Clinical heterogeneity, treatment patterns, and outcomes of advanced-age-onset myasthenia gravis in China: a retrospective cohort study.

OBJECTIVES

The clinical characteristics and outcomes of myasthenia gravis (MG) with onset at age 50 years or older, which commonly referred to as late-onset MG (LOMG), in elderly patients remain incompletely understood. This study aimed to address the clinical heterogeneity within LOMG and to clarify whether very-late-onset MG (≥70 years) constitutes a distinct phenotype requiring tailored management approaches.

METHODS

We analyzed data from 2783 patients enrolled in the MG Registry between April 1, 2009, and December 31, 2020. Patients with LOMG were further stratified into two subgroups: those with MG onset at age 50-69 years (referred to as Early-LOMG), and those with onset at age ≥70 years (referred to as advanced-onset MG, AOMG). Clinical features, diagnostic tests, treatments, and outcomes were compared across subgroups.

RESULTS

Of the 982 patients with LOMG, 191 (19.4 %) were classified as AOMG. Compared to patients with MG onset at age 50-69 years, those with onset at age ≥70 years (AOMG) had a higher proportion of females (57.6 % vs 48.7 %, p = 0.027), and were more frequently positive for AChR-Ab (81.2 % vs 70.4 %, p = 0.001) and Titin-Ab (32.5 % vs 22.5 %, p = 0.004), and were more likely to present with bulbar muscle involvement at onset (25.3 % vs 14.8 %) and during disease progression (53.7 % vs 38.6 %). The positive rate of repetitive nerve stimulation (RNS) testing was also higher in the AOMG group (57.1 % vs 35.8 %, p = 0.018). Thymoma was less frequent (12.1 % vs 29.6 %, p = 0.006), and fewer AOMG patients underwent thymectomy (2.6 % vs 31.0 %, p < 0.001). AOMG patients generally required fewer immunosuppressive therapies and achieved comparable functional outcomes. However, the mortality rate was significantly higher in the AOMG group (p = 0.020), primarily due to MG crisis.

CONCLUSIONS

AOMG exhibits distinct clinical features compared to Early-LOMG, characterized by a higher frequency of bulbar involvement, lower thymoma prevalence, less aggressive treatment, and higher mortality. Tailored management strategies are warranted for elderly patients with MG.