Pulmonary Pathology of the Rheumatic Diseases

Thoracic manifestations of the rheumatic diseases (RDs) are a significant cause of morbidity and mortality worldwide. The five RDs most frequently associated with pleuropulmonary disease are (1) rheumatoid arthritis (RA), (2) systemic lupus erythematosus (SLE), (3) progressive systemic sclerosis (PSS), (4) polymyositis/dermatomyositis (PM/DM), and (5) Sjögren syndrome (SS). The clinical presentation is highly variable, ranging from pleuritic pain alone to slowly progressive breathlessness accompanied by cough. On occasion RD may present acutely with overwhelming respiratory failure as the first pulmonary manifestation. In all of the RDs, the pathology is dominated by either or both inflammation and fibrosis, but the anatomical distribution in each varies somewhat. For example, airway-associated lymphoid hyperplasia is a common manifestation of SS, PM/DM preferentially involves the alveolar parenchyma, and pleural inflammation is most commonly seen in RA. Such changes may be detected radiologically as peribronchovascular disease in SS, ground-glass infiltrates in PM/DM, and pleural disease with effusion in RA. Some RDs are more commonly associated with distinctive histopathology, such as rheumatoid nodules in RA, or lymphoid hyperplasia in both RA and SS. Patients with PSS are at particular risk for pulmonary hypertension when the lung is involved. Also, statistically, acute lung injury occurs more commonly in some, such as SLE and PM/DM. The very common use of immunosuppressive agents in the treatment of RD creates additional diagnostic problems related to drug toxicity and infection. Finally, a major confounding factor occurs when preclinical RD presents first as pulmonary disease (particularly PM/DM), an occurrence that may invoke one of the so-called idiopathic interstitial pneumonias. The most common pleuropulmonary pathological manifestations of the five major RDs are presented and discussed with brief radiological correlations.