[A case of non-specific interstitial pneumonia in patient with microscopic polyangiitis]

Non-specific interstitial pneumonia developed as an initial manifestation in a patient with microscopic polyangiitis. A 62-year-old man was admitted to our hospital in March 2001, because of fever and intermittent myalgia of lower extremities. Chest X-ray had revealed reticular shadows in the bilateral middle and lower lung fields since 1996. Just before admission, the patient had been diagnosed as having nonspecific interstitial pneumonia (NSIP) from the specimen obtained by video-assisted thoracoscopic surgery (VATS) in another hospital. Physical examination on admission revealed bilateral episcleritis. Laboratory data showed elevated levels of CRP and KL-6, polyclonal gammaglobulinemia, positive rheumatoid factor and myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA). Sensory and motor nerve conducting velocities were delayed in left peroneal nerve, but not other nerves, suggesting mononeuropathy. Biopsied specimens of the left quadriceps revealed vasculitis of arteioles. In spite of positive proteinuria and hematuria, no pathological lesion was found in the kidney. From all of these findings, the patient was diagnosed as having microscopic polyangiitis (MPA) without renal involvement. Methylprednisolone pulse therapy followed by intravenous cyclophosphamide pulse therapy improved his clinical conditions such as pyrexia, cough, myalgia, episcleritis and respiratory symptoms with decreased titer of serum MPO-ANCA. Thereafter, the dose of prednisolone was successfully tapered to 10 mg/day without clinical relapse. In the present patient who developed demonstrated non-specific interstitial pneumonia as an initial manifestation of MPA, VATS provided useful diagnostic and prognostic information, leading to an appropriate therapeutic choice.