Myasthenia gravis

Myasthenia gravis is a rare autoimmune disease that affects the neuromuscular system. In autoimmune diseases, your immune system produces antibodies to attack your own healthy body cells.

• In myasthenia gravis, the antibodies attack your neuromuscular junction, which is the space between nerve and muscle, causing a problem with the signals sent between the nerves and the muscles.
• People who have myasthenia gravis experience fluctuating muscle weakness.

It's not clear why this happens, but it's been linked to issues with the thymus gland (a gland in the chest that's part of the immune system). Many people with myasthenia gravis have a thymus gland that's larger than normal. About1 in 10 people have an abnormal growth of the thymus called a thymoma.

Myasthenia gravis causes fluctuating muscle weakness which means that sometimes it improves and other times when it gets worse.

It often affects the eyes and face first, but usually spreads to other parts of the body over time. It can become hard to control your eye and eyelid movements, and to talk, chew and swallow. Common symptoms of myasthenia gravis include:

• droopy eyelids – one or both eyelids 
• double or blurred vision
• difficulty making facial expressions
• problems chewing and difficulty swallowing
• slurred speech
• weak arms or legs, unsteady walking
• shortness of breath and, occasionally, serious breathing difficulties.

The amount of weakness varies from person to person. It tends to be worse when you're tired and gets better after resting. Many people find they're worse near the end of the day, and better the next morning after getting some sleep. For some people, the symptoms can also have other triggers, such as stress, infections and certain medicines.

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Myasthenia gravis is diagnosed using a variety of tests:

• a blood test for the antibodies that are seen in myasthenia gravis (AChR antibodies)
• ice test – the healthcare provider examines you for improved eyelid droop after covering the eye for a minute or two with a cold pack
• nerve conduction tests and electromyography (a test that measures muscle function)
• injection of the medicine edrophonium to see its effect on muscle strength
• CT scan to look for abnormalities in the thymus gland (a small gland in the upper chest).

Avoiding triggers

The symptoms of myasthenia gravis can sometimes have a trigger, such as infection, emotional stress, or a reaction to medicine. Doing what you can to avoid your triggers may help.

Medicines

Some medicines may cause or worsen myasthenia gravis.

• Ask your doctor or pharmacist if it's safe to take any new medicines or herbal supplements.
• If you've started a new medicine and notice new or worsening myasthenia gravis symptoms, contact your doctor or nurse prescriber immediately. Types of medicines that may cause myasthenia gravis include some antibiotics, some statins and some medicines used for cancer.
• Myasthenia gravis may affect your response to some anaesthetics. If you're having an operation (surgery), tell your surgeon and anaesthetist  about your condition.

Other triggers

• Tiredness and exhaustion: Get plenty of rest and don't overexert yourself
• Stress: Learn more about tips to help reduce stress 
• Infections: Get your annual flu vaccine and talk to your healthcare provider about other vaccines that may prevent common infections.

Treatment to manage symptoms

This is often with a medicine called pyridostigmine. It can reduce muscle weakness, but the effect only lasts a few hours so you'll need to take it several times a day. For some people, this is the only medicine they need to control their symptoms. It doesn't affect disease progression but can improve symptoms.

Treatment to reduce the underlying autoimmune attack

There are short-term and long-term therapies.

• Short-term treatments in the hospital setting are plasma exchange or intravenous immunoglobulin, which are used in severe cases to rapidly decrease the concentration of circulating antibodies and bring about quick improvement.
• Long-term therapies are medicines which suppress the immune system, such as steroids, azathioprine, mycophenolate and rituximab.

Surgery

People with thymoma are usually treated with surgical removal of the thymus, called thymectomy.