gravis

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.

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.

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 it's possible for pregnant people who have myasthenia gravis to pass the antibodies to their unborn babies. 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.

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.

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

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.

NIH: National Institute of Neurological Disorders and Stroke

The thymus is a small organ in your upper chest, under your breastbone. Before birth and during childhood, the thymus helps the body make a type of white blood cell. These cells help protect you from infections.

Cancer of the thymus is rare. You are more likely to get it if you have other diseases such as myasthenia gravis, lupus or rheumatoid arthritis. Sometimes there are no symptoms. Other times, thymus cancer can cause:

• A cough that doesn't go away
• Chest pain
• Trouble breathing

Doctors use a physical exam, imaging tests, and a biopsy to diagnose thymus cancer. The most common treatment is surgery to remove the tumor. Other options include radiation therapy, chemotherapy, and hormone therapy.

NIH: National Cancer Institute

Neuromuscular disorders affect your neuromuscular system. They can cause problems with:

• The nerves that control your muscles
• Your muscles
• Communication between your nerves and muscles

These disorders can cause your muscles to become weak and waste away. You may also have symptoms such as spasms, twitching, and pain.

Examples of neuromuscular disorders include:

• Amyotrophic lateral sclerosis
• Muscular dystrophy
• Myasthenia gravis
• Spinal muscular atrophy

There can be different causes for these diseases. Many of them are genetic.This means they are inherited (run in families) or are caused by a new mutation in your genes. Some neuromuscular disorders are autoimmune diseases. Sometimes the cause is unknown.

Many neuromuscular diseases have no cure. But treatments may improve symptoms, increase mobility, and lengthen life.

Your immune system protects you from disease and infection by attacking germs that get into your body, such as viruses and bacteria. Your immune system can tell that the germs aren't part of you, so it destroys them. If you have an autoimmune disease, your immune system attacks the healthy cells of your organs and tissues by mistake.

There are more than 80 types of autoimmune diseases. They can affect almost any part of your body. For example, alopecia areata is an autoimmune disease of the skin that causes hair loss. Autoimmune hepatitis affects the liver. In type 1 diabetes, the immune system attacks the pancreas. And in rheumatoid arthritis, the immune system can attack many parts of the body, including the joints, lungs, and eyes.

No one is sure why autoimmune diseases happen. But you can't catch them from other people.

Autoimmune diseases do tend to run in families, which means that certain genes may make some people more likely to develop a problem. Viruses, certain chemicals, and other things in the environment may trigger an autoimmune disease if you already have the genes for it.

Millions of Americans of all ages have autoimmune diseases. Women develop many types of autoimmune diseases much more often than men. And if you have one autoimmune disease, you are more likely to get another.

The symptoms of an autoimmune disease depend on the part of your body that's affected. Many types of autoimmune diseases cause redness, swelling, heat, and pain, which are the signs and symptoms of inflammation. But other illnesses can cause the same symptoms.

The symptoms of autoimmune diseases can come and go. During a flare-up, your symptoms may get severe for a while. Later on, you may have a remission, which means that your symptoms get better or disappear for a period of time.

Doctors often have a hard time diagnosing autoimmune diseases. There's usually not a specific test to show whether you have a certain autoimmune disease. And the symptoms can be confusing. That's because many autoimmune diseases have similar symptoms. And some symptoms, such as muscle aches, are common in many other illnesses. So it can take a long time and some visits to different types of doctors to get a diagnosis.

To help your doctor find out if an autoimmune disease is causing your symptoms,:

• Learn about the health conditions in your family history. What health problems did your grandparents, aunts, uncles, and cousins have? Write down what you learn and share it with your doctor.
• Keep track of your symptoms, including how long they last and what makes them better or worse. Share your notes with your doctor.
• See a specialist who deals with the symptoms that bother you most. For example, if you have rash, see a dermatologist (skin doctor).

The treatment depends on the disease. In most cases, the goal of treatment is to suppress (slow down) your immune system, and ease swelling, redness, and pain from inflammation. Your doctor may give you corticosteroids or other medicines to help you feel better. For some diseases, you may need treatment for the rest of your life.

Your muscles help you move and help your body work. Different types of muscles have different jobs. There are many problems that can affect muscles. Muscle disorders can cause weakness, pain or even paralysis.

Causes of muscle disorders include:

• Injury or overuse, such as sprains or strains, cramps or tendinitis
• A genetic disorder, such as muscular dystrophy
• Some cancers
• Inflammation, such as myositis
• Diseases of nerves that affect muscles
• Infections
• Certain medicines

Sometimes the cause of muscle disorders is unknown.