The Anti-Neutrophil Cytoplasmic Antibodies (ANCA) are autoantibodies directed against antigens in the cytoplasm of granulocytes and monocytes. According to the broadly recognized classification system introduced at the Chapel Hill Consensus Conference, a group of anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) are identified with a manifestation of small to medium blood vessel damage, like e.g. Wegener's granulomatosis (WG, also granulomatosis with polyangiitis, GPA), microscopic polyangiitis (MPA), renal-limited vasculitis, and Churg-Strauss syndrome (CSS).
Vasculitis involves inflammation of the blood vessels. The inflammation can cause the walls of the blood vessels to thicken, which reduces the width of the passageway through the vessel. If blood flow is restricted, it can result in organ and tissue damage.
The ANCA titer correlates (although with some exceptions) with disease activity, therefore, quantitative determination of antibodies against MPO and PR3 are recommended for monitoring of patient treatment.
The specificity of the ANCAs (MPO or PR3) does not allow differentiating among the various AAVs (WG, MPA, CSS, etc.). Nevertheless, the presence of p-ANCA/MPO-ANCA is more suggestive of a diagnosis of MPA or pauci-immune necrotizing glomerulonephritis (PING), while c-ANCA/PR3-ANCA positivity is more frequently associated with WG.
Anti-glomerular basement membrane (GBM) disease, also known as Goodpasture’s disease, is a rare condition that causes inflammation of the capillary beds of the kidneys and lungs. Some patients with ANCA associated vasculitis will also have anti-GBM antibodies and the level of anti-GBM antibodies are correlated with the disease prognosis.