Myasthenia gravis is becoming more common in the United States, with a particularly sharp rise among older men, according to a new retrospective study covering more than 20 million insured adults. The research, published in a neurology journal, offers the first major update on the disease’s U.S. footprint in decades.
Generalized myasthenia gravis (gMG) is an autoimmune disease that causes peripheral motor weakness and fatigue because the immune system damages the neuromuscular synapse. While it has long been classified as rare, global data has hinted at rising numbers, consistent with broader increases seen in other autoimmune conditions. But U.S. figures had not been thoroughly examined in years.
Dr. Ye’s team at The Ohio State University analyzed data from adults aged 18 and older using a commercial insurance database, a Medicare database, and a Medicaid population.
The commercial and Medicare group accounted for most of the sample, while Medicaid covered about 10 million. The team applied an algorithm based on diagnosis and test codes to calculate incidence and prevalence between January 1, 2016, and December 31, 2018.
The adjusted prevalence of gMG came in at 316 per million in the commercial/Medicare group and 204 per million among Medicaid beneficiaries. Disease rates climbed steadily with age across both groups.
The most striking finding was in men aged 65 and older. In that demographic, prevalence reached 1,334 cases per million in the commercial/Medicare group and 372 per million in the Medicaid group. That pattern stands out because immunologic diseases typically skew toward women.
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That kind of reversal is worth pausing on. If the numbers hold up in future studies, it suggests something about how the disease interacts with aging in men—or how it gets diagnosed—that clinicians haven’t fully accounted for. The study itself can’t answer why the trend exists, but it gives researchers a much clearer target for the next round of questions.
The researchers acknowledged limitations, including potential misdiagnosis, miscoding, narrow algorithm definitions, and the absence of data on uninsured individuals. Still, they stressed the need for current U.S. data to guide clinical management and, eventually, personalized treatment strategies.
Neurologist Thomas Vidic, a fellow of the American Academy of Neurology practicing in Elkhart, Indiana, told the outlet that myasthenia gravis is a “more common” rare disease than many assume. He said regular reviews of disease incidence are important to confirm existing understanding “or as in this study, to see a deviation which requires us to rethink our understanding.”
The neurologist noted that the shift toward older males is unusual for immunologic disease.
“The fact that we are identifying a greater percentage [of older males] leads to speculation of causes, such as better control of other diseases, better identification of the diagnosis, or the need to identify new triggers,” he said. “I am not surprised by the trend [in the study by Ye et al], but the absolute numbers are greater than I would have predicted.”
A separate 2025 claims-based analysis of U.S. patient data from 2016 through 2019 found an adjusted incidence of 4.3 per 100,000 persons and prevalence of 35.7 per 100,000 persons. In that cohort, 32.1% of incident patients experienced at least one exacerbation within a year, and about half of those had two or more events. Roughly 10% experienced four or more.
Symptoms, Diagnosis, and What to Watch For
Weakness is the dominant symptom in myasthenia gravis, and the authors flagged eye muscle weakness in particular as a red flag. Many patients describe muscle weakness that fluctuates, worsens with activity, and improves with rest. But, the study authors wrote, “deep tendon reflexes are usually intact, even if the patient has marked weakness.”
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In the neurologist’s experience, the initial presentation can be mild and generic—patients report weakness, visual changes, or swallowing difficulties.
He says the condition should be part of the initial differential diagnosis when those symptoms appear. He added that “double or blurry vision that is worse after time and helped by rest is an early sign, and any fatigue helped more than expected by rest can be a symptom.”
The National Institute of Neurological Disorders and Stroke notes that symptom onset may be sudden. Changes in facial expression, shortness of breath, impaired speech, and muscle weakness of varying severity can all occur.
For clinicians suspecting gMG, antibody testing is a reasonable starting point. Bedside tests—including heat, ice pack, rest, and sustained upgaze tests—along with pharmacologic testing and electromyography (EMG) can also help confirm the diagnosis.
Treatment Options Have Expanded
International consensus guidance recommends pyridostigmine as part of initial treatment for most patients, with dose adjustments based on symptoms. It works by inhibiting acetylcholinesterase, increasing acetylcholine availability at the neuromuscular junction. However, these inhibitors are not recommended for patients who are positive for muscle-specific tyrosine kinase antibodies (MuSK+), because they can worsen symptoms.
Corticosteroids remain a key disease-modifying option because they work quickly. But long-term use carries risks, including weight gain, hypertension, diabetes, and osteoporosis. Clinicians are advised to use the lowest effective dose and consider steroid-sparing agents when appropriate.
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Common nonsteroidal immunosuppressants include azathioprine, mycophenolate mofetil, cyclosporine, methotrexate, and tacrolimus.
Azathioprine is the most widely used but has a delayed onset, with benefits typically appearing after 8 to 12 months. Mycophenolate mofetil is an alternative or second-line agent with effects emerging within 6 to 12 months, while methotrexate is considered a third-line choice with a response expected after 3 to 6 months.
Targeted therapies have grown considerably. Three complement C5 inhibitors—eculizumab (Soliris), ravulizumab (Ultomiris), and zilucoplan (Zilbrysq)—are FDA-approved for adults with acetylcholine receptor antibody-positive (AChR+) gMG. FcRn inhibitors, which reduce circulating pathogenic IgG antibodies, include rozanolixizumab (Rystiggo) for AChR+ or MuSK+ gMG and nipocalimab (Imaavy) for patients 12 and older with the same antibody profiles.
In May, the FDA expanded approval of efgartigimod (Vyvgart/Vyvgart Hytrulo) to all adults with gMG, regardless of antibody serotype. Inebilizumab (Uplizna), an anti-CD19 B-cell–targeted therapy, received FDA approval in December 2025 for AChR+ or MuSK+ gMG.
Vidic said the recently approved medications have been a major help. They are expensive, he acknowledged, but “the time to efficacy is much better than older medications,” and safety has improved.
For patients aged 18 to 50 with nonthymomatous generalized myasthenia gravis, the 2020 International Consensus Guideline recommends considering thymectomy early in the disease course to improve outcomes and reduce immunotherapy needs. It is strongly recommended when the disease remains inadequately controlled with immunotherapy or when treatment side effects become intolerable. Current evidence does not support its use for MuSK-negative, LRP4-negative, or agrin-antibody-positive generalized MG.