Refractory bulbar and respiratory dysfunction in a young Chinese woman with seronegative, muscle-specific tyrosine kinase antibody-positive myasthenia gravis: response to cyclophosphamide and rituximab treatment.

The use of cyclophosphamide and rituximab for patients with refractory myasthenia gravis has shown promising results. We report on a 31-year-old Chinese woman with acetylcholine receptor antibody-negative and muscle-specific tyrosine kinase antibody-positive generalised myasthenia gravis who had refractory bulbar dysfunction and respiratory failure despite immunosuppressive therapy and thymectomy, and partial and sustained responses to cyclophosphamide and rituximab treatment, respectively. Myasthenia crisis was diagnosed when she presented in the third trimester of pregnancy with dysphagia, bilateral ptosis, prominent fatigability, and respiratory failure. She required prolonged intensive care and non-invasive ventilatory support despite several courses of intravenous immunoglobulins and plasmapheresis. Pulse cyclophosphamide 500 mg/m(2) was given monthly for 4 consecutive months with a partial response. Rituximab 500 mg weekly was subsequently given for 4 weeks with a dramatic and sustained response. She remained symptom-free and assumed full maternal care at 1 year. To the authors' knowledge, this is the first report of a Chinese patient with refractory myasthenia gravis who responded to cyclophosphamide and rituximab.