Diagnosis and Management of Interstitial Lung Processes Associated with Rheumatoid Arthritis
Interstitial lung processes (ILD) are common yet insufficiently diagnosed complications of rheumatoid arthritis (RA), significantly increasing the morbidity and mortality of patients. ILD can occur at any stage of RA, presenting a diverse clinical picture. Usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) are the most common findings on high-resolution CT (HRCT). Some patients with RA-associated ILD may exhibit a progressive phenotype characterized by expanding fibrotic changes on HRCT, declining lung function, worsening respiratory symptoms, and early mortality. A recently published review summarizes strategies for screening, monitoring, and managing ILD in RA.
Prevalence and Risk Factors of RA-ILD
The prevalence of RA-ILD ranges from 10−61% depending on the disease definition used. Approximately 10−18% of patients with RA exhibit symptomatic or clinically significant ILD (abnormal findings on HRCT, deviations in lung function tests, and early mortality). Risk factors include older age, male gender, smoking, active synovitis, seropositive RA, and polymorphism in the MUC5B gene. However, ILD may also occur in RA patients without these risk factors.
Diagnosis and Screening of RA-ILD
Clinical examination of patients suspected of having RA-ILD includes lung function tests, HRCT, and in some cases, bronchoalveolar lavage (BAL). The gold standard for diagnosis is performing HRCT, which characterizes the type and severity of ILD and excludes other lung disorders (infections, malignancies, drug-induced damage). The most common finding is the UIP pattern (presence of reticulations, traction bronchiectasis, and honeycombing). The NSIP pattern is less common and shows signs of inflammation (ground glass opacities) along with reticulations. Surgical lung biopsy is reserved for patients with atypical findings on HRCT.
Early detection is crucial for prompt treatment of RA-ILD, as patients may already have significantly impaired lung function (reduced forced vital capacity /FVC/ and diffusing capacity for carbon monoxide /DLCO/) at the time of diagnosis. There is no standardized protocol for ILD screening in RA patients. The treating rheumatologist plays a key role, focusing on respiratory symptoms (e.g., exertional dyspnea, dry cough) at each check-up and performing lung auscultation. Patients presenting with progressive or abnormal auscultation findings (crepitus) should be referred for HRCT or to a pulmonologist. The absence of respiratory symptoms (dyspnea or cough) is not reliable, as many patients remain asymptomatic or their symptoms are underestimated due to limited mobility from joint involvement. Lung function tests and chest X-rays also have low sensitivity and specificity. Therefore, HRCT remains the best diagnostic tool, capable of detecting subclinical and asymptomatic forms of RA-ILD. For timely HRCT scheduling and to reduce radiation exposure, lung ultrasound can be used.
Monitoring and Management of RA-ILD
Regular follow-up of RA-ILD patients is vital for detecting progression. Similar to screening, there are no standardized monitoring protocols. Practically, it is appropriate to check for symptoms during each rheumatology visit, measure FVC and DLCO every 3−6 months, and perform HRCT annually. This helps identify ILD progression as well as other complications (pulmonary hypertension, neoplasia). For further deterioration in patients with moderate to severe lung involvement, lung function tests are the most sensitive method, more so than HRCT. Despite uncertainties in the role of HRCT and lung function tests, both are complementary and crucial for monitoring RA-ILD patients.
There are no international guidelines for RA-ILD therapy. Treatment must be individualized and tailored to the patient's needs, based on a multidisciplinary assessment of ILD severity and progression, joint involvement, other RA manifestations, and comorbidities. HRCT findings can also influence treatment. Primarily inflammatory conditions respond better to anti-inflammatory or immunosuppressive therapy than fibrosing diseases. Studies on RA treatments, particularly methotrexate, have shown it slows down RA-ILD progression and mitigates lung function decline. Due to insufficient data from randomized clinical trials, the effects of mycophenolate, cyclophosphamide, and corticosteroids remain inconclusive. The impact of drugs used in ILD treatment has also been explored. The INBUILD study investigated the efficacy of nintedanib in 663 ILD patients, 89 of whom had RA-ILD. Results confirmed a reduced decline in lung function over 1 year and during long-term follow-up. Nintedanib is approved for patients with chronic progressive fibrosing ILD. Those with severe RA-ILD unresponsive to maximal pharmacological treatment may be candidates for lung transplantation.
Conclusion
Despite known risk factors, ILD in RA patients may develop even without these factors, often detected at an advanced stage. Early detection and regular monitoring of RA-ILD patients are crucial. The ideal treatment goal is achieving RA remission and halting ILD progression, although this is rarely achieved in practice. A multidisciplinary team is essential for managing and monitoring this condition, tailoring approaches and treatment goals to the individual patient's needs.
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Source: Koduri G., Solomon J. J. Identification, monitoring, and management of rheumatoid arthritis-associated interstitial lung disease. Arthritis Rheumatol 2023 Jul 3, doi: 10.1002/art.42640 [Epub ahead of print].
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