Association between antibody status and exacerbation in patients with myasthenia gravis who achieved minimal manifestation or better status.

OBJECTIVE

This study aimed to investigate the rate of exacerbation and risk factors associated with exacerbation in patients with myasthenia gravis (MG) who had achieved minimal manifestation or better status (MMS).

METHODS

This was a single-center retrospective cohort study. This study included patients with MG aged > 15 years who had attained MMS between July 2015 and June 2020. The outcome was defined as exacerbation occurring after the patient had achieved MMS. The enrolled patients were followed up until the outcome occurred or up to 60 months. To account for potential confounding variables, a stratified multivariate Cox proportional hazards model and propensity-score analyses were used.

RESULTS

A total of 238 patients were enrolled in the study, including 199 (83.6%) antibody-positive and 39 (16.4%) double-seronegative patients. Overall, 134 (56.3%) patients experienced exacerbation during the follow-up period, with a median time to the outcome of 33 months. Double seronegativity was associated with a lower risk of exacerbation in the stratified Cox model (hazard ratio [HR] 0.412, 95% confidence interval [CI] 0.225-0.754) and in propensity score analyses (HR 0.501, 95% CI 0.274-0.917 in the adjusted analysis and HR 0.540, 95% CI 0.297-0.982 in the overlap-weighted analysis). Similar results were observed in the sensitivity analysis. Subgroup analyses implied that the presence of thymoma and the performance of thymectomy were identified as negative prognostic factors in seronegative patients.

CONCLUSION

More than half of the patients with MG experienced exacerbation after achieving MMS in this Chinese population. Double seronegativity was an independent protective factor against exacerbations.