Medullary angiitis and pauci-immune crescentic glomerulonephritis.

Although almost all pathological diagnoses made from a native kidney biopsy come from careful examination of the renal cortex, certain diseases have a characteristic medullary component. Medullary angiitis has histological features of interstitial hemorrhage in the medulla with an associated polymorphonuclear leukocyte infiltrate. These findings are primarily found in the setting of antineutrophil cytoplasmic antibody-associated vasculitis. Medullary angiitis identified in the setting of negative immunofluorescence is most suggestive of pauci-immune crescentic glomerulonephritis, as presented in this case.