What Is The Cause Of Myasthenia Gravis?

In general, the primary cause of Myasthenia gravis is the interruption of signal transmission between the nerve cells and the muscles. The muscles receive erroneous signals from the nerve cells, which impair their voluntary function. It is a chronic condition, that is progressive in nature and is incurable.

This condition affects the voluntary muscles, that is, the muscles that control the eye movements, mouth, throat, and limbs. The brain fails to control these muscles, which leads to their weakening and impairment of their function. The muscles of the person with this condition may get tired too soon because of their weakening.

How do the muscles lose their strength?

The neurons in your brain release neurotransmitters, which are chemical messengers that carry the signal from the brain to the muscles. The communication between your brain cells and neurons is established with the help of a neurotransmitter known as acetylcholine. This release of this chemical at the junction of the nerve cells and muscles signals the muscles to respond.

The muscles have receptor sites for acetylcholine chemicals. When nerve cells release acetylcholine, the chemical binds to the acetylcholine receptor sites in the muscles. And this is how the muscles respond to the brain’s commands to perform voluntary action.

In the case of Myasthenia gravis, these acetylcholine receptor sites on the muscles get destroyed due to some factors, and as a result, the muscle fails to receive the signals from the nerve cells. Instead, the muscles receive some incorrect signals, which affects their function and causes them to lose their strength.

Factors that lead to muscle weakening

There are various factors that can contribute to the exacerbation of muscle control, but the main reasons for Myasthenia gravis are given below:

Antibodies – The acetylcholine receptor sites present in the muscles receive some erroneous signals from the nerve cells. Since myasthenia gravis is an autoimmune disorder, the condition can be attributed to immune system action. The immune system releases anti-acetylcholine receptor antibodies, which destroy the acetylcholine receptor sites on the muscles and prevent the signal transmission to the organs.

Due to the lack of proper signal transmission, the muscle may act up and become completely weak. The organ corresponding to the affected muscle may fail to respond voluntarily.

Thymus gland – This gland is present in your chest just between your lungs. It forms a part of your immune system and is responsible for producing white blood cells or lymphocytes. Lymphocytes support your immune system in fighting infectious pathogens or foreign elements and preventing and protecting your body against any infection or disease.

In some people, this gland might grow bigger in size, and it may produce lymphocytes with incorrect instructions. These lymphocytes might trigger the release of anti-acetylcholine receptor antibodies which attack the acetylcholine receptor sites on the muscles and hinder signal transmission. This majorly affects muscle function.


The condition might become worse when you use the affected muscles repeatedly without letting them rest. Resting is essential for weak muscles, as it helps in restoring some strength in them. As the condition progresses, the symptoms might turn more severe, and resting time has to be increased correspondingly.

Certain muscles that control voluntary movements are affected in this condition. This condition commonly impairs the function of the following muscles:

  • Eye muscles – When these muscles become weak, the eyelids of one or both eyes become droopy. This condition is known as ptosis. Another symptom of this condition is double vision, called diplopia, wherein the person sees two images of an object.
  • Face muscles – The impairment of these muscles leads to a change in facial expressions.
  • Throat muscles – When throat muscles get affected, the person experiences difficulty in speaking, chewing, or swallowing. This might increase the risk of choking. Also, they might require a long time to chew as they might get tired halfway.
  • Neck muscles – The person may not be able to keep their neck straight or hold their head up for long.
  • Limb muscles – This makes the movements of arms and legs difficult. The person may have trouble while walking.

Factors that worsen the condition

  • Stress – Stress can deteriorate the symptoms even more. It can trigger physiological and hormonal changes in the body, which can make the condition worse.
  • Infection – Since myasthenia gravis is an autoimmune disorder, the introduction of any infectious pathogen can require immune system action. This can contribute to the worsening of the condition.
  • Surgery – Surgical procedures can increase the risk of myasthenia crisis, which may require the person to be put on mechanical ventilation and intensive care.
  • Medications – The side effects of certain medications and drugs can potentiate the risk of worsening of the condition.
  • Pregnancy – During pregnancy, the female goes through tremendous physiological and psychological changes. This can cause exacerbation of the condition.

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