Clinical characteristics and impairment of activities of daily living among patients with myasthenia gravis with differing degrees of muscle weakness: a real-world study of patients in the US and five European countries

Background: Real-world data were employed to determine clinical characteristics of patients with myasthenia gravis (MG) with differing degrees of muscle weakness, as defined using the Myasthenia Gravis Foundation of America (MGFA) classification system.

Methods: Data were drawn from the Adelphi MG Disease Specific Programme (DSP)™, a multinational (United States, France, Germany, Italy, Spain, United Kingdom) survey completed by physicians and their patients with MG in 2020. The association between MGFA class and impairment in activities of daily living (ADL) was tested using linear regression adjusting for sex and Charlson Comorbidity Index. Bivariate comparisons were performed for each individual item. A range of other clinical characteristics were also explored according to MGFA class.

Results: Among 1232 patients, those in MGFA class I had significantly lower ADL impairment versus class II or III/IV (adjusted for sex and Charlson Comorbidity Index) (p < 0.01). However, heterogeneity occurred within each MGFA class. Bulbar symptoms (impaired speech, difficulty swallowing, and/or difficulty chewing/choking on food) were reported in some class I patients (mild in 1.1-1.9% and moderate in 0.3-1.1% of patients) and class II patients (mild in 8.5-16.4%, moderate in 4.7-7.4%, and severe in 0.3-0.9% of patients), and shortness of breath was reported in some class I (mild in 0.5% of patients) and class II patients (mild in 9.8%, moderate in 4.8%, and severe in 0.3% of patients). Conversely, in 11.2-19.2% of class III/IV patients, bulbar symptoms and shortness of breath reported were only mild in severity. In line with this finding, despite significant correlations between MGFA class and several clinical characteristics, patients across every class were at risk of experiencing myasthenic crisis or hospitalization, experiencing comorbidities including anxiety and depression, and not being in remission.

Conclusions: Although MGFA class correlates with greater ADL impairment and presence of other clinical characteristics, there is variability between patients in each class in terms of symptoms experienced, overall disease burden, and the precise nature of ADL impairment.