ANCA Vasculitis: GPA, MPA and EGPA Explained

ANCA-associated vasculitis is a family of inflammatory diseases that can affect different organs. Understanding the subtype, the organs involved and the meaning of antibody tests helps explain why care differs from one person to another. ¹

This guide explains ANCA testing, the differences between GPA, MPA and EGPA, and the decisions behind treatment and follow-up. Information checked on 15 October 2026. It is educational information, not a personal diagnosis or prescription.

Call your local emergency number for severe breathing difficulty, gasping, inability to speak because of breathlessness, blue or grey lips, or sudden confusion. Do not wait for an ANCA result. ²⁵

Coughing up more than a few spots or streaks of blood, or blood with breathlessness, a fast heartbeat or chest or upper-back pain, needs emergency care. Even small streaks need prompt medical assessment. ¹⁵

What does ANCA-associated vasculitis mean?

Vasculitis means inflammation in blood-vessel walls. The consequences depend on where the affected vessels are and how much inflammation is present: a problem in the skin produces a different pattern from a problem in the kidneys or lungs. General symptoms, such as feeling unwell, may accompany organ-specific changes, but symptoms alone do not establish which vessels are involved. In ANCA-associated vasculitis, the familiar pattern may include respiratory and kidney disease, although the particular distribution varies between the different forms. ¹

ANCA stands for antineutrophil cytoplasmic antibodies. The name ANCA-associated vasculitis, often shortened to AAV, groups granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (EGPA). These diseases principally affect small vessels. The word “associated” matters: the disease family includes people without detectable ANCA. The international Chapel Hill naming framework describes GPA as involving granulomatous respiratory inflammation, MPA as lacking granulomatous inflammation, and EGPA as involving eosinophil-rich inflammation in a setting of asthma and eosinophilia. Granulomatous refers to a particular organized pattern of inflammatory cells in tissue. These descriptions help clinicians communicate, but they are disease definitions, not a checklist that independently proves a diagnosis. “Microscopic” describes the vessel pattern in MPA; it does not mean that the illness is necessarily mild. ³⁴

GPA, MPA and EGPA: related names, different patterns ³⁴

GPA commonly affects the upper respiratory tract, lungs and kidneys. MPA commonly involves the kidneys and lungs. These are patterns that guide investigation, rather than a requirement for every person to have every feature. ¹

For a closer look at the respiratory and kidney pattern of GPA, see our GPA symptoms and care guide. ¹

EGPA warrants particular consideration when asthma and chronic nose or sinus disease occur with eosinophilia and new systemic organ problems. Eosinophils are a type of white blood cell; their elevation is a clue to investigate, not proof of EGPA. Other eosinophilic disorders and alternative explanations need consideration. Systemic glucocorticoids can suppress the eosinophil count, so a result obtained after treatment may not describe the untreated illness. The clinician therefore reviews both the clinical history and the circumstances in which blood was taken. This is one reason why asthma plus a single abnormal blood count cannot establish the diagnosis, and why a currently normal count cannot by itself settle a complex assessment. ⁷

ANCA testing plays a different role in EGPA than many readers expect. Most people with EGPA do not have detectable ANCA; when present, the antibodies are usually directed against myeloperoxidase, or MPO. A positive result can support the investigation, but ANCA status cannot reliably divide everyone into one purely “vasculitic” group and another purely “eosinophilic” group. The clinical patterns overlap. Decisions about treatment must take actual organ involvement into account, rather than being assigned automatically from a positive or negative result. This distinction prevents two errors: dismissing possible EGPA because the test is negative, and assuming that a positive test alone identifies which medicine will work best. ²²

The evaluation of suspected EGPA considers the heart, lungs, kidneys, skin and nerves, as well as the airway history. Symptoms in one of these areas should be interpreted in the context of the whole illness. Assessment also needs to exclude other eosinophilic disorders. Coordinated specialist care is useful because a respiratory assessment alone may not answer a cardiac, neurological or kidney question. Depending on the presentation, rheumatology, renal, respiratory and ear, nose and throat expertise may all contribute. ⁶

How to read ANCA, PR3 and MPO results ³⁵

PR3-ANCA is more often linked to GPA and MPO-ANCA to MPA, but either antibody can occur with either diagnosis. ⁴

Laboratory reports may use two kinds of terminology. PR3-ANCA and MPO-ANCA identify the protein targeted by the antibodies: proteinase 3 or myeloperoxidase. The older terms c-ANCA and p-ANCA describe cytoplasmic or perinuclear staining patterns seen with indirect immunofluorescence. A staining description and an antigen target are different pieces of information, so they should not be read as interchangeable disease names. The international testing consensus supports high-quality PR3 and MPO immunoassays as a primary testing approach when GPA or MPA is suspected; an immunofluorescence test is not necessarily the first step in every laboratory. Consequently, a modern report can be useful even if it does not begin with the older pattern terminology. Neither a laboratory method nor an antibody label supplies the full diagnosis by itself. ³⁵

An ANCA test looks for autoantibodies, antibodies that react with components of the person’s own cells. Clinicians may request it when symptoms and other findings raise concern about autoimmune vasculitis. ANCA testing can also be used in other clinical investigations, including inflammatory bowel disease, so a positive result cannot simply be translated into “I have AAV.” Interpretation therefore brings together the test, symptoms, examination and other investigations. If the report is positive, the next step is to establish what it means in that setting, rather than to start treatment from the result alone. ²

Negative ANCA testing does not exclude GPA, MPA or a related pauci-immune inflammatory kidney presentation. Pauci-immune describes a pattern with little immune deposition on tissue testing; it is not a statement that inflammation is absent. When the clinical picture remains concerning, urine findings, kidney function, imaging and sometimes biopsy remain important. A negative blood test should not end an investigation when other evidence points toward active organ disease. ⁵

An ANCA level that rises or stays positive is not, by itself, a reason to increase immunosuppressive treatment. The ACR/Vasculitis Foundation guideline advises against changing the dose solely on that basis. A result can prompt closer assessment, but treatment needs to address demonstrated disease activity in the person being treated. Likewise, a numerical fall should not substitute for assessing a new symptom. This avoids exposing someone to additional treatment risk because of a laboratory change that has not been shown to represent a clinical relapse. ³

Why kidney and lung findings deserve prompt attention

The kidneys contain tiny filtering structures called glomeruli. When these are injured, blood or protein may leak into urine and filtration may worsen. Urine testing and blood tests therefore answer related but different questions: one looks for signs of leakage or inflammation, while the other helps assess kidney function. The appearance of urine is not a reliable substitute for laboratory testing. Blood pressure and the amount of protein leakage also help guide follow-up and kidney-protective care. Kidney involvement is one reason a clinician may request urine samples even when urinary symptoms are not the main complaint. Our glomerulonephritis guide explains inflammatory injury to these filters in more detail; not every form of glomerulonephritis is caused by AAV. ²⁴

Acute kidney injury can develop with few obvious symptoms. When symptoms do occur, they may include passing less urine, swelling, nausea, confusion or breathlessness. A marked reduction in urine or a new combination of these symptoms needs urgent clinical assessment. Clinicians use changes in creatinine, urine testing, observations and additional investigations to assess the cause and severity. Someone with serious kidney injury may need hospital treatment, and dialysis is sometimes necessary. Recovery varies: some people recover well, while others have lasting kidney impairment. It is therefore unsafe to promise that dialysis will always be temporary or that feeling better establishes recovery. The assessment must also consider fluid balance; a general instruction to drink more is not a substitute for advice tailored to the person’s kidney function and swelling. ¹⁶

Blood in sputum can have several causes, including infection and a blood clot in the lungs. It must not automatically be labelled a vasculitis flare, even in someone who already has AAV. Conversely, small amounts should not be ignored simply because the person feels reasonably well. The amount of blood and accompanying symptoms affect the urgency of assessment. More substantial bleeding, or bleeding with breathlessness, rapid heartbeat or chest or upper-back pain, requires emergency care. ¹⁵

Severe breathlessness is an emergency whether or not blood is visible in sputum. Gasping, being unable to get words out, blue or grey discoloration, or sudden confusion are warning signs that urgent help is needed. Breathlessness has many possible causes, and symptoms alone cannot establish which one is responsible. The absence of coughing blood is therefore not reassurance when breathing is severely impaired. ²⁵

How clinicians establish the diagnosis and severity

Diagnosis brings together the clinical pattern, high-quality PR3 or MPO testing and, when appropriate, tissue biopsy. A clinician assesses whether disease is threatening an organ or life rather than assuming a presentation is harmless because symptoms seem confined to one location. The same principle applies to follow-up: structured assessment of the person’s condition is more informative than treating an antibody result or B-cell count in isolation. Tests support this assessment, but no single laboratory measurement substitutes for establishing what is happening in the affected organ. When a negative antibody test conflicts with a strongly suggestive presentation, further investigation is warranted rather than automatic dismissal of the suspected diagnosis. ⁴

A kidney biopsy examines a small tissue sample to clarify abnormalities that blood and urine tests cannot fully explain. Persistent blood or protein in urine, or impaired kidney function, may lead a clinician to consider it. The tissue can show inflammation, scarring or another pattern of injury, helping answer both diagnostic and treatment questions. This distinction matters because established scarring and ongoing inflammation are not the same finding. Before a biopsy, the team reviews medicines and bleeding risks and discusses the procedure’s potential benefit and complications. Not everyone with suspected AAV needs a kidney biopsy, and a biopsy is interpreted alongside the rest of the assessment rather than treated as an isolated verdict about every organ. ¹⁴

In a rapidly deteriorating patient with a compatible presentation and positive PR3 or MPO antibodies, treatment should not be delayed simply to wait for a kidney biopsy. This is a specialist decision that balances diagnostic certainty against the risk of further organ injury. Biopsy may still provide valuable diagnostic and prognostic information. The urgency exception does not make tissue testing unnecessary in every case; it explains why the sequence of investigation and treatment can differ between someone who is stable and someone whose kidney function is worsening quickly. ⁵

Research classification criteria are designed to assemble comparable groups for studies, not to diagnose a person by self-scoring. In EGPA, a clinician also considers alternative eosinophilic and vasculitic conditions. Biopsy can be useful when feasible, but is not required in every diagnosis. Clinical interpretation remains necessary even when several familiar features are present. ⁷

Induction and maintenance have different goals ²⁹

Treatment of active disease and prevention of the next relapse are separate questions. Induction aims to bring active inflammation under control; maintenance is used after remission has been achieved. MAINRITSAN studied the maintenance question in people whose disease was already in remission after cyclophosphamide and glucocorticoids. Scheduled rituximab prevented major relapse more effectively than azathioprine during the original follow-up, while severe adverse events occurred with similar frequency. Most participants had GPA, and the trial did not include EGPA. The practical distinction is that evidence for a medicine after remission does not automatically establish how to treat an acute organ-threatening presentation. Nor does a successful maintenance study establish that everyone should receive the same medicine indefinitely. ²⁹

For GPA and MPA, maintenance commonly uses rituximab, with azathioprine or methotrexate among the alternatives. These options are not interchangeable instructions for self-treatment. The clinician chooses a strategy in the context of the person’s disease and treatment risks. Follow-up then asks whether the disease remains controlled and whether the plan is still appropriate, rather than assuming that a prescription never needs reassessment. ⁴

Treatment evidence for GPA and MPA

For severe GPA or MPA, rituximab with glucocorticoids is an established induction option alongside cyclophosphamide-based treatment. In RAVE, rituximab met the trial’s noninferiority standard for achieving remission without prednisone at six months, and a prespecified subgroup with relapsing disease favored rituximab. This supports an effective alternative, but it is not proof that rituximab is safer in every respect: the trial did not demonstrate significantly fewer adverse events overall. RAVE also excluded very advanced kidney dysfunction and lung hemorrhage requiring ventilatory support. Those limits matter when discussing a critically ill patient, whose presentation may fall outside the trial population. The study concerned GPA and MPA, not EGPA, so its findings should not be transferred wholesale to all three AAV subtypes. ²⁶

Evidence in renal vasculitis also includes RITUXVAS, a smaller trial in newly diagnosed disease with kidney involvement. Its rituximab-based group received cyclophosphamide as part of the regimen, and both treatment groups received glucocorticoids. Remission outcomes did not demonstrate superiority of the rituximab-based strategy. This detail is important when a summary claims that “rituximab alone” was compared with cyclophosphamide: that is not what this trial tested. Different studies can evaluate different combinations even when the same medicine appears in the headline. ²⁷

Steroid exposure is another treatment decision supported by trial evidence. PEXIVAS enrolled people with severe AAV defined by reduced kidney function or diffuse pulmonary hemorrhage. A reduced oral glucocorticoid regimen was noninferior to the standard regimen for the combined outcome of death or end-stage kidney disease, with fewer serious infections during the first year. In the same trial, plasma exchange did not significantly reduce that combined outcome in the overall study population. These findings argue against assuming that more steroid or an additional procedure must always produce a better result. They do not provide a home taper schedule, and an overall trial result does not resolve every possible clinical subgroup. Treatment still requires a supervised plan appropriate to the severity of the illness. ²⁸

LoVAS also compared lower and higher glucocorticoid exposure, with rituximab in both groups. The lower-dose approach met the study’s noninferiority criterion for remission and had fewer serious adverse events and serious infections. However, the trial excluded severe glomerulonephritis and alveolar hemorrhage. Its results strengthen the rationale for limiting steroid burden in the population studied, while preserving an important boundary: this was not the same population or protocol as PEXIVAS. For an individual patient, the appropriate starting strategy and subsequent reductions remain clinical decisions, particularly when kidney or lung involvement is severe. ³³

Plasma exchange remains a selective specialist option in certain severe kidney or pulmonary–renal presentations. It is neither a routine addition for everyone with AAV nor a procedure that can be ruled out from the diagnosis alone. ⁵

Previous relapse also changes the treatment conversation. RITAZAREM studied people with relapsing GPA or MPA whose remission had been reinduced with rituximab. Repeated scheduled rituximab prevented further relapse more effectively than azathioprine in that setting. Nevertheless, relapses still occurred during treatment and became frequent after treatment ended; infections and low immunoglobulin levels remained important concerns. The result supports maintenance as risk reduction, rather than a guarantee of cure. It also explains why a person who has already relapsed may be offered a different plan from someone with newly diagnosed disease. These findings are specific to a relapse-prone GPA/MPA population and do not establish the best maintenance strategy for EGPA. ³⁰

Why EGPA needs its own treatment discussion

Organ-threatening EGPA requires a different induction discussion from nonsevere disease. The ACR/Vasculitis Foundation guideline supports cyclophosphamide or rituximab with glucocorticoids for severe EGPA rather than replacing that approach with mepolizumab. The choice depends on the actual presentation. A treatment used successfully for asthma or eosinophilic symptoms should not automatically be assumed adequate for acute, serious systemic vasculitis. Disease severity and the threatened organ must be established before applying a treatment label. ³

Mepolizumab’s EGPA evidence includes MIRRA, which studied adults with relapsing or refractory disease while they continued standard care. Adding mepolizumab increased time in remission and reduced relapses compared with placebo, but many treated participants never met the trial’s remission definition. That definition combined absence of measured vasculitis activity with a low oral steroid requirement; it did not mean drug-free cure. Importantly, the trial excluded people with organ-threatening or life-threatening EGPA in the preceding three months. The evidence therefore supports treatment in the population studied, without proving that the medicine should replace severe-disease induction during an acute emergency. Understanding how remission was defined is also essential when comparing trial results with a person’s own experience. ³¹

MANDARA compared benralizumab with mepolizumab in adults with relapsing or refractory EGPA receiving standard care. Benralizumab met the prespecified noninferiority criterion for remission, but superiority was not established. Noninferiority means that the trial met its predefined comparison standard; it does not mean the two treatments are identical in every patient or that one is universally best. This trial likewise excluded recent organ-threatening or life-threatening disease. The two biologics can therefore be discussed as evidence-based options in the appropriate setting, while leaving acute severe presentations to a separate clinical assessment. ³²

Rituximab evidence in EGPA should also be described accurately. The fully published 2025 REOVAS trial did not demonstrate superiority of rituximab plus glucocorticoids over conventional induction. Conventional treatment used glucocorticoids alone or included cyclophosphamide for severe disease. Failure to show superiority is not the same as proving equivalence, and the investigators specifically noted that their design could not establish equivalence between rituximab and cyclophosphamide in severe EGPA. Older material describing REOVAS as available only in abstract form is now outdated. For a patient, the key lesson is that evidence from GPA or MPA cannot fill every EGPA evidence gap: the subtype and the precise question tested must remain part of the treatment discussion. ³⁶

Mepolizumab targets interleukin 5, a signaling protein relevant to eosinophils. Its United States label includes treatment of adults with EGPA, alongside separate indications for other conditions. An age authorization for asthma does not automatically establish the same authorization for EGPA, and regimens for different diseases should not be treated as interchangeable. The medicine is not intended to relieve acute bronchospasm. Someone receiving it still needs the appropriate plan for an acute breathing problem rather than assuming that a maintenance biologic acts as a rescue medicine. Reductions in corticosteroid treatment should be supervised; starting a biologic does not itself authorize an abrupt change in either systemic or inhaled steroid treatment. ¹³

Benralizumab targets the alpha subunit of the interleukin 5 receptor. The current United States prescribing information includes an adult EGPA indication. Its asthma indication has a different age scope, which should not be mistaken for pediatric EGPA approval. Before treatment, the prescriber reviews relevant precautions, including hypersensitivity reactions and parasitic worm infections. Starting it is also not a reason to abruptly stop inhaled or systemic corticosteroids. ¹²

Avacopan (Tavneos): safety and regulatory update

As of 15 October 2026, the United States and European Union regulatory situations must be distinguished. On 27 April 2026, the FDA’s Center for Drug Evaluation and Research proposed withdrawing Tavneos approval. The agency said reliable evidence of effectiveness was no longer demonstrated and that the application contained material untrue statements. A proposal is not a completed United States withdrawal: the FDA states that the medicine remains marketed unless the applicant removes it or the Commissioner orders removal. Patients and clinicians should discuss continued use and alternatives while the final marketing decision is pending. Older pages describing the original approval cannot be relied on as a complete account of the current situation. ⁸

In the European Union, the process has reached a different stage. The European Commission revoked the Tavneos marketing authorization on 4 August 2026, following the finding that pivotal efficacy data were no longer reliable and benefit was no longer shown to outweigh risk. The EMA advises against starting new patients and instructs clinicians to move existing patients to alternatives while monitoring liver function during the transition. This is a completed EU regulatory decision, rather than merely the earlier recommendation to revoke authorization. It should not be described as though it automatically establishes the medicine’s legal status in every other country. Anyone affected needs a locally appropriate specialist plan for alternative treatment. ¹⁰

Separately, the FDA warned on 31 March 2026 about serious and fatal liver injury in people taking avacopan, including vanishing bile duct syndrome. Symptoms such as yellowing of the skin or eyes, dark urine, pale stools, unusual itching or pain in the upper-right abdomen require immediate contact with the treating clinician. Liver blood testing is part of the safety response, and the FDA recommends closer testing early in treatment. A person already taking the medicine should promptly discuss liver monitoring and treatment alternatives with their specialist. The regulatory and safety developments are why this guide does not present older avacopan efficacy claims as current treatment advice. ⁹

Monitoring the disease and the medicines together

Rituximab requires attention to both infusion safety and longer-term infection risk. Its prescribing information warns about serious infusion reactions, infections and hepatitis B reactivation, and includes a warning about the rare brain infection progressive multifocal leukoencephalopathy. Pretreatment hepatitis B testing is important because a previous infection may become clinically relevant during immune suppression. Screening is therefore not limited to asking whether someone currently feels ill. Clinical and laboratory monitoring continue after treatment starts, and vaccination timing and reproductive plans should be discussed with the treating team. The Rituxan label includes GPA and MPA treatment with glucocorticoids in adults and children aged two years and older; that product-specific statement should not be assumed to describe every rituximab product’s authorization. Suitability and safety monitoring remain individual clinical decisions. ¹¹

Cyclophosphamide suppresses immune activity and may be used to control severe autoimmune disease, often before a different medicine is used for maintenance. Its monitoring reflects important risks: low blood-cell counts, infection, bladder injury, effects on fertility and later malignancy. Blood and urine tests help the team watch for problems during treatment, while past exposure remains relevant to future care. Fertility and reproductive plans should be discussed before treatment whenever the clinical situation allows, because these concerns can affect decisions and preparation. The name may be familiar from cancer treatment, but that does not mean all uses or regimens are interchangeable. Nor should general advice about hydration replace a plan adapted to someone with impaired kidney or heart function. The treating team needs to balance control of serious inflammation against these short- and longer-term risks. ²⁰

Azathioprine needs regular blood testing even when the disease seems quiet. Adverse effects can involve blood-cell counts, the liver, the pancreas or the digestive system. Testing of thiopurine methyltransferase, often abbreviated TPMT, can help assess toxicity risk, but it does not remove the need for ongoing monitoring. New infection symptoms, unusual bruising, vomiting or abdominal problems should be reported to the prescriber rather than attributed automatically to vasculitis. A complete medicine and supplement list also matters because interactions can change safety. The purpose of follow-up is therefore broader than asking whether the medicine appears to be controlling inflammation: it also checks whether the person can continue it safely. ¹⁸

Methotrexate used for inflammatory disease is generally taken weekly, not daily. Confusing that schedule is a serious medication-safety issue, so any uncertainty about the prescription needs clarification with the prescriber or pharmacist before taking it. Regular laboratory monitoring looks for blood-count and liver problems, and infection concerns also require attention. Folate supplementation and possible interactions should be reviewed as part of the prescription rather than improvised independently. Methotrexate is not appropriate for pregnancy, making reproductive plans an important discussion before treatment and when circumstances change. This does not provide a personal stopping timetable: the prescriber needs to advise on the individual situation. A maintenance prescription is still an active treatment with monitoring requirements, even when symptoms have improved substantially. ¹⁹

Glucocorticoids such as prednisolone can affect blood sugar, blood pressure, mood, bones and susceptibility to infection. The balance of benefit and harm depends partly on exposure, so monitoring should address these effects as well as control of vasculitis. After sustained treatment, the body may need a gradual supervised reduction; stopping suddenly can be dangerous. A written plan should explain how the prescribed dose changes and whom to contact if illness interrupts that plan. Some patients need a steroid card or an emergency plan for intercurrent illness. These arrangements are individualized and should come from the treating team, rather than from copying another patient’s taper. New symptoms during a reduction need assessment because the clinician must consider both the underlying condition and the consequences of changing steroid exposure. ²¹

Immune-suppressing treatment can change both vaccine safety and the strength of the response. Some live vaccines may be unsafe during significant immune suppression, whereas non-live vaccines can produce a weaker response than expected. Timing is particularly important around B-cell-depleting treatment, and some circumstances may require reassessment or repeat vaccination after immune recovery. The useful approach is to review the vaccine history with the treating team and use the current schedule for the person’s age, treatment and country. Patients should not stop immune medicines on their own to try to improve vaccine response. ¹⁷

For people receiving cyclophosphamide or rituximab, the ACR/Vasculitis Foundation guideline conditionally recommends preventive treatment against Pneumocystis pneumonia. Whether and how this applies should be discussed with the treating team alongside the overall infection-prevention plan. ³

What remission means for longer-term follow-up

Modern treatment has made many forms of vasculitis manageable as chronic disease, but remission does not guarantee that disease will never return. Current tests do not perfectly predict an individual relapse, which is one reason clinical follow-up continues after the initial illness settles. Research seeks better markers of activity and more individualized care. The continuing questions are whether inflammation is controlled, what organ problems remain and how treatment is affecting daily health. ²³

Care should also include understandable education, psychological support when needed and help with self-management. A shared symptom and medicine record can make conversations across specialties easier. Ask which team coordinates the plan, who reviews test results and how to obtain advice about new symptoms. These practical arrangements support specialist care when several organs or treatments are involved. ⁶

For further subtype-specific background, see our EGPA guide. This umbrella article focuses on the differences that affect testing, severity assessment and treatment decisions.

The original background video is retained below and has not been fully reviewed for this update. Use the current article and dated regulatory sources for updated testing and treatment information.