The Lung in Mixed Connective Tissue Disease

Abstract

Mixed Connective Tissue Disease (MCTD) remains a controversial classification within the field of connective tissue diseases. Since its original description in 1972 by Sharp et al, different alternative descriptions appear in the literature, such as “overlap syndrome” or “undifferentiated connective tissue disease.” The diagnosis is based on the presence of overlapping symptoms of systemic lupus erythematosus (SLE), systemic sclerosis (SS), and polymyositis (PM), and the detection of increased titers of anti-RNP (ribonucleoprotein) antibody. Sharp et al thought that these patients had a distinct rheumatological syndrome characterized by the absence of arthritis, renal disease, and pulmonary involvement, as well as a favorable prognosis. Further studies do not support this benign clinical course that spares the lung. Pulmonary abnormalities have been described in 25-85% of MCTD patients. The pulmonary manifestations are similar in presentation and severity as seen in PSS, SLE, and PM. The most common presentations include interstitial lung disease, pleural effusions, and pulmonary arterial hypertension. Less common pulmonary presentations are diffuse alveolar hemorrhage with isolated pulmonary capillaritis, rapidly progressive pulmonary arterial hypertension, small airway disease, pulmonary embolic disease, aspiration syndrome, and neuromuscular respiratory failure. The histologic descriptions of this lung involvement are sparse. Nevertheless, the need for lung biopsy should be determined on an individual basis and reserved for atypical presentations. Corticosteroids may be insufficient for the treatment of MCTD with pulmonary involvement. Early cytotoxic therapy has been advocated for interstitial lung disease and diffuse alveolar hemorrhage. This review will present the diagnosis, clinical features, controversies, pulmonary involvement, therapy, and prognosis of this relatively new disease.

Key Words:

mixed connective tissue disease - lung - pulmonary function tests - pulmonary fibrosis - diffuse alveolar hemorrhage - corticosteroids - cytotoxic agents