Rheumatoid arthritis (RA) is a chronic autoimmune disorder that primarily targets the joints, causing inflammation and damage. RA is a systemic disease, meaning the inflammatory process can affect organs throughout the body. The respiratory system is one of the most frequently involved sites outside of the joints. Lung complications represent a significant cause of illness and mortality for people with RA. The lungs can be affected by RA long before, or entirely independently of, joint symptoms.
How Rheumatoid Arthritis Affects Lung Tissues
The systemic inflammation associated with rheumatoid arthritis can damage multiple parts of the pulmonary system. The most common complication is Rheumatoid Arthritis-associated Interstitial Lung Disease (RA-ILD), which involves the interstitium, the delicate network of tissue surrounding the air sacs. In RA-ILD, the immune system attacks this tissue, leading to chronic inflammation and the formation of scar tissue, known as fibrosis. This scarring makes the lung stiff and less efficient at transferring oxygen into the bloodstream.
The membranes surrounding the lungs can also become inflamed, a condition known as pleuritis or pleural disease. Inflammation of the pleura, a thin, double-layered membrane, can lead to a buildup of excess fluid in the space between the layers, called a pleural effusion. Although often asymptomatic and detected only through imaging, pleural involvement is common in RA patients.
Another manifestation is the formation of rheumatoid nodules, which are lumps of inflammatory tissue that can appear in the lung parenchyma. These nodules are typically benign and may be single or multiple, often developing in the periphery of the lungs. They can occasionally cavitate or rupture, leading to complications like a pneumothorax or pleural effusion.
The airways are also susceptible to RA-related inflammation, resulting in conditions like bronchiolitis, which affects the small breathing tubes. This airway disease can be obstructive or constrictive, potentially leading to a narrowing of the bronchioles and difficulty with airflow.
Identifying Symptoms of Lung Involvement
Recognizing the signs of lung involvement is important because symptoms can be subtle and easily mistaken for general fatigue or other effects of RA. A persistent dry cough, one that does not produce mucus, is frequently reported as an early sign of pulmonary changes, particularly RA-ILD. This cough may be present for months before more serious respiratory issues become apparent.
Shortness of breath (dyspnea) is another significant symptom, especially during physical exertion. As the lung tissue becomes scarred and less compliant, it takes more effort to breathe, and exercise tolerance decreases gradually. Patients may notice that activities they once managed easily, like climbing stairs, now cause them to feel winded.
Chest pain can signal pleurisy, as the inflamed pleural linings rub against each other, causing a sharp discomfort that worsens with deep breathing or coughing. Systemic symptoms, such as unexplained low-grade fever, fatigue, and unintended weight loss, can also accompany active lung inflammation. Any new or worsening respiratory complaint in a person with RA should prompt a medical evaluation, as these symptoms are not unique to RA-related lung disease.
Testing and Treatment Approaches
When lung involvement is suspected, a structured evaluation process is initiated to determine the nature and extent of the damage. The gold standard imaging test for visualizing changes in the lung tissue is a High-Resolution Computed Tomography (HRCT) scan. This specialized CT scan provides detailed images that detect signs of scarring, inflammation, or nodules, helping classify the pattern of interstitial lung disease to guide treatment.
Pulmonary Function Tests (PFTs) measure how well the lungs are working, including their capacity and efficiency. These tests track metrics like forced vital capacity (FVC), which measures the amount of air exhaled after a deep breath, and the diffusing capacity of the lung for carbon monoxide (DLCO), which assesses oxygen transfer. A decrease in these values can confirm a restrictive lung pattern consistent with ILD.
Management of RA-related lung complications is dual-focused, addressing both the underlying systemic inflammation of RA and the specific lung condition. The first approach involves controlling the overall disease activity of RA using disease-modifying anti-rheumatic drugs (DMARDs) and biologics. Controlling systemic inflammation may help slow the progression of the lung disease.
For established RA-ILD, treatment may include corticosteroids and other immunosuppressive agents to reduce inflammation within the lung tissue. Newer therapies, such as anti-fibrotic medications like nintedanib, are used to slow the rate of decline in lung function for patients with progressive fibrosis. Effective care requires close collaboration between a rheumatologist and a pulmonologist to ensure a coordinated treatment plan.