Myelin Oligodendrocyte Glycoprotein G Antibody-Positive Paraneoplastic Myelopathy in Seminoma: A Case Report and Literature Review

Myelin oligodendrocyte glycoprotein-associated disorders (MOGAD) are autoimmune diseases that often manifest in the context of infections. They can also arise less commonly following vaccination but even more rarely in a paraneoplastic context. Herein, we will report a patient presenting with subacute inflammatory myelopathy after a fourth dose of the mRNA COVID-19 vaccine. Concurrently, a diagnosis of MOGAD was made with a metastatic abdominal seminoma. The patient was acutely treated with high-dose steroids followed by plasma exchange therapy and was subsequently started on a chemotherapy regimen for the underlying germ cell tumor. The patient had a complete resolution of neurological symptoms upon the last follow-up. Overall, 72 cases of COVID-19 vaccination associated with MOGAD were analyzed (median age at onset 39 years old; female to male ratio = 1.2:1). All cases occurred in adults except for an adolescent, with the majority occurring after vaccination with ChAdOx nCoV-19 (87%), and an average temporal profile between vaccination and symptom onset of 19 days. There were no reported cases after the third or fourth doses, and most patients were diagnosed with new-onset MOGAD after their first vaccine (76%). Although COVID-19 vaccination could be a potential causality, there are significant discrepancies between the reported cases and this patient, alongside the unlikely causality assessment obtained with the Bradford Hill criteria. Vaccination could unmask potential pre-existing autoimmune diseases, such as in this patient, where myelopathy was most likely part of a paraneoplastic syndrome associated with a newly diagnosed seminoma.