MUSK and myasthenia gravis: The diagnosis of MG includes detecting the typical antibodies: acetylcholine receptor (AChR-Abs) or muscle-specific tyrosine kinase (MuSK-Abs), however, in a small group of MG patients, these antibodies are absent in the presence of suggestive clinical features (double seronegative MG) while antibodies against low-density lipoprotein receptor-related protein 4, agrin, titin or ryanodine receptors may be demonstrated with suitable assays [2].