Myasthenic crisis.

Myasthenic crisis (MC) is a life-threatening manifestation of myasthenia gravis (MG) defined by respiratory insufficiency that requires the use of invasive or non-invasive ventilation. This is often the result of respiratory muscle weakness but can also be due to bulbar weakness with upper airway collapse. MC occurs in approximately 15%-20% of patients with MG usually within the first 2 to 3 y of the disease course. Many crises have a specific trigger with respiratory infections being most common; however, no specific trigger is found in 30%-40% of patients. MG patients with a history of MC, severe disease, oropharyngeal weakness, muscle-specific kinase (MuSK) antibodies and thymoma appear to be at higher risk. Most episodes of MC do not occur suddenly, providing a window of opportunity for prevention. Immediate treatment is directed toward airway management and removing any identified triggers. Plasmapheresis is preferred over intravenous immune globulin as the treatments of choice for MC. The majority of patients are able to be weaned from mechanical ventilation within 1 mo and the outcomes of MC are generally favorable. The mortality rate in United States cohorts is less than 5% and mortality in MC seems to be driven by age and other medical co-morbidities. MC does not appear to affect long-term prognosis as many patients are able to eventually achieve good MG control.