Myasthenia gravis: how does the disease progress?

How does myasthenia gravis progress?

The progression of myasthenia gravis varies from person to person, as does the location of the affected muscles. Sometimes the disease only affects the muscles of the eyes and eyelids. In other cases, general weakness begins within 2 years of the symptoms onset. Spontaneous evolution is variable, and the first signs of the disease, especially the eye problems, may remain isolated.

Myasthenia often worsens with time: the patient experiences convulsions, develops new symptoms and, within a few months, suffers from generalised weakness. The course of the disease is mainly characterised by alternating periods of remission and relapse. The duration of both varies greatly. The severity of the disease is mainly due to the attacks of respiratory disorders and dysphagia (swallowing disorder).

In other cases, the disease progression may be interspersed with periods of a more or less complete remission of varying duration, from a few months to several years. Myasthenia gravis usually reaches its peak of severity within the first 5 years. Patients with myasthenia gravis are often at risk of developing unpredictable episodes of respiratory failure.

The course of myasthenia gravis is therefore irregular and unpredictable. Although most of its complications are treatable, there are also some that may potentially be fatal for patients, for example respiratory complications.

Myasthenic crisis

Myasthenia gravis is a potentially fatal complication that occurs when the muscles that control breathing become too weak to function. It can occur during anxiety or panic attacks, and could lead to heart problems and even lung disease.

The onset of the seizure may occur a few days later, and is not always sudden. Urgent care is necessary, to provide the patient with mechanical ventilation. Certain drugs can also help patients recover their breathing capacity.

In most cases, myasthenic crisis is caused by errors in the communication between the neurons and the muscles. The message transmitted by the neuron to the muscle is not correct or does not exist, which leads to generalised muscle weakness, or even severe forms of paralysis.

Treatment is based on respiratory assistance and intensive care. Various treatments can be combined: intravenous immunoglobulin injection, which consists of injecting antibodies to counter the action of the immune system and reduce the impact of the attack, or plasmapheresis (a process that filters the patient's plasma to remove the antibodies involved). This may be supplemented by readjustment or initiation of steroid therapy and immunosuppressants, and adjustment of anticholinesterase therapy.

Thymus

Approximately 15% of patients with myasthenia gravis present with tumours of the thymus; these can progress along with the disease.

Thymus is a gland located at the junction of the neck and chest and is essential for the normal development of the immune system.

As a rule, it is larger in size in children than in adults and becomes inactive during puberty. However, in people with myasthenia gravis, it usually remains active. Most of these tumours, called thymomas, are non-cancerous and only few patients die from them.

Thymus is usually removed by thymectomy to prevent the cancer from spreading.

Other complications

People with myasthenia gravis are likely to develop other autoimmune diseases such as hyperthyroidism, rheumatoid arthritis and lupus.