MUSK and myasthenia gravis: To date, several pathogenic MG-associated autoantibodies have been identified, including acetylcholine receptor antibodies (AChR-Ab), muscle-specific tyrosine kinase receptor antibodies (MuSK-Ab), low-density lipoprotein receptor-related protein 4 antibodies (LRP4-Ab), titin antibodies (Titin-Ab), and antibodies against the ryanodine receptor calcium release channel (RyR-Ab) (3, 4).