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, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Hello, dear readers, and welcome to a bonus edition of our monthly letters column. We are receiving a lot of questions about the various respiratory tract infections that become common this time of year and will have columns on them soon. In the meantime, with such full inboxes, we’ll dive right into your letters.

-- We heard from a reader regarding a column about gastroesophageal reflux disease, or GERD. Commonly known as heartburn, it occurs when acid surges up from the stomach and into the esophagus, where it causes irritation and damage. “I was prescribed antacids to help with discomfort from GERD, but they were of minimal help,” he wrote. “Then I read that drinking alkaline water would neutralize the pepsin in the esophagus. I did that and have been much more comfortable ever since.”

Pepsin, which digests protein, is one of the acids produced by the stomach. During episodes of acid reflux, pepsin can become lodged in the tissues of the esophagus. It has been found that when you drink alkaline water with a pH of 8.8, it can help neutralize the effects of pepsin. However, it is important to understand that GERD is the reason pepsin has reached the esophagus. That makes the lifestyle changes discussed in the column important. These include reaching a healthful weight; eating smaller meals; minimizing high-fat, acidic and spicy foods; and avoiding eating before bed.

-- A recent column about how going for even a short walk after a meal can help with blood sugar control has received a lot of positive responses. We heard from a reader in California who used the column to persuade his wife to get out of the kitchen and into the neighborhood. “I often go for a walk after dinner. It’s a chance to visit with our neighbors and spend some time outdoors. When I tried to get my wife to join me, she would say that she had to get the kitchen cleaned up instead,” he wrote. “Well, her latest A1C test came back as pre-diabetes. I remembered what I read in your column about walking after a meal and shared it with her. Long story short, she comes for a walk with me now, and afterward I help her with the dishes. Win-win across the board.” Thank you for sharing such a good outcome. We think you’ll be happy to know that two other aspects of your evening walk -- socializing and spending time in nature -- have been shown to contribute to improved emotional and cognitive health.

-- Another reader interested in the idea that walking soon after a meal can help with blood sugar control asked us to provide the source material. The information was published in the Feb. 11, 2022, issue of the journal Sports Medicine. It can be found online.

We love hearing from you, so thank you for taking the time to write. If it occurs to you, please let us know your city or region. And a quick reminder -- we cannot review personal medical information, offer a diagnosis or second opinion or comment on specific medications or treatment plans.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I was recently sick with what I thought was the flu. I had a fever, sore throat and a terrible cough. I have asthma, so my husband insisted that I see our family doctor. She said that I did have the flu, but I also had acute bronchitis. Can you please explain what that is?

Dear Reader: Acute bronchitis is a respiratory tract infection that involves two of the major airways in the lungs. It is usually caused by a viral infection, and as happened with you, it can follow a case of the flu. Less often, a bacterial infection can be the cause. If left untreated, acute bronchitis can lead to more serious health problems, including pneumonia. People living with asthma and those who smoke have an increased risk of developing bronchitis during a respiratory illness.

To better understand the condition, we should begin with a bit of anatomy. When you breathe in, air enters through the nose or mouth and is directed into the trachea. Also referred to as the windpipe, this is the long, flexible tube that carries air toward the lungs. At its base, the trachea splits into two branches. These are the bronchi. (For fellow science nerds, each one is called a bronchus.) One of these branches leads to the left lung and the other to the right lung.

After the bronchi enter the lungs, they continue to divide into increasingly smaller and narrower branches, much like the canopy of a tree. At their smallest, now known as bronchioles, they connect to the more than 280 million tiny air sacs, or alveoli, located deep within each lung. These alveoli do the crucial work of delivering oxygen to the blood and receiving carbon dioxide, which is a waste product, to be exhaled.

When someone has bronchitis, it means that an infection of some kind has caused the inner lining of the bronchi to become inflamed. The immune system increases the production of mucus in the bronchi in an effort to trap and clear out the invading microbes, leading to the primary symptom of bronchitis. This is a deep, hacking cough, which typically brings up thick phlegm. It may range in color from clear to yellow to greenish.

People with bronchitis may feel short of breath and hear a wheezing sound as they breathe. Lingering irritation can cause continued coughing for several weeks after the initial infection has cleared. Because the increase in mucus production can decrease the amount of oxygen delivered to the blood by the alveoli, people with bronchitis often feel fatigue and tire easily during exertion. Additional symptoms of this illness are similar to those of other upper respiratory tract infections. They include fever, headache, body aches, chills and a sore throat.

Treatment focuses on management of symptoms. This includes medications to ease cough and physical discomfort and to lower fever. Expectorants, which thin out mucus and make it easier to expel, may be prescribed. It is important to stay hydrated, get plenty of rest and not overdo it when you return to your daily routine.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)