Idiopathic Multicentric Castleman Disease Occurring Shortly after mRNA SARS-CoV-2 Vaccine

Idiopathic Multicentric Castleman Disease (iMCD) is a potentially life-threatening systemic disease whose complex symptomatology is due to cytokine dysregulation. We, herein, present a case of severe iMCD occurring in a previously healthy young man shortly after mRNA SARS-CoV-2 vaccination, responding to interleukin-6 blockade with siltuximab. Six months after the completion of siltuximab, the patient remained without any signs of iMCD or inflammation, indicating a temporal trigger of the disease. This case not only adds to the potential pathogenetic spectrum of MCD, but also extends the clinical picture of potential but rare adverse events following COVID-19 immunization.