Outcome of thymectomy in myasthenia gravis patients at Neurological Institute of Thailand

Abstract

Background & Objective: Myasthenia gravis is the most common neuromuscular junction disorders and is caused by autoantibodies against acetylcholine receptors at the postsynaptic muscle endplate. Although thymectomy is current standard treatment but the benefit in long-term outcomes and in non- thymomatous generalized MG patients with negative AChR antibody are still unclear. The objective is to determine the treatment outcomes of thymectomy in non-thymomatous generalized MG patients with or without AChR antibody and identify features related to remission. Methods: Retrospective chart review of the patients diagnosed with non-thymomatous generalized MG from January 1st, 2014 to December 31th, 2018. Patients were classified into two groups: patients with thymectomy (thymectomy group) and patients with no thymectomy (medication group). Results: Seventy-six patients were included. All baseline clinical features, investigations and treatment response were compared. At 6 and 12 months follow up, most patients in both groups had a good response to treatment. At 24 months follow up, ratio of patients in thymectomy group with complete stable remission is higher than in medication group (25% vs. 7.5%) and all patients in this group had positive acetylcholine receptor antibody. The patients in thymectomy group required lower dosage of prednisone, azathioprine and cholinesterase inhibitors than in medication group. Conclusion: Thymectomy was associated with a high probability of achieving remission, reduced cholinesterase inhibitors and immunosuppressive drugs when compared to medication group. Therefore, thymectomy should be strongly considered for non-thymomatous generalized MG patient with positive AChR antibody; and may be considered in non-thymomatous generalized MG patients with negative AChR antibody.