Anti-Neutrophil Cytoplasmic Antibody (ANCA)-Negative Small Vessel Vasculitis: A Rare Cause of Pulmonary Renal Syndrome

Pulmonary renal syndrome (PRS) is characterized by both diffuse alveolar haemorrhage and glomerulonephritis as pathological features. Several immunologic and non-immunologic mechanisms including anti-neutrophil cytoplasmic antibody (ANCA)-positive vasculitis, anti-glomerular basement membrane disease, and systemic lupus erythematosus are commonly involved in the pathogenesis of the syndrome. We herein present a 60-year-old woman, non-smoker, who presented with fever, polyarthralgia, and the spreading of generalized purpuric rashes. The patient displayed rapid deterioration over the following two weeks marked by progressive declining renal function followed by haemoptysis. The patient was subsequently diagnosed with PRS, which was confirmed by the radiological evidence of alveolar haemorrhage and the histopathological evidence of pauci-immune glomerulonephritis. All immune markers including ANCA were negative. The patient was successfully treated with hemodialysis and immunosuppressive therapy. ANCA-negative vasculitis is a rare entity and even more rare as an etiology of PRS. An early diagnosis of this disease and its timely intervention is crucial.