All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Myasthenia gravis
Medical expert of the article
Last reviewed: 12.07.2025
Myasthenia is an autoimmune disease characterized by episodes of muscle weakness and fatigue, which is caused by the destruction of acetylcholine receptors by humoral and cellular immune factors. It most often affects young women and elderly men, although it can occur at any age. Symptoms of myasthenia are aggravated by muscle strain and are relieved by rest. It is diagnosed by intravenous administration of edrophonium, which reduces weakness for a short time. Treatment of myasthenia includes anticholinesterase drugs, immunosuppressants, glucocorticoids, thymectomy, and plasmapheresis.
Myasthenia gravis is an acquired autoimmune disease characterized by weakness and pathological fatigue of skeletal muscles. The incidence of myasthenia is less than 1 case per 100,000 population per year, and the prevalence is from 10 to 15 cases per 100,000 population. Myasthenia is especially common in young women and men over 50 years of age.
[ Causes of myasthenia
Myasthenia gravis results from an autoimmune attack on postsynaptic acetylcholine receptors, which disrupts neuromuscular transmission. What triggers the formation of autoantibodies is unknown, but the disease is associated with thymus pathology, thyrotoxicosis, and other autoimmune disorders. The role of the thymus in the development of the disease is unclear, but in 65% of cases of myasthenia the thymus is hyperplastic, and in 10% there is a thymoma. Predisposing factors include infections, surgery, and certain medications (eg, aminoglycosides, quinine, magnesium sulfate, procainamide, calcium channel blockers).
Rare forms of myasthenia. In the ocular form, only the external muscles of the eye are affected. Congenital myasthenia is a rare disease with an autosomal recessive type of inheritance. It is more likely the result of structural disorders of the postsynaptic receptor than the consequence of an autoimmune process. Ophthalmoplegia is common.
12% of children whose mothers suffer from myasthenia are born with neonatal myasthenia. This is due to the passive penetration of IgG antibodies through the placenta. General muscle weakness passes in a few days - weeks, parallel to the decrease in the antibody titer in the child's blood.
Symptoms of myasthenia
The most common symptoms of myasthenia are ptosis, diplopia, and muscle weakness after exercise. The weakness goes away after rest, but recurs with repeated exercise. In 40% of cases, the eye muscles are initially affected, later the prevalence of this lesion reaches 85%. In the first 3 years, in most cases, the process generalizes. Weakness in the proximal parts of the limbs is common. Sometimes patients complain of boulevard disorders (e.g., voice changes, nasal regurgitation, asphyxia, dysphagia). In this case, sensitivity and deep tendon reflexes do not change. The severity of the disorders fluctuates over a period of several hours - days.
Myasthenic crisis - severe generalized tetraparesis or life-threatening weakness of the respiratory muscles, develops in about 10% of cases. It is often associated with an infection that activates the immune system. Once respiratory failure begins, respiratory arrest can occur very quickly.
Diagnosis of myasthenia gravis
The diagnosis is based on the complaints, clinical picture and data from special studies. To assess the lesion, the patient is asked to tense the muscle until fatigue (e.g., keep the eyes open until ptosis develops, or count loudly until speech is impaired); then 2 mg of edrophonium, a short-acting anticholinesterase drug (<5 min), is administered intravenously. If no adverse reactions (e.g., bradycardia, atrioventricular block) develop within 30 s, another 8 mg is administered. The criterion for a positive test is rapid (<2 min) recovery of muscle function. In most cases of myasthenia, the test is positive, as in many other neuromuscular diseases. Performing the test may cause increased weakness due to a cholinergic crisis (see below). A resuscitation kit and atropine (as an antidote) should be on hand during the test.
Even with a clearly positive anticholinesterase test, to confirm the diagnosis it is necessary to determine the level of antibodies to acetylcholine receptors in the blood serum and conduct an EMG. Antibodies are detected in 90% of cases of generalized myasthenia and only in 50% of cases of the ocular form. The level of antibodies does not correlate with the severity of the disease.
Stimulation with a burst of impulses (2-3 per 1 second) on EMG in 60% of cases of myasthenia reveals a significant decrease in the amplitude in the sequence of action potentials.
Once myasthenia is diagnosed, a CT or MRI scan of the chest is performed to look for thymoma. Screening tests are performed to detect autoimmune diseases that often accompany myasthenia (eg, vitamin B12 deficiency , thyrotoxicosis, rheumatoid arthritis, systemic lupus erythematosus). Pulmonary function tests (eg, forced vital capacity) help assess the risk of respiratory arrest. In myasthenic crisis, it is necessary to identify the source of infection.
How to examine?
Who to contact?
Treatment of myasthenia gravis
Patients with respiratory arrest require intubation and mechanical ventilation. Anticholinesterase drugs and plasmapheresis alleviate complaints, and glucocorticoids, immunosuppressants, and thymectomy reduce the severity of the autoimmune reaction. In congenital myasthenia, anticholinesterase drugs and immunomodulatory treatment are ineffective and should not be used.
Symptomatic treatment of myasthenia
The basis of symptomatic treatment - anticholinesterase drugs - do not affect the cause of the disease, rarely alleviate all complaints, and myasthenia may become refractory to their use. Pyridostigmine is started with 30-60 mg orally every 3-4 hours and, if tolerated, is increased to a maximum dose of 180 mg 6-8 times a day. In case of severe dysphagia, especially in the morning, prolonged-release capsules of 180 mg can be taken at night, but their effect is weaker. If parenteral administration is necessary (for example, due to dysphagia), neostigmine can be used (1 mg corresponds to 60 mg of pyridostigmine). Anticholinesterase drugs can cause spastic abdominal pain and diarrhea. In such cases, atropine is prescribed at 0.4-0.6 mg orally or propantheline 15 mg 3-4 times a day.
Cholinergic crisis is muscle weakness caused by overdose of neostigmine or pyridostigmine. A mild crisis may be difficult to distinguish from spontaneous worsening of myasthenia. However, severe cholinergic crisis is characterized by excessive lacrimation, hypersalivation, tachycardia, and diarrhea, whereas myasthenia does not. When patients who are responding well to treatment worsen, some clinicians perform an edrophonium test because it is positive only in myasthenic crisis and not in cholinergic crisis. Others recommend simply providing respiratory support and discontinuing anticholinesterase medications for several days.
Immunomodulatory treatment of myasthenia gravis
Immunosuppressants suppress the autoimmune reaction and slow down the course of the disease, but do not provide a rapid reduction in complaints. With intravenous administration of immunoglobulin 400 mg / kg 1 time / day for 5 days, in 70% of cases, improvement occurs in 1-2 weeks.
Glucocorticoids are usually needed in maintenance therapy, but in myasthenic crisis they do not have an immediate effect, and after a high dose of glucocorticoids, a sharp deterioration occurs in more than half of the cases. Therefore, they start with 20 mg once a day, every 2-3 days the dose is increased by 5 mg up to 60-70 mg and then switch to 1 dose every other day. Improvement occurs after several months; then the dose is reduced to the necessary minimum.
Azathioprine 2.5-3.5 mg/kg once daily may be as effective as glucocorticoids, although it may not be effective for many months. Cyclosporine 2-2.5 mg/kg orally twice daily may reduce the dose of glucocorticoids. These drugs require special caution. Methotrexate, cyclophosphamide, and mycophenolate mofetil may be effective.
Thymectomy is appropriate for most patients under 60 years of age with generalized myasthenia. The operation should be performed in all cases of thymoma. Subsequently, remission or reduction of maintenance therapy is possible in 80% of cases.
During myasthenic crisis and before thymectomy in patients refractory to therapy, plasmapheresis may be effective.
Drugs