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Diseases > Microscopic Polyangiitis (MPA) > What is it?

What is MPA?

Microscopic polyangiitis (MPA) belongs to a family of diseases called “vasculitis”. In MPA, this vasculitis results in inflammation of the small blood vessels that supply tissues in the kidneys, lungs, nerves, skin and other organs. Other diseases in this family include granulomatosis with polyangiitis (also known as Wegener’s granulomatosis) and esosinophilic granulomatosis with polyangiitis (also known as Churg-Strauss). All diseases in this family feature inflammation of blood vessels (vasculitis).

What causes MPA?

The cause of MPA is unknown at this time, but it is thought to be an autoimmune disease. This means that something causes your immune system to go awry. It begins to attack small blood vessels and causes inflammation.

The word inflammation comes from the Latin word inflammare which means to light on fire. You can think of it like this: in people with MPA, small blood vessels in certain areas of the body are “on fire” and are eventually damaged. This can cut off blood supply to vital organs.

Who gets MPA?

Microscopic polyangiitis is a rare disease. It can affect anyone, but is more typically found in people over 50. It affects men and women equally.

How is MPA diagnosed?

Microscopic polyangiitis can be difficult to diagnose because there are no symptoms that are unique to the disease. In some cases, symptoms can appear quickly. Other times, they can take a while to develop.

A rheumatologist – a specialist in arthritis and autoimmune diseases – may be required to diagnose the disease. Your rheumatologist will take a complete history and perform a thorough physical examination. This is usually followed by blood tests, x-rays and other types of tests.

What tests are done to diagnose MPA?

Special blood tests can help to confirm the diagnosis of MPA. Sometimes this is not enough and a tissue biopsy is needed to confirm the diagnosis. This involves taking a very small sample of tissue through a needle.

These are some of the other tests that can help diagnose MPA:

  • Complete blood count (CBC)
  • Anti-neutrophil cytoplasmic antibody (ANCA) test
  • Erythrocyte sedimentation rate (ESR)
  • C-reactive protein (CRP)
  • Creatinine to measure the function of your kidneys
  • Urinalysis to look for protein or blood in the urine – a sign the kidneys are involved
  • Chest x-ray and/or CT scan to look for lung involvement
  • EMG or Nerve Conduction Studies can be performed to look for nerve involvement

Read more – What is it going to do to me?