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Introduction

Pleuropulmonary involvement associated with the collagen vascular diseases occurs frequently. All the structures within the respiratory tract may be affected, either separately or in combination. This includes the respiratory muscles, the pleura, the conducting airways, and the lung parenchyma—the small airways, the interstitium, or the pulmonary vessels. Moreover, these patients experience an increased incidence of community-acquired pneumonia as well as pneumonia associated with the immunosuppressive drugs employed for treatment. Anti–tumor necrosis factor-α (anti–TNF-α) agents increase the risk for infections, particularly mycobacterial pathogens, both tuberculous and nontuberculous. Cytotoxic drugs, particularly methotrexate and gold, can also induce various noninfectious interstitial reactions, which are often difficult to distinguish from a primary interstitial complication of a collagen vascular disease.1

Although most pulmonary complications appear in an established case of a collagen vascular disease, lung disease may precede the more typical systemic manifestations.2 For example, in both rheumatoid arthritis and polymyositis–dermatomyositis, the interstitial lung disease may precede the joint and muscle disease for several months to several years. This is also the case, but to a lesser extent, for scleroderma. In one study, 19% of patients initially diagnosed with idiopathic pulmonary fibrosis developed a collagen vascular disease over a period of 1 to 11 years, primarily rheumatoid arthritis or polymyositis–dermatomyositis. These individuals were younger and more likely to be women. Pleuritis with or without effusion sometimes heralds the onset of rheumatoid arthritis or systemic lupus erythematosus (SLE). An acute immunologic pneumonitis or diffuse alveolar hemorrhage has been reported to be the signal event in SLE, polymyositis–dermatomyositis, and mixed connective-tissue disease.

The incidence of the pleuropulmonary complications (Table 60-1) is variable. Interstitial lung disease is reported to be as high as 60% in premortem and 100% in postmortem studies in scleroderma. In contrast, interstitial lung disease in ankylosing spondylitis is an uncommon event. In general, the incidence of interstitial lung disease is increasing for most of the collagen vascular diseases, primarily due to increased recognition and more sensitive screening techniques such as high-resolution computed tomography and bronchoalveolar lavage, which will detect abnormalities in both asymptomatic as well as symptomatic patients with normal chest radiographs. Prior studies assessing the incidence of disease relied on physiologic testing, which included spirometry, lung volumes, and diffusing capacity but did not measure rest and exercise gas exchange, which is the most sensitive physiologic marker of interstitial lung disease and pulmonary vascular disease.

Table 60-1Pulmonary Complications of the Collagen Vascular Diseases

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