Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of autoimmune diseases that cause inflammation in blood vessels. Many patients and even some doctors struggle to differentiate the three main subtypes – granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA) – because they all share many symptoms. However, accurate identification is crucial for effective treatment.
What is ANCA-Associated Vasculitis?
AAV isn’t a single disease but a collection of conditions where the body’s immune system mistakenly attacks small to medium-sized blood vessels. This happens because of autoantibodies called ANCAs, which target neutrophils (a type of white blood cell). Over time, inflammation damages blood vessels, restricting blood flow and leading to organ damage.
Doctors classify AAV into three primary types: GPA, MPA, and EGPA, each with distinct features that influence how the disease progresses and how it’s treated.
The Three Main Subtypes
Granulomatosis with Polyangiitis (GPA)
Formerly known as Wegener’s granulomatosis, GPA is the most common form of AAV. It affects the kidneys, lungs, ears, nose, throat, and sinuses. A hallmark of GPA is the formation of granulomas – clusters of white blood cells that develop around inflamed blood vessels and organs.
Early symptoms often mimic a severe cold:
- Cough
- Earache
- Nasal congestion
- Sinus headache
- Runny nose
As the disease progresses, more serious signs can appear:
- Coughing up blood
- Hearing loss
- Kidney failure
- Muscle weakness
Microscopic Polyangiitis (MPA)
MPA is the second most common subtype and shares many symptoms with GPA. However, MPA typically doesn’t cause granulomas. This form frequently affects the kidneys, nerves, skin, joints, and lungs, with kidney inflammation occurring in about 80% of patients.
Common symptoms include:
- Abdominal pain
- Cough or coughing up blood
- Eye pain
- Fatigue
- Fever
- Muscle or joint pain
- Skin rashes
Eosinophilic Granulomatosis with Polyangiitis (EGPA)
EGPA is the rarest subtype, previously called Churg-Strauss syndrome. It impacts multiple organs, including the lungs, kidneys, and gastrointestinal tract. A key feature of EGPA is an abnormally high number of eosinophils – a type of white blood cell – accumulating in the blood and tissues.
EGPA typically unfolds in three phases:
- Asthma and respiratory symptoms: Often the first sign, sometimes years before other symptoms appear.
- Eosinophilia: An excessive number of eosinophils in the blood or tissues.
- Vasculitis: Inflammation of blood vessels affecting the skin, lungs, nerves, and other organs.
Why Does Subtype Matter?
Identifying the specific subtype of AAV is crucial because it guides treatment decisions. Each subtype has distinct clinical patterns and affects the body differently. The subtype influences prognosis, relapse risk, and the types of screenings a doctor will order.
For example, GPA is often linked to a specific ANCA type (cANCA), while MPA is more associated with another (pANCA). EGPA may not always show detectable ANCA levels.
Treatment Approaches
Treatment for AAV focuses on suppressing inflammation and preventing organ damage. The goal is remission, where symptoms disappear, followed by maintenance therapy to keep the disease under control. Treatment depends on the subtype and severity of symptoms.
Common medications include:
- Corticosteroids: To reduce inflammation.
- Monoclonal antibodies (Rituximab): To suppress the immune system.
- Chemotherapy (Cyclophosphamide): For severe cases, though often replaced by Rituximab due to fewer side effects.
- Other immunosuppressants (Methotrexate, Azathioprine, Mycophenolate mofetil): For long-term maintenance.
Recent advancements have also led to FDA-approved drugs specifically for EGPA, like mepolizumab and benralizumab, which target eosinophils and reduce steroid use.
Conclusion
ANCA-associated vasculitis encompasses three distinct subtypes: GPA, MPA, and EGPA. Accurate diagnosis is vital because treatment varies depending on the specific form of the disease. While all subtypes involve inflammation of blood vessels, understanding their unique characteristics allows doctors to tailor therapy for optimal patient outcomes.
