[Collagen diseases with pulmonary involvement]

Pulmonary involvement is a common feature in patients with various collagen diseases. Some types of the pulmonary involvement are resistant to currently available treatment regimens and thus considered as intractable conditions. These include acute/subacute interstitial pneumonia in dermatomyositis, pulmonary interstitial fibrosis in scleroderma, and diffuse alveolar hemorrhage. Acute/subacute interstitial pneumonia with the histology of diffuse alveolar damage (DAD) is mainly occurred in patients with amyopathic or hypomyopathic dermatomyositis who lack autoantibodies to aminoacyl tRNA synthetases. Intensive immunosuppressive treatment in the early phase of the disease may be effective for this intractable complication. Nearly one-third of patients with scleroderma have slowly progressive pulmonary interstitial fibrosis, leading to end-stage respiratory failure. Non-specific interstitial pneumonia (NSIP) with an excessive fibrotic change is a major histology of these patients. There are accumulating evidences showing the effectiveness of cyclophosphamide in patients with this intractable condition, especially those with active alveolitis. Diffuse alveolar hemorrhage is a fatal complication mainly occurred in patients with systemic lupus erythematosus and those with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, including microscopic polyangitis (MPA) and Wegener's granulomatosus. Immediate diagnosis and introduction of intensive treatment are necessary to save the patients with this complication.