A case of refractory myasthenia gravis positive for anti MuSK antibody that was successfully treated with double filtration plasmapheresis

Abstract

We report a 55-year-old female with myasthenia gravis (MG) positive for muscle-specific tyrosine kinase (MuSK) antibody. Her disease was remarkably improved by double filtration plasmapheresis (DFPP). Thymectomy and a variety of immunosuppressive medications have been provided since she was diagnosed as having MG in 2000. On June 3, 2005, she was admitted to our hospital due to MG crisis with acute respiratory failure and soon required a mechanical ventilator. Although the conventional immune-suppressive treatments including steroid pulse therapy and a high-dose intravenous immunoglobulin were given, the clinical condition worsened. When DFPP therapy was added to immne-suppressive drugs, she showed a rapid recovery of respiration and bulbar symptoms accompanied by a reduction of anti MuSK antibody titers. Her general condition was quite improved regardless of reduced doses of immune-suppressive drugs and she was discharged on the 81st hospital day after she received surgery for vascular access construction for anticipated DFPP. At present, the patient is successfully being treated with a combination of periodic DFPP and oral immunosuppressant therapy, 30 mg of prednisolone (alternatively) and 3 mg of tacrolimus (daily). Anti MuSK antibody-positive myasthenia gravis is thought to be a rare disease that tends to induce respiratory crisis and is often refractory toward conventional drug therapy. This case report suggests that DFPP may be an alternative arm against anti MuSK antibody-positive MG.