Myasthenia Gravis May Heighten Risk for Severe COVID-19 and Poorer Outcomes

Risk for hospitalization for and mortality from COVID-19 was higher among patients with myasthenia gravis compared with the general population. These were the findings of a study published in JAMA Network Open.

The autoimmune disorder, myasthenia gravis, is caused by antibodies targeting the neuromuscular junctions, causing fatigue and muscular weakness. In general, individuals with autoimmune diseases have been at higher risk for worse COVID-19 outcomes; however, little myasthenia gravis-specific data are available.

Researchers from University of Toronto sourced data for this retrospective population-based matched cohort study from administrative health data collected in Ontario, Canada between January 2020 and August 2021. Adults with myasthenia gravis (n=4,411) were matched with 5 nonmyasthenia gravis control individuals (n=22,055) from the general population and control individuals with rheumatoid arthritis (RA; n=22,055). Risk for COVID-19 infection, hospitalization, and mortality at 30 days were evaluated.

The myasthenia gravis, general population, and RA cohorts comprised patients mean age, 67.7 (SD, 15.6), years; 51.6%, were women; 3.9%, 2.5%, and 2.8% lived in a long-term residence facility; and the average Charlson Comorbidity Index score was 0.8 (SD, 1.4), 0.5 (SD, 1.1), and 0.7 (SD, 1.4), respectively.

A positive COVID-19 test occurred among 3.9% of the patients with myasthenia gravis, 3.0% of the general population, and 3.0% of the patients with RA. Risk for a positive COVID-19 test was associated with myasthenia gravis compared with the general population (hazard ratio [HR], 1.25; 95% CI, 1.06-1.48) and patients with RA (HR, 1.24; 95% CI, 1.05-1.48).

Among the individuals with COVID-19, the rates of emergency department (ED) visits (36.6% vs 24.4% vs 29.9%), hospitalizations (30.5% vs 15.1% vs 20.7%), intensive care unit (ICU) admissions (6.7% vs 3.9% vs 5.1%), and deaths (14.6% vs 8.5% vs 9.9%) were higher among the myasthenia gravis cohort compared with the general population or patients with RA, respectively.

Overall, compared with both control cohorts, myasthenia gravis associated with increased risk for ED visit (HR range, 1.49-1.84), hospitalization (HR range, 1.79-2.48), and mortality (HR range, 1.83-2.11).

By the end of the study period, 80.3% of the myasthenia gravis cohort and 81.2% of the general population had received 2 doses of the COVID-19 vaccine and the proportion of unvaccinated individuals was 16.4% and 15.8%, respectively.

Individuals who had received at least 1 dose of vaccine were less likely to test positive for COVID-19 among the myasthenia gravis (HR, 0.43; 95% CI, 0.30-0.60) and general population (HR, 0.70; 95% CI, 0.57-0.84) cohorts.

These trends may not be generalizable for later waves of the COVID-19 pandemic.

The researchers concluded, “Our population-based cohort study highlights the increased risk of severe outcomes among people with MG who contract COVID-19, as well as the safety and effectiveness of vaccination for this population. Our results support the prioritization of people with MG [myasthenia gravis] for vaccination as well as for consideration of early therapeutics for COVID-19, such as antivirals and/or monoclonal antibodies.”

Disclosures: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.