Ask the doctors: Study suggests link between bacteria in gut microbiome and MG
Dear Doctors: My sister has been diagnosed with myasthenia gravis. It started last year, when she turned 38, and it has been getting worse. I would like to know more about the condition. Also, I have heard that a study says the gut microbiome is involved. Can you please talk about that?
Dear Reader: Myasthenia gravis, also known as MG, is a somewhat rare autoimmune disorder. It occurs when the immune system mistakenly attacks compounds produced by the body that are integral to allowing muscle fibers to contract. MG disrupts the communication pathways between the skeletal muscles and the nerves that animate them. This causes weakness in those muscles, along with fatigue, each of which can intensify throughout the day. MG can occur at any age, but it becomes more common among women at about age 40 and in men after about age 60.
The condition often begins with progressive weakness in the muscles around the eyes. This is known as ocular myasthenia gravis. One or both eyelids may begin to droop, it can become difficult to keep the eyelids open, and the person may experience blurred or double vision. About half of cases of ocular MG progress to include the muscles of the legs, hips, arms, face or neck. This is known as generalized myasthenia gravis. It can become difficult to rise from a chair, navigate stairs, raise or use the arms, control facial expressions and chew or swallow. Generalized MG can also affect the muscles that control the diaphragm and those that connect the ribs, which can interfere with breathing.
At this time, there is no cure for myasthenia gravis. Treatment depends on the scope and severity of each person’s symptoms and how quickly the disease is progressing. It can include medications to improve neural activity, corticosteroids to dampen immune system response or immunosuppressant drugs. None of these is completely effective, and each has the potential for side effects. That’s what makes studies like the one you are asking about so important.
A growing body of research continues to find that the gut microbiome and the immune system work together to maintain the health of the body. There is also persuasive evidence that an imbalance in the populations of microorganisms in the gut can contribute to a range of diseases, disorders and conditions. This includes myasthenia gravis.
When scientists in Spain and Italy explored the role of the gut in MG several years ago, they saw intriguing results. They compared fecal samples from 10 adults living with MG with those from 10 adults of the same age and sex who do not have the disorder. All participants lived in the same region. When the researchers analyzed the types and quantities of microorganisms present in the fecal samples, and ran their genetic profiles, they found striking differences between the two groups. Specifically, unusually large populations of certain bacteria were associated with an elevated risk of developing MG. The researchers hope that further research will lead to the development of prebiotics or probiotics that can modulate the microbiota of MG patients and improve, or even eliminate, symptoms.
Send your questions to askthedoctors@mednet.ucla.edu.