Antineutrophil cytoplasmic antibodies (ANCA) are a group of autoantibodies produced when a person’s immune system mistakenly targets and attacks its own neutrophil proteins. Two of the most commonly targeted proteins are myeloperoxidase (MPO) and proteinase 3 (PR3). This results in the production of antibodies to MPO and/or PR3. The ANCA blood test detects the presence or absence of these autoantibodies by looking at the pattern…Antineutrophil cytoplasmic antibodies (ANCA) are a group of autoantibodies produced when a person’s immune system mistakenly targets and attacks its own neutrophil proteins. Two of the most commonly targeted proteins are myeloperoxidase (MPO) and proteinase 3 (PR3). This results in the production of antibodies to MPO and/or PR3. The ANCA blood test detects the presence or absence of these autoantibodies by looking at the pattern of fluorescence on a slide under a microscope. Antineutrophil cytoplasmic antibodies may be present in a variety of autoimmune disorders that cause inflammation and damage to blood vessels, predominantly small blood vessels, throughout the body (systemic vasculitis). Vasculitis can cause tissue and organ damage due to the narrowing and obstruction of these small blood vessels and the subsequent loss of blood supply. It can also produce areas of weakness in blood vessel walls, known as aneurysms, which have the potential to rupture. The symptoms experienced by a person with small vessel systemic vasculitis depend upon the degree of autoimmune activity and the parts of the body involved. Early in the disease process, symptoms are often nonspecific – they include fatigue, fever, weight loss, muscle aches, and night sweats. As the disorder progresses, vascular damage may affect the functioning of the kidneys, eyes, skin, lungs, and liver. This can cause a wide range of symptoms related to these organ systems. PR3 antibodies are most frequently seen in Granulomatosis with polyangitis (GPA). MPO antibodies are most often associated with microscopic polyangitis but may also be seen in people with pauci-immune necrotising glomerulonephritis, Churg-Strauss syndrome, and GPA.For more about these conditions, visit the Vasculitis UK. See MoreSee Less
