What Causes Myasthenia Gravis?

Myasthenia gravis (MG) can affect people of any age. It is an autoimmune disorder, which leads to the weakening of the muscles that control voluntary actions. This condition mostly affects the eyes, mouth, throat, and limbs. It is a lifelong condition that keeps progressing and getting worse. It is necessary to get the treatment, which will slow down its progression.

According to the National Institutes of Health, the causes of myasthenia gravis are:

Antibodies –Myasthenia gravis is caused because of the poor transmission of the signals between the nerves and muscles. The place where the nerve cells interact with the muscles, they control is called the neuromuscular junction. When the signal transmission at the junction is interrupted, this can potentiate the risk of myasthenia gravis.

For voluntary action, the brain cells and neurons communicate with the help of neurotransmitter chemicals known as acetylcholine, and the information is passed to the target muscles through the release ofacetylcholine chemicals between the nerve cells and muscles. These chemicals bind to the sites, which are called acetylcholine receptors on the muscle. This causes the muscles to contract, and this is how the brain controls the voluntary action by signaling it to the muscles.

However, people with this condition suffer due to the weakening of these muscles. This happens when the acetylcholine receptors of the muscles do not receive the signals from the nerve cells. The immune system of MG-affected people destroys these binding sites on the muscles by releasing antibodies. Therefore, antibodies released by the immune system damage the acetylcholine receptors and prevent signal transmission, which leads to the weakening of the muscles.

Thymus gland – Thymus is a small gland in the lymphatic system that is present in the chest between the lungs. It is a part of your immune system, and it produces white blood cells (lymphocytes), also known as T-cells. T-cells support your immune system to effectively fight off any infection or disease and keep your body safeguarded against any illness.

Some studies revealed that, in people with MG, this gland is a bit larger than its usual size and it can affect the signal transmission between the nerve cells and the muscles. This gland might produce white blood cells with erroneous instructions, which makes the immune system destroy its own T-cells and produce antibodies in large amounts. These antibodies block the signal transmission at the neuromuscular junction, which causes the muscles to lose their strength.

 Mother-to-child – A pregnant woman having this disease might transfer the antibodies to the developing fetus, which potentiates the risk of myasthenia gravis in the developing fetus. The antibodies might enter the placenta and the fetus. The baby might be weak and develop breathing problems. They may take a few months to recover, as the symptoms are generally temporary.

Emotional stress – Various studies have concluded that acute emotional stress can contribute to the worsening of the symptoms of myasthenia gravis. It can also trigger a myasthenia crisis that may arise when the muscles that are responsible for controlling your breathing function get severely damaged. Myasthenia crisis is a condition that is characterized by respiratory failure and as a result, the person requires mechanical ventilation for breathing.

Respiratory infection – Infections related to the respiratory tract are common contributors to myasthenia gravis deterioration. MG patients need to be careful, as respiratory tract infection can exacerbate the condition and the consequences can turn severe.

 Surgical procedures – Surgery can increase the possibility of myasthenia crisis. The person suffering from myasthenia crisis requiresintensive care and mechanical ventilation.

 Medications – The side effects of certain medications and drugs can induce the deterioration of myasthenia gravis. People having this disease must avoid taking medications certain types of drugs to prevent the exacerbation of their condition. Some drugs that need to be avoided during MG are antibiotics, beta-blockers, anesthetics, quinine gluconate, quinine, phenytoin, etc.

Diagnostic tests

According to the Mayo Clinic website, your healthcare provider will check your symptoms to confirm whether you are experiencing myasthenia gravis. They will ask you about your medical history and conduct your physical examination. They may suggest a combination of tests to identify the cause of this chronic condition. The tests may include:

  • Neurological examination – The healthcare provider will check your muscle response by testing your muscle strength, sensitivity to light or touch, balance, coordination, reflexes, and muscle tone.
  • Blood sample tests – These tests will reveal the type of antibodies that affect the neuromuscular junction sites.
  • Ice pack test – This test is done to analyze your eye’s muscle response to the stimulus of ice.
  • Imaging – These are scanning tests done by CT scans and MRIs.
  • Repetitive nerve stimulation – This test analyzes whether your muscles are receiving signals from the nerve cells. It involves the use of electrodes that are attached to your skin over the muscle that needs to be tested.
  • Single fiber electromyography (EMG) – This involves the insertion of a thin wire electrode into the muscles by piercing the skin. This test checks whether the brain is able to send signals to the muscles.
  • Pulmonary function tests –It is done to see if the condition is causing or going to cause breathing problems.

A combination of these tests will help your healthcare provider to rule out the treatment appropriate to your condition.

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