A Case of Different Organ Responses to Immunosuppressive Therapy In a Microscopic Polyangiitis Patient with Interstitial Lung Disease

Microscopic polyangiitis (MPA) is an idiopathic autoimmune disease characterized by systemic vasculitis associated with antineutrophil cytoplasmic autoantibodies. Interstitial lung disease is a less recognized manifestation of MPA and has a poor prognosis. A 61-year-old man presented with persistent cough, sputum and dyspnea. Laboratory examination revealed microscopic hematuria and renal insufficiency. Perinuclear anti-neutrophil cytoplasmic autoantibodies were positive according to serological testing. Computed tomography scans showed bibasilar reticulation and honeycombing in a peripheral distribution. Therefore, renal biopsy was performed, and MPA was diagnosed. After treating with corticosteroids and immunosuppressive agents, the patient had a complete renal response but progressive interstitial lung disease. We report a case of MPA presenting with interstitial lung disease in which the patient experienced different responses in each organ. (Korean J Med 2014;86:84-88)