Microscopic polyangiitis is inflammation of mainly small blood vessels throughout the body.
Microscopic polyangiitis is rare. It can occur at any age. The cause is unknown. People with this disorder usually have abnormal antibodies called antineutrophil cytoplasmic antibodies in their blood.
Most people have a fever, feel tired, and lose weight. Muscles and joints often ache.
Various organs may be affected:
Other organs are affected less often.
Doctors suspect the diagnosis based on symptoms. Blood and urine tests are done. These tests cannot specifically identify the disorder but can confirm that inflammation is present. Blood tests can also help doctors detect bleeding in the digestive tract. Blood is tested for abnormal antibodies, such as antineutrophil cytoplasmic antibodies, which attack certain white blood cells. Levels of erythrocyte sedimentation rate (ESR) and C-reactive protein, white blood cells, and platelets can be very high, indicating active inflammation. The level of red blood cells can be very low, indicating severe anemia due to bleeding in the lungs. A sample of urine is tested for red blood cells and protein. This information can help doctors determine whether the kidneys are affected.
A chest x-ray is usually done to determine whether the lungs are affected. The x-ray can also help doctors determine whether there is bleeding in the lungs. If there are signs of bleeding, a flexible viewing tube is inserted through the nose or mouth into the airways to directly view the lungs (bronchoscopy). This procedure can confirm the presence of bleeding (or infection, another possible cause of respiratory tract symptoms).
A biopsy of affected tissue (usually the skin, lungs, or kidneys) is done to confirm the diagnosis.
If symptoms are mild, a corticosteroid plus another drug that suppresses the immune system (immunosuppressant), such as azathioprine or methotrexate, are given. If vital organs are affected, cyclophosphamide, a stronger immunosuppressant, or rituximab and high doses of a corticosteroid are used. Sometimes plasma exchange (plasmapheresis) or methylprednisolone (given by vein [intravenously]) is used.
Last full review/revision April 2013 by Carmen E. Gota, MD