What is microscopic polyangiitis?
Microscopic polyangiitis (MPA) is a rare form of vasculitis that causes inflammation in small blood vessels. It can affect many parts of the body, most often the kidneys and lungs. Left untreated, it can lead to organ damage. MPA disease most often affects older adults but can occur at any age, in any gender, and across all ethnic backgrounds.
MPA is usually treated by rheumatologists who specialize in autoimmune disease management. They may also work with kidney or lung specialists, depending on which organs are affected. At Penn Medicine, we take a team-based approach to care, bringing together experts from multiple specialties to diagnose and treat MPA.
Microscopic polyangiitis symptoms
MPA can cause different symptoms depending on which parts of the body are affected. Some people have mild symptoms at first, while others develop signs of organ involvement.
Common symptoms include:
- Fever
- Fatigue
- Unexplained weight loss
- Muscle or joint pain
- Kidney inflammation
- Skin rashes or sores
- Nerve problems like numbness or tingling
- Shortness of breath
- Swelling in the legs or feet
When the kidneys are involved, MPA may cause blood or protein in the urine and reduce kidney function, sometimes progressing to kidney disease if not treated. In the lungs, it can cause conditions like interstitial lung disease.
What causes microscopic polyangiitis?
MPA is an autoimmune disease. This means the immune system, which normally protects you from infections, mistakenly attacks your own blood vessels, causing inflammation and damage.
Many people with MPA have a type of antibody in their blood called anti-neutrophil cytoplasmic antibodies (ANCA). These antibodies may cause certain white blood cells to attack small blood vessels. The exact trigger for this reaction isn’t known, but factors like infections, toxins, or genetics may play a role.
Microscopic polyangiitis diagnosis
To diagnosis MPA, your provider will order blood and urine tests. Since MPA is often linked to ANCA, you may have a blood test to check for these antibodies.
Your provider may confirm the diagnosis with a small tissue sample (biopsy) from an affected area. This can include tissues from your kidney, lung, skin, nerves, or muscles. A nerve conduction study may be done to identify a site for biopsy, while high-resolution imaging can check for signs of lung disease.
Microscopic polyangiitis treatment
Treatment for MPA depends on how serious the disease is. Most people start with a high-dose steroid and an immunosuppressive drug to reduce inflammation and control the immune system. This approach is often used when important organs like the kidneys or lungs are affected.
Once the disease is under control and in remission, your provider may gradually lower your steroid dose while continuing immunosuppressive medication to help prevent a relapse.
Specialized care for rare immune health disorders
A diagnosis of MPA can be overwhelming, especially if the disease is affecting major organs like the kidneys or lungs. At Penn Medicine, we focus on helping you reach remission, when the inflammation is under control and no longer causing harm. Even though MPA is uncommon, our rheumatologists treat more people with this condition than most centers. This experience means we’ve seen the many ways it can appear, and we know how to respond quickly.
Because MPA can affect different parts of the body, your care team may include experts from several specialties, including kidney, lung, and nerve care. Our specialists work side by side, sharing knowledge to guide your treatment. You may also have the opportunity to participate in clinical trials, giving you access to promising new therapies before they’re widely available.