MUSK and myasthenia gravis: MG may be classsified based on clinical manifestations (ocular or generalized), age of onset (before 50 years and after 50 years), antibody status (anti-AChR, anti-MuSK, anti-LRP4, seronegative) and thymus pathology (normal/atrophic thymus pathology, thymic hyperplasia and paraneoplastic occurrence associated with thymoma).