A Case of COVID-19 With Myasthenic Crisis

Coronavirus disease 2019 (COVID-19) infection can increase the risk of myasthenic crisis. Dexamethasone has been widely used to manage severe COVID-19 infection. Paradoxically, steroids are effective for treating myasthenia gravis; however, when they are started in high doses, there is an associated risk of steroid-induced exacerbation. This case report describes an 86-year-old male with seropositive generalised myasthenia gravis, whose course had been stable for years. At the time of his COVID-19 diagnosis, he was on pyridostigmine and prednisolone 10 mg daily. He was treated with IV dexamethasone 6 mg daily, remdesivir, and antibiotics. On day 10 of admission, he had a sudden deterioration with a Glasgow Coma Scale (GCS) score of 3. Arterial blood gas (ABG) showed a new type 2 respiratory failure suggesting myasthenic crisis. Although his ABG improved after commencing bilevel positive airway pressure (BiPAP), his condition continued to deteriorate and he died the next day. A decision not to intubate and ventilate had been made given his poor clinical state and low chance of recovery. His myasthenic crisis was likely precipitated by the COVID-19 infection, although steroids, azithromycin, and doxycycline also have the potential to cause the worsening of myasthenia gravis. Further studies are needed to evaluate the efficacy and risk of steroid use in this patient population. Ventilatory failure may occur insidiously and is often difficult to detect, especially in elderly and delirious patients in whom performing a neurological examination can be difficult. Regular ABG and bedside measures of forced vital capacity may be considered to monitor the development of type 2 respiratory failure.