Clinical Features Vary Across Myasthenia Gravis Foundation Classes

There exists significant individual variability of patient symptoms and overall disease burden from myasthenia gravis within Myasthenia Gravis Foundation of America (MGFA) classes; therefore, clinicians should not rely on MGFA class to draw conclusions about an individual, according to a study in BMC Neurology.¹

“Patients across every class still experienced adverse outcomes. Myasthenic crisis, hospitalization, and comorbidities including anxiety and depression were still experienced by a number of those in class I or II,” the authors wrote.

Individual differences for presence and severity of defined ocular and bulbar symptoms and needing help with oral hygiene or getting up from a chair were especially marked by variability, according to the study. Some patients in every MGFA class exhibited clinical characteristics reflective of less-than-ideal disease control. Many patients in class I or II (ocular MG and mild generalized MG, respectively) were not considered to be in remission (7.4% and 12.1%), had experienced a myasthenic crisis (9.1% and 21.0%) or hospitalization (34.5% and 47.7%) at some point since diagnosis, and/or experienced comorbid depression (12% and 14.3%) or anxiety (13.6% and 17.4%).

On a group level, activities of daily living (ADL) impairment increased with increasing MGFA classification in terms of the site and degree of muscle weakness, which was in line with previous findings that MG-ADL score correlated with MGFA class. Patients in class I had a marginal mean (SE) score of 1.9 (0.3) compared with 3.5 (0.3) in class II and 6.0 (0.5) in class III/IV. Patients with class I had significantly lower scores vs class II or class III/IV (adjusted for sex and Charlson Comorbidity Index) (P < .01). Significant differences in the proportion of patients in each response category persisted according to MGFA class (P < .001). Response categories included symptom absent/mild/moderate/severe and assistance required/not required.

In this study, the medical records of 1232 patients and survey data from 222 doctors were analyzed from the US and 5 European countries; most patients had class I (29.8%) or class II (47.0%) myasthenia gravis. | Image Credit: ©syahrir-stock.adobe.com

The rates of patients who had experienced a myasthenic crisis were significantly different (9.1%, 21.0%, and 41.1% in class I, II and III/IV, respectively), as were rates of patients not in remission (7.4%, 12.1%, and 40.6%). Rates of medication use also presented substantial differences:

• Nonsteroidal immunosuppressants:23.6%, 38.7%, and 51.1% in class I, II and III/IV, respectively
• Corticosteroids: 22.1%, 29.5%, and 44.5%
• Intravenous immunoglobulin: 0.9%, 5.5% and 12.0%

The mean number of concomitant conditions appeared to be correlated with the site and degree of muscle weakness in a clinically meaningful manner, the authors concluded.

The study analyzed 1232 patient medical records and survey data from 222 doctors gathered in 2020 in the US and 5 European countries, collected by the Adelphi MG Disease Specific Programme. Patients in MGFA classes III and IV were merged into a single group because of the number of survey respondents. Overall, 367 (29.8%) of patients were MGFA class I (ocular MG), 579 (47.0%) were class II (mild, generalized MG), and 286 (23.2%) were class III/IV (moderate/severe, generalized MG).

MG patients are difficult to classify because of the fluctuating extent and severity of MG and the variable predominance of the muscle groups involved.²

“These results highlight the variability between patients assessed as having the same degree of muscle weakness, in terms of the symptoms experienced, their disease burden, and the impact on their ADL. They also highlight the impact of poor disease control on a patient’s lived experience, across every MGFA class,” the authors wrote.

References

1. Pesa J, Choudhry Z, de Courcy J, et al. 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. BMC Neurol. 2024;24(1):385. doi:10.1186/s12883-024-03869-9

2. Jaretzki A, Barohn RJ, Ernstoff RM, et al. Myasthenia gravis: recommendations for clinical research standards. Task Force of the Medical Scientific Advisory Board of the Myasthenia Gravis Foundation of America. Ann Thorac Surg. 2000;70(1):327-334. doi:10.1016/s0003-4975(00)01595-2