We appreciate Meisel et al. [1] for exploring the correlation between antibody level and activity of myasthenia gravis (MG). However, some concerns are raised here.The correlation between titin antibody level and MG severity was found to be different in various patients with different thymus pathology and related to different therapeutic mechanisms. In Chen et al.'s study [2], the cross-sectional correlation was much higher in MG patients with thymoma than in those with hyperplastic and normal thymus, and prevalence of titin antibody was associated with different thymomatous pathology. The higher correlation between antibody level and severity was presumed to be as a result of a complex mechanism of thymoma instead of a direct effect by titin antibody. In Liu et al.'s study [3], thymomatous patients constituted a major proportion in all three treatment groups. The decrease of titin