Microscopic polyangiitis is inflammation of mainly small vessels throughout the body.

• People have a fever, lose weight, and have achy muscles and joints, as well as various other symptoms depending on the organs affected.
• Biopsy is done to confirm the diagnosis.
• Treatment depends on disease severity but includes corticosteroids and drugs that suppress the immune system (immunosuppressants).

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. Some people also have hepatitis B or C.

Symptoms

Most people have a fever and lose weight. Muscles and joints often ache.

Various organs may be affected:

• Kidneys: The kidneys are affected in up to 90% of people. Blood may appear in the urine, but often there is no sign of kidney malfunction until it is severe. Kidney failure may develop rapidly unless diagnosis and treatment are prompt.
• Respiratory tract: People may have nosebleeds or facial pain due to sinusitis. If the lungs are affected, bleeding in the lungs may occur, causing people to cough up blood. The lungs may fill with fluid, and scar tissue may eventually develop. Either problem causes difficulty breathing. Bleeding in the lungs, which may occur early in the disorder, requires immediate medical attention.
• Skin: About one third of people have a rash of reddish purple spots and bumps, usually on the legs, feet, or buttocks. The nails may contain thin purplish lines, indicating bleeding (called splinter hemorrhages).
• Digestive tract: Abdominal pain, nausea, vomiting, and diarrhea may occur. Stools may contain blood.
• Nerves: People may have tingling, numbness, or weakness in a limb.
• Brain: Headache may result if the arteries to the brain are affected. Less often, bleeding in the brain (cerebral hemorrhage), stroke, or seizures occur.

Other organs are affected less often.

Diagnosis

Doctors suspect the diagnosis based on symptoms. Blood and urine tests are done. These tests cannot 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. 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 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.

A biopsy of affected tissue (usually the skin, lungs, or kidneys) is done to confirm the diagnosis.

Treatment

If symptoms are mild, a corticosteroids plus another drug that suppresses the immune system (immunosuppressant), such as azathioprine or methotrexate, is used. If vital organs are affected, cyclophosphamide, a stronger immunosuppressant, and a corticosteroid are used. Sometimes plasma exchange (plasmapheresis) or methylprednisolone, given intravenously, is used.

Last full review/revision April 2008 by Carmen E. Gota, MD