Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare immune disorder that affects blood vessels, particularly in the lungs and respiratory system. It develops gradually, often beginning with asthma or allergies, then progressing through stages that can eventually affect multiple organs throughout the body. Early and accurate diagnosis is essential, though the condition presents unique challenges for both patients and healthcare professionals.
Introduction: Who Should Undergo Diagnostics
Anyone with a history of severe allergies or asthma who begins experiencing unusual symptoms should consider seeking medical evaluation for EGPA. This condition typically affects middle-aged adults, with the average age at diagnosis around 50 years, though it can occur across a broad age range. The disease affects men and women equally and is extremely rare in children.[3][5]
The typical patient with EGPA is a middle-aged individual with new-onset asthma or asthma that has recently worsened. If you have developed asthma as an adult, particularly when accompanied by nasal allergies, chronic sinus infections, or nasal polyps, this may warrant closer medical attention. These respiratory symptoms often appear long before any other signs of EGPA emerge, sometimes years before the diagnosis is made.[15]
You should seek diagnostic evaluation if you experience a combination of asthma with other concerning symptoms. These include unexplained fever, unintended weight loss, extreme fatigue, or a general feeling of being unwell that persists without clear cause. Additional warning signs include numbness or tingling in your hands or feet, muscle and joint pain, skin rashes or lesions, chest pain, heart palpitations, or digestive symptoms like stomach pain and diarrhea. Because EGPA affects small blood vessels throughout the body, symptoms can appear in multiple organ systems, making the pattern of symptoms an important diagnostic clue.[1][4]
The disease develops gradually through distinct phases, and recognizing the progression is crucial. The first phase often lasts for years and is characterized by respiratory symptoms like asthma, allergic rhinitis, chronic sinusitis, and nasal polyps. During this stage, many people experience ongoing sinus pressure, sneezing, nasal congestion, and the typical symptoms of asthma including coughing, wheezing, and shortness of breath.[1]
As the condition progresses into the second phase, you may develop additional symptoms related to eosinophils—a type of white blood cell—accumulating in tissues. This phase can bring chest pain, difficulty breathing, heart palpitations, skin rashes, and gastrointestinal issues. The third and most serious phase involves inflammation of blood vessels themselves, which can lead to symptoms like severe nerve pain, numbness, shooting pains in the extremities, and muscle weakness or wasting in the hands or feet.[1][4]
Classic Diagnostic Methods
Diagnosing EGPA requires a comprehensive approach because no single test can confirm the condition. Instead, doctors use a combination of your medical history, physical examination, laboratory tests, imaging studies, and sometimes tissue samples to reach a diagnosis. The process can be challenging because EGPA symptoms overlap with many other conditions, and the disease progresses through different stages with varying presentations.[14]
The diagnostic journey typically begins with a detailed review of your medical history and a thorough physical examination. Your doctor will ask about the onset and progression of your symptoms, particularly focusing on when asthma began, whether it was new or worsening, and what other symptoms have developed over time. The specific combination of symptoms, the pattern of organ involvement, and the timeline of their appearance all provide important diagnostic clues.[15]
Blood Tests
Blood tests play a central role in diagnosing EGPA. The most characteristic finding is eosinophilia, which means an abnormally high number of eosinophils in the blood. Eosinophils are a type of white blood cell that normally helps fight infections and plays a role in allergic reactions. In healthy people, eosinophils typically make up 5 percent or less of the total white blood cell count. In EGPA, this percentage can rise dramatically, sometimes reaching as high as 60 percent. With EGPA, eosinophil levels are often double the normal amount or higher.[1][15]
Another important blood test looks for anti-neutrophil cytoplasmic antibodies (ANCA). These are proteins that the immune system produces, and they can suggest the presence of EGPA. However, this test presents a diagnostic challenge because ANCA is positive in only 30 to 40 percent of EGPA cases. This means that many people with EGPA will have negative ANCA results, so a negative test does not rule out the disease.[3][9]
The presence or absence of ANCA helps doctors understand which type of EGPA a patient has. ANCA-positive patients tend to have more blood vessel inflammation (vasculitis) and kidney involvement, while ANCA-negative patients often have more eosinophil-related tissue damage, particularly in the heart and lungs. Understanding this distinction helps guide treatment decisions.[3]
Imaging Tests
Various imaging tests help doctors see what is happening inside your body and identify organ damage. A chest X-ray is often one of the first imaging tests performed because the lungs are frequently affected in EGPA. X-rays can reveal abnormal shadows or infiltrates in the lungs, though only about one-third of patients show these findings.[15]
More detailed imaging may be obtained through computed tomography (CT) scans of the chest or sinuses. CT scans provide cross-sectional images that show more detail than regular X-rays and can reveal inflammation in the sinuses or lungs, as well as other abnormalities. Doctors may also order magnetic resonance imaging (MRI) scans to examine soft tissues in more detail or to look at specific organs that may be affected.[14]
If heart problems are suspected, an echocardiogram may be performed. This test uses sound waves to create moving pictures of your heart, allowing doctors to see how well your heart is pumping and whether there is any inflammation or damage to the heart muscle or valves. Heart involvement in EGPA can be serious and sometimes life-threatening, so evaluating heart function is an important part of the diagnostic process.[7][14]
Tissue Biopsy
When other tests suggest EGPA, doctors may recommend taking a small sample of tissue to examine under a microscope. This procedure, called a biopsy, provides direct evidence of the disease by showing characteristic features such as inflamed blood vessels (vasculitis), accumulations of eosinophils in tissues, and sometimes granulomas—small masses of immune cells that form when tissues are inflamed.[14]
Biopsies can be taken from several different sites depending on which organs are affected. Common biopsy sites include the lungs, skin, or nerves. A lung biopsy may be performed through bronchoscopy, where a thin tube with a camera is inserted through the airways to collect tissue samples. Skin biopsies are simpler procedures where a small piece of affected skin is removed for examination. Nerve biopsies may be done when there is significant nerve involvement causing numbness, tingling, or weakness.[15]
Not all patients require a biopsy for diagnosis. If the combination of symptoms, blood test results, and imaging findings strongly suggest EGPA, doctors may proceed with treatment without a tissue sample. However, when the diagnosis is uncertain or when other conditions need to be ruled out, a biopsy can provide definitive evidence.[14]
Additional Diagnostic Tests
Depending on your symptoms and which organs may be affected, your doctor may order additional tests. If nerve damage is suspected, electromyography (EMG) and nerve conduction studies can assess how well your nerves are functioning and identify areas of damage. These tests measure the electrical activity of muscles and the speed at which nerves send signals.[15]
Urine tests may be performed to check kidney function and look for signs of kidney inflammation or damage. The kidneys contain many small blood vessels, making them vulnerable to vasculitis. Finding protein or blood in the urine can indicate kidney involvement.[15]
Sinus X-rays or CT scans specifically focused on the sinuses can reveal chronic inflammation, polyps, or other abnormalities in the nasal passages and sinuses. Since nasal symptoms and sinusitis are common early features of EGPA, documenting these findings helps support the diagnosis.[15]
Distinguishing EGPA from Other Conditions
One of the biggest challenges in diagnosing EGPA is distinguishing it from other conditions that cause similar symptoms. Asthma alone is very common and does not mean someone has EGPA—only a tiny minority of people with asthma develop vasculitis. However, the specific combination of adult-onset or worsening asthma, high eosinophil counts, and symptoms affecting multiple organ systems helps narrow the diagnosis.[15]
EGPA shares features with other types of vasculitis, particularly granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA). What distinguishes EGPA is the presence of asthma, allergic rhinitis, and markedly elevated eosinophil counts—features not typically seen in GPA or MPA. The abundance of eosinophils and the presence of granulomas in tissue samples help differentiate EGPA from these related conditions.[3][15]
Other conditions that can cause high eosinophil counts must also be considered and ruled out. These include parasitic infections, drug reactions, certain cancers, and other eosinophilic disorders. The pattern of organ involvement, the presence of vasculitis, and the specific combination of symptoms help doctors distinguish EGPA from these other possibilities.[9]
Diagnostics for Clinical Trial Qualification
When patients are being considered for enrollment in clinical trials studying new treatments for EGPA, more standardized and specific diagnostic criteria are typically applied. Clinical trials require careful documentation of the disease to ensure that all participants truly have EGPA and to allow researchers to compare results across different patients and studies accurately.
Clinical trials often use established classification criteria to define EGPA. While these criteria were originally developed to classify the disease for research purposes rather than for individual diagnosis, they provide a structured framework. The criteria typically require the presence of asthma along with eosinophilia in the blood, plus evidence of vasculitis affecting two or more organs. Additional features that support the diagnosis include a history of allergies, abnormalities in the sinuses, infiltrates visible on chest X-rays or CT scans, and the finding of eosinophils outside blood vessels when tissue is examined under a microscope.[9]
For clinical trial enrollment, blood tests documenting the degree of eosinophilia are essential. Researchers need baseline measurements of eosinophil counts to track how they change with treatment. ANCA testing is also standard, as the presence or absence of these antibodies may influence which treatments are most appropriate and helps identify disease subgroups.[9]
Imaging studies provide objective evidence of organ involvement. Chest CT scans document lung abnormalities, while other imaging may be required to assess involvement of the heart, kidneys, or other organs. Some trials may require specific types of imaging or repeat imaging at regular intervals to monitor how the disease responds to treatment.[9]
Assessment of disease severity and activity is crucial for clinical trial participation. Researchers often use scoring systems to quantify how active the disease is and which organs are affected. The Five Factor Score (FFS) is one such tool that assesses the severity of EGPA based on the presence of certain features associated with worse outcomes, including kidney involvement, heart involvement, gastrointestinal involvement, and older age. Patients with higher scores have more severe disease and may be candidates for trials testing more intensive treatments.[10]
Lung function tests may be required to document the severity of asthma and to track changes over time. These tests measure how much air you can breathe in and out and how quickly you can exhale. Improvement in lung function can be an important outcome measure in clinical trials.[9]
Some clinical trials may require tissue biopsies to confirm the diagnosis before enrollment, particularly if participants need to have specific pathological features. Trials testing new medications may also require documentation that patients have either not responded to standard treatments or have experienced disease relapse, ensuring that the trial enrolls people who need alternative therapies.[9]
Additional specialized tests might be performed as part of clinical trial screening. These could include more detailed cardiac assessments such as cardiac MRI or special blood tests measuring markers of inflammation or eosinophil activity. The specific tests required depend on the trial design and what the researchers are trying to measure.[9]
Quality of life questionnaires and symptom diaries are often part of clinical trial assessments. These tools help researchers understand not just whether laboratory values improve, but whether patients feel better and can function better in their daily lives. Documenting your symptoms and their impact before starting trial treatment provides a baseline for comparison.[9]
Regular monitoring throughout a clinical trial involves repeating many of these diagnostic tests. Blood work, imaging, physical examinations, and symptom assessments are typically performed at scheduled intervals to track disease activity, treatment response, and any side effects. This intensive monitoring ensures patient safety and generates the data needed to determine whether a new treatment is effective.[9]
