Rheumatoid arthritis is a chronic, progressive, systemic, autoimmune condition for which there is no known cure. It is a common disorder affecting approximately 2.1 million Americans.

While it is technically a form of arthritis, rheumatoid arthritis is a true systemic disease in which multiple organ systems can be affected.

Among these are the skin with vasculitic ulcers, eyes leading to scleritis or episcleritis (inflammatory eye disease), glands that make saliva and tears leading to dryness of the eyes and mouth, lymph nodes sometimes causing lymphoma, cardiovascular system leading to early heart attack and stroke, and the lungs.

Lung involvement can take multiple forms. Rheumatoid arthritis can cause pleurisy (inflammation of the lining of the lungs), nodules within the lungs, pneumonia, inflammation of the small airways (bronchitis and bronchiolitis), and inflammation of the lung tissue. This latter condition is called interstitial lung disease.

Patients with rheumatoid arthritis are examined clinically and sometimes interstitial lung disease is a finding that is picked up on physical examination.

Prior to starting drugs such as TNF inhibitors (Enbrel, Humira, Remicade), a chest x-ray is also obtained and sometimes interstitial lung disease is found then. However, chest x-ray is not very sensitive for picking up interstitial lung disease early.

A recent study found some disturbing evidence that oftentimes patients with rheumatoid arthritis may have subclinical interstitial lung disease. This means that the lung disease is there without any symptoms.

The researchers found that "preclinical interstitial lung disease detected by high-resolution computed tomography is prevalent and progressive in patients with rheumatoid arthritis." (Arch Intern Med 2008;168:159-166). High resolution computerized tomography is a fine detail CAT scan technique.

The prevalence of asymptomatic interstitial lung disease in rheumatoid arthritis is unknown. The authors of the study said, though, that "given the availability of new therapeutic options, early identification and treatment may improve outcomes."

The authors recruited 64 patients with rheumatoid arthritis without shortness of breath or cough and 10 with rheumatoid arthritis and pulmonary fibrosis (interstitial lung disease).

High-resolution computed tomography identified preclinical interstitial lung disease in 21 of the asymptomatic patients (33%).

Pulmonary function tests such as air flow and lung volumes which measure lung function were normal in the interstitial lung disease patients at baseline, but gas exchange (the ability to transfer oxygen into the lungs and get rid of carbon dioxide out of the lungs) was impaired in patients with no interstitial lung disease.

During a mean follow-up of 2 years, repeat scanning showed disease progression in 12 subjects with preclinical interstitial lung disease and in 6 subjects with pulmonary fibrosis; the rate of change was low and similar in the two groups.

"In this cohort of patients with rheumatoid arthritis, preclinical interstitial lung disease is prevalent and progressive," the authors stated.

They also wrote: "The natural history of disease resembles that of pulmonary fibrosis, and high resolution computed tomography is more sensitive than pulmonary function test measurements in detecting early progression of preclinical interstitial lung disease."

Two thirds of patients with lung disease and less than one quarter without lung disease had a history of smoking, and the mean number of pack-years smoked was significantly higher in the lung disease group. Therefore, the authors say, clinicians should recommend that patients with rheumatoid arthritis should stop smoking.

The scientists concluded: "High resolution computed tomography may be indicated to identify early preclinical ILD in patients with RA whose physical examinations reveal crackles."

Author's note: I agree with these findings and always send patients for a CAT scan of the lungs if I detect crackles on physical examination. The presence of lung disease is also a prompt to become more aggressive with treatment.