Written by Gemini

Introduction to the Disease Spectrum

Eosinophilic granulomatosis with polyangiitis (EGPA), historically designated by the eponym Churg-Strauss syndrome, is a rare, complex, and potentially life-threatening systemic necrotizing vasculitis. Clinically characterized by a quintessential triad of adult-onset severe asthma, profound peripheral and tissue eosinophilia, and small-to-medium vessel vasculitis, EGPA occupies a highly unique pathological niche. It represents a clinical and immunological bridge between primary hypereosinophilic syndromes (HES) and the classic anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV), a category it shares with granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA).   

The disease was first delineated in 1951 by pathologists Jacob Churg and Lotte Strauss, who identified a consistent pattern of severe asthma, fever, hypereosinophilia, and granulomatous necrotizing vasculitis in a series of 13 autopsy cases, originally terming the condition “allergic granulomatosis and angiitis”. The epidemiological profile of EGPA demonstrates an annual global incidence ranging from 0.5 to 4.2 cases per million individuals, with a prevalence estimated between 10.7 and 22.3 cases per million. The condition typically presents in patients aged 40 to 60 years, with no significant sex predilection, though specific subsets of organ involvement may skew demographically.   

The classical clinical progression of EGPA unfolds over three sequential, albeit frequently overlapping, phases. The initial prodromal phase is defined by severe, late-onset atopic and allergic manifestations—most notably bronchial asthma, allergic rhinitis, and recurrent nasal polyposis—which can precede systemic vasculitic disease by up to a decade. This is followed by the eosinophilic phase, characterized by marked peripheral blood eosinophilia and aggressive eosinophilic infiltration into vital organs, predominantly the lungs, gastrointestinal tract, and myocardium. Ultimately, the disease evolves into the vasculitic phase, wherein necrotizing inflammation of the small and medium-sized blood vessels yields catastrophic systemic manifestations, including mononeuritis multiplex, palpable purpura, and pauci-immune glomerulonephritis. However, this linear progression is rarely absolute in modern clinical practice; phases frequently coexist, masking the underlying systemic nature of the condition and contributing to a profound diagnostic delay. Retrospective cohort analyses reveal that EGPA has the longest diagnostic delay among all AAVs, with a median time from first symptom to confirmed diagnosis of 454.5 days, a duration that extends even further when asthma and nasal polyps are the sole initial manifestations.   

Genomic Architecture and Immunological Endotypes

The pathogenesis of EGPA is intensely multifactorial, driven by an intricate interplay between genetic predisposition, uncharacterized environmental triggers, and profound dysregulation of both the innate and adaptive arms of the immune system. The hallmark of EGPA immunology is a hyperactive Type 2 (T2) inflammatory response, augmented by autoreactive B-cell activation and pathogenic neutrophil engagement.   

The ANCA Status Dichotomy

Historically viewed as a monolithic entity, contemporary genomic and clinical analyses—spearheaded by extensive genome-wide association studies (GWAS) such as those by Lyons et al.—have fundamentally reclassified EGPA into at least two distinct genetic and pathophysiological endotypes, largely segregated by ANCA status. While categorized under the AAV umbrella, only 30% to 40% of EGPA patients are ANCA-positive, almost exclusively exhibiting a perinuclear ANCA (p-ANCA) immunofluorescence pattern directed against myeloperoxidase (MPO).   

The genetic landscape of these two subsets diverges sharply. The ANCA-positive variant demonstrates a robust genetic association with the HLA class II DQ haplotype (specifically HLA-DRB4/DRB1), a genetic signature it shares heavily with MPO-positive MPA. This profound MHC association suggests that the ANCA-positive phenotype is primarily an autoimmune, vasculitis-driven disease mediated by a loss of tolerance to neutrophil antigens. In these patients, the binding of ANCA to MPO on primed neutrophils triggers a respiratory burst, degranulation, and the release of neutrophil extracellular traps (NETs), leading to direct endothelial necrosis.   

Conversely, ANCA-negative EGPA completely lacks this MHC association. Instead, GWAS data reveal that ANCA-negative disease is genetically linked to non-MHC variants in the GP33 and IL5/IRF1 loci. These loci are intimately involved in mucosal barrier function and the regulation of Type 2 cytokines, positioning ANCA-negative EGPA closer to intrinsic mucosal dysregulation and primary eosinophilic disorders rather than a traditional autoimmune vasculitis. Recent single-cell RNA sequencing (scRNA-seq) studies have further differentiated EGPA from closely related conditions like severe eosinophilic asthma (SEA). While SEA is characterized by a Tumor Necrosis Factor (TNF)-predominant pathway activation, EGPA exhibits a distinct interferon (IFN-I)-driven inflammatory signature, which may account for its broader systemic manifestations and frequent resistance to conventional asthma therapies.   

The Eosinophilic Axis and Upstream Alarmins

Regardless of ANCA status, eosinophils remain the central effector cells mediating catastrophic tissue damage in EGPA. The T2 immune cascade is driven by the profound overexpression of Interleukin-5 (IL-5), the master cytokine responsible for the maturation, bone marrow egress, tissue recruitment, and survival of eosinophils. Upstream of IL-5, epithelial-derived alarmins—including thymic stromal lymphopoietin (TSLP), IL-25, and IL-33—are secreted in response to environmental or mucosal insults. These alarmins strongly activate innate lymphoid cells type 2 (ILC2s) and Th2 lymphocytes, prompting a massive, self-sustaining release of IL-5, IL-4, and IL-13.   

Upon activation and tissue infiltration, eosinophils undergo extensive degranulation, releasing highly toxic proteins such as eosinophil cationic protein (ECP), major basic protein (MBP), and eosinophil-derived neurotoxin. These proteins induce direct cytotoxicity, oxidative stress, and structural tissue remodeling. Furthermore, activated eosinophils release pro-thrombotic factors and interact directly with endothelial cells, contributing to microvascular occlusion and ischemic damage independent of traditional ANCA-mediated necrotizing vasculitis. This dual mechanism of tissue injury—eosinophil-mediated microvascular occlusion alongside ANCA-mediated necrotizing vasculitis—explains the diverse and unpredictable organ involvement seen in EGPA.   

Spectrum of Clinical Manifestations

Due to the dual pathogenic engines driving EGPA, the disease is notoriously multisystemic. The specific pattern of organ involvement carries profound implications for both prognostic stratification and the selection of precision therapeutics.

Respiratory and Otorhinolaryngological Involvement

The respiratory tract is the most universally affected system in EGPA. Severe, late-onset bronchial asthma is present in over 95% of patients and is almost always the earliest clinical indicator during the prodromal phase. Unlike typical allergic asthma, EGPA-associated asthma is exceptionally refractory to conventional inhaled corticosteroid therapy and remains heavily dependent on systemic glucocorticoids, frequently resulting in significant iatrogenic morbidity prior to a formal EGPA diagnosis. Alongside asthma, upper airway disease is ubiquitous, manifesting as allergic rhinitis, chronic rhinosinusitis, and recurrent nasal polyposis, occurring in 50% to 70% of patients. EGPA patients are thus frequently referred to pulmonologists, allergists, or otorhinolaryngologists long before rheumatological evaluation.   

A highly specific, morbid, and frequently under-recognized manifestation of EGPA is eosinophilic otitis media (EOM). EOM presents as a highly viscous, eosinophil-rich middle ear effusion that is notoriously resistant to conventional antibiotics, standard middle-ear interventions, or tympanostomy tubes. Driven by the localized overproduction of IL-5, eotaxin, and IgE, EOM can rapidly progress. The dense accumulation of eosinophilic cationic proteins and neurotoxins within the middle ear can penetrate the round window membrane, leading to severe inner ear damage, sensorineural hearing loss, and ultimately, irreversible deafness.   

Neurological Manifestations: Peripheral and Central

Neurological involvement is a defining hallmark of the vasculitic phase of EGPA. Peripheral neuropathy is observed in roughly 50% to 70% of cases, classically presenting as mononeuritis multiplex. This condition results from immune-complex deposition and necrotizing vasculitis of the vasa nervorum, leading to severe epineural vessel ischemia and subsequent acute axonal degeneration. Patients typically experience sudden-onset, highly asymmetric, painful sensory loss and motor weakness, manifesting clinically as acute foot drop or wrist drop. In cases where clinical ambiguity persists, a sural nerve biopsy is frequently performed. Histopathology commonly reveals severe axonal loss, Wallerian degeneration, and prominent perivascular eosinophilic infiltration, providing definitive, tissue-level confirmation of the disease.   

Central nervous system (CNS) involvement is significantly rarer, affecting fewer than 10% of patients, but it carries a disproportionately high risk of permanent morbidity and mortality. CNS manifestations include subarachnoid hemorrhage, pachymeningitis, and ischemic stroke. Detailed retrospective analyses indicate that ischemic stroke in EGPA presents with distinct neuroimaging patterns, often being bilateral and multifocal. Notably, CNS infarction correlates strongly with concomitant cardiac involvement; the hypercoagulable state induced by profound eosinophilia, combined with cardioembolism stemming from eosinophilic endomyocarditis, dramatically elevates the risk of stroke, with one cohort demonstrating an odds ratio of 15.0 for stroke in the presence of cardiac disease.   

Cardiovascular Involvement: The Primary Driver of Mortality

Cardiac involvement occurs in approximately 20% to 46% of patients. It is predominantly observed within the ANCA-negative cohort and remains the absolute leading cause of premature death in EGPA. Profound eosinophil infiltration into the myocardium initiates acute eosinophilic myocarditis, which, if left unchecked, rapidly evolves into endomyocardial fibrosis, restrictive cardiomyopathy, intractable heart failure, and fatal arrhythmias.   

Because overt clinical symptoms of cardiac involvement are often delayed, irreversible structural damage frequently precedes clinical recognition. Therefore, Cardiac Magnetic Resonance (CMR) imaging is the gold standard for early detection, characteristically demonstrating subendocardial and mid-myocardial late gadolinium enhancement (LGE), indicative of active inflammation and early fibrosis. Echocardiographic evidence of left ventricular diastolic dysfunction or elevated serum biomarkers, such as NT-proBNP and troponin (CK-MB), mandate immediate CMR evaluation and aggressive immunosuppression to prevent fatal cardiac remodeling.   

Gastrointestinal and Renal Involvement

Gastrointestinal (GI) disease affects roughly 20% to 50% of EGPA patients, presenting either with insidious, non-specific symptoms such as chronic abdominal pain and diarrhea, or catastrophic surgical emergencies including bowel ischemia, stricturing enteritis, and spontaneous perforation. The pathogenesis involves dense eosinophilic infiltration of the bowel wall coupled with occlusive mesenteric vasculitis. GI involvement is officially recognized as a severe prognostic factor linked to significantly increased mortality. Notably, histological diagnosis via endoscopy is notoriously difficult, as routine mucosal biopsies are frequently too superficial to sample the deeper submucosal vessels where the vasculitis resides. Emerging literature also suggests potential infectious triggers; for instance, cases of severe gastrointestinal EGPA have been documented immediately following toxigenic Clostridium difficile infections, suggesting that localized mucosal inflammation may unmask the underlying autoimmune dysregulation.   

Renal involvement in EGPA is notably less frequent (approximately 20% to 30%) and generally less severe than in GPA or MPA. When it occurs, it is overwhelmingly seen in the ANCA-positive subset, manifesting clinically as a pauci-immune focal segmental necrotizing glomerulonephritis with crescent formation. This leads to microscopic hematuria, proteinuria, and progressive renal insufficiency, though progression to end-stage renal disease is less common than in other AAVs.   

Evolution of Diagnostic and Classification Criteria

The diagnosis of EGPA has historically been plagued by delays due to its evolving clinical stages and significant overlap with other eosinophilic and autoimmune conditions. Early diagnostic frameworks, such as the Lanham criteria (1984), demanded the simultaneous presence of asthma, peak eosinophilia >1,500 cells/µL, and systemic vasculitis affecting at least two extrapulmonary organs. While highly specific, these criteria were heavily criticized for delaying diagnosis, as they essentially required physicians to wait until irreversible, multi-organ damage occurred before initiating specific therapies.   

In 1990, the American College of Rheumatology (ACR) improved diagnostic sensitivity by requiring four of six features for classification: asthma, eosinophilia >10%, mono/polyneuropathy, non-fixed pulmonary infiltrates, paranasal sinus abnormality, and extravascular eosinophils on biopsy. However, as the understanding of AAV endotypes expanded, these criteria struggled to effectively differentiate EGPA from newly recognized mimics, particularly variants of GPA and hypereosinophilic syndromes.   

The 2022 ACR/EULAR Classification Criteria

To align with modern clinical data and biomarker profiles, the American College of Rheumatology and the European Alliance of Associations for Rheumatology (ACR/EULAR) jointly published radically revised classification criteria for EGPA in 2022. Developed through a rigorous, multi-national prospective cohort study comprising nearly 5,000 patients with vasculitis and comparator diseases, these criteria utilize a weighted scoring system that incorporates both positive clinical predictors and critical negative serological detractors.   

Note: The criteria are applicable only after a diagnosis of small- or medium-vessel vasculitis is clinically established and mimics have been excluded. A cumulative score of ≥ 6 yields a sensitivity of 85% and an exceptional specificity of 99% for EGPA..   

The inclusion of negative parameters (-3 for PR3-ANCA, -1 for hematuria) acts as a crucial differentiator. PR3-ANCA positivity heavily skews the diagnostic probability toward Granulomatosis with Polyangiitis (GPA), while isolated severe hematuria is more statistically representative of Microscopic Polyangiitis (MPA). Comparative validation studies have demonstrated that these new criteria exhibit almost perfect agreement with expert clinician diagnosis and the European Medicines Agency (EMEA) algorithm.   

Diagnostic Biomarkers: Differentiating EGPA from HES

Differentiating EGPA from Hypereosinophilic Syndrome (HES) remains a prominent clinical hurdle, particularly in ANCA-negative patients who present with severe tissue eosinophilia but lack overt histological evidence of vasculitis. Both diseases feature hypereosinophilia and organ infiltration; however, EGPA uniquely features necrotizing vasculitis, extravascular granulomas, and a near-universal asthmatic prodrome.   

To bridge this diagnostic gap, molecular biomarkers have been heavily investigated. Eotaxin-3 (CCL26), a potent eosinophil chemoattractant secreted by endothelial and epithelial cells, has emerged as a highly sensitive and specific diagnostic tool. Serum eotaxin-3 levels are markedly elevated in active EGPA but remain comparatively low in HES, as well as in isolated eosinophilic asthma or other connective tissue diseases. At a threshold of 80 pg/mL, eotaxin-3 demonstrates 87.5% sensitivity and 98.6% specificity for differentiating active EGPA from its mimickers.   

Furthermore, CCL17 (TARC), a Th2 chemoattractant, and serum IgG4 are frequently elevated in active EGPA, correlating strongly with overall disease activity and organ involvement scores. In cases of diagnostic uncertainty regarding renal involvement, urinary soluble CD163 (usCD163) and CD25 have proven to be reliable non-invasive markers for active crescentic glomerulonephritis. A novel study of eicosanoids in exhaled breath condensate also found elevated levels of the arachidonic acid metabolite 12-HETE specifically in active EGPA, providing another potential non-invasive diagnostic avenue.   

Prognostic Stratification: The Five-Factor Score

Prognostication in EGPA relies heavily on the Five-Factor Score (FFS), originally formulated by the French Vasculitis Study Group in 1996 and subsequently revised in 2009. The FFS identifies distinct, severe clinical manifestations that independently predict mortality.   

The 2009 revised FFS assigns +1 point for each of the following four severe systemic manifestations:

1. Age > 65 years
2. Cardiac involvement (e.g., endomyocarditis, heart failure, LGE on CMR)
3. Gastrointestinal involvement (e.g., severe bleeding, perforation, infarction)
4. Renal insufficiency (defined as stabilized peak creatinine ≥ 150 µmol/L)

Interestingly, the presence of Ear, Nose, and Throat (ENT) symptoms (such as nasal polyposis or allergic rhinitis) is protective, associated with a lower relative risk of death, and acts as a detractor (-1 point) in the scoring system. Survival correlates inversely with the score: patients with an FFS of 0 exhibit a 5-year mortality rate of approximately 9%, whereas a score of 1 correlates with a 21% mortality rate, and a score of ≥ 2 is associated with a dramatic escalation to a 40% 5-year mortality rate. The FFS not only aids in prognostication but critically guides the aggressiveness of the initial induction therapy.   

Therapeutic Landscape: From Broad Immunosuppression to Precision Biologics

The management of EGPA has undergone a massive paradigm shift over the past decade. Historically, treatment relied entirely on non-specific systemic immunosuppression, leading to significant iatrogenic morbidity. Today, therapeutic algorithms stratify patients based on disease severity (via the FFS), ANCA status, and specific organ involvement, increasingly incorporating targeted biologic agents to minimize the profound morbidities associated with long-term glucocorticoid exposure.

Conventional Remission Induction and Maintenance

For decades, the cornerstone of EGPA therapy has been high-dose systemic glucocorticoids (GCs). For patients with non-severe disease (FFS = 0), glucocorticoids alone have traditionally been utilized for remission induction. However, for life- or organ-threatening disease (FFS ≥ 1, particularly involving cardiac, central nervous system, or severe gastrointestinal/renal manifestations), aggressive combination therapy is mandated.   

Induction therapy in severe EGPA combines high-dose GCs with Cyclophosphamide (CYC). Following the attainment of remission (typically after 3 to 6 months), maintenance therapy is implemented using agents with lower long-term toxicity profiles, such as Azathioprine (AZA), Methotrexate (MTX), or Mycophenolate Mofetil (MMF). The 2022 EULAR guidelines emphasize shared decision-making and aggressive mitigation of steroid toxicity, advocating for reduced-dose GC regimens and stringent control of cardiovascular risk factors (e.g., tight blood pressure control, lipid management), given that long-term steroid exposure profoundly exacerbates the cardiovascular morbidity already inherent to EGPA.   

The Role of B-Cell Depletion: Rituximab

Rituximab (RTX), a chimeric anti-CD20 monoclonal antibody, induces profound B-cell depletion and has revolutionized the treatment of GPA and MPA (as evidenced in the RAVE and RITUXVAS trials). Its application in EGPA, however, is more nuanced due to the differing immunopathology. In ANCA-positive EGPA with dominant vasculitic features (e.g., glomerulonephritis or severe mononeuritis multiplex), RTX is highly effective and is now recognized as a first-line alternative to cyclophosphamide for induction therapy.   

The efficacy of RTX for remission maintenance in EGPA was recently evaluated in the Phase III MAINRITSEG trial, which compared fixed-dose RTX (500 mg every 6 months for 18 months) against daily Azathioprine (2 mg/kg/day). While RTX demonstrated overwhelming superiority in maintaining remission in broader AAV populations (as seen in the MAINRITSAN trials), the MAINRITSEG results in EGPA suggested comparable overall efficacy between RTX and Azathioprine for maintaining vasculitis remission. However, RTX was significantly superior in maintaining remission with ultra-low dose prednisolone (≤ 4 mg/day), reinforcing its value as a steroid-sparing agent in specific vasculitic phenotypes.   

Inhibiting the Eosinophilic Axis: Anti-IL-5 Therapies

The most significant advancement in EGPA management involves the targeted inhibition of the IL-5 pathway, directly neutralizing the core eosinophilic pathology. The introduction of these biologics has dramatically shifted the treatment goal from mere disease suppression to deep, steroid-free remission.   

Mepolizumab

Mepolizumab is a humanized monoclonal antibody that binds directly to soluble circulating IL-5, preventing it from interacting with the IL-5 receptor α chain (IL-5R$\alpha$) on the surface of eosinophils. The pivotal double-blind, placebo-controlled MIRRA trial evaluated mepolizumab at a high dose (300 mg subcutaneously every 4 weeks) in patients with relapsing or refractory EGPA. Mepolizumab demonstrated overwhelming superiority over placebo: 28% of treated patients accrued ≥ 24 weeks of remission (compared to a mere 3% on placebo), and 32% achieved clinical remission at weeks 36 and 48 (versus 3% on placebo). Crucially, mepolizumab allowed for substantial glucocorticoid sparing, with 44% of participants tapering their prednisolone dose to ≤ 4 mg/day.   

Longitudinal real-world evidence confirms mepolizumab’s efficacy not only in controlling asthma and systemic symptoms but also in refractory localized manifestations. For instance, in eosinophilic otitis media, mepolizumab has been shown to restore hearing and prevent structural middle-ear damage. Furthermore, cardiac MRI data suggest that prolonged IL-5 inhibition with mepolizumab can induce profound reverse cardiac remodeling, resolving endomyocarditis and restoring ejection fractions in patients with severe, previously intractable cardiac involvement. Survival analyses from Japanese cohorts report highly favorable 5-, 10-, and 20-year survival rates (95.0%, 91.4%, and 85.2%, respectively) following the integration of mepolizumab into routine care.   

Benralizumab

Benralizumab offers a distinctly aggressive mechanistic approach. Rather than binding soluble IL-5, benralizumab is a humanized monoclonal antibody directed against the IL-5R$\alpha$ subunit on the surface of eosinophils and basophils. Crucially, benralizumab is afucosylated; the removal of fucose from the Fc region of the antibody enhances its affinity for the Fc$\gamma$RIIIa receptor (CD16) on Natural Killer (NK) cells and macrophages. This modification triggers rapid, potent antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). Unlike mepolizumab, which prevents eosinophil maturation, benralizumab induces the near-complete and rapid apoptosis of both tissue-resident and circulating eosinophils.   

The landmark Phase III MANDARA trial directly compared benralizumab (30 mg) to mepolizumab (300 mg) in patients with relapsing/refractory EGPA. The study successfully demonstrated that benralizumab was non-inferior to mepolizumab in achieving clinical remission (59% vs. 56%, respectively) and facilitating steroid tapering. Pharmacokinetic/pharmacodynamic (PK/PD) modeling suggests that due to its ADCC mechanism, benralizumab achieves a more profound (99.5% depletion vs 76.1% at 12 weeks) and sustained depletion of tissue-level eosinophils with minimal rebound between doses. Real-world comparative cohorts have corroborated these findings, indicating comparable overall safety and efficacy, with benralizumab occasionally demonstrating superior rates of deep complete remission at 12 months, likely due to its rapid cytolytic effects.   

Depemokimab: The Next Generation

Depemokimab represents the latest evolution in IL-5 inhibition. It is a first-in-class, ultra-long-acting anti-IL-5 monoclonal antibody engineered with a specific “YTE” mutation (amino acid substitutions M252Y/S254T/T256E) in its Fc region. This mutation dramatically increases the antibody’s binding affinity to the neonatal Fc receptor (FcRn) within the acidic environment of intracellular endosomes. This robust bond facilitates cellular recycling back into the bloodstream rather than lysosomal degradation, extending the terminal half-life of depemokimab to approximately six months.   

This ultra-long half-life allows depemokimab to be administered subcutaneously only twice yearly (every 26 weeks). Model-informed drug development (MIDD) and phase 3 data from the SWIFT and NIMBLE trials have shown profound reductions in eosinophil counts and asthma exacerbations. While primarily approved for severe eosinophilic asthma and chronic rhinosinusitis with nasal polyps, phase 3 evaluations for its use in EGPA (at a projected 200 mg bi-annual dose) hold massive promise for significantly reducing treatment burden and enhancing long-term compliance.   

Targeting Upstream Alarmins: Tezepelumab

Despite the remarkable success of IL-5 inhibitors, a subset of patients remains refractory, experiencing persistent asthma, EOM, or sinonasal disease despite near-total peripheral blood eosinophil depletion. This suggests the involvement of broader T2 inflammatory pathways driven by alternative cytokines (IL-4, IL-13) or persistent tissue-level inflammation. Tezepelumab is a human monoclonal antibody targeting TSLP, an epithelial alarmin situated at the very apex of the inflammatory cascade. By inhibiting TSLP, tezepelumab prevents the downstream activation of ILC2s, Th2 cells, mast cells, and basophils, effectively silencing the production of multiple pro-inflammatory cytokines simultaneously.   

Recent case reports and small clinical cohorts have demonstrated remarkable efficacy using off-label tezepelumab for patients with EGPA whose asthma or EOM failed to respond to high-dose mepolizumab or benralizumab. In several instances, switching to tezepelumab resolved severe refractory symptoms, successfully tapered systemic steroids, and even suppressed ANCA titers. Innovative staggered regimens—alternating bi-monthly doses of tezepelumab and mepolizumab—have been used to achieve comprehensive control of highly complex, multi-compartment disease without the prohibitive cost of concurrent dual-biologic therapy. However, clinicians must note a potential paradox: upstream blockade with tezepelumab might allow localized sputum or tissue eosinophilia to persist despite systemic symptom control, necessitating careful longitudinal monitoring.   

The Dupilumab Paradox: Unmasking EGPA

Dupilumab targets the IL-4 receptor alpha (IL-4R$\alpha$) subunit, effectively inhibiting both IL-4 and IL-13 pathways. It is highly effective for severe asthma, chronic rhinosinusitis with nasal polyps, and atopic dermatitis. However, its widespread use in populations highly enriched for T2 inflammation has unveiled a dangerous paradoxical phenomenon: the precipitation, exacerbation, or “unmasking” of full-blown EGPA.   

Mechanistically, IL-4/IL-13 blockade prevents eosinophils from traversing the vascular endothelium into tissues. While this halts tissue remodeling, it leads to a profound pooling of eosinophils in the peripheral blood (hypereosinophilia). Furthermore, by excellently controlling asthma symptoms, dupilumab enables clinicians to rapidly withdraw systemic glucocorticoids. This rapid steroid taper removes the suppressive immunological “lid” on a previously subclinical vasculitic process, culminating in acute, severe EGPA presentations. Patients may suddenly develop mononeuritis multiplex, cardiac events, or ischemic strokes. While it remains debated whether dupilumab directly triggers the disease or merely unmasks a pre-existing condition, extreme vigilance is required. Rising peripheral eosinophilia combined with new neurological, cardiac, or systemic symptoms following dupilumab initiation must immediately prompt diagnostic investigation for EGPA and the cessation of the offending biologic.   

Emerging Triggers: The Intersection of COVID-19 Vaccination and EGPA

The mass administration of mRNA vaccines (e.g., BNT162b2, mRNA-1273) during the global COVID-19 pandemic revealed rare but notable immune-mediated phenomena. In the pharmacovigilance literature, several well-documented case reports have described the sudden onset or severe relapse of EGPA occurring within a narrow temporal window (typically 2 to 14 days) following mRNA SARS-CoV-2 vaccination.   

These post-vaccination presentations are often severe and explosive, featuring profound hypereosinophilia, immune thrombocytopenia (ITP), and multi-organ vasculitis, including ischemic strokes and rapid-onset motor neuropathies (e.g., bilateral foot drop). While a definitive causal relationship is difficult to prove conclusively given the baseline incidence rates of the disease, the tight temporal correlation strongly suggests an immunological trigger. The robust innate and adaptive immune stimulation provided by the mRNA lipid-nanoparticle platform may act as a catalyst in genetically susceptible individuals, tipping a smoldering T2/autoreactive environment into overt, life-threatening clinical vasculitis.   

Conclusion

Eosinophilic granulomatosis with polyangiitis remains a profoundly complex disorder at the intersection of allergy, immunology, and rheumatology. The traditional view of EGPA as a single continuous syndrome has been rightfully challenged by genomic and clinical evidence, delineating it into distinct endotypes: an ANCA-positive, neutrophil-driven vasculitic phenotype, and an ANCA-negative, IL-5-driven eosinophilic phenotype. This pathophysiological divergence mandates a highly tailored, precision-medicine approach to clinical management.

The 2022 ACR/EULAR classification criteria provide a robust, highly specific modern framework for accurate diagnosis, while the revised Five-Factor Score remains critical for prognostic stratification and guiding induction therapy. The therapeutic landscape has progressed immensely, moving far beyond the broad toxicity of universal cyclophosphamide and indefinite glucocorticoid reliance. Today, therapies are exquisitely targeted: B-cell depletion with rituximab secures remission in vasculitic variants, while the profound modulation of the eosinophilic axis using mepolizumab or the highly cytolytic benralizumab has revolutionized the care of tissue-infiltrative disease. The impending clinical arrival of ultra-long-acting agents like depemokimab, and the exploration of apex-alarmin inhibitors like tezepelumab, signal a future where sustained, steroid-free remission in EGPA is not merely an aspiration, but a standard clinical expectation. Ongoing surveillance of emerging environmental triggers, precise biomarker utilization, and awareness of paradoxical drug reactions remain essential to safely navigating the evolving management of this intricate systemic vasculitis.pubmed.ncbi.nlm.nih.govEosinophilic Granulomatosis With Polyangiitis (Churg-StraussOpens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic granulomatosis with polyangiitis: A review – PubMedOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Granulomatosis With Polyangiitis – PMC – NIHOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic granulomatosis with polyangiitis – Advances in … – PMCOpens in a new windowmdpi.comGenetic and Non-Genetic Contributions to Eosinophilic … – MDPIOpens in a new windowmdpi.comChurg-Strauss Syndrome or Eosinophilic Granulomatosis … – MDPIOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Granulomatosis with Polyangiitis: Latest Findings andOpens in a new windowpmc.ncbi.nlm.nih.govGastrointestinal Involvement of Eosinophilic Granulomatosis withOpens in a new windowexplorationpub.comEosinophilic granulomatosis with polyangiitis – Open ExplorationOpens in a new windowfrontiersin.orgExpert review and recommendations on the diagnosis … – FrontiersOpens in a new windowpmc.ncbi.nlm.nih.govThe diagnostic pathway and time to diagnosis in ANCA-associatedOpens in a new windowresearchgate.net2022 American College of Rheumatology/European Alliance ofOpens in a new windowpmc.ncbi.nlm.nih.govSevere hypereosinophilia in a patient treated with dupilumab … – PMCOpens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic granulomatosis with polyangiitis: case report … – PubMedOpens in a new windowiris.unibs.itGenome-wide association study of eosinophilic granulomatosis withOpens in a new windowpubmed.ncbi.nlm.nih.gov[Eosinophilic granulomatosis with polyangiitis: a review article]Opens in a new windowpmc.ncbi.nlm.nih.govAirway immune profiles and therapeutic implications of IGF1 inOpens in a new windowincitefulmed.comEGPA Biology: Eosinophils & ANCA Status Explained – Inciteful MedOpens in a new windowpmc.ncbi.nlm.nih.govTezepelumab for refractory eosinophilic granulomatosis with … – PMCOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Otitis Media: Modern Aspects of Pathogenesis, ClinicalOpens in a new windowpubmed.ncbi.nlm.nih.govComparative Insights on IL-5 Targeting with Mepolizumab … – PubMedOpens in a new windowresearchgate.netThe management of type 2 inflammatory respiratory diseasesOpens in a new windowpmc.ncbi.nlm.nih.govAnti-IL5/IL-5 receptor therapies for eosinophilic granulomatosis withOpens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic Granulomatosis with Polyangiitis: Clinical PathologyOpens in a new windowpmc.ncbi.nlm.nih.govDupilumab-induced Eosinophilic Granulomatosis with PolyangiitisOpens in a new windowpmc.ncbi.nlm.nih.govDiagnosis and Treatment Pathway for Eosinophilic GranulomatosisOpens in a new windowpmc.ncbi.nlm.nih.govEfficacy of Biologics on Refractory Eosinophilic Otitis Media … – PMCOpens in a new windowpmc.ncbi.nlm.nih.govClinical Manifestations, Pathogenesis, Diagnosis and Treatment ofOpens in a new windowresearchgate.netIsolated vasculitis of the peripheral nervous system – ResearchGateOpens in a new windowcambridge.orgNeuromuscular Cases (Part II)Opens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Granulomatosis With Polyangiitis Following COVID-19Opens in a new windowpmc.ncbi.nlm.nih.govHigh-resolution ultrasound of peripheral neuropathies in … – PMCOpens in a new windowpmc.ncbi.nlm.nih.govOrphan Peripheral Neuropathies – PMC – NIHOpens in a new windoward.bmj.comEULAR recommendations for the management of ANCA-associatedOpens in a new windowpubmed.ncbi.nlm.nih.govClinical features of central nervous system involvement in patientsOpens in a new windowpubmed.ncbi.nlm.nih.govIschemic stroke in eosinophilic granulomatosis with polyangiitisOpens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic granulomatosis with polyangiitis – PubMedOpens in a new windowpmc.ncbi.nlm.nih.govClinical Characteristics of EGPA Patients in Comparison to GPAOpens in a new windowpubmed.ncbi.nlm.nih.govDetecting cardiac involvement with magnetic resonance in patientsOpens in a new windowpmc.ncbi.nlm.nih.govA case of eosinophilic polyangiitis with granulomatosis that evolvedOpens in a new windowpmc.ncbi.nlm.nih.govCardiac Involvement in Eosinophilic Granulomatosis with … – PMCOpens in a new windowpmc.ncbi.nlm.nih.govCardiac Magnetic Resonance Imaging Findings in Patients WithOpens in a new windowpmc.ncbi.nlm.nih.govGastrointestinal Eosinophilic Granulomatosis with PolyangiitisOpens in a new windowresearchgate.net(PDF) Eosinophilic Granulomatosis with Polyangiitis and DiffuseOpens in a new windowpmc.ncbi.nlm.nih.govGastrointestinal involvement in granulomatosis with polyangiitis – PMCOpens in a new windowpmc.ncbi.nlm.nih.govPerformance of the 2022 American College of Rheumatology … – PMCOpens in a new windowacademic.oup.comEosinophilic granulomatosis with polyangiitis: understanding theOpens in a new windowpubmed.ncbi.nlm.nih.govValidation of new ACR/EULAR 2022 classification criteria for antiOpens in a new windowresearchgate.net2022 American College of Rheumatology/European Alliance ofOpens in a new windoward.bmj.comCorrespondence on ‘2022 American College of RheumatologyOpens in a new windowpmc.ncbi.nlm.nih.govBiomarkers in Connective Tissue Diseases – PMC – NIHOpens in a new windowpubmed.ncbi.nlm.nih.govThe Five-Factor Score revisited: assessment of prognoses … – PubMedOpens in a new windowfrontiersin.orgEosinophilic granulomatosis with polyangiitis – Advances inOpens in a new windoward.bmj.com’Five Factor Score in patients with eosinophilic granulomatosis withOpens in a new windowpmc.ncbi.nlm.nih.govGastrointestinal lesions of eosinophilic granulomatosis with … – PMCOpens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic granulomatosis with polyangiitis (Churg-StraussOpens in a new windowpmc.ncbi.nlm.nih.govEffectiveness of low-dose mepolizumab in refractory eosinophilicOpens in a new windowpmc.ncbi.nlm.nih.govPractical Management of ANCA-Associated Vasculitis – PMC – NIHOpens in a new windowpmc.ncbi.nlm.nih.govMolecular Pathogenesis and Targeted Therapies in EosinophilicOpens in a new windoward.bmj.comassociated vasculitis: 2022 update’ by Hellmich et alOpens in a new windowpmc.ncbi.nlm.nih.govMechanisms, clinical manifestations and management of … – PMCOpens in a new windowdoi.orgTargeting Immunologic Pathways in Eosinophilic GranulomatosisOpens in a new windowresearchgate.netRituximab for maintenance of remission in ANCA-associated vasculitisOpens in a new windowdovepress.comEosinophilic Depletion with Benralizumab, Mepolizumab, andOpens in a new windowpmc.ncbi.nlm.nih.govSystematic literature review informing the 2022 update of the … – PMCOpens in a new windowvasculitides.comThe MIRRA trial: Mepolizumab (Nucala) or placebo for the treatmentOpens in a new windowvasculitides.comPosts – VasculitidesOpens in a new windowpmc.ncbi.nlm.nih.govLong-term mepolizumab treatment reduces relapse rates in superOpens in a new windowpubmed.ncbi.nlm.nih.govCase Report: Sequential use of tezepelumab and mepolizumab forOpens in a new windowpubmed.ncbi.nlm.nih.govMepolizumab therapy improves endomyocarditis in seropositiveOpens in a new windowpmc.ncbi.nlm.nih.govImproved long-term prognosis of eosinophilic granulomatosis withOpens in a new windowpmc.ncbi.nlm.nih.govComparative Insights on IL-5 Targeting with Mepolizumab andOpens in a new windowpubmed.ncbi.nlm.nih.govBiological functions and clinical efficacy of IL-5/IL-5Rα-targetedOpens in a new windowpubmed.ncbi.nlm.nih.govBenralizumab versus Mepolizumab for Eosinophilic GranulomatosisOpens in a new windowwithpower.comBenralizumab for Hypereosinophilic Syndrome (NATRON Trial)Opens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic Depletion with Benralizumab, Mepolizumab, andOpens in a new windowpubmed.ncbi.nlm.nih.govMepolizumab versus benralizumab for eosinophilic granulomatosisOpens in a new windowauthorea.comMepolizumab vs Benralizumab for Eosinophilic Granulomatosis withOpens in a new windowpubmed.ncbi.nlm.nih.govComparative efficacy of mepolizumab and benralizumab in severeOpens in a new windowresearchgate.netSwitching to twice-yearly depemokimab from mepolizumabOpens in a new windowpmc.ncbi.nlm.nih.govEmerging systemic treatments for asthma and allergic diseases – PMCOpens in a new windowpubmed.ncbi.nlm.nih.govModel-Informed Approach Speeds Depemokimab Clinical … – PubMedOpens in a new windowfrontiersin.orgDepemokimab and the twice-yearly regimen – FrontiersOpens in a new windowpmc.ncbi.nlm.nih.govCase Report: Sequential use of tezepelumab and mepolizumab forOpens in a new windowpubmed.ncbi.nlm.nih.govTezepelumab for refractory eosinophilic granulomatosis … – PubMedOpens in a new windowpmc.ncbi.nlm.nih.govStraight to Phase III: Model‐Informed Approach Speeds … – PMCOpens in a new windowpmc.ncbi.nlm.nih.govSuccessful Treatment of Refractory Asthma Clinically Diagnosed AsOpens in a new windowpubmed.ncbi.nlm.nih.govSuccessful Treatment of Refractory Asthma Clinically Diagnosed AsOpens in a new windowpubmed.ncbi.nlm.nih.govEffectiveness of tezepelumab in preventing relapse of eosinophilicOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Granulomatosis With Polyangiitis (EGPA) ManifestingOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Organ Complications Associated with DupilumabOpens in a new windowpmc.ncbi.nlm.nih.govA Case of Eosinophilic Granulomatosis with Polyangiitis EmergingOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilia and Adverse Effects of Dupilumab for RespiratoryOpens in a new windowtandfonline.comDetection and Management of Eosinophilia in Asthmatic Adults andOpens in a new windowpubmed.ncbi.nlm.nih.govEosinophilic Granulomatosis with Polyangiitis Relapse after COVIDOpens in a new windowpdfs.semanticscholar.orgNew Onset of Eosinophilic Granulomatosis with PolyangiitisOpens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Granulomatosis with Polyangiitis after mRNA-1273Opens in a new windowpmc.ncbi.nlm.nih.govEosinophilic Granulomatosis with Polyangiitis Relapse after COVIDOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new windowOpens in a new 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