Plasmaexchange in the treatment of myasthenia gravis associated with thymoma.

BACKGROUND: All patients with thymomatous Myasthenia Gravis (MG) should undergo early and total thymectomy, but controversy abounds in the choice of chronic immunosuppressive agents. The value of plasmaexchange (PE) in MG has been clearly established in preoperative preparation and treatment of myasthenic crisis. Whether PE may be used in the chronic long-term therapy of patients with thymomatous MG in addition to conventional immunosuppressive agents and cholinesterase inhibitors is yet to be answered.

CASE HISTORY: We present a 40-year old woman with an 11 year history of MG. Thymectomy was done during the first year of the disease and the histopathologic finding was thymoma. To sustain clinical remission after thymectomy she continued with immunosuppression with methylprednisolone and cyclosporin A (or azathioprine) in addition to cholinesterase inhibitors. Despite the almost continuous immunosuppression, the disease course continued with fluctuating myasthenic weakness which few times progressed to myasthenic crisis requiring mechanical ventilation. During myasthenic crisis we performed 6-8 plasmapheresis at 2-3 day intervals in addition to conventional immunosuppressive therapy. The disease rapidly worsened in January 2000 and we started with intermittent plasmapheresis (3-6 procedures at 2-3 day intervals, every 6-8 weeks) in order to sustain remission. With this therapeutic protocol, during 20 months follow-up we managed to prevent myasthenic crisis and to avoid ventilatory support.

CONCLUSIONS: Plasmaexchange could be used as a successful and safe therapeutic tool in chronic long-term therapy in addition to conventional immunosuppressive agents to sustain remission in patients with MG. This is particularly important in the treatment of patients with thymomatous MG because they have an increased frequency of myasthenic crisis and often respond poorly an to immunosuppression with steroids or other immunosuppressants.