MUSK and myasthenia gravis: AChR, acetylcholine receptor antibody; AF, atrial fibrillation; AZT, azathioprine; F, female; IVIG, intravenous immunoglobulin; M, male; MG, myasthenia gravis; MR, mitral regurgitation; MuSK, muscle-specific kinase; NICM, non-ischemic cardiomyopathy; OSA, obstructive sleep apnea; PE, pulmonary embolism