We report a case of 36-year-old woman with myasthenia gravis (MG) combined with mediastinal leiomyosarcoma(LMS) and Stevens-Johnson syndrome (SJS). She was admitted to ICU with the symptoms of acute onset headache,diplopia, ptosis, dysphagia, general weakness, and respiratory difficulty for several days. Physical examination revealedtachypnea, decreased breath sounds and dullness to percussion in right lower chest. Neurologic examination showedptosis, diplopia, decreased gag reflexes, and generalized proximal weakness. Laboratory studies revealed increasedserum acetylcholine receptor antibodies and positive Tensilon test. Chest CT showed a huge mass in the right middlemediastium but no evidence of thymic enlargement. Mediastinal LMS was diagnosed by ultrasound-guided needle biopsy.The myasthenic symptoms were fluctuated in spite og intravenous immunoglobulin, plasmapheresis, and corticosteroid.During therapy, SJS developed. She died 4 months after the onset of the myasthenic symptoms despite thechemotherapy for LMS.
