What is microscopic polyangiitis?
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 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 blood vessels become inflamed, they can
only react in limited ways. 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.
What are the symptoms of MPA?
Because many different organ systems may be involved,
a wide range of symptoms are possible in MPA. Patients who have MPA may feel
generally ill and fatigued, have fever, or have loss of appetite and weight.
They usually also have symptoms related to areas of involvement such as
shortness of breath or coughing up of blood from disease affecting the lungs,
rashes, muscle and/or joint pain. 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.
What causes 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.
Who is affected by MPA?
MPA can occur in people of all ages, from children to the elderly, and appears to affect men and women equally.