Overview

Myasthenia gravis (my-us-THEE-nee-uh GRAY-vis) is characterized by weakness and rapid fatigue of any of the muscles under your voluntary control.

Myasthenia gravis is caused by a breakdown in the normal communication between nerves and muscles.

There is no cure for myasthenia gravis, but treatment can help relieve signs and symptoms, such as weakness of arm or leg muscles, double vision, drooping eyelids, and difficulties with speech, chewing, swallowing and breathing.

Though myasthenia gravis can affect people of any age, it's more common in women younger than 40 and in men older than 60.

Myasthenia gravis care at Mayo Clinic

Source: http://www.mayoclinic.com

Symptoms

Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used repeatedly. Because symptoms usually improve with rest, your muscle weakness may come and go. However, myasthenia gravis symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease.

Although myasthenia gravis can affect any of the muscles that you control voluntarily, certain muscle groups are more commonly affected than others.

Eye muscles

In more than half the people who develop myasthenia gravis, their first signs and symptoms involve eye problems, such as:

• Drooping of one or both eyelids (ptosis).
• Double vision (diplopia), which may be horizontal or vertical, and improves or resolves when one eye is closed.

Face and throat muscles

In about 15 percent of people with myasthenia gravis, the first symptoms involve face and throat muscles, which can cause:

• Altered speaking. Your speech may sound very soft or nasal, depending upon which muscles have been affected.
• Difficulty swallowing. You may choke very easily, which makes it difficult to eat, drink or take pills. In some cases, liquids you're trying to swallow may come out your nose.
• Problems chewing. The muscles used for chewing may wear out halfway through a meal, particularly if you've been eating something hard to chew, such as steak.
• Limited facial expressions. Your family members may comment that you've "lost your smile" if the muscles that control your facial expressions have been affected.

Neck and limb muscles

Myasthenia gravis can cause weakness in your neck, arms and legs, but this usually happens along with muscle weakness in other parts of your body, such as your eyes, face or throat.

The disorder usually affects arms more often than legs. However, if it affects your legs, you may waddle when you walk. If your neck is weak, it may be hard to hold up your head.

When to see a doctor

Talk to your doctor if you have difficulty:

• Breathing
• Seeing
• Swallowing
• Chewing
• Walking
• Using your arms or hands
• Holding up your head

Source: http://www.mayoclinic.com

Causes

Antibodies

Your nerves communicate with your muscles by releasing chemicals (neurotransmitters) that fit precisely into receptor sites on the muscle cells at the nerve-muscular junction.

In myasthenia gravis, your immune system produces antibodies that block or destroy many of your muscles' receptor sites for a neurotransmitter called acetylcholine (as-uh-teel-KOH-leen). With fewer receptor sites available, your muscles receive fewer nerve signals, resulting in weakness.

Antibodies may also block the function of a protein called a muscle-specific receptor tyrosine kinase (TIE-roh-seen KIE-nays). This protein is involved in forming the nerve-muscular junction. When antibodies block the function of this protein, it may lead to myasthenia gravis. Research continues to study how the antibodies inhibiting this protein are related to the development of myasthenia gravis.

Thymus gland

Researchers believe that the thymus gland, a part of your immune system situated in the upper chest beneath your breastbone, may trigger or maintain the production of the antibodies that block acetylcholine.

Large in infancy, the thymus is small in healthy adults. In some adults with myasthenia gravis, however, the thymus is abnormally large. Some people with myasthenia gravis also have tumors of the thymus (thymomas). Usually, thymomas aren't cancerous (malignant).

Other causes

Some people may have myasthenia gravis that isn't caused by antibodies blocking acetylcholine or the muscle-specific receptor tyrosine kinase. This type of myasthenia gravis is called antibody-negative myasthenia gravis. Antibodies against another protein, called lipoprotein-related protein 4, may play a part in the development of this condition.

Genetic factors also may be associated with myasthenia gravis.

Rarely, mothers with myasthenia gravis have children who are born with myasthenia gravis (neonatal myasthenia gravis). If treated promptly, children generally recover within two months after birth.

Some children are born with a rare, hereditary form of myasthenia, called congenital myasthenic syndrome.

Factors that can worsen myasthenia gravis

• Fatigue
• Illness
• Stress
• Some medications — such as beta blockers, quinidine gluconate, quinidine sulfate, quinine (Qualaquin), phenytoin (Dilantin), certain anesthetics and some antibiotics

Source: http://www.mayoclinic.com

Diagnosis

To diagnose your condition, your doctor will review your symptoms and your medical history and conduct a physical examination. Your doctor may conduct several tests, including:

Neurological examination

Your doctor may check your neurological health by testing your:

• Reflexes
• Muscle strength
• Muscle tone
• Senses of touch and sight
• Coordination
• Balance

The key sign that points to the possibility of myasthenia gravis is muscle weakness that improves with rest. Tests to help confirm the diagnosis may include:

Edrophonium test

Injection of the chemical edrophonium chloride (Tensilon) may result in a sudden, although temporary, improvement in your muscle strength. This is an indication that you may have myasthenia gravis.

Edrophonium chloride blocks an enzyme that breaks down acetylcholine, the chemical that transmits signals from your nerve endings to your muscle receptor sites.

Ice pack test

If you have a droopy eyelid, your doctor may conduct an ice pack test. In this test, a doctor places a bag filled with ice on your eyelid. After two minutes, your doctor removes the bag and analyzes your droopy eyelid for signs of improvement. Doctors may conduct this test instead of the edrophonium test.

Blood analysis

A blood test may reveal the presence of abnormal antibodies that disrupt the receptor sites where nerve impulses signal your muscles to move.

Repetitive nerve stimulation

In this nerve conduction study, doctors attach electrodes to your skin over the muscles to be tested. Doctors send small pulses of electricity through the electrodes to measure the nerve's ability to send a signal to your muscle.

To diagnose myasthenia gravis, doctors will test the nerve many times to see if its ability to send signals worsens with fatigue.

Single-fiber electromyography (EMG)

Electromyography (EMG) measures the electrical activity traveling between your brain and your muscle. It involves inserting a fine wire electrode through your skin and into a muscle to test a single muscle fiber.

Imaging scans

Your doctor may order a CT scan or an MRI to check if there's a tumor or other abnormality in your thymus.

Pulmonary function tests

Your doctor may perform pulmonary function tests to evaluate whether your condition is affecting your breathing.

Source: http://www.mayoclinic.com

Complications

Complications of myasthenia gravis are treatable, but some can be life-threatening.

Myasthenic crisis

Myasthenic crisis is a life-threatening condition that occurs when the muscles that control breathing become too weak to do their jobs. Emergency treatment is needed to provide mechanical assistance with breathing. Medications and blood-filtering therapies help people to again breathe on their own.

Thymus tumors

About 15 percent of people with myasthenia gravis have a tumor in their thymus, a gland under the breastbone that is involved with the immune system. Most of these tumors, called thymomas, aren't cancerous (malignant).

Other disorders

People with myasthenia gravis are more likely to have the following conditions:

• Underactive or overactive thyroid. The thyroid gland, which is in the neck, secretes hormones that regulate your metabolism. If your thyroid is underactive, you may have difficulties dealing with cold, weight gain and other issues. An overactive thyroid can cause difficulties dealing with heat, weight loss and other issues.
• Autoimmune conditions. People with myasthenia gravis may be more likely to have autoimmune conditions, such as rheumatoid arthritis or lupus.

Lifestyle and home remedies

Supplementing your medical care with these approaches may help you make the most of your energy and cope with the symptoms of myasthenia gravis:

• Adjust your eating routine. Try to eat when you have good muscle strength. Take your time chewing your food, and take a break between bites of food. Small meals eaten several times a day may be easier to handle. Also, try eating mainly soft foods and avoid foods that require more chewing, such as raw fruits or vegetables.
• Use safety precautions at home. Install grab bars or railings in places where you may need support, such as next to the bathtub or next to steps. Keep your floors clean, and move any loose rugs out of areas where you may walk. Outside your home, keep paths, sidewalks and driveways cleared of leaves, snow and other potential debris that could cause you to stumble.
• Use electric appliances and power tools. You may lose energy quickly when conducting tasks. Try using an electric toothbrush, electric can openers and other electrical tools to perform tasks when possible.
• Wear an eye patch. Consider wearing an eye patch if you have double vision, as this can help relieve the problem. Try wearing the eye patch while you write, read or watch television. Periodically switch the eye patch to the other eye to help reduce eyestrain.
• Plan. If you have chores, shopping or errands to do, plan the activity to coincide with the time at which you have the most energy. Also, try to reduce extra walking in your house when working on projects, as it may reduce your energy.

Source: http://www.mayoclinic.com

Coping and support

For people with myasthenia gravis and their family members, coping with the disease may be difficult.

If you have myasthenia gravis, find ways to relax. Stress may worsen your condition.

Also, ask for help with tasks if you need it. Your family and friends may be able to assist you with tasks that are difficult.

If you're a family member of someone with myasthenia gravis, try to be understanding of your loved one's emotions as he or she adjusts to the condition. Read about myasthenia gravis and learn about what your family member is experiencing.

You and your family members may benefit from participating in a support group. A support group may offer a place for you to meet people who understand what you and your family members are going through.

Source: http://www.mayoclinic.com