What other disorders are associated with ANCAs

What other disorders are associated with ANCAs?

Commonly, c-ANCA positivity represents the presence of anti-PR3 antibodies and is associated with a small number of diseases. In contrast, p-ANCA and “atypical ANCA” (the term for ANCA patterns that are not clearly c-ANCA or p-ANCA) may be due to a variety of different antibodies and can be present in a wide range of diseases. Specific antibodies that may result in positive p-ANCA or atypical ANCA patterns include antibodies directed against MPO, elastase, cathepsin G, lactoferrin, and β-glucuronidase. p-ANCA in the setting of GPA, MPA, EGPA, or RLV is usually due to anti-MPO antibodies (p-ANCA should typically be against MPO if the patient has vasculitis). p-ANCA present in other disorders is less well characterized but is usually not due to antibodies directed against MPO:

• Goodpasture (anti-GBM antibody) disease: between 10% and 40% will have positive ANCA, usually against MPO. These patients tend to have worse kidney disease prognosis.

• Most rheumatic disorders (rheumatoid arthritis, SLE, Sjögren’s syndrome, systemic sclerosis, polymyositis, Buerger disease, relapsing polychondritis) have had positive ANCAs reported with varying but low frequency (<20%). ANCA is usually p-ANCA, directed against proteins other than MPO. The clinical significance is uncertain, but in some clinical scenarios such as lupus nephritis, ANCA presence may be associated with a worse prognosis. Several cases of p-ANCA associated vasculitis have been reported in patients with limited and diffuse systemic sclerosis.

• Inflammatory bowel disease: between 60% and 80% of patients with ulcerative colitis and up to 25% of patients with Crohn disease have positive ANCAs. It is usually p-ANCA directed against a nuclear envelope or a neutrophil granule protein, but not MPO.

• Autoimmune liver disease: p-ANCA (not MPO) or atypical ANCA is seen in primary sclerosing cholangitis (70%), chronic active hepatitis, and primary biliary cholangitis.

• Cystic fibrosis: up to 80% to 90% of patients have positive p-ANCA, most commonly against BPI protein in the primary azurophilic granules of neutrophils. It is notable that patients with cystic fibrosis frequently have Gram-negative infections of their airways.

• Infections: human immunodeficiency virus, subacute bacterial endocarditis, leprosy, malaria, acute parvovirus B19, and acute infectious mononucleosis. Note that all three ANCA patterns have been reported for patients with Mycobacterium tuberculosis infections .

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