[A case of mixed connective tissue disease with acute interstitial pneumonitis].

A 43-years-old woman was admitted to the Hokkaido University Hospital because of high fever, muscle weakness and dyspnea in May 1993. She had has muscle weakness of upper extremities since December 1992. She had developed swollen hand, polyarthralgia and Raynaud's phenomenon. High fever and severe dyspnea developed in May 1993. Chest roentogenogram was normal in April 1993. Physical examination showed Velcro rales in both lower lung fields. Her laboratory data showed increased muscle enzymes, high titers of anti-nuclear-antibody (1: 1280) and anti-RNP-antibody (index 199.4 (normal < 7)). Anti-DNA, anti-Sm and anti-Jo-1-antibodies were all negative. Blood gas analysis showed severe hypoxemia. Chest roentogenogram revealed diffuse bilateral interstitial infiltrates prominent in the bases. Diagnosis of mixed connective tissue disease with acute interstitial pneumonitis was made. She was treated with steroid pulse therapy (methylprednisolone 1 g x 3 days) followed by high dose oral prednisolone (60 mg/day), and diffuse interstitial infiltrates disappeared within one week. Prednisolone could be tapered to 17.5 mg/day without relapse. Acute interstitial pneumonitis is a rare complication of mixed connective tissue disease, but may be life threatening. In such cases, high dose steroid therapy should be started without delay.