Case of MPO-ANCA positive interstitial pneumonitis and necrotizing, crescentic glomerulonephritis

A 52-year-old man was admitted to our hospital in July 1995, because of intermittent claudication, paresthesia on foot and gross hematuria. Chest radiograph in 1988 revealed bilateral interstitial shadows and proteinuria had been pointed out since 1992. On admission, chest X-ray and computed tomography showed diffuse interstitial shadow, however it had not been changed for several years. Laboratory tests revealed elevated level of erythrocyte sedimentation rate, C-reactive protein, immunoglobulin, rheumatoid factor, IgG-rheumatoid factor, and immune complex. Serum MPO- ANCA were positive. Although serum creatinine level and renal function test were normal, renal biopsy demonstrated crescentic formation and necrotizing vasculitis. Immunofluorescence and electron microscopy demonstrated no remarkable deposit in glomerulus. A diagnosis of microscopic polyarteritis necrotizing and crescentic glomerulonephritis (NCGN) was made. Treatment was initiated with 30 mg of prednisolone, followed by marked improvement of intermittent claudication, and decreased titer of serum MPO-ANCA. Previous reports have demonstrated the association of MPO-ANCA with rapidly progressive NCGN, microscopic polyarteritis, and occasionally pulmonary hemorrhage recognized as pulmonary-renal syndrome. However, the present case suggests the possibility that another disease subset may also be associated with MPO ANCA, which is characterized by interstitial pneumonitis and slowly progressive glomerulonephritis.