D2.192 - IgE-Mediated Immunotherapy-Induced Eosinophilic Granulomatosis with Polyangiitis (EGPA)
Case report
Background
Eosinophilic Granulomatosis with Polyangiitis (EGPA), formerly known as Churg-Strauss syndrome, is a rare systemic vasculitis characterized by asthma, eosinophilia, and small-vessel inflammation. The exact pathogenesis remains unclear, but EGPA arises from dysregulated immune responses. Subcutaneous immunotherapy (SCIT), which modulates IgE-mediated immunity, could potentially trigger or exacerbate EGPA in genetically susceptible individuals. This case highlights the need for careful risk assessment in allergic patients with eosinophilic disorders.
Case Presentation
A 42-year-old male with allergic asthma, chronic rhinosinusitis, and mild eosinophilia (600 cells/μL) began SCIT for ragweed and birch pollen allergies. After undergoing a standard up-dosing regimen over 12 weeks and transitioning to monthly injections, he developed:
- Worsening asthma with frequent exacerbations
- Fatigue, myalgia, and weight loss
- Mononeuritis multiplex (paresthesia and weakness in extremities)
- Marked eosinophilia (2,800 cells/μL, 45% of total WBC)
- Positive perinuclear antineutrophil cytoplasmic antibodies (p-ANCA)
- Elevated inflammatory markers (ESR: 65 mm/hr, CRP: 20 mg/L)
A diagnosis of EGPA was confirmed based on the revised ACR criteria. SCIT was discontinued, and the patient was started on high-dose corticosteroids (prednisolone 1 mg/kg/day) and cyclophosphamide, leading to clinical improvement. Due to persistent eosinophilia and asthma symptoms, azathioprine was introduced for maintenance therapy.
Discussion
The development of EGPA shortly after SCIT initiation raises the question of whether SCIT contributed to disease activation or if it occurred independently. Proposed mechanisms include:
1. IgE-Mediated Eosinophilic Activation: SCIT may increase eosinophilic inflammation by enhancing allergen-specific IgG.
2. Th2/Th17 Dysregulation: SCIT may unintentionally exacerbate immune responses in patients with eosinophilic disorders.
3. Unmasking of Latent Autoimmunity: SCIT may accelerate EGPA onset in genetically predisposed individuals.
Conclusion
SCIT should be carefully considered in patients with pre-existing eosinophilia or autoimmune predisposition. Screening for eosinophilia and ANCA positivity before initiating SCIT in high-risk individuals could be beneficial. In settings where biologic therapy (anti-IL-5) is unavailable, a combination of corticosteroids and immunosuppressants (such as cyclophosphamide or azathioprine) remains the standard treatment for severe or refractory cases. Further studies are needed to clarify whether SCIT can directly contribute to EGPA onset or if this case represents an incidental association.
