Microscopic Polyangiitis (MPA) and kidney disease

What is microscopic polyangiitis (MPA)?

MPA is an autoimmune disease that can cause inflammation of small- to medium-sized blood vessels leading to damage to your kidneys, joints, lungs, nerves, skin, and other organs. An autoimmune disease causes your body's immune system to attack itself. MPA is a form of  anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis, which is one of the 20 forms of vasculitis that affect blood vessels (tubes in your body that allow blood to get from your heart to the rest of the body).  

MPA is rare. It affects 1 to 3 people out of 100,000 people in the United States. It most commonly occurs in older adults, although the disease can affect people of all ages and genders.

What causes MPA? 

It is known that MPA is associated with anti-neutrophil cytoplasmic auto-antibodies (ANCA). Antibodies are proteins in your blood that identify and defend your body from invaders, like germs and viruses. ANCA are antibodies that mistake infection-fighting white blood cells for invaders and attack them. These attacks cause the release of destructive chemicals from the white blood cells, which leads to inflammation and damage of blood vessels.  

Some people with ANCA do not have any kind of vasculitis, as ANCA can present in various other diseases. It is not understood what causes the disease in some people. It is possible that multiple factors contribute to developing MPA. 

What are the symptoms of MPA?

Symptoms of MPA can vary depending on which organ systems are affected. Symptoms may be mild or severe and can develop slowly over a period of months or years, or quickly in a matter of days. 

Symptoms can include: 

• Flu or cold-like symptoms, such as fevers, fatigue, weakness or body aches 
• Cough, sometimes coughing up blood  
• Shortness of breath  
• Nerve problems, such as tingling, numbness or weakness in one body part (a foot, for example) 
• Joint and muscle pain  
• Eye irritation 
• Stomach pain 
• Skin rashes  
• Weight loss 

Kidney disease caused by MPA often does not show symptoms. Injury to the kidneys may not be obvious until the kidney function is very low, or if the kidneys have stopped working completely. If you have any type of vasculitis, talk to your doctor about which tests you need to check how well your kidneys are working and how often you need to repeat these tests.  

MPA often takes a long time to diagnose and is often misdiagnosed due to non-specific presenting symptoms. Stand up for your health and ask your doctor to check for MPA if you think you have it.

How does MPA affect the kidneys? 

MPA harms the glomeruli in your kidneys. Glomeruli are filters made up of tiny blood vessels called capillaries in your kidneys. These clean your blood by filtering out waste products. If the glomeruli are damaged, it can lead to your kidneys not working as they should and the kidneys would begin to filter out important parts of the blood and not just waste. If not treated, this can lead to  kidney failure. 

How do doctors treat MPA? 

Doctors use different types of medicines to treat MPA.: These act on inflammation, and may include:  

• B-cell-depleting medicines, which work by disturbing and changing B-cells, a type of white blood cell that produces antibodies
• Alkylating agents, which are medicines that have a harmful effect on immune cells
• Glucocorticoids, also called steroids, which suppress many parts of the immune system
• Complement system modulators, which are medicines that affect a part of the immune system that protects against bacteria and viruses 

MPA is usually a chronic condition, with periods where the disease is active, and other periods where it is not. The initial goal of treatment is to help patients enter remission, which is when there is absence of signs or symptoms related to the active disease. This phase of treatment is called "induction." Once remission is achieved, Doctors will then transition a patient to "maintenance" treatment, which is to help keep the disease in remission. During treatment, doctors will:  

• Keep track of your symptoms and any evidence of inflammation to see how well the treatment is working
• Use blood and urine (pee) tests to keep track of how well your kidneys are working

MPA symptoms can come back or new symptoms can arise after being in remission. This is often called a "relapse".  It would be treated similarly to the original medicines you were given. 

What type of doctors treat MPA? 

MPA affects different areas of your body, so you may be treated by a team of specialists, such as: 

• Rheumatologists – doctors who treat the immune system and diseases of the muscles and bones, such as arthritis 
• Nephrologists – kidney doctors  
• Pulmonologists – lung and respiratory (breathing) system doctors  
• Otolaryngologists – ear, nose and throat doctors 
• Dermatologists – skin doctors 
• Neurologists – doctors who treat the nervous system 

How will I know if I have MPA?

There is no one test for MPA. To help make a diagnosis, doctors will look at your medical history, have you talk about your symptoms, run specific tests and do a physical exam to look for evidence of vasculitis.  

Common tests include:  

• Urine (pee) tests to check for red blood cells and protein 
• Blood tests, such as ANCA testing  
• Imaging tests, such as X-rays, CT scans, or ultrasound   

If your doctor thinks you have MPA, they may recommend a biopsy (tissue sample) of your kidneys, skin or lung to confirm a diagnosis.

Can I prevent MPA? 

You cannot prevent MPA. If you have MPA, talk with your doctor about how to manage your symptoms and prevent further damage to your kidneys or other organs.  

If your doctor diagnoses MPA before it damages your kidneys, you can help prevent having kidney damage:  

• Take your medicines as your doctor tells you  
• Go to your doctor visits  
• Get any tests your doctor recommends  
• Talk to your doctor about any new or worsening symptoms 
• Incorporate lifestyle changes, like following a healthy eating plan, being active, limiting alcohol, or quitting smoking or using tobacco. 

Where can I learn more about MPA?

If you or a loved one has been diagnosed with MPA learn more and connect with others by visiting the Vasculitis Foundation.