ABSTRACT
Background: Myasthenia Gravis (MG) is an autoimmune disease of the neuromuscular junction characterized by fluctuating, fatigable weakness of specific muscles. Most new MG cases have no identifiable triggers, though infections have been suggested as provoking factor. In the literature have been recently described few newly diagnosed and exacerbation MG cases associated both with SARS-CoV2 infection and COVID-19 vaccine. Case presentation: A 67-year-old smoker woman presented to the Emergency Department with worsening dyspnoea and fluctuating diplopia some days apart the second dose of BNT162b2 COVID-19 vaccine. Neurological examination revealed hypophonia, diplopia, inferior limbs' weakness and fatigability, therefore MG was suspected. Computed tomography of the thorax excluded thymoma. Magnetic resonance imaging of the brain was unremarkable. The clinical suspicion of MG was confirmed by serological demonstration of MuSK antibodies and neurophysiological studies. Despite early administration of anticholinesterase inhibitors, the patient experienced a myasthenic crisis with respiratory failure requiring invasive ventilatory support. She was subsequently treated with intravenous immunoglobulin, plasma exchange and steroids resulting in clinical improvement. She was finally discharged with anticholinesterase inhibitors and long-term immunosuppression therapy. Conclusions: New onset MG following COVID-19 vaccine has rarely been described in the literature, but clinicians should be aware of this possible association to achieve earlier diagnosis and more favourable outcomes.