MUSK and myasthenia gravis: Myasthenia gravis (MG) is the most common disorder of neuromuscular transmission resulting from antibodies to acetylcholine receptor (AChR), muscle‐specific kinase (MuSK), lipoprotein‐related protein 4, or other components in the postsynaptic membrane at the neuromuscular junction (NMJ).1, 2 This usually leads to characteristically fluctuating muscle weakness.