Myasthenia gravis, also called acquired myasthenia gravis, is a rare autoimmune disease that affects neuromuscular junctions. It causes muscle weakness which worsens with physical effort. Women are generally more affected than men.
Symptoms vary a lot from patient to patient, and as the disease progresses. This condition is characterised by episodes of exacerbation followed by periods of remission.
Certain factors can trigger a flare-up: weather changes (heat waves, extreme cold, humidity, etc.), or periods of stress or emotional breakdown (bereavement, divorce, pregnancy, etc.).
In general, muscle weakness is aggravated during a physical effort. Women can find their symptoms get worse during their period.
Different forms of myasthenia gravis exist: the symptoms can be systemic, or they can affect only certain muscles (of the eyes, throat, face).
The most dangerous form is the one affecting lung muscles, as it can cause respiratory failure. In this case the patient requires urgent care.
Note that as the muscles of the heart, intestine, blood vessels and genitourinary system function differently, they can never become affected by myasthenia gravis.
Causes and risk factors
Myasthenia gravis is an autoimmune disease caused by the immune system malfunction. The immune system produces antibodies that attack the neuromuscular junctions. The origin of this disruption is unknown.
Myasthenia gravis can occur at any age; the onset is usually between ages 20 and 40.
Diagnosis can be made difficult by the fluctuation of symptoms over time.
Different tests can be performed to establish the diagnosis of myasthenia gravis:
- Physical tests to assess muscle strength,
- An electromyogram (EMG), which measures the electrical activity of nerves and reveals a potential dysfunction in communication between nerves and muscles. It allows to confirm the diagnosis,
- Blood tests to check for anti-acetylcholine receptor antibodies. Such tests are not carried out for diagnostic purposes, as patients with myasthenia gravis may not develop antibodies of this type, but they constitute an additional element that can help establish the diagnosis in case these antibodies are present,
- An abnormality of the thymus (a gland located behind the breastbone) is also often associated with myasthenia gravis: its volume tends to increase in patients affected by the disease. The thymus plays a role in the body’s defense mechanisms.
Drug treatments are mostly used for this condition.
Antibodies produced by the immune system mainly target an acetylcholine receptor (a molecule found between the nerve and the muscle, which allows information to be passed from one to another). One of the treatment types aims at improving communication between the nerve and the muscle: these drugs are called anticholinesterase inhibitors.
It is also possible to use corticosteroids, immunosuppressants or even monoclonal antibodies (rituximab) to regulate the immune system. For the same purpose, it is possible to set up immunoglobulin therapy or therapeutic plasma exchange (plasmapheresis).
If the size of the thymus increases, surgery may be performed to remove it.
Physiotherapy sessions can help the patient relax the muscles and learn to recognize and accept his or her limits.
Living with the disease
Regular follow-up visits are compulsory. It is necessary to inform all your healthcare professionals about your diagnosis because certain drugs, such as beta-blockers or certain antibiotics can destabilise the disease and worsen the symptoms.
When the disease is well managed, it is quite possible that the symptoms reduce, or that the disease goes into remission, more or less prolonged.
Thanks to the treatments available today, more and more people with myasthenia gravis are able to continue working.
Published 24 Nov 2021