What is microscopic polyangiitis (MPA)?

Microscopic Polyangitis Illustration

Microscopic polyangiitis (MPA) is an uncommon disease. It is the result of blood vessel inflammation (vasculitis), which can damage organ systems. The areas most commonly affected by MPA include the kidneys, lung, nerves, skin, and joints. MPA shares many common features with another form of vasculitis called granulomatosis with polyangiitis (GPA, formerly called Wegener's Granulomatosis), and treatment approaches for these illnesses are similar.

What is vasculitis?

Vasculitis is a general term that refers to inflammation of the blood vessels. When inflamed, the blood vessel may become weakened and stretch forming an aneurysm, or become so thin that it ruptures resulting in bleeding into the tissue. Vasculitis can also cause blood vessel narrowing to the point of closing off the vessel entirely. This can cause organs to become damaged from loss of oxygen and nutrients that were being supplied by the blood.

MPA affects small to medium-sized blood vessels, which directly reflects on the type of tissue injury that is seen in this disease.

Microscopic Polyangitis Narrowing

Who is affected by microscopic polyangiitis (MPA)?

MPA can occur in people of all ages, from children to the elderly, and appears to affect men and women equally.

What causes microscopic polyangiitis (MPA)?

The cause of MPA is unknown. MPA is not a form of cancer, it is not contagious, and it does not usually occur within families. Evidence from research laboratories strongly supports the idea that the immune system plays a critical role in MPA such that the immune system causes blood vessel and tissue inflammation and damage.

What are the features of microscopic polyangiitis (MPA)?

Because many different organ systems may be involved, a wide range of symptoms and signs are possible in MPA. Patients who have MPA may feel generally ill and fatigued, have a fever, or have a loss of appetite and weight. They usually also have symptoms related to areas of involvement such as rashes, muscle and/or joint pain. When MPA affects the lungs they may have shortness of breath or coughing up of blood. MPA affecting the nerves may cause an abnormal sensation followed by numbness or loss of strength. Any combination of these symptoms may be present.

Kidney disease caused by MPA often does not produce symptoms. Inflammation of the kidney may not be apparent to the patient until the kidneys begin to stop working. Therefore, it is very important for the doctor, in dealing with any form of vasculitis, to always examine the urine.

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