Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease that primarily targets the lining of the joints, leading to inflammation, pain, and eventual joint damage. Because RA is systemic, its influence extends far beyond the musculoskeletal system, allowing the immune dysfunction to attack healthy tissues throughout the body. Pulmonary involvement is a common and serious extra-articular manifestation of RA. This lung involvement can sometimes be the first sign of the disease, even before joint symptoms appear, underscoring the importance of vigilance for respiratory changes in people with RA.
Specific Lung Conditions Caused by Rheumatoid Arthritis
RA-driven inflammation can affect nearly every structure in the respiratory system, including the airways, lung lining, and lung tissue. Interstitial Lung Disease (ILD) is the most common and concerning pulmonary complication associated with RA. ILD involves inflammation and progressive scarring (fibrosis) of the interstitium, the tissue surrounding the air sacs (alveoli). This scarring stiffens the lungs, reducing their ability to transfer oxygen into the bloodstream and causing shortness of breath and a persistent cough.
Pleurisy is another manifestation, involving inflammation of the pleura, the double-layered membrane surrounding the lungs. Pleurisy causes sharp chest pain that worsens with deep breathing and may lead to a buildup of fluid called a pleural effusion. While small effusions are often asymptomatic, larger collections can compromise lung function and cause breathlessness. Rheumatoid nodules, small rounded lumps of inflammatory tissue, can also form in the lungs. These nodules are usually benign but can occasionally break down, potentially causing a collapsed lung or infection.
Bronchiolitis Obliterans, sometimes called constrictive bronchiolitis, is a less frequent but severe form of airway disease affecting the smallest airways. This condition causes the small bronchioles to become chronically inflamed and progressively narrowed or blocked by scar tissue. The resulting obstruction prevents air movement, causing breathlessness and wheezing that can worsen rapidly. Other airway issues, such as bronchiectasis (permanent widening and damage of the main airways), can also occur, increasing susceptibility to recurrent infections.
The Mechanism of RA-Related Lung Damage
RA is fundamentally a disorder of immune system malfunction where defenses mistakenly target healthy tissues. The systemic nature allows inflammatory cells and signaling molecules that damage joints to migrate to the pulmonary system and cause injury. Chronic inflammation in the lungs damages the delicate epithelial cells lining the airways and alveoli. This damage triggers an aberrant repair process, resulting in the excessive deposition of collagen and other components, which manifests as fibrosis or scarring.
Specific autoantibodies significantly drive this pathology. High levels of rheumatoid factor and anti-citrullinated protein antibodies (ACPAs) are strongly associated with an increased risk of RA-related lung disease, especially ILD. These antibodies may target citrullinated proteins within the lung tissue, initiating the autoimmune response directly at the pulmonary site. Genetic predisposition combined with environmental factors, such as cigarette smoking, fuels this mechanism. Smoking can trigger the citrullination process and exacerbate the autoimmune attack, and in some people, the immune process may even originate in the lungs before joint symptoms appear.
Recognizing and Diagnosing Pulmonary Complications
Initial signs of RA-related lung involvement can be subtle and often masked by reduced physical activity due to joint disease. The most common warning signs are a persistent, dry cough and shortness of breath (dyspnea). Breathlessness is typically exertional at first, occurring during physical activity, but can progress to happen even at rest as the disease advances. Chest pain may also be reported, particularly if inflammation involves the pleural lining.
Physicians use several tools to confirm a diagnosis and determine the specific type and extent of lung involvement. High-Resolution Computed Tomography (HRCT) scans are the gold standard for visualizing the lung parenchyma, revealing inflammation, ILD scarring patterns, effusions, and nodules. Pulmonary Function Tests (PFTs) are non-invasive breathing tests that measure how well the lungs are working. These tests often reveal a restrictive pattern, where the lung volume is reduced, and a reduced capacity for oxygen transfer. In complex cases, procedures like bronchoalveolar lavage (BAL) or a lung biopsy may be necessary to confirm the diagnosis or rule out other causes. Early detection allows for timely intervention to slow the progression of irreversible scarring.
Treatment and Management Strategies
The primary approach to treating RA-related lung disease involves aggressively managing the underlying systemic inflammation that drives the condition. This requires using medications that modulate or suppress the immune system, such as Disease-Modifying Anti-Rheumatic Drugs (DMARDs) and biologic therapies. Medications like mycophenolate and rituximab are often used to treat the pulmonary manifestations and reduce the immune attack on the lung tissue. However, the choice of therapy is complex because some traditional RA treatments, such as methotrexate, require careful monitoring if lung involvement is present, due to the risk of drug-induced lung injury.
For people with progressive Interstitial Lung Disease, specific anti-fibrotic medications, such as nintedanib, are used to slow the rate of lung function decline. These agents interfere with the signaling pathways that promote scar tissue formation in the lungs. Supportive care is a major component for those with advanced disease. This includes supplemental oxygen therapy and pulmonary rehabilitation programs, which teach breathing techniques and exercises to improve quality of life. Effective management relies on integrated care between the rheumatologist and the pulmonologist, ensuring a coordinated and personalized treatment strategy.