Myasthenia Gravis

DEFINITION


When Mbah Dukun surving on internet, he gets message from Nilla Gustian. Nilla wants information about Myasthenia Gravis.

What is Myasthenia Gravis?
Myasthenia Gravis (MG) is a chronic, autoimmune disease that causes muscle weakness and excessive muscle fatigue. The name comes from Greek and Latin words meaning "grave muscle weakness." But most cases of MG are not as "grave" as the name implies.
The disease can vary in severity and distribution of weakness between individuals, and in any one patient the symptoms fluctuate with relapses and remissions. MG can resolve spontaneously, but for most patients MG persists for life. It can be life threatening, but 90% of patients become symptom-free with modern treatments.
MG produces progressive weakness and fatigue and sporadic abnormal in skeletal muscles, which get worse after exercise and repetition of movement, but can be corrected with drugs antikholineterase.
Usually, this disorder that attacks the muscles controlled by cranial nerves (face, lips, tongue, neck, and throat) but can also attack other muscles.
MG followed the explosion of anger and periodic remissions that can not be predicted. Treatment was not known, but drug therapy can improve symptoms and allow patients to live relatively normal, except during the outburst occurred.
When the disease involves the respiratory system, it can endanger lives.






EPIDEMIOLOGY

Patient asks to Mbah Dukun Bagong: Who is at risk of developing MG and  Is MG hereditary?

Mbah Dukun Bagong answers:

MG affects all races and can develop at any age from childhood to extreme old age. Young patients are more commonly women, whereas older patients, over 50 years, are more often men. People who inherit a tendency to develop autoimmune disease are at increased risk of developing MG, so a patient with MG may have another autoimmune disease, such as diabetes or thyroid disease, or have a relative with autoimmune disease. Occasionally MG develops in patients with rheumatoid arthritis who are given the drug penicillamine. In these cases, the MG symptoms usually disappear when the drug is stopped.
MG is not an inherited disease and does not usually occur in families. This is in contrast to the congenital myasthenic syndromes that are genetic disorders (see below). However, it is thought that an individual’s genetic make-up is one factor, of perhaps many, that leads them to develop MG, and it may occasionally be found in more than one family member. 

Estimates of the number of people affected by MG vary, ranging from 5 to 14 people per 100,000. It occurs in all ethnic groups and both sexes. It most commonly occurs in: 

• young adult women (under 40) 

• older men (over 60)MG can occur at any age. Children sometimes develop it as well. MG is not passed down through the family. You can’t “catch it” from some-one who has it. The disease rarely occurs in more than one member of the same family. If a woman with MG becomes pregnant, sometimes the baby gets antibodies from the mother and has MG symptoms for a few weeks or months after birth. This is called neo-natal myasthenia. The symptoms can be treated and the baby does not have per-manent MG. A group of rare disorders called congeni-tal myasthenic syndromes (CMS) can pro-duce symptoms similar to MG. Unlike MG, these disorders are not autoim-mune disorders but are caused by defec-tive genes. Because of these genes, the nerve-muscle junctions in the body cannot work properly. CMS usually starts at or near birth. But it can start in childhood or even adulthood.

PATHOLOGY

Patient asks to Mbah Dukun Bagong: Tell me pathology of Myasthenia Gravis?

Mbah Dukun Bagong answers:

 

The voluntary muscles of the entire body are controlled by nerve impulses that arise in the brain. These nerve impulses travel down the nerves to the place where the nerves meet the muscle fibers. Nerve fibers do not actually connect with muscle fibers. There is a space between the nerve ending and muscle fiber; this space is called the neuromuscular junction.
When the nerve impulse originating in the brain arrives at the nerve ending, it releases a chemical called acetylcholine. Acetylcholine travels across the space to the muscle fiber side of the neuromuscular junction where it attaches to many receptor sites. The muscle contracts when enough of the receptor sites have been activated by the acetylcholine. In MG, there is as much as an 80% reduction in the number of these receptor sites. The reduction in the number of receptor sites is caused by an antibody that destroys or blocks the receptor site.
Antibodies are proteins that play an important role in the immune system. They are normally directed at foreign proteins called antigens that attack the body. Such foreign proteins include bacteria and viruses. Antibodies help the body to protect itself from these foreign proteins. For reasons not well understood, the immune system of the person with MG makes antibodies against the receptor sites of the neuromuscular junction. Abnormal antibodies can be measured in the blood of many people with MG. The antibodies destroy the receptor sites more rapidly than the body can replace them. Muscle weakness occurs when acetylcholine cannot activate enough receptor sites at the neuromuscular junction. 

SYMPTOMS

Patient asks to Mbah Dukun Bagong: How can we know MG symptoms?
Mbah Dukun Bagong answers:



Dominant symptoms of this disease are skeletal muscle weakness and fatigue. In the early stages, certain muscles are susceptible to fatigue, but no other symptoms. Ultimately, this phenomenon is getting worse and can cause paralysis.Normally, muscles felt strong in the morning and weakened throughout the day, especially after exercise. Short break for a while can restore muscle function. Growing muscle weakness; finally some muscle to not function at all. Symptoms that occur depending on the affected muscle groups; this phenomenon is increasingly becoming the menstrual period and after emotional stress, too long in the sun or the cold or infection.The appearance of symptoms can occur suddenly or from within. In many patients, weak eye closure, the closed eyelids, and double vision is the beginning of this disorder. Patients usually have nasal regurgitation of fluids that often occurs and difficulty chewing and swallowing.Because of this disorder, sufferers are often afraid of choking. Patients also experienced difficulty breathing. Because the eyelids are closed, the patient should raise his head to look toward the back, neck muscles become too weak to support the head without being short.Miastenik crisis patients (respiratory disturbance that appears suddenly) can be susceptible to pneumonia and other respiratory tract infections. This situation can get worse so that it requires mechanical ventilation and airway emergency.

 DIAGNOSE

Patient asks to Mbah Dukun Bagong: How to Diagnose?
Mbah Dukun Bagong answers:



The history and examination of the patient can suggest the diagnosis but it is important to confirm the diagnosis by special investigations: Antibodies to the acetylcholine receptor are found in 85% of patients with generalised MG, and 50% of patients with ocular MG. They are detected by a blood test.
Electromyography (EMG) is performed by a specialist doctor and involves measuring the electrical response in the muscle with a very fine needle. An electrical stimulus is applied to a nerve and the response in the muscle is recorded. It is a very sensitive test, showing an abnormality in most patients with MG, but is not available at all hospitals.
Tensilon® test, an injection of Edrophonium is given which results in a rapid but short-lived improvement in symptoms in many patients.
Chest scan should be done to check whether the thymus is abnormal as many patients with MG have an enlarged thymus, and some have a benign tumour.

Treatments for Myasthenia Gravis (MG)

Patient asks to Mbah Dukun Bagong: How to manage patient with Myasthenia Gravis?
Mbah Dukun Bagong answers:


 There is no known cure for MG, but there are effective treatments that allow many-but not all-people with MG to lead full lives. Common treatments include medications, thymectomy and plasmapheresis. Spontaneous improvement and even remission may occur without specific therapy.
Medications are most frequently used in treatment. Anticholinesterase agents (e.g., Mestinon®) allow acetylcholine to remain at the neuromuscular junction longer than usual so that more receptor sites can be activated. Corticosteroids (e.g., prednisone) and immunosuppressant agents (e.g., Imuran®) may be used to suppress the abnormal action of the immune system that occurs in MG. Intravenous immunoglobulins (IVIg) are sometimes used to affect the function or production of the abnormal antibodies also.
Thymectomy (surgical removal of the thymus gland) is another treatment used in some patients. The thymus gland lies behind the breastbone and is an important part of the immune system. When there is a tumor of the thymus gland (in 10-15% of patients with MG), it is always removed because of the risk of malignancy. Thymectomy frequently lessens the severity of the MG weakness after some months. In some people, the weakness may completely disappear. This is called a remission. The degree to which the thymectomy helps varies with each patient.
Plasmapheresis, or plasma exchange, may be useful in the treatment of MG also. This procedure removes the abnormal antibodies from the plasma of the blood. The improvement in muscle strength may be striking, but is usually short-lived, since production of the abnormal antibodies continues. When plasmapheresis is used, it may require repeated exchanges. Plasma exchange may be especially useful during severe MG weakness or prior to surgery.
Treatment decisions are based on knowledge of the natural history of MG in each patient and the predicted response to a specific form of therapy. Treatment goals are individualized according to the severity of the MG weakness, the patient's age and sex, and the degree of impairment. 






References:


1. http://forum.um.ac.id

2. http://www.myasthenia.org

3. http://www.mdi.ie

4. http://www.neurology.org

5. http://www.wrongdiagnosis.com

6. http://jama.ama-assn.org