immunosuppressive abilities, but it also diminishes the level of B and T cells therefore increasing the risk of infection
- Tumor necrosis factor α blockers- adalimumab, infliximab.
- For patients with life-threatening infections, stimulation of granulocyte production is used by giving granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor
- High-dose corticosteroids can also increase granulocyte count
Splenectomy is sometimes performed in some patients who:
- Have a severe condition
- Do not respond to pharmacological treatment
- Experience constant, serious infections
- Have hemolysis or recurrent skin ulcers
Although splenectomy is sometimes performed and it has good effects on educing anemia, thrombocytopenia, neutropenia and therefore incidence of infections, the long term effects are not known [2,4].
It has been estimated that 1-3% of all patients with rheumatoid arthritis are affected by Felty syndrome. It is 3 times more common in females than in males. It mostly affects Caucasian populations at the age of 50 to 70 years.
Felty syndrome has similar symptoms and has to be differentiated from:
- Reaction to drugs
- Myelodisplastic disorders like leukemia (when in combination with rheumatoid arthritis, also known as pseido-Felty´s syndrome)
- Stills disease
- Systemic lupus erythematosus
- Chronic bacterial endocarditis [2,3]
In some cases, Felty syndrome can cause severe and life threatening conditions like:
- Rupture of the spleen
- Life-threatening infection
- Toxic reaction to drug therapy, that can cause conditions like Steven-Johnson syndrome
- Portal hypertension
- Gastrointestinal bleeding
Without proper treatment, infections due to Felty syndrome can be fatal. For example, infections like flu can be very dangerous to patients with Felty syndrome. Also, rheumatoid arthritis is likely to get worse and patient will have permanent disability. Patients who suffer from rheumatoid arthritis and use immunosuppressive therapy are advised to have flu shots and take extra caution not to get sick [2,3].
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- Information about Felty syndrome: https://rarediseases.org/rare-diseases/felty-syndrome/
- Symptoms, causes and treatment: http://emedicine.medscape.com/article/329734-overview#a2
- Detailed medical information: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=GB&Expert=47612
- Patient information: https://medlineplus.gov/ency/article/000445.htm
- Clinical manifestations and diagnostics of Felty síndrome: http://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-feltys-syndrome#H7