GC–MS Reveals Gut Microbiota Links to Myasthenia Gravis

The gut microbiome seems to play a role in myasthenia gravis (MG), but it's not always clear what that connection means biologically. To dig into this, researchers set out to see whether the bacteria living in the gut, and the chemical byproducts they produce, look different in people with MG compared to healthy people. They used gas chromatography–mass spectrometry (GC–MS) alongside 16S rRNA gene sequencing to map out which bacteria were present and in what amounts, and to measure metabolite levels, in both MG patients and healthy controls (HCs). A paper based on their work was published in the Journal of Neuroimmunology.¹

What is Myasthenia Gravis, and Why Are Researchers Looking at the Gut Microbiome in Connection with It?

The annual global incidence of the neurological autoimmune disease MG is about 10–29 cases per one million people, with a worldwide prevalence of about 150–250 cases per one million people.^2,3 The main symptoms of MG include drooping eyelids, double vision, trouble swallowing, weak chewing, and muscles that tire out easily, all of which get worse with physical activity. MG is a long-term condition that tends to slowly worsen over time, with occasional flare-ups along the way.²

The cause of MG still is not fully understood, but it seems to involve a mix of immune system issues, genetics, and environmental factors, including microorganisms. One area that's gotten a lot more attention lately is the gut microbiome. It's essentially the body's biggest point of contact with the outside world, and it normally exists in a relationship that benefits both the bacteria and the person they live in.⁴ The bacteria in our gut do a lot of important work for us. They break down food our bodies can't digest on their own, help keep harmful pathogens from taking hold, play a role in shaping how our immune system responds both in the gut and throughout the body, and even help produce certain essential vitamins.⁵ In addition, gut bacteria play a role that cannot be replaced when it comes to keeping the body's immune defenses, both the ones we're born with and the ones we build up over time, working properly.⁶ 

What Did the Study Find About Gut Bacteria and Metabolites in MG Patients?

For this study, researchers collected stool samples from 50 people with MG and 15 HCs for comparison. They also gathered clinical information on the MG patients, including several standard scoring systems that measure symptom severity, daily functioning, quality of life, muscle strength, and antibody levels tied to the disease, which allowed them to determine whether specific gut bacteria lined up with how severe a patient's symptoms were.¹

The research team found clear differences in the gut bacteria of MG patients compared to healthy people. One type of bacteria, Streptomyces, showed up consistently linked to MG regardless of whether patients were on treatment. In patients who had yet to start treatment, two other bacteria, Acinetobacter and Escherichia-Shigella, were also tied to having the disease. Another bacterial group, Lachnospiraceae, tended to be lower in patients with more severe symptoms and antibody levels, but higher in those with better muscle strength scores. The team also stated that theyfound a specific set of metabolites in the blood that could reliably tell MG patients apart from the HC group.¹

“The gut microbiota and their metabolites,” write the authors of the paper,¹ “exert important effects on MG. The microbiota is closely related to clinical indicators, such as the severity of the disease. Intervention with gut microbes in MG patients may be a new treatment strategy.”

What are the Limitations of These Findings?

However, the researchers admit that their study has some limitations worth keeping in mind. The number of participants was small, especially in the healthy comparison group, which means the findings might not hold up as strongly as a larger study would. Because of this, the researchers also could not break things down further to compare different subtypes of MG, since splitting the group up even more would have made the results even less reliable. Furthermore, all MG patients participating in the study had the same type of antibody linked to MG; therefore, it isunclear whether these findings would apply to people with MG driven by other antibodies. Finally, since this was a one-time snapshot rather than a study that followed people over time, the researchers could not prove that the gut bacteria changes cause MG, only that they are connected somehow. The team suggests that larger studies across multiple locations are needed to dig deeper into these gut bacteria and metabolite changes, figure out what's driving them, tell different forms of MG apart, and eventually explore whether probiotics could help as a treatment.¹

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References

1. Wu, Q.; Li, J.; Li, H. et al. Intestinal Flora and Metabolite Changes: Uncovering Pathogenic Mechanisms in Myasthenia Gravis. J Neuroimmunol. 2026, 419, 578996. DOI: 10.1016/j.jneuroim.2026.578996
2. Dresser, L.; Wlodarski, R.; Rezania, K. et al. Myasthenia Gravis: Epidemiology, Pathophysiology and Clinical Manifestations. J Clin Med. 2021, 10 (11), 2235. DOI: 10.3390/jcm10112235
3. Punga, A. R.; Maddison, P.; Heckmann, J. M. et al. Epidemiology, Diagnostics, and Biomarkers of Autoimmune Neuromuscular Junction Disorders. Lancet Neurol. 2022, 21 (2), 176-188. DOI: 10.1016/S1474-4422(21)00297-0
4. Zheng, D.; Liwinski, T.; Elinav, E. Interaction Between Microbiota and Immunity in health and Disease. Cell Res. 2020, 30 (6), 492-506. DOI: 10.1038/s41422-020-0332-7
5. Hillman, E. T.; Lu, H.; Yao, T. et al. Microbial Ecology Along the Gastrointestinal Tract. Microbes Environ. 2017, 32 (4), 300-313. DOI: 10.1264/jsme2.ME17017
6. Thaiss, C. A.; Zmora, N.; Levy, M. et al. The Microbiome and Innate Immunity. Nature 2016,535 (7610), 65-74. DOI: 10.1038/nature18847