MUSK and myasthenia gravis: MG: myasthenia gravis; AChRa: acetylcholine receptor; MUSK: muscle-specific kinase; MGFA: MG-Foundation of America; MG-CS: MG-Composite Scale; MG-ADL: MG-Activities of Daily Living; MG-QoL-15r: MG-Quality of Life-15-revised; QMG: Quantitative-MG; NA: not applicable.