Background and purpose: Approximately, 50% of myasthenia gravis (MG) patients initially present with purely ocular symptoms. Of these, about 60% will develop secondary generalized MG, typically within 2 years. Risk factors for secondary generalization are still controversial. In this study, we reviewed clinical parameters, thymic pathologies and medical treatments of MG patients with purely ocular symptoms at onset to investigate risk factors for secondary generalization.
Methods: In this monocentric retrospective study, we reviewed consecutive patients who underwent robotic thymectomy between January 2003 and October 2017 in Charite Universitaetsmedizin Berlin. We used univariate and multivariate Cox proportional hazards regression models to identify factors associated with secondary generalization. Survival curves were plotted using Kaplan-Meier method and log-rank tests were performed to analyze the association between corticosteroids use and secondary generalization in subgroups defined by anti-AChR antibody status and thymic pathology.
Results: One hundred and eighty of 572 MG patients who underwent robotic thymectomy were eligible for inclusion, of whom 110 (61.1%) developed a secondary generalized MG over a mean follow-up time of 23.6 months. The presence of a thymoma (HR 1.659, 95% CI (1.52-2.617), P = 0.029) was the only risk factor for secondary generalization in our series. Treating with corticosteroids was associated with a lower conversion rate in ocular myasthenia patients with thymic hyperplasia (n = 55, P = 0.028), but not with other thymic pathologies including thymoma and normal or atrophic thymus.
Conclusions: The conversion rate in ocular myasthenia was high in our series, predicted by the presence of a thymoma. Our findings suggest that corticosteroids can prevent secondary generalization in ocular myasthenia patients with thymic hyperplasia, which requires further research.
Keywords: Corticosteroids; Ocular myasthenia; Risk factor; Secondary generalization; Thymectomy.