Relapse of Eosinophilic Granulomatosis With Polyangiitis (EGPA) Despite Maintenance Treatment With Low-Dose Mepolizumab.

We present the case of an ANCA+ EGPA patient with a long disease history and remission for over 8 years (between 2015 and 2023), who developed a life-threatening relapse marked by diffuse alveolar haemorrhage and mononeuritis multiplex despite low dose mepolizumab (100 mg q4w) maintenance therapy. She was treated with pulse dose corticosteroids, rituximab, and mepolizumab at an increased dose of 300 mg q4w. This treatment regimen led to clinical and serological improvement, but she has persistent neuropathic pain and reduced handgrip strength. Use of low dose mepolizumab in high risk EGPA patients (i.e., life-threatening disease, prior organ involvement) might be insufficient to prevent relapses causing permanent organ damage such as sensory or motor paralysis. It is important to take into account the EGPA phenotype based upon ANCA serology as well as type and severity of organ involvement, as these characteristics might be associated with different treatment requirements and responses.