When Anti-Neutrophil Cytoplasmic Antibody Fails: A Case of Anti-Neutrophil Cytoplasmic Antibody Negative Granulomatosis With Polyangiitis.

Granulomatosis with polyangiitis (GPA) is a vasculitis of small and medium-sized vessels and presents with varying signs and symptoms. It includes upper and lower airway manifestations and glomerulonephritis with a positive antineutrophil cytoplasmic antibody (ANCA) in serology in 90% of cases. However, about 10% of cases with GPA can have negative serology, often resulting in a diagnostic delay. Obtaining a tissue pathology is needed to confirm GPA. Here we present a 77-year-old male who presented with generalized weakness and loss of appetite and was found to have glomerulonephritis and bilateral opacities in the lungs with a negative ANCA. He was diagnosed with ANCA negative granulomatosis with polyangiitis after a renal biopsy revealed necrotizing inflammation with crescent formation. He was successfully treated with systemic glucocorticoids and rituximab. In conclusion, prompt diagnosis and treatment of ANCA negative vasculitis are required to decrease mortality.