De novo myasthenia gravis in a patient with malignant melanoma after concurrent SARS-CoV-2 vaccination and immune checkpoint inhibitor therapy: Case report and literature review

In recent years, the advent and increasingly common use of immune checkpoint inhibitors (ICIs) in cancer treatment have been notable. While ICIs have shown relatively better toxicity profiles compared to traditional chemotherapy agents, they are linked to a unique range of toxicities known as immune-related adverse events (irAEs), stemming from immune system dysregulation. Following the coronavirus disease 2019 (COVID-19) pandemic, cancer patients were universally categorized as the highest priority subgroup for vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), despite being excluded from vaccine trials. The exclusion of cancer patients from vaccine trials has raised concerns within the scientific community about the potential for a hyperactive autoimmune response, which could lead to severe irAEs in patients receiving concurrent ICIs and anti-SARS-CoV-2 vaccines. Retrospective studies have indicated subtle safety concerns for mRNA vaccines in cancer patients who have undergone ICI treatment, with none of these studies encompassing inactivated anti-SARS-CoV-2 vaccines. Here, we present a case of a patient with malignant melanoma who developed fatal myasthenia gravis (MG) following concurrent vaccination with Sinopharm's inactivated COVID-19 vaccine (BBIBP-CorV) and initiation of pembrolizumab. Additionally, we examine current research on the relationship between anti-SARS-CoV-2 vaccination and irAEs in patients treated with ICIs and propose a potential mechanism responsible for the fatal MG in our patient.