Myasthenia Gravis

What is myasthenia gravis?

From: MedlinePlus, National Library of Medicine

Myasthenia gravis, sometimes called MG, is a chronic (long-lasting) disease that causes weakness in your voluntary muscles. The voluntary muscles are the ones that you can control. They include the muscles you use for:

• Eye and eyelid movement
• Facial expressions
• Chewing
• Talking
• Swallowing
• Breathing
• Moving your arms and legs

You can also have weakness in other muscles. This weakness gets worse with activity, and better with rest.

Myasthenia gravis is a type of autoimmune disease. In autoimmune diseases, your immune system attacks the healthy cells of your organs and tissues by mistake.

What causes myasthenia gravis?

From: MedlinePlus, National Library of Medicine

Myasthenia gravis is caused by an error in how nerve signals are sent to muscles. These signals get blocked at the nerve-muscle junction. This junction is the place where the nerve endings connect with the muscles they control.

Normally, this is how the signals work:

• The signals travel down a nerve that controls movement in the muscle
• The nerve endings release a substance called acetylcholine
• Acetylcholine binds to the muscle tissue at the nerve-muscle junction
• This causes the muscle to contract (move)

But in someone with myasthenia gravis, the body's own immune system makes antibodies that block the binding of acetylcholine to the muscle. This makes the muscles weaker.

The thymus gland, which is part of your immune system, may play a role in myasthenia gravis. Normally, your thymus gland is active and growing when you are a child. It makes white blood cells to fight infections. At puberty, it starts getting smaller and is replaced by fat. It is usually small by the time you are an adult. But in many adults with myasthenia gravis, the thymus gland stays large. And some people with myasthenia gravis can get thymomas, which are tumors of the thymus. The are usually benign (not cancer), but they can sometimes become cancerous.

Who is more likely to develop myasthenia gravis?

From: MedlinePlus, National Library of Medicine

Although myasthenia gravis can affect people of any age, it is most common in young adult women (under age 40) and older men (over age 60). It is usually not inherited (passed down in families).

Myasthenia gravis normally does not affect infants. But if you are pregnant and have myasthenia gravis it's possible to pass the antibodies to your fetus. The baby can then be born with neonatal myasthenia. This condition is usually temporary, and the symptoms typically go away within two to three months after birth.

What are the symptoms of myasthenia gravis?

From: MedlinePlus, National Library of Medicine

The symptoms of myasthenia gravis will depend on which muscles are affected. The symptoms often include:

• Weakness of the eye muscles
• Drooping of one or both eyelids
• Blurred or double vision
• Changes in facial expressions
• Trouble swallowing
• Shortness of breath
• Speech problems
• Weakness in the arms, hands, fingers, legs, and neck

Different people have different levels of muscle weakness. And the weakness can vary from day to day. Some days it might be mild, and other days it might be worse. Physical activity often makes the muscle weakness worse.

Some people with myasthenia gravis can get severe weakness that affects the muscles that control breathing. This is called a myasthenic crisis, and it is a life-threatening emergency.

How is myasthenia gravis diagnosed?

From: MedlinePlus, National Library of Medicine

There are many other conditions that can cause muscle weakness, so myasthenia gravis can be hard to diagnose. To find out if you have myasthenia gravis, your health care provider:

• Will ask about your medical history and symptoms
• Will do a physical exam, including a neurological exam
• Will likely order tests for myasthenia gravis, including: Blood tests Imaging tests Electromyography (EMG) and nerve conduction studies

What are the treatments for myasthenia gravis?

From: MedlinePlus, National Library of Medicine

There is no cure for myasthenia gravis, but treatments that can improve muscle weakness and help with symptoms. They include:

• Anticholinesterase medicines, which can improve nerve-to-muscle messages and make muscles stronger.
• Immunosuppressive medicines, which are medicines that decrease your body's immune system responses. They can lower your body's production of abnormal antibodies.
• Monoclonal antibodies, which can also help decrease your body's immune system responses.
• Plasmapheresis (plasma exchange) and intravenous immunoglobulin, which are procedures to remove abnormal antibodies from your blood. They are usually used in severe cases. They can help with symptoms for a few weeks or months.
• Thymectomy, surgery to remove the thymus gland. It can reduce the symptoms of myasthenia gravis, possibly by rebalancing the immune system.

Lifestyle changes may be helpful for some people. The changes could include regular gentle exercise, getting enough rest, and eating healthy foods.

Some people with myasthenia gravis go into remission. This means that they do not have symptoms. The remission is usually temporary, but sometimes it can be permanent.

Genetic causes described in the linked summary

From: MedlinePlus Genetics

Researchers believe that variations in particular genes may increase the risk of myasthenia gravis, but the identity of these genes is unknown. Many factors likely contribute to the risk of developing this complex disorder.

Myasthenia gravis is an autoimmune disorder, which occurs when the immune system malfunctions and attacks the body's own tissues and organs. In myasthenia gravis, the immune system disrupts the transmission of nerve impulses to muscles by producing a protein called an antibody that attaches (binds) to proteins important for nerve signal transmission. Antibodies normally bind to specific foreign particles and germs, marking them for destruction, but the antibody in myasthenia gravis attacks a normal human protein. In most affected individuals, the antibody targets a protein called acetylcholine receptor (AChR); in others, the antibodies attack a related protein called muscle-specific kinase (MuSK). In both cases, the abnormal antibodies lead to a reduction of available AChR.

The AChR protein is critical for signaling between nerve and muscle cells, which is necessary for movement. In myasthenia gravis, because of the abnormal immune response, less AChR is present, which reduces signaling between nerve and muscle cells. These signaling abnormalities lead to decreased muscle movement and the muscle weakness characteristic of this condition.

It is unclear why the immune system malfunctions in people with myasthenia gravis. About 75 percent of affected individuals have an abnormally large and overactive thymus, which is a gland located behind the breastbone that plays an important role in the immune system. The thymus sometimes develops tumors (thymomas) that are usually noncancerous (benign). However, the relationship between the thymus problems and the specific immune system malfunction that occurs in myasthenia gravis is not well understood.

People with myasthenia gravis are at increased risk of developing other autoimmune disorders, including autoimmune thyroid disease and systemic lupus erythematosus. Gene variations that affect immune system function likely affect the risk of developing myasthenia gravis and other autoimmune disorders.

Some families are affected by an inherited disorder with symptoms similar to those of myasthenia gravis, but in which antibodies to the AChR or MuSK proteins are not present. This condition, which is not an autoimmune disorder, is called congenital myasthenic syndrome.

Inheritance described in the linked summary

From: MedlinePlus Genetics

In most cases, myasthenia gravis is not inherited and occurs in people with no history of the disorder in their family. About 3 to 5 percent of affected individuals have other family members with myasthenia gravis or other autoimmune disorders, but the inheritance pattern is unknown.

Which doctor should you see?

The suggested department for discussing Myasthenia Gravis is Neurology, with a neurologist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• Which nervous-system findings help explain the symptoms?
• Would an assessment of walking, communication or daily function be helpful?
• Are rehabilitation or other specialist services relevant?

Treatment discussions and follow-up

Where the source describes treatments, these are an overview of possible care, not a prescription for an individual. Ask which option applies to the confirmed diagnosis, what benefit is expected, what adverse effects to watch for and how progress will be assessed. Availability, approvals and local practice can differ from the country described in the source.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

The collected references do not establish a complete prevention or long-term outlook section for this entry. Missing information should not be interpreted as proof that prevention is impossible or that a particular outcome is inevitable. Ask what is known for the exact subtype, stage and personal circumstances, and which uncertainties remain.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.