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Microscopic polyangiitis (MPA)

What is the cause of microscopic polyangiitis?
What are the symptoms of microscopic polyangiitis?
How is the diagnosis of microscopic polyangiitis made?
What is the treatment for microscopic polyangiitis?
What is the prognosis for microscopic polyangiitis?

Microscopic polyangiitis (MPA) most commonly involves inflammation of the small blood vessels serving the kidneys, lungs, nerves, skin and joints. MPA has much in common with another small vessel vasculitis called granulomatosis with polyangiitis (Wegener’s), and the treatments to control these diseases are similar.

What is the cause of microscopic polyangiitis?

The cause of MPA is unknown, but evidence suggests it is an autoimmune disorder.

The attack on the immune system seems to trigger production of p-ANCA (antineutrophil cytoplasmic antibodies). Eventually these antibodies may multiply excessively as part of the immune system’s response to an infection, malignancy or drug therapy. This can result in damage to the vascular system.

What are the symptoms of microscopic polyangiitis?

Because MPA can affect many different organs, many symptoms are possible in any combination, including:

  • Fatigue
  • Fever
  • Loss of appetite
  • Weight loss
  • Shortness of breath
  • Inflammation and redness of the eyes
  • Rash of red spots, skin bumps or nodules
  • Muscle and/or joint pain
  • Coughing up blood (if lungs are involved)
  • Numbness or loss of strength (if nerves are involved)

MPA may cause kidney disease, hence the importance of urinalysis.

How is the diagnosis of microscopic polyangiitis made?

Suspicion of MPA can be confirmed by a number of sources, including:

  • Medical history
  • Physical examination
  • Blood tests including testing for antineutrophil cytoplasmic antibodies (ANCA), specifically perinuclear ANCA (p-ANCA)
  • Urinalysis
  • Imaging tests such as X-rays, computed tomography (CT) or magnetic resonance imaging (MRI) scans

If the examinations or tests suggest a diagnosis of MPA, a biopsy (tissue sample) of an affected organ can be performed to confirm the presence of vasculitis.

What is the treatment for microscopic polyangiitis?

The primary medications to treat this disease are immunosuppressives. If critical organs are involved, corticosteroids such as prednisone may be combined with another immunosuppressive medication such as cyclophosphamide (Cytoxan), methotrexate (Methotrex) or azathioprine (Imuran). In April 2011, rituximab (Rituxan) was approved by the FDA when used in combination with glucocorticoids.

In acute cases, plasmapheresis may be required to remove ANCA antibodies. Plasmapheresis is a procedure in which blood plasma is removed from the circulation and replaced by fluid, protein or donated plasma.

What is the prognosis for microscopic polyangiitis?

It is estimated that on average, after five years of illness, over 80% of people have survived the effects of MPA, including patients with the most severe cases. About 50% of MPA patients experience relapses, but for most people, remission can be achieved again.

Medication toxicity remains a major concern in microscopic polyangiitis. Therefore, it is very important that patients get regular check-ups, be vaccinated and be constantly monitored for any infection or side effects of therapy. All patients affected by MPA should be under the supervision of a skilled health team that is familiar with these conditions, their treatment and the side effects of immunosuppressive medications.


Contact Name
Rush Vasculitis Clinic
Contact Phone
(312) 563-2800
Contact E-mail

Orthopedic Building
1611 W. Harrison St., Suite 510
Chicago, IL 60612

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