What is Microscopic polyangiitis (MPA)

Microscopic polyangiitis is characterized by pauci-immune, necrotizing, small-vessel vasculitis without clinical or pathological evidence of necrotizing granulomatous inflammation.

Statistics on Microscopic polyangiitis (MPA)


In the US: The annual incidence is 3.6 cases per million persons. Prevalence is 1-3 cases per 100,000 population.

Internationally: Incidence is approximately 2 cases per 100,000 persons in the United Kingdom and approximately 1 case in 100,000 persons in Sweden.

Renal failure and pulmonary involvement are the major causes of morbidity and mortality.

With treatment, Falk and Guillevin reported 2- and 5-year survival rates of 75% and 74% respectively.

In the United States, the disease is more frequent among caucasian persons than African/African American persons.

Males are affected slightly more frequently than females.

The age of onset is approximately 50 years.

Risk Factors for Microscopic polyangiitis (MPA)

The cause of MPA is unknown at this stage. However, enough is known about some of its components that allow a description in general terms on how MPA affects the body.

MPA is clearly a disorder that is controlled and dictated by the immune system; the precise events leading to the immune system dysfunction (hyperactivity), however, remain unclear. Many elements of the immune system are involved in this process: neutrophils, macrophages, T and B lymphocytes, antibodies and many others.

How is Microscopic polyangiitis (MPA) Diagnosed?

Renal biopsy: similar findings to those seen in granulomatosis with polyangiitis (formerly known as Wegener’s granulomatosis) but no granulomata are found.

Prognosis of Microscopic polyangiitis (MPA)

Remission: With treatment, 90% of patients improve and 75% achieve complete remission. The 5-year survival rate is approximately 75%.

Relapse: Of patients with Microscopic Polyangiitis, 30% relapse in 1-2 years.

How is Microscopic polyangiitis (MPA) Treated?

Corticosteroids: First line of treatment for induction of remission and usually for maintenance. For induction of remission, use IV methylprednisone. For maintenance, use prednisone.

Immunosuppressive agents: Can be used as part of treatment for induction of remission and a single agent in maintenance treatment.

  • Methotrexate


  • Azathioprine

    Microscopic polyangiitis (MPA) References

    1. http://www.emedicine.com
  • Watts RA, Jolliffe VA, Carruthers DM: Effect of classification on the incidence of polyarteritis nodosa and microscopic polyangiitis. Arthritis Rheum 1996 Jul; 39(7): 1208-12.


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