New-Onset Myasthenia Gravis Confirmed by Electrodiagnostic Studies After a Third Dose of SARS-CoV-2 mRNA-1273 Vaccine

Abstract

Coronavirus disease 2019 vaccine-related pathology is a rare occurrence with few reported cases. We report on a case of a 60-yr-old man experiencing symptoms of dysphagia, dysarthria, diplopia, and weakness with onset 6 days after receiving a third full dose of SARS-CoV-2 vaccine (mRNA-1273 vaccine) in August 2021, which he received outside of the Center for Disease Control recommended guidelines, at 4 mos after his second dose of the Moderna vaccination course in March 2021. The Food and Drug Administration Emergency Use Authorization for mRNA-1273 booster was established in October 2021.Over the next month, the patient's symptoms progressed including his inability to swallow, requiring hospitalization due to dehydration and malnutrition. Evaluation including laboratory prompted referral for electrodiagnostic studies consisting of repetitive nerve stimulation studies and needle electromyography, confirming a case of new onset bulbar myasthenia gravis.

FIGURE 1

Waveforms (A) and diagram (B) generated during repetitive nerve stimulation study of the right nasalis (facial nerve). There is evidence of greater than 10% decrement of amplitude of the action potentials during repetitive nerve stimulation significant for postexercise exhaustion characteristic of myasthenia gravis.