Lungs are frequently involved in rheumatic diseases, but it is still unclear whether they are the origin or the site of manifestation. Recognizing and mapping the involvement patterns on the CT in time is the main clinical challenge as they serve as the starting point for further therapeutic action.
After cardiovascular complications, interstitial lung disease (ILD) is the second leading cause of death in people suffering from rheumatoid arthritis (RA). The pathogenesis of ILD, however, has remained largely unclear. Currently, there is growing debate as to whether RA begins in the lungs or manifests there in the course of the disease. Unambiguous results are not available at present.
On the one hand, there are documented patients with rheumatic diseases who do not show a manifest ILD, but who do develop lymphocytic alveolitis. On the other hand, there are also patients with manifest ILD who were found to have autoimmune markers in the absence of rheumatic disease.
There is no doubt that diagnostic clarification in both directions is recommended. In other words, every patient with an initial diagnosis of rheumatoid arthritis should also undergo a pneumological examination. In addition, patients with ILD should be screened for relevant autoantibodies and extrapulmonary symptoms.
Diagnosing cases of ILD is usually done with high-resolution computed tomography (HR-CT). Depending on the rheumatic disease, this helps to identify a variety of involvement patterns of the lung parenchyma. An interdisciplinary team of radiologists, rheumatologists and pulmonologists will ideally evaluate the diagnosis, as the findings will also determine the appropriate treatment for the individual patient.
ILD can manifest in multiple anatomic structures:
There are differences in the frequency distribution of the structures involved between the individual rheumatic diseases. While rheumatoid arthritis, for example, primarily affects the lung parenchyma, respiratory tract and pleura and less frequently the vessels, the opposite is true for systemic lupus erythematosus (SLE). In the latter case, the vessels belong to the most commonly affected areas. With regard to ankylosing spondylitis, one can typically observe an apically localized cystic-fibrotic remodeling.
Treatments depend on the nature of lung involvement. The main focus lies on anti-inflammatory or immunosuppressive regimens, with steroids being particularly effective in many cases. Other substances are methotrexate and mycophenolate. No conclusive results are yet available for the use of anti-TNF-α, rituximab, cyclophosphamide, and azathioprine.
A number of pharmaceuticals used for the treatment of rheumatic diseases, however, are themselves the cause of ILD as a result of their toxic effect on the lungs. It is imperative that they be taken into account prior to diagnosis. Substances with potentially harmful effects include:
What is clear is that lung involvement is common in rheumatic diseases and can affect all anatomical structures. The type and severity of the manifestation are highly relevant both in terms of prognosis and therapy and should be taken into account when making treatment decisions, ideally as part of an interdisciplinary team.
Source:
Ewig S, Bollow M. Lungenmanifestationen bei adulten rheumatischen Erkrankungen [Pulmonary manifestations in adult rheumatic diseases]. Z Rheumatol. 2021 Feb;80(Suppl 1):13-32. German.