Association of Neuromyelitis Optica Following Thymectomy in Myasthenia Gravis: Case Report and Retrospective Literature Review of 16 Patients (P2.091)

OBJECTIVE : A Retrospective literature review identifying an association of Neuromyelitis Optica (NMO) with the occurrence of thymectomy in patients with Myasthenia Gravis (MG). BACKGROUND : MG is an autoimmune disorder caused by an antibody attack on the postsynaptic muscle nicotinic acetylcholine receptor at the neuromuscular junction. The NMO IgG1 autoantibody binds aquaporin 4 (AQP4) in approximately 75% of NMO patients. AquaPorin 4 is exhibited at the neuromuscular junction. It is also expressed in thymocytes of patients with MG and thymoma. This likely denotes a conjunct target in autoimmune disorders affecting both sites. DESIGN/METHODS : Hospital chart review and a retrospective review of the literature in PubMed using the terms "Myasthenia Gravis," "Thymectomy," and "Neuromyelitis Optica." Case Report: 18 y/o RH AAF with no significant medical history had progressive onset of weakness in her extremities with gradual diplopia, ptosis and difficulty swallowing starting 11/2010. Brain and Cervical Spine MRI with gadolinium were normal. Acetylcholine Receptor Antibody was positive and an EMG was consistent with a neuromuscular junction defect. MG was diagnosed. Thymectomy was done 3/2011, and approximately 4 weeks later she experienced lower extremity weakness and constipation. Cervical spine MRI exhibited C4-7 enhancing lesions. NMO was diagnosed using the 2006 revised set of diagnostic criteria for NMO. RESULTS : A PubMed review of the literature reported 15 previous cases of patients with MG who subsequently developed NMO. We are reporting the 16 th patient who had MG and later developed NMO. Demographics: 15/16 female, age range 10-49 years old (mean 27 years). 14/16 (87.5%) patients with MG, who underwent thymectomy, went on to develop NMO. CONCLUSIONS : Thymectomy in Myasthenic patients may lead to immune dysregulation and predispose them to subsequently develop NMO. Physicians and patients must be educated on the risks and benefits of thymectomy, including the risk of developing NMO. Disclosure: Dr. Nasir has nothing to disclose. Dr. Vedanarayanan has nothing to disclose. Dr. Herndon has received personal compensation for activities with Biogen Idec, and Bayer Pharmaceuticals Corp. Dr. Herndon holds stock and/or stock options in Novartis.