Myasthenia gravis (MG) is an autoimmune Disease that affects the neuromuscular junction and generally leads to muscle weakness and fatigability. Cases with MG who have no Detectable circulating antibodies (Abs) to acetylcholine receptor (AChR) are defined as having seronegative MG (SNMG). In 2001, a new serum antibody against muscle-specific tyrosine kinase (MuSK) was revealed in SNMG cases and was present in 70% of AChR- Ab- seronegative MG cases. The specific Disease course, especially in response to standard treatment and the prognostic path of MuSK- MG cases, still needs further observation and disquisition. The cases responding to the plasma pheresis exchange in Anti ACHR negative or seronegative group are less. Our case did respond to the Plasmapheresis treatment modality.