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Medical Author:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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What is Felty's syndrome?

Felty's syndrome is a complication of long-standing rheumatoid arthritis. Felty's syndrome is defined by the presence of three conditions: rheumatoid arthritis, an enlarged spleen (splenomegaly), and an abnormally low white blood count. Felty's syndrome is uncommon. It affects less than 1% of patients with rheumatoid arthritis.

What are the symptoms of Felty's syndrome?

Some patients with Felty's syndrome have more infections, such as pneumonia or skin infections, than the average person. This increased susceptibility to infections is attributed to the low white blood counts that are characteristic of Felty's syndrome. Ulcers in the skin over the legs can complicate Felty's syndrome.

What causes Felty's syndrome?

The cause of Felty's syndrome is not known. Some patients with rheumatoid arthritis develop Felty's syndrome but most do not. White blood cells are produced in the bone marrow. There seems to be an active bone marrow function in patients with Felty's syndrome, producing white cells, despite the low numbers of circulating white blood cells. White cells may be stored excessively in the spleen of a patient with Felty's syndrome. This is especially true in patients with Felty's syndrome that have antibodies against the particular type of white blood cells usually affected (cells called granulocytes or neutrophils).

How is Felty's syndrome diagnosed?

There is no single test for Felty's syndrome. It is diagnosed based on the presence of the three conditions mentioned above. Most patients do have rheumatoid arthritis antibodies (rheumatoid factor) in the blood.