What is Myasthenia Gravis (MG)?
Myasthenia gravis (MG) is a chronic autoimmune disorder that affects the communication between nerves and muscles, causing muscle weakness and fatigue, particularly in the muscles that control eye movement, facial expression, chewing, swallowing, and speaking.
Symptoms of MG
The symptoms of Myasthenia gravis (MG) can vary widely among affected individuals, but the most common ones include:
- Double vision or drooping eyelids
- Difficulty chewing, swallowing, or speaking
- Weakness in the arms, legs, neck, or diaphragm, leading to shortness of breath
- Unstable gait or difficulty maintaining balance
- Facial muscle weakness or paralysis, leading to difficulty smiling or closing the eyes fully
- Trouble with fine motor movements, such as writing or buttoning clothes
- Episodes of muscle spasms or twitching
- Difficulty holding up the head or maintaining an upright posture.
- Generalized weakness that may worsen during illness, stress, or after prolonged activity.
Causes and risk factors of MG
Myasthenia gravis (MG) is an autoimmune disorder in which the body's immune system produces antibodies that attack and damage the receptors on the muscle cells. This leads to a decreased number of functioning receptors and a reduction in the ability of nerves to communicate with the muscles. Factors that may contribute to the development of MG include:
- Genetics: Some people may inherit a specific genetic variation that increases their susceptibility to developing the disorder
- Thymus gland abnormalities: In some cases, people with MG may have an abnormally large or overactive thymus gland, which can trigger the autoimmune response that leads to MG
- Infections: Certain viral or bacterial infections have been associated with the development of MG, as they can trigger the autoimmune response that leads to the disorder
- Gender and age: Women are more likely to develop MG than men, and the condition is most commonly diagnosed in younger women (<40 years) and older men (>60 years)
- Other autoimmune disorders: People with other autoimmune disorders, such as rheumatoid arthritis or lupus, may be at higher risk of developing MG
Diagnosis and Treatment of MG
Diagnosis of MG usually involves a combination of clinical evaluation, laboratory tests, and neurophysiological studies. A doctor may start by taking a medical history and conducting a physical examination to look for characteristic signs of muscle weakness and fatigue. Blood tests can be done to measure the levels of certain antibodies, such as acetylcholine receptor antibodies and muscle-specific tyrosine kinase antibodies, which are often elevated in people with MG. Electromyography and nerve conduction studies can also be performed to assess muscle and nerve function. Additionally, a CT scan or MRI scan of the chest can be performed to check for the size of the thymus gland.
The treatment of MG involves a combination of medication and supportive therapies. Medications such as acetylcholinesterase inhibitors (e.g. pyridostigmine) can help improve muscle strength by helping electrical signals travel between the nerves and muscles. Immunosuppressive medications such as corticosteroids (e.g. prednisolone) can be used to suppress the immune system and reduce the production of antibodies that attack the receptors of muscle cells. In some cases, intravenous immunoglobulin or plasmapheresis may be recommended to remove the harmful antibodies from the blood.
Supportive therapies for MG may include respiratory support, such as the use of a ventilator, in severe cases of respiratory muscle weakness. Physical therapy and rehabilitation can also help improve muscle strength and mobility, as well as prevent complications such as joint contractures and pressure sores. In some cases, surgery may be recommended to remove the thymus gland.
Summary
Myasthenia gravis (MG) is a chronic autoimmune disorder that causes muscle weakness and fatigue, which worsens after periods of activity and improves with rest. MG can lead to a variety of symptoms, including double vision or dropping eyelids, difficulty speaking or swallowing, weakness in limbs, and difficulty maintaining balance. Diagnosis of MG typically involves a medical examination, blood tests, nerve conduction studies, and electromyography. Treatment options include medication to improve the communication between nerves and muscles, immunosuppressive drugs, plasmapheresis, and intravenous immunoglobulin.
