[Interstitial pneumonia associated with mixed connective tissue disease--marked improvement with azathioprine]

A 55-year-old man who complained dyspnea on exertion was given a diagnosis of interstitial pneumonia associated with mixed connective tissue disease, based on symptoms and on physical and laboratory findings. Soon afterward, he experienced an acute exacerbation of the interstitial pneumonia. He was given three courses of steroid pulse therapy and cyclophosphamide, but his condition worsened. After administration of azathioprine in addition to corticosteroids, his respiratory status improved. The dose of corticosteroids was tapered and the patient has been free of disease for two years. Pulmonary involvement in mixed connective tissue disease has been considered to be relatively benign and easily treated with corticosteroids. Recently, however, many cases of corticosteroid-resistant disease with poor outcome have been reported. Azathioprine was very effective against the interstitial pneumonia in this case, but general conclusions about the most effective type of immunosuppressive agent and the timing of its administration must await the results of further study.