A Challenging Clinical Scenario of ANCA-Associated Vasculitis Featuring Rapidly Progressive Crescentic Glomerulonephritis, Neutropenic Colitis, and Pancytopenia

Introduction: With a peak incidence between 65 and 75 years, though it can occur at any age, ANCA-associated vasculitis (AAV) exhibits a slight male predominance. AAV shows geographical and race/ethnic differences in prevalence and encompasses various clinicopathologic phenotypes, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), eosinophilic GPA (EGPA), and renal-limited necrotizing and crescentic glomerulonephritis (NCGN). It primarily affects small vessels (arteries, arterioles, venules, and veins) in any organ. The activity in the bone marrow is typically diagnosed through a biopsy with the presence of granulomas, accompanied by serum antibodies and systemic symptoms. Case Description: We present a 58-year-old with ANCA GPA vasculitis diagnosed 3 years ago. Initial symptoms included episcleritis, blurred vision, rhinitis, sinusitis, headaches, and migraines. Treatment included methotrexate, prednisone, and folic acid. In late August 2023, polyarthralgia, polyarthritis, and macroscopic hematuria emerged. Creatinine rose to 6.0, urea to 250, with neutropenic colitis due to Clostridium difficile. Suspected acute kidney injury or vasculitis activity required renal replacement therapy. A bone marrow biopsy showed no vasculitis response. Tests for ANA, SSA/Ro, HIV, HCV, HBV were negative. Kidney biopsy revealed small vessel pauciimmune vasculitis. Improvement followed rituximab induction. Glomerular filtration rate is 30 ml/min, and the patient is hemodialysis free Discussion: This case underscores the significance of performing biopsies to diagnose AAV in patients with systemic activity. Even though the patient's bone marrow biopsy showed no evidence of granulomas and they were exposed to methotrexate despite prophylactic treatment, it is possible that systemic vasculitis activity affected the bone marrow, which went undiagnosed in the sample obtained. These cases emphasize the need for a comprehensive clinical evaluation and interdisciplinary management.