Microscopic polyangiitis

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Overview
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.

Diagnosis
Laboratory tests show an increased sedimentation rate, reduced red blood count, antineutrophil cytoplasmic antibodies (p-ANCA) directed against [MPO(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.

Cause
This condition, the clinical picture of which may include many features of systemic lupus erythematosis, has been reported to have been caused by antibiotics and also by certain infections, though, as with many autoimmune diseases, the causes remain to a large extent unknown.

Treatment
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.