ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODY (ANCA)
ANTINEUTROPHIL CYTOPLASMIC ANTIBODIES(ANCA)
- ANCA’s are the heterogeneous group of autoantibodies directed against antigens which are found within primary granules of neutrophil and in the lysosomes of monocytes and in endothelial cells.
- Description based on immunofluorescence pattern of staining of ethanol-fixed neutrophils.
With immunofluorescence two principal patterns are recognized:
1. Anti-proteinase-3 (PR3-ANCA)
- Previously referred to as “Cytoplasmic (c-ANCA)” (image A)
- This shows cytoplasmic localization of staining and target antigen is proteinase-3 (PR3), a neutrophil granule constituent.
- Typically found in Wegener’s granulomatosis(95%)
2. Anti-myeloperoxidase (MPO-ANCA)
- Previously referred to as “Perinuclear staining (p-ANCA)” (image B)
- This shows perinuclear staining and target antigen here is myeloperoxidase (MPO).
Typically found in
- Microscopic polyangiitis
- Churg-Strauss syndrome
- Idiopathic crescentic glomerulonephritis
- Goodpasture’s syndrome.
- Also associated with certain non-vasculitic entities (rheumatic & nonrheumatic autoimmune diseases, Inflammatory bowel diseases.
- Infections such as endocarditis & hepatitis B, bacterial airway infection in patients with cystic fibrosis.
- Remember that either of these antibodies may occur in a patient with ANCA associated small vessel vasculitis.
Exam Important
- Hepatitis B is associated with an immune-mediated vasculitis characterized by p-ANCA antibodies.
- C-ANCA positivity indicates, antibody formed against Proteinase 3.
- Proteinase-3, in neutrophil azurophilic granules, is the major cANCA antigen.
- The major target for pANCA is the enzyme myeloperoxidase.
- There are two major categories of ANCA.
- pANCA pattern of staining has been associated with non-vasculitic entities such as rheumatic and nonrheumatic autoimmune diseases.
- ANCA associated with Wegner’s granulomatosis is c-ANCA.
- pANCA is sensitive and specified for Idiopathic crescentic glomerulonephritis.
- ANCA positive vasculitis is Wegener’s Granulomatosis, Churg-Strauss syndrome, Microscopic PAN
- Goodpasture syndrome is positive for pANCA.
- The most likely diagnosis in a patient presenting with respiratory symptoms i.e. cough, hemoptysis and glomerulonephritis and CANCA levels in serum found to be raised is Wegener’s granulomatosis.
- ANCA associated with crescentic glomerulonephritis is seen in Wegener’s granulomatosis, microscopic polyangiitis.
- The most likely diagnosis in a 20-year-old male presenting with mucus and repeated gastrointestinal bleeding and positive for ANCA is Ulcerative Colitis.
- Likely diagnosis in a patient presenting with hemoptysis and hematuria few weeks after a respiratory tract infection with the presence of ANCA antibodies is Goodpasture’s syndrome.
- cANCA Positivity is specific for Wegener’s granulomatosis.
- p-ANCA is characteristic for Microscopic Polyangitis.
- c-ANCAs are present in up to 95% of cases of Wegener’s granulomatosis.
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