Objective:

To estimate the prevalence and incidence of myasthenia gravis (MG) in the United States (US) and describe patient demographics. 

Background:

MG is an autoimmune disease mediated by antibodies disrupting various postsynaptic components at the neuromuscular junction. Estimates of the prevalence and incidence of MG in the US vary and robust studies describing this population are lacking. 

Design/Methods:

This retrospective study used Inovalon data from 2016 through 2020, covering nearly 170 million lives and containing professional and institutional medical claims from Commercial, Medicare Advantage, and Medicaid payers. Confirmation of MG diagnosis was made using a previously validated, peer-reviewed methodology. We conducted a prevalence estimation in 2019 and an incidence estimation across 2018 and 2019. MG diagnoses, age at initial diagnosis, gender, comorbidities, race, and ethnicity were analyzed.  

Results:

For the prevalence estimation, 14,373 patients with MG were identified. Extrapolating this to the US population using census data gives an estimate of 116,255 patients living with MG in the US. For patients 18 and over, a raw incidence rate of 4.86 patients per 100,000 patient-years was found with an adjusted rate of 5.16 per 100,000 patient-years. 

Conclusions:

This was a relatively short observational study (1-2 years). MG identification relied on billing diagnoses and was limited primarily to Medicaid and commercially insured patients, therefore older patients are likely underrepresented.  However, the validity of the datasets used in this analysis give particular strength to the prevalence, incidence, and demographics observed in this study, which support the need for continued research in MG.