Anti-interleukin-5 efficacy in an inclisiran-triggered eosinophilic myocarditis: a case report.

Background: Eosinophilic myocarditis is a rare condition that can be associated with hypersensitivity reactions. Endomyocardial biopsy (EMB) is required for diagnosis, especially when cardiac magnetic resonance (CMR) is inconclusive. Immunosuppressive treatment is usually limited to corticosteroids.

Case Summary: Two days following an inclisiran injection for dyslipidaemia management, a 72-year-old Caucasian male with a history of coronary artery disease experienced progressive shortness of breath. Suspecting a hypersensitivity reaction to inclisiran, corticosteroids were administered. After discontinuing corticosteroids, the patient experienced recurrent dyspnoea. Laboratory tests indicated eosinophilia, increased serum immunoglobulin E (IgE), and positive specific serum IgE for . Imaging tests and a lung biopsy revealed pulmonary aspergillosis, while CMR showed myocardial inflammation. The patient was initially treated with itraconazole and steroid therapy. However, he was re-hospitalized for worsening of the cardiac and respiratory condition after tapering steroids. A diagnosis of severe eosinophilic asthma associated with allergic bronchopulmonary aspergillosis was established. Löffler's endocarditis related to -induced eosinophilia was suspected and confirmed by repeated CMR and an EMB. Mepolizumab, an interleukin-5 (IL-5) inhibitor, was initiated resulting in symptom resolution and absence of inflammation at the 6-month follow-up CMR.

Discussion: This case describes an uncommon response to inclisiran that resulted in -induced, steroid-dependent, eosinophilic systemic inflammation, resulting in severe asthma and endocarditis. It demonstrates how biological IL-5 inhibitors are effective in treating both components, emphasizing the necessity of a multidisciplinary strategy.