What is rheumatoid factor?
Disease description:
I am a retired worker. In the past one or two years, I have been experiencing persistent pain in both knees, especially on rainy or cloudy days. Later, after seeing a doctor, I was told that I have rheumatoid factor. May I ask, what is going on?
Doctor's answer (1)
Dr. Yang Tiesheng
Rheumatoid factor (RF) is an autoantibody directed against the Fc fragment of denatured IgG molecules. It is commonly found in the serum and joint fluid of patients with autoimmune diseases such as rheumatoid arthritis and Sjögren's syndrome.
The main types include IgM-RF, IgG-RF, IgA-RF, and IgE-RF, among which IgM-RF is the most common. The production of rheumatoid factor may be related to chronic infections caused by viruses, mycoplasma, and other pathogens, which stimulate the body to produce IgG antibodies that subsequently become denatured. This denatured IgG then acts as a new antigen, promoting the production of anti-IgG antibodies by the body, which are known as rheumatoid factors.
The positivity rate of rheumatoid factor varies among different diseases. For example, approximately 60% to 80% of patients with rheumatoid arthritis test positive for rheumatoid factor. Additionally, rheumatoid factor can be used to assist in the diagnosis of other diseases such as systemic lupus erythematosus and Sjögren's syndrome.
