Myasthenia Gravis Causes and Symptoms


Myasthenia Gravis is a chronic autoimmune disorder that affects the voluntary muscles of the body. It may start from our eye muscles and slowly progress to involve other muscles including our breathing muscles, when it can become life threatening also. Typically, the weakness is least in the morning and starts increasing with increasing muscle activity. It is most obvious on repetitive work by the same group of muscles.

This disease is more common in women and often affects the age group of 20-40 years. It is usually not inherited, but can occur in newborns and young children also (Neonatal & Juvenile Myasthenia Gravis). It may occasionally start in late age also.

What causes Myasthenia Gravis?

Nerve – muscles junction transmission defect:

The root cause of problem in myasthenia gravis is a blockade that develops at the junction of nerves and the muscle (neuromuscular plate), wherein, the impulses coming through the nerves for the contraction of the muscle are unable to pass across the neuromuscular junction, and hence, do not reach the muscle leading to muscle weakness and failure. The neuromuscular blockade is due to certain chemicals produced in the body which block the receptor sites on the muscle thereby blocking the transmission of message coming from the nerve.

Role of Thymus Gland in Myasthenia Gravis:

The Thymus gland is present in the chest area under the breast bone. This gland is large in size during infancy and plays a significant role in the development of the body’s immune system. As the age increases, the gland reduces in size and becomes tiny by the time teenage starts. In patient of myasthenia gravis, the thymus usually continues to be large. The exact role of thymus in myasthenia gravis is not yet very clear, however, it is believed that an abnormal thymus in these patients sends improper signal to the immune cells to develop antibodies that ultimately block the receptors on the muscles leading to failure of neuromuscular junction transmission. Although, this is believed to be the root cause, it is probably not the sole cause, otherwise removal of thymus gland would have led to disappearance of symptoms in 100% of the patients, which unfortunately is not the case. A lot of research work is currently on to find the exact signalling pathways and the cells involved which ultimately lead to blockade of the neuromuscular junction.

Symptoms of MG:

Muscle weakness is the main problem in myasthenia gravis. However, it can sometimes present in ways where it can get misinterpreted with numerous other conditions.

The common symptoms of the condition are:

  • Drooping of the one or both the eyelids (ptosis).
  • Double vision – i.e. seeing all objects as double. However, it resolves if one eye is closed.
  • Weakness of limbs which can involve upper limb or lower limb or other leading to symptoms like difficulty in walking, difficulty in being able to work, objects falling from the hand, etc.
  • Limited expressions – difficulty in smiling and a rigid or expressionless face because of involvement of facial muscles.
  • Difficulty in chewing because of involvement of muscles of chewing.
  • Difficulty in swallowing or regurgitation of food from nose because of involvement of swallowing muscles.
  • Breathing difficulty due to involvement of respiratory muscles.

 

Sometimes when the symptoms are only double vision and drooping of eyelids, it is mistaken as an eye problem and patients are treated for the same. Sometimes the neck muscle involvement leads to pain in the neck and misdiagnosed as cervical spondylosis and treated accordingly. The limb involvement and weakness may sometimes lead the patients to orthopedic specialists. In numerous cases, we see patients presenting to various specialists with diagnosis delayed for quite some time. The key issue is that the symptoms are minimum in the morning (overnight rest leads to recovery of muscle fatigue) and as the muscles are used during the day, the weakness becomes more and more pronounced. This kind of temporal pattern should always arouse suspicion for myasthenia gravis even if the symptoms are vague.

Occasionally, when the symptoms are still minimal and acute attack of fever etc can precipitate the symptoms and progress rapidly to breathing muscles involvement creating a serious life threatening situation.


Dr Arvind Kuamr


Comments for “Myasthenia Gravis Causes and Symptoms”

  1. Reply

    Thanks for the enlightenment

    Pawan,
  2. Reply

    How to cure from Myasthenia

    SUDHANHU SAHOO,

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