Microscopic polyangiitis (MPA) is an ill-defined autoimmune disease characterized by pauci-immune, necrotizing, small-vessel vasculitis without clinical or pathological evidence of necrotizing granulomatous inflammation. Because many different organ systems may be involved, a wide range of symptoms are possible in MPA. Purpura and livedo may be present.
The list of signs and symptoms mentioned in various sources for Microscopic Polyangiitis includes the 7 symptoms listed below: * Nephritis * Pulmonary hemorrhage * Bleeding into the skin * Peripheral neuropathy * Abdominal pain * Muscle pain * Joint pain Note that Microscopic Polyangiitis symptoms usually refers to various symptoms known to a patient, but the phrase Microscopic Polyangiitis signs may refer to those signs only noticable by a doctor.
This condition, the clinical picture of which may include many features of systemic lupus erythematosis, has been reported. While the mechanism of disease has yet to be fully elucidated, the leading hypothesis is that the process is begun with an autoimmune process of unknown etiology that triggers production of ANCA. These antibodies will circulate at low levels until a pro-inflammatory trigger - such as infection, malignancy, or drug therapy. The trigger upregulates production of ANCA. Then, the large number of antibodies make it more likely that they will bind a neutrophil. Once bound, the neutrophil degranulates. The degranulation releases toxins that cause endothelial injury, that is, damage to vessels of glomeruli.
Laboratory tests show an increased sedimentation rate, reduced red blood count, antineutrophil cytoplasmic antibodies (p-ANCA) directed against myeloperoxidase (a constituent of neutrophil granules), and protein and red blood cells in the urine. The test for anti-glomerular basement membrane antibody (GBM), which is positive in Goodpasture's syndrome, is negative.
The customary treatment involves long term dosage of prednisone, alternated or combined with cytotoxic drugs, such as cyclophosphamide or azathioprine. Plasmapheresis may also be indicated in the acute setting to remove ANCA antibodies. Rituximab has been investigated.