D1.154 - Mepolizumab treatment in a patient with severe eosinophilic granulomatosis with polyangiitis: a case report

Background: Mepolizumab is an anti IL-5 humanized monoclonal antibody that binds to the alpha chain of the IL-5 receptor. It reduces the production, activation, migration and survival of eosinophils, as well as the maturation of B cells and the production of antibodies. The purpose of this study was to show the efficiency of mepolizumab in regulation of the activity of eosinophilic granulomatosis with polyangiitis (EGPA) and IgG4 antibody production. Methods: We used the medical history and medical data (findings of bronchoscopy, bronchoalveolar lavage, lung and nasal mucosa histopathologies) available in the hospital's electronic information system for the patient which was referred for pulmonary rehabilitation after left lower lobectomy with decortication due to necrotising pneumonia. Complete blood count, IgE,and IgG4 concentrations, pulmonary function tests, and HRCT were performed. Results: Initial blood tests showed hypereosinophilia (1.92´10⁹/L), elevated IgG4 (10.5 g/L), high total IgE (1181 kIU/L) and polysensitisation to inhalatory allergens. Spirometry and methacholine test showed severe uncontrolled asthma with a mixed obstructive-restrictive pattern (FEV1 1.4 L, z-3.42) and bronchial hyperactivity. Preoperative bronchoscopy with bronchoalveolar lavage was inconclusive. Postoperative pathology reported organising pneumonia with necrosis and polymorphonuclear infiltration. Previous nasal polyp histology confirmed extravascular eosinophil-predominant inflammation. High-Resolution Computed Tomography (HRCT) scan revealed multiple consolidations, reticulations, ground-glass opacities (GGO) and a residual bronchopleural fistula. Asthma remained uncontrolled despite Global Initiative for Asthma step V therapy with multiple exacerbations requiring systemic glucocorticoids (8 mg daily). Add-on mepolizumab 100 mg subcutaneously every 4 weeks was initiated, leading to a rapid drop in eosinophil count to 0.02´10⁹/L and IgG4 to 4.13g/L within one month. HRCT after 6 months showed almost complete resolution of GGO. Pulmonary function progressively improved, with a stable FEV1 (2.09 L), and persistent but reduced airflow limitation. Conclusions: During 1.5-year follow-up, the patient experienced no asthma exacerbations or IgG4 increase, had no clinical or radiological signs of new pulmonary infiltrates. Mepolizumab at an asthma treatment dose was effective in maintaining remission of EGPA in a patient with increased IgG4 levels.