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What is myasthenia gravis?

Myasthenia gravis is a neuromuscular autoimmune system disease affecting the skeletal muscles. It is a long-term condition which can affect various parts of the body, largely the eyes, the face, and the swallowing muscles.

Prognosis

The prognosis of patients with myasthenia gravis is generally good, providing they receive the right treatment. The mortality rate for myasthenia gravis in the early 1900s was at around 70%, but this figure has now dropped to around 3-5%.

Symptoms of myasthenia gravis

Myasthenia gravis causes muscle weakness and worsens as the muscles are used. Symptoms usually improve with rest. Muscle weakness may vary, but the symptoms of myasthenia gravis progress over time and usually peak within a few years of the onset of the disease. Myasthenia gravis can damage any muscle that you control voluntarily, but it affects some muscle groups more than others.

Medical tests for myasthenia gravis

For the specialist to make a correct diagnosis of the disease, they will perform different medical tests. They will also analyse your symptoms and review your medical history. The various tests include:

• Neurological examination
• Edrophonium test
• Ice pack test
• Blood tests
• Repeated nerve stimulation
• Single-fibre electromyography
• Imaging tests
• Pulmonary function tests.

What causes myasthenia gravis?

There are several factors that can lead to myasthenia gravis.

Firstly, antibodies: in every human body, nerves communicate with muscles by emitting chemical substances called neurotransmitters that join their corresponding muscle cell receptors at the neuromuscular junction. With this disease, the immune system creates antibodies that destroy or block many muscle receptors of a neurotransmitter called acetylcholine. As a result, with fewer receptors the muscles receive fewer nerve connections, leading to weakness.

The thymus may be another cause: scientists believe that the thymus, the gland that forms part of the immune system and is located at the top of the chest under the breastbone, can increase or maintain the production of antibodies that block acetylcholine.

Other causes: some cases of myasthenia gravis have nothing to do with antibodies that block acetylcholine or the receptor of a specific muscle. In other words, this type of myasthenia will lead to seronegative myasthenia gravis. Antibodies against another type of lipoprotein receptor-related protein can affect the onset of the disease. Myasthenia gravis can also be due to genetic factors.

However, there are certain risk factors that can worsen the damage caused by myasthenia gravis, including: fatigue, complications with another disease, stress and medications such as beta-blockers, quinidine gluconate, quinidine sulphate, quinine, phenytoin and some anaesthetics and antibiotics. 

Can it be prevented?

There are currently no known measures to prevent myasthenia gravis, because the specific causes of this type of autoimmune disease are still unknown.

Treatments for myasthenia gravis

Specialists may use different treatments, either alone or in combination with other techniques, to relieve the symptoms of myasthenia gravis. These include:

• Medication
• Cholinesterase inhibitors
• Corticosteroids
• Immunosuppressants
• Intravenous therapy
• Plasmapheresis
• Intravenous immunoglobulin
• Monoclonal antibodies
• Surgery
• Video-assisted thymectomy
• Robotic thymectomy.

Which specialist treats it?

A neurologist is generally the specialist responsible for treating myasthenia gravis, but others may be consulted depending on the treatment path.