p-ANCA, or Perinuclear Anti-Neutrophil Cytoplasmic Antibodies, show a perinuclear staining pattern.
This pattern occurs because the vast majority of the antigens targeted by ANCAs are highly cationic (Positively charged) at pH 7.00. During ethanol fixation, antigens which are more cationic migrate and localize around the nucleus, attracted by its negatively charged DNA content. Antibody staining therefore results in fluorescence of the region around the nucleus.
By far the most common p-ANCA target is myeloperoxidase (MPO), a neutrophil granule protein whose primary role in normal metabolic processes is generation of oxygen radicals.
p-ANCA is associated with several medical conditions:
- It is fairly specific, but not sensitive for ulcerative colitis, so is not useful as a sole diagnostic test. When measured together with Anti-saccharomyces cerevisiae antibodies (ASCA), p-ANCA has been estimated to have a specificity of 97% and a sensitivity of 48% in differentiating patients with ulcerative colitis from normal controls.
- about 50% of cases of Churg-Strauss syndrome
- A majority of primary sclerosing cholangitis
- sometimes polyarteritis nodosa (only in the variant microscopic polyangitis, usually negative in typical polyarteritis nodosa)
- microscopic polyangiitis 
- Focal necrotising and crescentic glomerulonephritis
- Rheumatoid arthritis
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Anti-nuclear antibody Anti-mitochondrial antibody Anti-cytoplasm antibody Cell membrane Extracellular Multiple locations Ungrouped Vasculitis/arteritis: systemic vasculitis (M30–M31, 446) Large vessel Medium vessel Small vesselPauci-immuneHypersensitivity vasculitis/Henoch–Schönlein purpuraUngrouped OtherGoodpasture's syndrome · Sneddon's syndrome
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