Epidemiology: Myasthenia gravis can occur in all age groups and can develop in both sexes. The incidence rate is about 10-20 per 1 million people. The prevalence rate is 15 times higher than the incidence rate, and both are on the rise.
Immune mechanism: Myasthenia gravis is an acquired autoimmune disease focusing on the AChR of the postsynaptic membrane at the neuromuscular junction, AChR antibody-mediated, cellular immune-dependent, and complement-involved.
Pathology: Thymoma myasthenia gravis may be either thymomatous or non-thymomatous myasthenia gravis. Approximately 50% of thymomas are combined with myasthenia gravis, 15% of myasthenia gravis is combined with thymoma, and 70% of myasthenia gravis is combined with thymic hyperplasia.
Clinical manifestations: about 53%-85% of MG patients have ptosis, diplopia, blurred vision and other eye symptoms as the first symptoms, 44%-80% of these patients will progress to generalized MG. 50% of these patients will gradually involve ball muscles, neck muscles, limb muscles and respiratory muscles within two years and progress to generalized MG. Respiratory.
Clinical features: fluctuating skeletal muscle weakness, light in the morning and heavy in the evening, relieved after rest and aggravated after exertion.
Diagnostic process.
1, clinical history: the patient complained of symptoms of weakness of extraocular muscles, pharyngeal muscles, cervical muscles, limb muscles and respiratory muscles, and this muscle weakness has fatigue and fluctuating characteristics.
2.Clinical examination: neurological examination, fatigue test, orbital ice test, sleep test, rest test, and neostigmine test, which show that muscle weakness is aggravated or improved.
3. Auxiliary examinations: electrophysiological examination, serum AChR antibody and MuSK antibody, mediastinal CT.
4.Other: thyroid function and morphological examination, cranial MRI, etc.
Differential diagnosis.
1, exclude actinic nerve palsy, talocrural nerve palsy, abducens nerve palsy, Horner syndrome due to cerebral hemisphere lesions, brainstem lesions, cavernous sinus lesions, supraorbital fissure, orbital apical lesions, etc.
2. exclusion of other neuromuscular junction disorders, such as Lambert-Eaton syndrome, botulism, congenital myasthenia gravis syndrome, etc.
3, exclude myogenic diseases, such as chronic progressive extraocular muscle paralysis and other mitochondrial diseases, oculomotor-type myotonic dystrophy, oculopharyngeal-type myotonic dystrophy, thyroid-related ophthalmomyopathy, congenital ophthalmomyopathy, etc.
4. exclusion of dystonic disorders, such as blepharospasm and Meige’s syndrome.
5. exclude ophthalmogenic diseases, such as inflammatory pseudotumor, lid membrane ptosis, senile skin laxity, etc.
Treatment principles
Six main treatment methods.
1, cholinesterase inhibitors, is the drug of choice for the treatment of various types of myasthenia gravis.
2, corticosteroids, glucocorticoids are the first-line immunosuppressants, improving the symptoms of myasthenia gravis with obvious effect.
3, immunosuppressants or immunomodulators, other immunosuppressants azathioprine (AZA), cyclophosphamide (CTX), methotrexate (MTX), cyclosporine (CyA), morte-macrolimus (MMF), tacrolimus (FK506), rituximab (RTX), complement inhibitors, etc. have a certain effect.
4.Immunoglobulin intravenous injection, is the choice for resuscitation of critically ill patients.
5.Plasma replacement, is the choice for resuscitating critically ill patients.
6.Thymectomy, which is an elective treatment measure. For thymomatous MG, once diagnosed, it should be resected; for patients with systemic MG, elective thymectomy is recommended; for oculomotor MG, although not routinely recommended, thymectomy can be an option for patients with AChR antibody-positive oculomotor MG who are ineffective with drug therapy, recurrent, and aged between 15 and 60 years old.
Four basic strategies.
1. symptomatic treatment: cholinesterase inhibitors, the
2, rapid short-term immunomodulatory therapy: plasma exchange and immunoglobulin intravenous injection.
3. chronic long-term immunomodulatory therapy: hormones and immunosuppressants.
4. Thymectomy.
Recommended principles.
1, once the diagnosis of MG is confirmed, the first cholinesterase inhibitor is given.
2.Patients with thymoma undergo thymectomy.
3, AChRab positive, early stage of disease, systemic MG, patients who are ineffective to cholinesterase inhibitors should undergo thymectomy, preferably within 1 year.
4, Progressive MG can be considered immunosuppressive. It is recommended that prednisone be given first, along with diphosphonates, acid suppressants, and azathioprine. If azathioprine is not effective and cannot be tolerated, other immunosuppressive drugs can be considered.
5. Intravenous immunoglobulin and plasma exchange are suitable for short-course treatment in critical conditions and exacerbations, as well as for the preparation of critically ill patients before surgery.
Prognosis
Myasthenia gravis is a lifelong disease and a treatable disease.
The conversion rate of the systemic form is 30% to 80%.
After immunotherapy, the complete remission rate is 10%-22%, the remission rate of residual mild symptoms is 40%-45%%, and the partial improvement rate is 68%-87% With improved medical treatment and survival, the life expectancy of people is extended and the survival rate of MG is improved as well as the mortality rate is reduced by 5%-9%.