Active and Mild Chronic Necrotizing Crescentic Glomerulonephritis With Severe Medullary Angiitis in an Elderly Male Patient: A Case Report.

Pauci-immune crescentic glomerulonephritis (GN) is a rapidly progressive form of GN typically associated with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and may present with rare but severe histologic findings such as medullary angiitis. We describe a 69-year-old male patient with no prior medical history who presented with worsening renal function following a recent hospitalization for what is thought to be pneumonia and presumed prerenal azotemia. On readmission, he was found to have an elevated serum creatinine of 5.42 mg/dL, significant hematuria and proteinuria, elevated inflammatory markers, and normocytic anemia. Further evaluation revealed positive P-ANCA at a 1:640 titer and elevated serum IgG. A renal biopsy confirmed the diagnosis of pauci-immune necrotizing crescentic GN with both acute and chronic features, severe medullary angiitis, and arterial nephrosclerosis. The patient was treated with intravenous pulse methylprednisolone, followed by rituximab and avacopan, resulting in significant improvement in renal function without the need for dialysis. This case highlights the diagnostic challenge of distinguishing intrinsic renal disease from prerenal azotemia in the setting of acute illness and underscores the importance of considering AAV in patients presenting with unexplained acute kidney injury and systemic inflammatory markers. Medullary angiitis, although infrequently reported, may be associated with more severe renal disease and should be recognized as a potential marker of disease severity. Early biopsy and prompt initiation of immunosuppressive therapy can lead to substantial renal recovery, even in the presence of chronic histologic damage.