MICROSCOPIC POLYANGIITIS

By Gary M. White, MD


Also known as microscopic polyarteritis, this systemic vasculitis affects the small and medium sized arteries. Necrotizing glomerulonephritis is very common and pulmonary capillaritis often occurs. ANCA positivity is strongly associated and either P-ANCA (perinuclear) or C-ANCA (cytoplasmic) may be positive. Antimyeloperoxidase autoantibodies are particularly associated.

Clinical

Palpable purpura is the main cutaneous finding. It may flare every 4-6 weeks, associated with constitutional symptoms (e.g., fever, myalgias, anorexia).

Differential Dx

The diagnosis of this disease is one of exclusion. Asthma and peripheral eosinophilia would strongly suggest the Churg-Strauss syndrome. Necrotizing granulomatosis of the upper or lower respiratory tract would strongly suggest Granulomatosis with Polyangiitis.

Treatment

Referral to a rheumatologist is in order. In the past, prednisone has been effective. Dapsone, CSA and azathioprine have been tried.

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