Infections are a frequent complication in people with RA. Their risk for developing lung infections or pneumonia is also increased, which constitutes a serious problem.
In medical studies, investigators have found that people with RA were nearly twice as likely as people without RA to develop infections, even after adjusting the rates for age, gender, smoking status, low white blood cell count, glucocorticoid use, and diabetes mellitus. The sites of infection with the highest risk ratios were the bones, joints, skin, and soft tissue.
Possible explanations for the increased risk of infection include RA-related immunologic abnormalities, the effects of immunosuppressant drugs, and disease-related factors such as immobility, joint surgery, rheumatoid lung disease, and Felty's syndrome. In addition, patients with RA who also have other diseases such as diabetes mellitus, chronic obstructive pulmonary disease (COPD), and renal failure may have an even higher risk of developing infections. Which of these factors are the most important contributors to the increased risk of infection associated with RA has not been established.
Recent evidence suggests that an abnormality exists in the white blood cells (the T cells) of patients with RA, even when the disease is in its earliest stages. This abnormality may impair the body's immunological response to bacteria and viruses, leaving it unable to fight off these intruders and resulting in increased infection rates.
Corticosteroids (or, more simply, steroids) are commonly used to treat rheumatic diseases. Unfortunately, their ability to control RA symptoms comes at the expense of increased immunosuppression, which increases the risk for infections. In one study involving nearly 17,000 people with RA, researchers found that more than 70% of patients were prescribed prednisone (a steroid) at least once during the course of their disease and 35% to 45% used prednisone regularly. Evidence from studies like this one has also indicated that there is a relationship between the dose of steroids and the risk of pneumonia. This association is seen even with small daily doses of steroids—less than 5 mg.
The use of disease-modifying antirheumatic drugs (DMARDs, such as sulfasalazine, hydroxychloroquine, and leflunomide), apart from corticosteroids, did not appear to increase infection risk, even after adjustment for demographic and disease-related variables. The effects of the dosages of methotrexate used in RA are less clear, with some studies showing a mildly increased risk of infection and others demonstrating no such increased risk.
Disease-modifying antirheumatic drugs (DMARDs)
A class of medications that are used to treat arthritis and other rheumatic conditions. Examples include methotrexate, leflunomide, and sulfasalizine.