Prognostic Analysis of Thymoma-Associated Myasthenia Gravis

Background: Myasthenia gravis (MG) is an autoantibody-mediated neuromuscular disorder. Approximately 10-20% of all MG patients experience thymoma (benign tumor arising from thymus tissue). Thymectomy has been the standard of care for thymomatous myasthenia gravis (TMG). However, the clinical outcome of TMG after thymectomy has not been sufficiently studied, especially the long-term prognosis. Therefore, the aim of this study was to analyze the clinical characteristics contributing to the prognostic factors of TMG. Methods: We reviewed 70 TMG patients in the Xiangya Hospital and classified them into the minimal manifestation (MM) group and No MM group, according to the long-term treatment outcome. MM-or-better status was defined as the goal treatment for TMG patients. We collected and analyzed the demographic data, the WHO classification of thymoma, MG-associated antibody levels, disease severity, treatment-related data as well as clinical outcome at six months. Variables selected by univariate analysis were used in the multivariate logistic regression model to identify the prognostic factors. Results: The differences in clinical outcome at six months and worst QMGS were significant, while the differences in other factors were insignificant between groups. Clinical outcome at six months (OR=23.5 95% CI 2.4-231.5, P=0.007) and dyspnea before thymectomy (OR=0.2, 95% CI 0.03-0.75, P=0.021) were identified as the prognostic factors of longterm treatment. Conclusion: Demographic and clinical features were similar in TMG patients treated at our hospital. The early achievement of MM-or-better status may indicate a good outcome in the long term. Dyspnea before thymectomy appears to associate with a poor prognosis. Keywords: myasthenia gravis, thymoma, the WHO classification, clinical presentation, prognostic factors