ANCA-negative Pauci-immune Vasculitis, an Often-missed Clinical Entity: A Case Report

The kidneys are frequently affected by antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), which comprises renal-restricted vasculitis, eosinophilic granulomatosis with polyangiitis (EGPA), microscopic polyangiitis (MPA), and granulomatosis with polyangiitis (GPA). The most prevalent kidney disease is glomerulonephritis. On direct immunofluorescence (DIF), they show an absence of any immune complex deposition and hence are regarded as "pauci-immune glomerulonephritis" (PIGN). Around 10-40% of AAV are ANCA negative (seronegative PIGN). They tend to show a more limited disease, fewer extra-renal manifestations, and a lower overall Birmingham Vasculitis Activity Score (BVAS). In the absence of ANCA positivity in blood, a consistent clinical picture supported by tissue diagnosis is the only tool to diagnose such cases. Here we present a case of a 58-year-old male who presented with a history of prolonged fever, hematuria, and generalized palpable purpura all over the body. His blood for ANCA was negative. After a kidney biopsy, he was finally diagnosed with ANCA-negative pauci-immune vasculitis and was treated with rituximab.