Myasthenia Gravis (MG)

Brief Description

Myasthenia Gravis (MG) is an autoimmune disease that causes weakness and rapid fatigue of voluntary muscles. It occurs when the immune system attacks the receptors for acetylcholine, a substance that transmits the impulse from the motor neuron to the muscle, blocking the transmission of nerve impulses to muscles and thus causing an anomalous muscle exhaustion.

Any muscular district can be involved: from ocular mobility muscles to muscles of the neck, face, torso and limbs, including those used for swallowing and breathing. Cardiac and smooth muscles are not involved.


Causes

The causes of the immune response that characterises myasthenia gravis are not known. Often, especially in adults, the disease is associated with an enlarged thymus or cancer of the thymus gland (thymoma). There also seems to be a certain familiarity in the predisposition to the disease.


Symptoms

Typical symptoms include muscle weakness and exhaustion, a lack of strength that is usually more pronounced during the evening and aggravated by exercise.

The voluntary muscles affected vary from person to person and even within the same individual throughout the day: it may cause drooping eyelids (ptosis), double vision (diplopia), impaired facial expression, impaired speech (dysphonia) and difficulties in swallowing (dysphagia), as well as weakness in the arms, hands, fingers, legs and neck. In the most severe cases respiratory muscles can also be affected.

The disease often presents phases of remission alternated to exacerbation periods.


Cures and Therapy

  • Drug treatment: varies depending on the patient and can be based on corticosteroids, immunosuppressants, plasmapheresis, immunoglobulin administration.
  • Periodic inspection of the thymus and thymectomy, i.e. the surgical removal of the thymus gland , if necessary
  • Milder forms (often the ocular types) may disappear spontaneously
  • Non-invasive mechanical ventilation when respiratory muscles are affected
  • Management of excessive secretions through respiratory therapy exercises and use of a cough assistant.