MYASTHENIA GRAVIS (MG) is an autoimmune neuromuscular transmission disorder where well-defined autoantibodies against muscle and muscle cell membrane molecules are directly pathogenetic. Myasthenia gravis is characterized by weakness and rapid fatigue of any of the muscles under voluntary control.
CAUSES
1. Antibodies - Myasthenia gravis, the immune system produces antibodies that block or destroy many muscle receptor sites for a neurotransmitter called acetylcholine. With fewer receptor sites available, muscles receive fewer nerve signals, resulting in weakness. Antibodies can also block the function of a muscle -specific receptor tyrosine kinase.
2. Thymus gland - The thymus gland is part of the immune system located in the upper part of the chest below the sternum. The thymus gland triggers or maintains the production of antibodies that block acetylcholine. Large in infancy, the thymus gland is small in healthy adults. In some adults with myasthenia gravis, the thymus gland is unusually large.
Sign & symptoms
Muscle weakness caused by myasthenia gravis worsens as the affected muscle is used. Because symptoms usually improve with rest, muscle weakness can come and go. However, the symptoms tend to progress over time, usually reaching their worst within a few years after the onset of the disease.
1. Eye muscles
2. Face and throat muscles
3. Neck and limb muscles
