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Microscopic Polyangiitis (MPA)

What is microscopic polyangiitis?

Microscopic polyangiitis (MPA) is a condition that causes small blood vessels to be inflamed. It’s a rare type of vasculitis. The disease can damage the blood vessels and cause problems in organs around the body. MPA most often affects people in their 50s and 60s, but it can happen at any age.

Blood vessels carry blood around the body. Arteries carry blood with oxygen from the heart around the body. Arterioles are small branches of arteries. Veins carry blood back to the heart. Venules are small branches of veins. The smallest blood vessels are called capillaries. These tiny blood vessels trade oxygen and nutrients for waste products. 

Until recently, healthcare providers thought MPA was a form of a condition called polyarteritis nodosa. But MPA affects smaller vessels and causes different problems. Healthcare providers now treat it as a separate condition.

MPA often causes damage in the filtering part of the kidneys. This damage may cause blood and protein to be lost in the urine. This may also cause loss of kidney function. MPA can also affect the lungs, the skin, the eyes, and the nervous system.

What causes microscopic polyangiitis?

Researchers are working to understand the causes of MPA. Certain genes may be a cause. Problems with the immune system may also be a cause. MPA sometimes happens along with an autoimmune disease, such as rheumatoid arthritis (RA). An autoimmune disease is caused by a problem with the immune system. The immune system’s job is to protect the body from disease. It does this by attacking things in the body, such as viruses, that may cause harm. When you have an autoimmune disease, your immune system attacks your own body.

Other possible causes may be infections caused by viruses. Reaction to some types of medicines can also start an inflammation in the blood vessels.

What are the symptoms of microscopic polyangiitis?

MPA can cause problems throughout your body. The inflammation may come and go. The symptoms can get better or worse at times. Common symptoms of MPA include:

  • Leg swelling and dark-colored urine from kidney problems

  • Skin bumps and spots

  • Weight loss

  • Tingling or numbness due to nerve damage

  • Fever

  • Tiredness

  • Weakness

  • Aches in joints or muscles

  • Cough, shortness of breath

  • Sinus problems

  • Ear problems, such as pain or infection

  • Eye problems, such as pain or visual disturbance

The kidneys are the organs most often affected. But you may not have kidney symptoms until the damage is serious. The kidney symptoms can suddenly get worse and then get better again. In some cases, kidney damage may cause no symptoms. But there is still loss of kidney function.

How is microscopic polyangiitis diagnosed?

MPA can be hard to diagnose. Many MPA symptoms may be caused by other health problems. Always see your healthcare provider for a diagnosis. Quick diagnosis and treatment can help prevent lifelong (permanent) organ damage.

Your healthcare provider will ask about your health history and your symptoms. They will give you a physical exam. Your provider may check your skin for rashes and look for signs of nerve damage. They may need to take a sample (biopsy) from your skin or kidneys to look for damage.

You may have a blood test to look for antineutrophil cytoplasmic (ANCA) antibodies. This test can help confirm a diagnosis. But not everyone with MPA has ANCA antibodies. Also not everyone with ANCA antibodies has the same condition.

You may also need tests, such as:

  • Urine test to check for blood and protein

  • X-rays or CT scan of the chest to look for lung damage

  • X-rays of the blood vessels to see which vessels look inflamed

  • Biopsy from your kidney or lung

The physical exam, blood test, biopsies, and other tests together can help your healthcare provider form a diagnosis.

Quick diagnosis and treatment can help control the condition. You may need to see several types of healthcare providers. For example, you may need to see a rheumatologist. This is a provider who treats joint diseases, autoimmune diseases, and vasculitis. You may see other providers to focus on kidney or lung problems.

How is microscopic polyangiitis treated?

The goal of treatment is to prevent permanent organ and nerve damage. Your treatment will likely start with steroids. These medicines reduce inflammation. You take these medicines by mouth (oral). Or in some cases they are given by IV (intravenous) line into a vein. Steroids can cause side effects. Talk with your healthcare provider about the best way to deal with the side effects.

You may also need to take other medicines that suppress the immune system. These are called immunosuppressants. They also help control the inflammation. The first round of this therapy is needed to bring the disease under control. It’s called induction therapy. Once the active inflammation is gone, you may be able to take lower doses of medicines. This is called maintenance therapy. This can help to reduce the risk that the disease will flare up again.

Induction therapy often lasts for about 3 to 6 months. It may include:

  • Steroids (glucocorticoids) to reduce inflammation

  • Cyclophosphamide, an immunosuppressant

  • Methotrexate, an immunosuppressant

  • Rituximab, an injected medicine that acts on the immune system

Maintenance therapy often lasts for about 12 to 18 months or longer. It may include:

  • Azathioprine, an immunosuppressant

  • Methotrexate

  • Low-dose steroids

  • Rituximab

You may need antibiotics to protect against infection while on immunosuppressive therapy.

What are possible complications of microscopic polyangiitis?

If untreated, MPA can cause permanent damage to the organs. The most common complication is kidney failure.

The strong medicines needed to treat the condition can cause side effects. Steroids can increase the risk of bone loss, high blood pressure, mood changes, high blood sugar, muscle weakness, and skin problems. Immunosuppressant medicines can increase the risk of infections.

In addition, people with MPA may have bouts of severe tiredness (fatigue), pain, and other problems related to their condition.

Living with microscopic polyangiitis

With treatment, most people with MPA have a good outcome. Your healthcare provider can help you manage the condition. They may give you advice about dealing with medicine side effects and preventing infections.

You will likely need close follow-up to watch for possible relapse. It’s very important to stick with your medicine routine. This can help to prevent complications and organ damage. It's also important to keep up physical activity and good nutrition, even if you don’t feel your best. Your provider can help you with the best treatment plan for you. Work closely with them for the best outcome.

This condition affects all aspects of a person's life. Coping with its symptoms, medicine side effects, financial strain, and daily functional challenges can be overwhelming. It is not uncommon for both patients and caregivers to have feelings of anxiety and depression. Ask your healthcare provider about professional counseling support if you or your caregiver often feel:

  • Sad

  • Hopeless

  • Grouchy

  • Helpless

  • Not interested in activities or hobbies

Some people also find support groups very helpful. Ask your provider about MPA support groups in your area or online.

Key points about microscopic polyangiitis

  • MPA is a form of vasculitis that affects mainly the small blood vessels. These include arterioles, venules, and capillaries.

  • MPA is an inflammatory disease that can cause damage in many parts of the body, such as the kidneys, lungs, skin, and nerves. Symptoms may include fatigue, weakness, fever, weight loss, rashes, muscle and joint aches, and numbness or tingling.

  • Researchers don’t fully know the cause of the condition. It may involve a problem that causes an immune reaction against the body’s own blood vessel cells.

  • Diagnosis is done with a physical exam, urine and blood tests, and biopsies.

  • Treatment is done with steroids and immunosuppressant medicines. Once the disease is under control, you may take maintenance therapy for a year or more, to reduce the chance of relapses.

  • It’s important to work closely with your healthcare provider. With treatment, most people with MPA can manage the condition.

  • MPA can have a major emotional impact for both you and your caregiver. Consider professional counseling or attending a support group to help you manage.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions.

Online Medical Reviewer: Mahammad Juber MD
Online Medical Reviewer: Marianne Fraser MSN RN
Online Medical Reviewer: Stacey Wojcik MBA BSN RN
Date Last Reviewed: 2/1/2024
© 2000-2024 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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