Treatment of Myasthenia Gravis Exacerbation or Crisis With Efgartigimod

Inclusion Criteria: * Adults ≥ age 18 years with known generalized MG as identified by characteristic signs of generalized MG on clinical assessment and positive serology for AchR antibodies as well as one of the following: 1. Documented positive response to cholinesterase inhibitors such as pyridostigmine or edrophonium 2. Abnormal decrement on slow repetitive nerve stimulation testing 3. Abnormal single fiber EMG * Evidence of worsening weakness requiring hospital admission for stabilization and change in therapy as determined by a neuromuscular expert including: 1. Quantitative Myasthenia Gravis (QMG) scale ≥ 11 2. MG-ADL score ≥ 6 3. Worsening weakness that is unlikely to be ameliorated by adjustment of current medications including impaired respiratory status, dysarthria, dysphagia, difficulty chewing, limb weakness, diplopia, ptosis. * Ability to sign consent and be enrolled within 24 hours of hospital admission. For participants transferred to University of Colorado Hospital, the time of admission/presentation to the outside hospital is counted towards this 24-hour cap. Exclusion Criteria: * MG worsening thought to be related to active infection or due to medications (e.g. fluoroquinolone or aminoglycoside antibiotics, magnesium, chloroquine derivatives) * Intubation prior to ability to sign informed consent or intubation within 24 hours of hospitalization * Use of IVIG within 2 weeks, or having undergone plasma exchange or received efgartigimod in the 4 weeks prior to admission * Current ongoing use of ravulizumab or eculizumab (monoclonal antibody C5-complement inhibitors). * Other medical conditions that, in the opinion of the investigator and treating clinicians, might interfere with the validity of assessment measures used in the study (e.g. steroid myopathy, CNS pathology, severe arthritis, fractures, etc.). This criterion is a standard exclusion in MG trials and relates solely to other conditions that reduce muscle power or range of motion and would thus worsen scores on assessment measures like the QMG due to non-MG conditions. * Known history of coagulopathy, blood clotting, recent severe bleeding (e.g. GI bleed). * Pregnancy or breastfeeding. Pregnancy must be excluded for all potential participants who are able to become pregnant prior to initiation of treatment. * IgG levels \< 600mg/dL * Evidence of active or chronic Hepatitis B infection, untreated Hepatitis C infection, HIV with low CD4 (\<200) count.