What are the Pulmonary manifestations of Rheumatoid Arthritis
• Pleural disease: Pleurisy and pleural effusions (often unilateral) occur commonly in RA but are symptomatic in <5%. They can occasionally be the first manifestations of RA. Pleural effusions are characterized as cellular exudates with high protein and lactate dehydrogenase levels, a low glucose level (resulting from a defect in the transport of glucose across the pleura), and frequently a low pH (masquerading as an infection). Tuberculosis must be ruled out in patients at risk.
• Nodules: Rheumatoid nodules in the lung may be solitary or multiple and can cavitate or resolve spontaneously. Caplan’s syndrome involves multiple nodules occurring in the lungs of RA patients who are coal miners (a pneumoconiosis in the setting of RA). In patients at risk (smokers), lung cancer needs to be ruled out.
• Interstitial lung disease (ILD): ILD occurs commonly in RA patients but is symptomatic and progressive in <10%. In RA, the usual interstitial pneumonia (UIP) pattern of ILD is most common, which is in contrast to the nonspecific interstitial pneumonia (NSIP) pattern that is most common in other connective tissue disease associated-ILDs. RA-ILD is more common in males and smokers. Fibrosis primarily involves the lower lobes. Occasionally, ILD can antedate the onset of arthritis.
• Organizing pneumonia (OP): Can be secondary to RA or disease-modifying antirheumatic drugs (DMARDs). OP is less common, but more responsive to corticosteroid therapy, than RA-associated bronchiolitis obliterans (BO), UIP, or NSIP.
• Airways disease: Airways disease in RA can range from mild disease that may only be seen on imaging to an emphysema-like disease with more significant airway obstruction. In addition, bronchiectasis may be seen. The most severe form of airways disease is BO, also called constrictive bronchiolitis. Patients have acute onset of dyspnea, a hyperinflated chest x-ray, and small airway obstruction on pulmonary function tests. This condition can be rapidly fatal. Smoking may play some role in all of these airway findings. Finally, upper airway disease may be seen in the form of cricoarytenoid disease that can mimic tracheal stenosis.