Background: Neutrophil predominant capillaritis and interstitial inflammation is an uncommon renal biopsy finding, with a broad differential diagnosis. Case: A 77-year-old woman presented with a complicated history including vasculitis, cryoglobulinemia, malaise, and systemic symptoms, which progressed to acute kidney injury. Renal biopsy demonstrated prominent neutrophilic capillaritis with interstitial inflammation, and fibrinoid deposits in medullary capillaries and interstitium. Glomeruli showed membranoproliferative glomerulonephritis, but no crescents or necrosis. Discussion: We interpret the capillary and interstitial changes as evidence of cryoglobulin-associated vasculitis, and discuss the differential diagnosis of this uncommon histologic pattern of renal pathology, including other vasculitides, infection, ischemia-infarction, collagen vascular disease, and antibody-mediated allograft rejection, among others.
- Necrotizing capillaritis
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