What is myasthenia gravis and how does it affect muscles?

Myasthenia gravis, sometimes referred to as MG, is a chronic disease that affects the body's voluntary muscles. These are the muscles that a person controls, including those used for eye and eyelid movement, facial expression, chewing, speaking, swallowing, breathing, and moving the arms and legs. Myasthenia gravis is characterized by muscle weakness that worsens with activity and improves with rest [1].

Myasthenia Gravis as an Autoimmune Disease

Myasthenia gravis is classified as an autoimmune disease, which means the body's immune system mistakenly attacks its own healthy cells and tissues [1]. In a normal state, nerve signals travel to muscles through an area called the neuromuscular junction. When a signal arrives, nerve endings release a chemical called acetylcholine, which binds to specific receptors on muscle tissues, causing the muscle to contract [1].

However, in the case of myasthenia gravis, the immune system produces antibodies that prevent acetylcholine from binding to its receptors on the muscles or destroy these receptors [2]. This disruption in communication between nerves and muscles leads to muscle weakness and difficulty with movement [1].

The Role of the Thymus Gland

The thymus gland, which is part of the immune system, plays a potential role in myasthenia gravis. In children, the thymus is active and grows, producing white blood cells to fight infection. After puberty, it begins to shrink and is replaced by fatty tissue [1]. However, in many adults with myasthenia gravis, the thymus gland remains large [1]. Some people may also develop tumors in the thymus gland called thymomas, which are often benign but can sometimes become cancerous [1].

Symptoms of Myasthenia Gravis

Symptoms of myasthenia gravis vary depending on the muscles affected, and the severity of the weakness can fluctuate from day to day. Common symptoms include [2]:

• Weakness of eye muscles, causing drooping of one or both eyelids (ptosis) [1].
• Blurred or double vision (diplopia) [1].
• Changes in facial expression [1].
• Difficulty swallowing [1].
• Speech problems [1].
• Shortness of breath [1].
• Weakness in the muscles of the arms, hands, fingers, legs, and neck [1].

In some cases, the weakness may extend to the muscles that control breathing, leading to a serious condition called a "myasthenic crisis," which requires immediate emergency medical care [2]. A myasthenic crisis can be triggered by infection, stress, surgery, or an adverse reaction to medications [2].

Diagnosis and Treatment Steps

Because the symptoms of myasthenia gravis are similar to other conditions that cause muscle weakness, diagnosis can be difficult [1]. A physician will review medical history and symptoms, and perform a physical and neurological examination [1]. Diagnostic tests may include blood tests to detect antibodies, imaging tests, and electromyography (EMG) and nerve conduction studies [1].

There is currently no cure for myasthenia gravis, but treatments are available to improve muscle weakness and alleviate symptoms [1]. These treatments include anticholinesterase medications, immunosuppressive drugs, monoclonal antibodies, as well as procedures like plasmapheresis and intravenous immunoglobulin for severe cases. Surgery to remove the thymus gland (thymectomy) may also be recommended [1]. Lifestyle changes, such as regular gentle exercise, getting enough rest, and eating a healthy diet, can be beneficial for some people [1]. For more information on available treatment options, you can visit Myasthenia Gravis: How Autoimmunity Affects Muscles and Treatment Options (Arabic).

It is important to follow up with a healthcare provider regularly to evaluate the effectiveness of treatment and adjust it as needed, as individual responses to treatment vary [2]. In the event of acute symptoms such as severe shortness of breath, emergency care should be sought immediately [2].

Medical references

• Myasthenia Gravis
• Myasthenia Gravis