Which diseases are associated with ANCAs?
Patients who are ANCA-positive should have ELISA testing for specific antibodies directed against PR3 and MPO, which are the most relevant autoantibodies associated with an underlying systemic necrotizing vasculitis. Other disease associations with C-ANCA and P-ANCA are typically negative for anti-PR3 and anti-MPO antibodies:
• C-ANCA (PR3-positive): Granulomatosis with polyangiitis, microscopic polyangiitis (usually P-ANCA), eosinophilic granulomatosis with polyangiitis (rare)
• P-ANCA (MPO-positive): Microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis, pauci-immune glomerulonephritis (renal-limited vasculitis), Goodpasture’s disease, drug-induced syndromes (hydralazine, propylthiouracil, minocycline, others)
• P-ANCA (MPO-negative): Autoimmune gastrointestinal disorders (ulcerative colitis, primary sclerosing cholangitis, autoimmune hepatitis), rheumatic diseases ( RA, SLE, many others ), cystic fibrosis, HIV infection, certain other acute and chronic infectious or neoplastic diseases (rare)
• Anti-HNE: Antibodies against human neutrophil elastase are commonly seen in ANCA-positive disease associated with cocaine cut with levamisole. The ANCA staining pattern is atypical or perinuclear but can be cytoplasmic or have multiple patterns.
Pearl : If C-ANCA is not against PR3 or P-ANCA is not against MPO, look for causes other than vasculitis for the positive ANCA.