by Dimitrios Pappas, MD (Former fellow and faculty member. Current affiliation, Columbia University)
Rheumatoid Arthritis is a chronic inflammatory disease that leads to chronic pain, high rates of disability and unemployment (1-8). Furthermore, the lifespan of RA patients is shortened by approximately 10 years (1-7), and standardized mortality ratios for RA range from 1.28 to 3.0 (2).
Respiratory causes, are a significant contributor to excess mortality in patients with RA ranking as the second major cause of death in this patient population (9). While the treatment of rheumatoid articular disease has greatly improved in recent years, as measured by disease activity and quality of life instruments, these benefits have not extended to RA-associated lung disease.
A number of pulmonary manifestations are associated with RA. The most common is interstitial lung disease (ILD) which leads to pulmonary fibrosis (PF) during which the lung parenchyma is involved (10).
Interstitial lung disease (ILD) is not only the most common but also the most serious form of lung involvement in RA. Radiographic changes such as fibrosis, and physiological changes such as restriction or decreased diffusing capacity on pulmonary function testing, may precede symptoms by years; however, once clinically apparent, ILD is associated with significant mortality (11). The reported prevalence of subclinical and symptomatic (clinically evident) ILD in RA varies depending on the method of detection and ranges between 1 and 58% (12-16).
Recently, attention has been drawn to the higher prevalence or Chronic Obstructive Pulmonary Disease (COPD) in patients with RA. COPD has been reported to occur more frequently in patients with RA than in general population even after adjusting for smoking, and is believed to have a more pronounced impact on survival compared to COPD in patients without RA (17).
Thus, both restrictive (ILD) and obstructive lung disease produce clinically important effects in patients with RA. However, their diagnosis is often delayed as the early signs and symptoms may be indolent, non-specific and masked by reduced physical activity due to articular disease. Respiratory complaints may be under-reported and/or unrecognized in RA patients with lung disease as individuals with RA are generally less physically active due to joint pain and chronic fatigue and thus less likely to experience symptoms such as dyspnea on exertion. In addition the nature of the symptoms of lung involvement overlap with symptoms of cardiac disease, another common comorbidity in RA, thus potentially constituting the diagnosis of respiratory disease even more prodigious.
In a recent study at Hopkins (unpublished data), we observed a high prevalence of Pulmonary Function Tests (PFT) abnormalities in a selected population of RA patients and a considerable frequency of respiratory symptoms as assessed by a formal questionnaire.
Analytically, we identified that out of the 159 patients who underwent PFT testing, 45 (28%) demonstrated at least one predefined abnormality. Restrictive lung disease was observed in 12 (7.6%), obstructive lung disease in 18 (11.3%) and impaired diffusing capacity in 31 (19.8%). Impaired diffusion in conjunction with restriction or obstruction was observed in 16 of those subjects, while the remaining 15 (9.6%) had isolated impaired diffusion. Pulmonary symptoms were reported by 78 patients (42%) when asked about the presence of cough, phlegm, wheezing, and breathlessness.
Only seventeen patients (37.8%) of the 45 patients with abnormal PFTs reported a prior known diagnosis of lung disease in the form of emphysema (8 patients), asthma (8 patients) or rheumatoid lung disease (2 patients).
In conclusion, rheumatoid arthritis should be viewed as a multisystem disease affecting multiple organs. Vigilance for lung involvement is necessary among rheumatologists and patients. Despite the absence of effective treatments for advanced respiratory disease it is possible that therapeutic intervention at an early stage may be beneficial. It has been suggested that early diagnosis and treatment with antifibrotic agents may alter the prognosis of pulmonary fibrosis (18, 19). Similarly, early intervention in patients with RA and COPD would improve quality of life and performance status.
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