Case Presentation: A 72-year-old Caucasian woman without a known history of Myasthenia Gravis (MG) presented to the emergency department (ED) with profound fatigue and shortness of breath for 1 week. The patient had received her second Moderna COVID-19 vaccine dose 1.5 weeks prior to presentation.The patient reported that she was in her normal state of health up until 1 week ago when she started having progressive fatigue and shortness of breath. The symptoms worsened to the point that she was unable to lie flat and walk up a flight of stairs or perform her activities of daily living.In the ED, her initial exam was notable for rapid, shallow respirations, reduced proximal muscle strength, and neck flexor weakness. Evaluation for acute coronary syndrome, including serial EKGs and serial troponin-I were unremarkable. A computed tomography angiogram was negative for pulmonary embolism or thymoma, however demonstrated lung hypo inflation and peri diaphragmatic atelectasis. COVID-19 testing and broad infectious workup were negative. During her ED stay, she developed bilateral ptosis which improved after 2 minutes of local cooling. Her respiratory status deteriorated with reduced Negative inspiratory force (NIF) and vital capacity and she was electively intubated for an impending respiratory crisis. We initiated Plasma exchange, and pyridostigmine, for high suspicion of Myasthenic Crisis (MC). Her serology came back positive for acetylcholine-receptor binding, blocking, and modulating antibodies. Once Myasthenia Gravis was confirmed and active infection ruled out, she was started on immunosuppression with Prednisone and Mycophenolate mofetil, and further plasma exchange and her symptoms gradually improved. She was ultimately extubated and discharged to in-patient rehabilitation for residual weakness.In the absence of any other identifiable trigger, it was concluded that her Myasthenic Crisis was precipitated by her recent COVID-19 vaccination.

Discussion: Myasthenia Gravis is an autoimmune disorder of the postsynaptic neuromuscular junction characterized by antibodies against acetylcholine receptors, resulting in weakness of the ocular, bulbar, limb, or respiratory muscles. A myasthenic crisis may be precipitated by a variety of factors including infection, surgery, pregnancy, immunosuppression tapering, certain medications, and even some vaccines, including HPV. A key question during the COVID-19 pandemic is whether vaccines against SARS-CoV-2 precipitate a myasthenic crisis. As of November 2021, only three cases have been reported in the medical literature of the COVID-19 vaccine precipitating MC. We have described a rare case of MC precipitated by the Moderna COVID-19 vaccine.

Conclusions: In conclusion, this patient experienced a myasthenic crisis as an initial presentation of myasthenia gravis shortly after completing her COVID-19 vaccination series. This is a rarely reported event to date. Additional case reporting will help determine the incidence rate of myasthenic crisis post-COVID-19 vaccination.