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Pediatric Vasculitis
About Microscopic Polyangiitis (MPA)
Last Updated on February 25, 2025.
Microscopic polyangiitis (MPA) is one of several types of autoimmune disease in which your body’s immune system, which is meant to protect you, gets confused and attacks its own blood vessels (arteries, arterioles, veins, venules, capillaries) to cause inflammation. This is known as vasculitis. MPA most commonly affects the small-to medium-sized blood vessels, particularly involving the kidneys, lungs, nerves, skin, and joints. MPA can worsen rapidly, so early diagnosis and treatment are essential to prevent kidney or respiratory damage, or organ failure.
We are grateful to Dr. Linda Wagner-Weiner for her contributions to the information on this page.
MPA is a rare disease in which there is inflammation of blood vessels (vasculitis). Inflammation is a normal protective immune system response to injury, irritation, or infection, but in MPA the inflammation leads to swelling and narrowing of blood vessels, which can make it harder for blood to flow to organs and tissues.
In MPA, the affected blood vessels are primarily small and medium-sized, which include the arteries, veins, venules, arterioles, and capillaries that supply blood all over the body. Inflammation of these vessels can affect many organs, frequently causing injury to and decreased function of the affected organs. The kidneys are the organs affected most often in MPA, followed by the lungs. The skin, nerves, eyes, joints and other areas of the body may also be affected in MPA.
MPA is considered an auto-immune vasculitis, which means that your immune system mistakenly attacks your body by producing an antibody against self (auto-antibody). The antibody found in the majority of patients with a diagnosis of MPA is called anti-neutrophil cytoplasmic antibody (ANCA). ANCA is also found in two other vasculitis diseases – granulomatosis with polyangiitis (GPA) and eosinophilic granulomatosis with polyangiitis (EGPA). These three vasculitis illnesses which are associated with the presence of ANCA are called ANCA-associated vasculitis or AAV. A blood test is used to determine the presence of ANCA. Not everyone who has MPA will test positive for ANCA.
The cause(s) of MPA are not currently known. As in the case of other vasculitis illnesses, it is thought that a combination of increased genetic risk and an unknown environmental trigger may lead to this disease. Because the cause of MPA is unknown, there is no way to prevent its occurrence. It is not contagious and does not appear to run in families.
MPA is more common in adults than children. MPA presents most commonly in people in their 50s and 60s. It is a very rare disease in children, reported less than half as often as pediatric GPA (another form of ANCA associated vasculitis), which is estimated to affect 0.5 to 5 children per million. The average age of MPA presentation in children is 10 to 12 years. It affects girls 3 to 8 times more often than boys. The incidence of MPA appears to be higher in Asia compared to Western countries.
Symptoms of MPA may be non-specific initially. Non-specific means symptoms that are seen in many different illnesses such as fever and tiredness. These early symptoms are not unique to MPA. More symptoms develop as the vessel inflammation causes injury to and decreased function of various organs. Symptoms of MPA may include:
- Fever, malaise (feeling unwell), and fatigue
- Decreased appetite and weight loss
- Aching in muscles or joints; arthritis (painful, inflamed joints)
- Skin rashes
- Kidney-related problems: dark-appearing urine or blood in urine
- Lung problems: shortness of breath, cough (sometimes with blood)
- Nerve problems: numbness, pain, tingling, possible foot drop
- Abdominal problems: pain, nausea
- Eye problems: irritation, redness, pain and/or visual disturbance
MPA can be a difficult disease to diagnose because the initial symptoms are often non-specific – meaning these symptoms, such as fever and tiredness, can occur in many different illnesses. It is not uncommon for the diagnosis to be made when there is already injury to the kidneys and other organs. Diagnosis is made based on clinical symptoms, physical examination and testing of blood and urine, as well as radiology studies and biopsies. Many new patients with MPA are hospitalized at the onset of the disease because of the severity of their symptoms.
Blood tests
- Complete blood count (CBC): This often shows anemia (low hemoglobin).
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP): These tests reflect inflammation in the body and are usually elevated at diagnosis and if/when the disease flares. A flare in vasculitis refers to the disease becoming active again (causing new damage) after a period of time when the disease was controlled or in remission (not causing damage).
- Complete metabolic panel (CMP): This may show elevated creatinine and BUN which occur when there is a decrease in kidney function.
- Anti-neutrophil cytoplasmic antibodies (ANCA): This antibody against self (autoantibody) is present in the majority of patients with MPA. There are two types of ANCA antibodies. P-ANCA, which targets the antigen myeloperoxidase (MPO) is seen more commonly in MPA than C-ANCA which targets proteinase 3 (PR3). Patients with granulomatosis with polyangiitis (GPA), another type of ANCA-associated vasculitis, are more commonly positive for C-ANCA. A small number of patients with MPA do not have a positive ANCA at all.
Urine tests
Blood and elevated levels of protein are usually seen in the urine of patients who have kidney involvement.
Imaging studies
X-rays (especially chest x-rays), echocardiogram (ultrasound of the heart), and CT scans (usually of the lungs) may be performed to look for areas of inflammation and injury.
Biopsies
Biopsies are often necessary to confirm a diagnosis of MPA. A biopsy also gives your doctor important information such as how much inflammation is present and how much injury may have occurred. This knowledge may help guide medical treatment decisions.
A biopsy is a medical procedure that involves the removal of a sample of tissue or cells from an affected blood vessel or organ, which is examined under a microscope for signs of inflammation or tissue damage. In MPA, biopsies are performed most often on the kidneys.
The overall purpose of treatment is to calm the body’s immune system so that it no longer attacks itself. This is known as immunosuppression.
Your doctor’s goal when treating MPA is to quiet down the inflammation as quickly and safely as possible in order to improve organ function, prevent permanent damage, and importantly, help you feel better. This is achieved by suppressing the immune system with medications called immunosuppressants. The treatment program is usually divided into two phases: remission-induction and remission-maintenance.
Remission-induction phase
This phase lasts 4 to 6 months following the diagnosis of MPA. The goal of this phase is to get the MPA into a remission, which means that there will be no signs of active disease or inflammation. The medications used during this phase may include:
- Glucocorticoids: These are usually given by IV initially (methylprednisolone) at high doses, followed by a change to lower daily doses by mouth (prednisone or prednisolone).
- Cyclophosphamide: A chemotherapy medication given by IV every 3-4 weeks, for up to 4 to 6 months.
- Rituximab: This is a newer medication, called a biologic, which targets a particular part of the immune system – the B-cell lymphocytes. This is given in a few doses over a period of weeks. Its impact can last up to 6 months, and sometimes longer.
Your doctor often chooses either cyclophosphamide or rituximab for treatment during this remission-induction phase. However, sometimes your physician may choose to give both these medications in the beginning of your treatment.
- Plasma exchange or plasmapheresis (PLEX): This is a medical procedure during which you are attached to a machine by tubes going into your blood vessels. The machine separates the blood, removing the plasma (the liquid part of blood) from your blood and replacing it with donor plasma or plasma substitute. The hope is that this will quickly slow the inflammation process. It is used only in very ill patients. The literature is divided as to how effective PLEX is.
Remission-maintenance phase
This is started immediately after the remission-induction phase is completed, when the MPA is hopefully in remission with no signs of inflammation. During this phase, glucocorticoids are given in very low doses or not at all. This phase usually lasts for at least two and sometimes up to four or more years. It is not clear at this time how long to continue the maintenance phase, as it is recognized that flares in MPA may occur. Your doctor will usually treat you with one of the following medications during the remission-maintenance phase:
- Rituximab: This is given every 6 months, usually at half the dose that was given during the induction phase.
- Azathioprine: This is an immunosuppressive medication given daily by mouth.
- Methotrexate: This is an immunosuppressant medication given weekly, either by mouth or by an injection under the skin (subcutaneously).
A common concern with all medications which suppress the immune system is the increased risk of infection. Your doctor will make sure that childhood vaccinations are up-to-date, and that additional vaccines (annual flu shot, Covid-19 vaccination, and pneumonia vaccines) are given. Your doctor will generally avoid giving live vaccines while you are on these medications.
Glucocorticoids are very effective in quieting down inflammation but may cause side-effects. These side effects are more likely to occur with higher doses of glucocorticoids and a longer duration of treatment with glucocorticoids. Many potential side-effects are similar in adults and children, including weight gain, increased blood pressure, acne, mood changes and sleeping difficulties. In a growing child, growth in height will be suppressed, with catch-up growth often seen when glucocorticoids are discontinued. Puberty may be delayed. There is also concern of weaker bones (osteoporosis) with prolonged treatment with glucocorticoids.
Your medical team should discuss possible side-effects of all medications prior to starting treatment.
The treatment goals for MPA are to quiet the inflammation quickly and to prevent organ injury. However, by the time some children present with symptoms and are diagnosed with this disease, irreversible damage may have already occurred. Kidney involvement is present in 80-90% of children at the time of MPA diagnosis. At presentation or over time, up to 20% will lose all kidney function and require dialysis or kidney transplant. Sometimes a patient who presents with kidney failure at diagnosis will have a return of kidney function with aggressive medical treatment, but not always.
The lungs are affected in about 45% of children at diagnosis. The majority of children will have good improvement of lung function with initial treatment. A small percentage of children may continue to have respiratory, or breathing problems which will be monitored by the medical team clinically, by pulmonary function testing, and by radiology studies. The majority of children with nerve and skin involvement at diagnosis have complete improvement or resolution of their symptoms with treatment.
Information on long-term outcomes for people with MPA comes primarily from studies of adults with this disease. Flares occur in 20-40% of patients, usually within the first 4 years of diagnosis. Mortality rates in adults with MPA are increased in those who are older, who smoke, have other underlying conditions or present with more severe disease. The most common cause of death is infection, which is related to suppression of the body’s immune system by the treatment medications.
Although flares may occur in patients with MPA, it is important to recognize that many patients will continue to remain in remission over time.
Your doctor will monitor you closely to gauge your response to treatment and to watch for any signs of disease flare once you are in remission. They will continue to follow you throughout your childhood years and then transition you to the adult medical setting when you are older (usually between 18 to 22 years of age).
Overall, MPA in children is similar to MPA in adults. However, in children, girls may be affected more often than boys, while in adults there is a more equal risk for men and women. Children usually tolerate medications better, as they do not have other medical issues that adults often have (e.g., those related to smoking or to underlying medical diseases, such as high blood pressure, obesity or diabetes).
The effect of MPA on the lives of children is different than in adults. Children and adolescents may not be able to understand their diagnosis or treatment plan as well as some adults can. At the time of their diagnosis, they are often going through the normal stages of physical, behavioral and social development, which is already likely a challenging time for young people. The symptoms of MPA and its treatment may impact day-to-day life. School attendance and taking part in activities in which kids often participate may be affected. This may affect emotional and social well-being. Your doctor may refer you and your family to mental health specialists, who will assist you during difficult times.
Children and young people are often more resilient than adults. They tend to adapt better to change than many older people do. Also, very helpful and important, are the support and care that will come from your family and your large medical team.
Treating MPA requires a team of professionals. The pediatric rheumatology team consists of a pediatric rheumatologist, nurses (which may include a nurse practitioner or physician assistant), social worker, psychologist and sometimes physical/occupational therapists. Important medical consultants include a kidney specialist (nephrologist), lung doctor (pulmonologist), and if indicated, a neurologist (treats disorders of the nervous system), dermatologist (treats disorders of the skin) and ophthalmologist (eye doctor).
Having a chronic disease like MPA can be challenging for both you and your family. It is very important that you receive the support and guidance you need from your medical team and through other resources. Encouragement and emotional support from your relatives and friends are especially important. Talking with a mental health specialist or connecting with other children with chronic diseases has been helpful to many.
School is an important part of the life of all children and adolescents. MPA may affect your school attendance and academic performance, and may interfere with your ability to fully participate in social and sports activities. We recommend that accommodations be made at school to help you succeed in all aspects of your education. These accommodations are usually provided by programs such as a 504 plan or sometimes an IEP, which are available in the United States. Your healthcare facility may have a social worker that can help you and your parents navigate the process of setting up one of these programs.
Learn more about school accommodations.
Order a free pediatric vasculitis empowerment kit which contains a guide for teachers.
It is good for you to stay active physically and participate in hobbies and other activities which you enjoy. Having MPA does not mean that you cannot live the life you want to live. Our goal is to have all young people with MPA live long and fulfilling lives.
Researchers and physicians are actively working on improving pediatric-specific vasculitis treatments. Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website. For information about clinical trials being conducted at the National Institutes of Health (NIH) in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222 TTY: (866) 411-1010 Email: prpl@cc.nih.gov
Learn more about participating in research.
While the Arthritis Foundation focuses on patients with arthritis, there are many resources available for children with any autoimmune disease including symptom management, school guidance, summer camps, and support groups.
https://www.arthritis.org/juvenile-arthritis
Microscopic Polyangiitis Videos
Current Treatments for GPA and MPA including Avacopan
ACR_VF Guidelines: GPA-MPA Breakout
Research Insights: Improving Diagnostics and Treatment of Small-Vessel Vasculitis
MPA Patient Hero: Kathy Olevsky
