Microscopic Polyangiitis Presenting as Idiopathic Pulmonary Fibrosis: Is Anti-Neutrophilic Cytoplasmic Antibody Testing Indicated?

We report a 55-year old woman with microscopic polyangiitis who presented with idiopathic pulmonary fibrosis and 1 year later developed hematuria and proteinuria. She had a high serum level of perinuclear anti-neutrophilic cytoplasmic antibodies. Renal angiogram was normal. The diagnosis of microscopic polyangiitis was confirmed by renal biopsy, which showed pauci-immune crescentic glomerulonephritis.The patient received immunosuppressive therapy and improved markedly. Consideration of small vessel vasculitis is important in the differential diagnosis of idiopathic pulmonary fibrosis.