Incidence and Prevalence

Global Incidence and Prevalence of Myasthenia Gravis: Latest Estimates

Incidence Rates

Recent epidemiological studies worldwide suggest an incidence of acetylcholine receptor antibody-positive myasthenia gravis of up to 29 cases per 1 million people per year in the past 5-10 years. In the United States, the diagnosed incidence of MG in 2021 was calculated to be 3.1 per 100,000 persons (31 per million). Another US study reported an age-and sex-standardized incidence of 68.5 new cases per million person-years in the commercially/Medicare-insured cohort and 49.7 new cases per million person-years in the Medicaid-insured population.

In the East Midlands of the United Kingdom, the average annual incidence rate was 17.6/1,000,000 (95% CI 10.7-28.6). In South Korea, a nationwide population-based epidemiological study found the standardized incidence rate was 2.44 per 100,000 person-years (24.4 per million) in 2011.

In Cape Town, South Africa, the annual incidence rate for seropositive MG was 11.2 per million per year (95% confidence interval 8.7-14.3), and for South Africa overall, it was 2.6 per million/year (95% CI 2.2-2.9). After adjusting for those presumed to have seropositive MG without a confirmatory test, the annual incidence rate for Cape Town was 12.6 per million (95% CI 9.9-15.9).

Muscle-specific tyrosine kinase antibody-positive myasthenia gravis and Lambert-Eaton myasthenic syndrome are about 20 times less common than acetylcholine receptor antibody-positive myasthenia gravis.

Prevalence Rates

The diagnosed prevalence of Myasthenia Gravis in the United States in 2021 was calculated to be 37.0 per 100,000 persons. In Nordic countries (2000-2020), the overall prevalence per 100,000 was 18.56 (95% CI 18.31 to 18.81) in Denmark, 20.89 (95% CI 20.62 to 21.16) in Finland, and 23.42 (95% CI 23.21 to 23.64) in Sweden.

In South Korea, the standardized prevalence rates were 9.67 and 10.66 per 100,000 persons in 2010 and 2011, respectively.

Demographic Patterns

Incidence rates generally increase with age in both men and women, with higher rates observed in younger women (<50 years) compared to men of matching age, and higher rates in older men (≥65 years) compared to women of the same age group. In South Korea, the incidence and prevalence rates peaked in the elderly population aged 60 to 69 years for both sexes.

In Cape Town, the incidence rate in females was 15.3 per million/year (95% CI 11.2-20.4), and in males, 6.8 per million/year (95% CI 4.1-10.7). The incidence rate of seropositive MG in Cape Town was 6 times greater in those presenting after the age of 50 years than in those with earlier disease onset.

Trends

A global trend of increasing prevalence and incidence of MG has been observed in the last few decades. This increase in prevalence may be due, in part, to improvements in diagnostics but also to an aging global population and immunosenescence, as the largest increases in MG prevalence have been in patients ≥65 years old.

Over the past 120 years, mortality associated with myasthenia gravis has steadily decreased while the incidence of MG has increased. While mortality due to MG has been ≤5% for at least the past 25 years, the prevalence of MG has increased.

Study Design Parameters

Recent Studies

Recent Myasthenia Gravis Clinical Trials

RAISE Trial (2023)

• Randomized, double-blind, placebo-controlled, phase 3 trial at 75 sites globally
• Intervention: Zilucoplan (0.3 mg/kg once daily by self-injection) - a complement C5 inhibitor
• Efficacy: Greater MG-ADL score reduction from baseline to week 12 compared to placebo (-4.39 vs -2.30; difference: -2.09; p=0.0004)
• Safety: Treatment-emergent adverse events in 77% of zilucoplan patients vs 70% in placebo; most common was injection-site bruising (16%)

ADAPT+ Study (2023)

• Open-label, single-arm, multicenter extension study for up to 3 years
• Intervention: Efgartigimod (10 mg/kg) administered as 4 weekly intravenous infusions per cycle
• Efficacy: For AChR-Ab+ participants, >90% had clinically meaningful improvement in MG-ADL scores across first 10 treatment cycles
• Safety: 84.8% reported ≥1 treatment-emergent adverse event; most frequent: headache (24.8%), COVID-19 (15.2%), nasopharyngitis (13.8%)

MycarinG Study (2023)

• Randomized, double-blind, placebo-controlled, phase 3 study at 81 centers globally
• Intervention: Rozanolixizumab (7 mg/kg or 10 mg/kg) - a neonatal Fc receptor blocker given subcutaneously once weekly for 6 weeks
• Efficacy: Clinically meaningful improvements in patient-reported and investigator-assessed outcomes
• Safety: Most frequent adverse events were headache (45% in 7 mg/kg, 38% in 10 mg/kg), diarrhea and pyrexia; generally well tolerated

CHAMPION MG Trial (2024)

• Ongoing open-label extension study
• Intervention: Ravulizumab administered every 8 weeks based on body weight
• Efficacy: Improvements maintained through 60 weeks; LS mean change from baseline in MG-ADL score was -4.0 (p<0.0001)
• Safety: Well tolerated with no meningococcal infections reported

REGAIN Study (2021)

• 26-week, phase 3, randomized, double-blind, placebo-controlled study with open-label extension
• Intervention: Eculizumab for AChR+ refractory generalized myasthenia gravis
• Efficacy: More eculizumab-treated patients achieved 'minimal symptom expression' versus placebo (21.4% vs 1.7%; p=0.0007)
• Safety: Long-term tolerability consistent with previous reports

These recent clinical trials demonstrate significant advances in targeted therapies for myasthenia gravis, with multiple novel mechanisms showing clinically meaningful improvements in patient outcomes while maintaining favorable safety profiles. The development of these therapies represents important alternatives to traditional treatments like corticosteroids, which carry substantial risks of severe adverse effects with long-term use.