Rheumatoid factor is an antibody that is not usually found in the blood of someone who doesn't have rheumatoid arthritis but is detectable in 80 percent of adults with the condition. It can also be present in patients with other auto-immune diseases, according to MedicineNet. People with high levels of rheumatoid factor tend to have a more aggressive type of disease or are at risk for rheumatoid nodules and rheumatoid lung disease. Other diseases and conditions can produce high levels of rheumatoid factor, including cancer, chronic infection, cirrhosis, inflammatory lung disease such as sarcoidosis, mixed connective tissue disease, scleroderma and lupus, according to Mayo Clinic.
Rheumatoid arthritis is an inflammatory disease that is characterized by the body attacking its own tissues. It can affect multiple joints, primarily in the synovial membrane. Pain, swelling and redness result from the erosion of cartilage, states the Centers for Disease Control and Prevention. Rheumatoid arthritis is believed to be caused by a faulty immune response.
