Figure 219

Fibrinoid necrosis obliterating the wall of an arteriole in a renal biopsy specimen from a patient with Henoch-Schonlein purpura (hematoxylin and eosin). Involvement of renal vessels other than glomeruli is rare in Henoch-Schonlein purpura.

ANCA Small Vessel Vasculitis

FIGURE 2-20 (see Color Plate)

C-ANCA staining pattern of ethanol-fixed normal human neutrophils in an indirect immunofluorescence assay of serum. Approximately 90% of C-ANCA are specific for proteinase 3 (PR3-ANCA) in specific immunochemical assays, such as enzyme immunoassay (EIA) [8-10].

FIGURE 2-21 (see Color Plate)

P-ANCA staining pattern of ethanol-fixed normal human neu-trophils in an indirect immunofluorescence assay of serum. Approximately 90% of P-ANCA in patients with nephritis or vasculitis are specific for myeloperoxidase (MPO-ANCA) in specific immunochemical assays, such as EIA. P-ANCA in patients with other types of inflammatory disease, such as inflammatory bowel disease are typically not specific for MPO. Using ethanol-fixed neu-trophils as substrate, nuclear staining caused by anti-nuclear antibodies (ANA) cannot be distinguished confidently from nuclear staining caused by P-ANCA. Using formalin-fixed neutrophils as substrate, P-ANCA stain the cytoplasm but ANA do not. The difference in staining pattern between ethanol and formalin fixed cells is due to the artifactual diffusion of solubilized cationic ANCA-antigens to the nucleus during substrate preparation of the ethanol-fixed cells, as opposed to immobilization of the antigens in the cytoplasm by covalent crosslinking during formalin fixation.

Pauci-immune crescentic glomerulonephritis

Microscopic polyangiitis

Wegener's granulomatosis

P-ANCA/MPO-ANCA C-ANCA/PR3-ANCA

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