Life-Threatening Eosinophilic Granulomatosis With Polyangiitis During Omalizumab Therapy for Chronic Urticaria: Missed Diagnosis, Induction, or Unmasking?

Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare form of vasculitis characterized by late-onset asthma, eosinophilia, and systemic manifestations involving small- and medium-sized vessels. We report a severe case of EGPA occurring during treatment with omalizumab in a patient diagnosed with chronic urticaria. A 67-year-old woman presented with acute dyspnea, epistaxis, hemoptysis, and fatigue. Her medical history included late-onset asthma and chronic urticaria with persistent eosinophilia and elevated IgE levels, under treatment with omalizumab. Laboratory investigation revealed eosinophilia and elevated inflammatory markers, while chest computed tomography demonstrated bilateral ground-glass opacities. Bronchoalveolar lavage showed marked eosinophilia and progressively hemorrhagic sequential aliquots, confirming diffuse alveolar hemorrhage. Autoimmune panel was positive for MPO-p-ANCA, supporting the diagnosis of EGPA. The patient was initially treated with high-dose intravenous methylprednisolone, followed by rituximab. Despite treatment initiation, the patient rapidly deteriorated, requiring endotracheal intubation and admission to the intensive care unit. Treatment was escalated with therapeutic plasma exchange and intravenous cyclophosphamide. After a prolonged hospitalization, the patient gradually recovered and was transferred for rehabilitation. This case report highlights the diagnostic challenges of EGPA and the importance of early recognition. Whether omalizumab unmasked, coincided with, or induced EGPA remains uncertain. Clinicians should investigate unexplained, persistent eosinophilia as it could be an expression of a systemic disease.