What is myasthenia gravis? It easily causes fatigue!

Myasthenia gravis may be very unfamiliar to many people, and most people don’t know what myasthenia gravis is. This is an autoimmune disease that easily causes muscle fatigue. It has a great impact on people's body and life, and the incidence rate is also very high.

1. Overview

Myasthenia gravis is an autoimmune disease that primarily affects acetylcholine receptors on the postsynaptic membrane of the neuromuscular junction. The main clinical manifestations are partial or systemic skeletal muscle weakness and fatigue. The symptoms worsen after activity and are relieved after rest and treatment with cholesterase inhibitors. The incidence rate is 8-20/100,000, and the prevalence rate is 50/100,000. The incidence rate is higher in southern my country. Patients with myasthenia gravis often have other autoimmune diseases such as hyperthyroidism, thyroiditis, systemic lupus erythematosus, rheumatoid arthritis, and pemphigus.

2. Pathogenesis

Currently, MG is considered to be the most classic autoimmune disease, and its pathogenesis is related to the damage of AchR mediated by autoantibodies. It is mainly mediated by AchR antibodies. With the participation of cellular immunity and complement, the AchR on the postsynaptic membrane is destroyed in large quantities, unable to generate sufficient end plate potential, leading to postsynaptic membrane transmission dysfunction and muscle weakness. The immune response to AchR is closely related to the thymus. 65%-80% of MG patients have thymic hyperplasia, and 10%-20% have concomitant thymoma. The "myoid cells" in the thymus have the antigenicity of AchR and promote the production of AchR antibodies.

3. Disease pathology

The main pathological changes of myasthenia gravis occur at the neuromuscular junction, where the synaptic cleft is widened, the postsynaptic membrane wrinkles become shallower and their number decreases, and immunoelectron microscopy shows postsynaptic membrane disintegration, a significant reduction in AchR, and deposition of IgG-C3-AchR-bound immune complexes. There are no obvious changes in the muscle fibers themselves, but sometimes muscle fiber coagulation, necrosis, and swelling can be seen. Muscle atrophy can be seen in chronic diseases.

4. Clinical manifestations

The disease can occur at any age, from newborns to the elderly. The peak incidence in women is between 20 and 30 years old, and in men is between 50 and 60 years old, and is often accompanied by thymoma. A few patients have a family history. The onset is insidious, and the course of the disease fluctuates, with remissions and relapses alternating. Patients in the advanced stage cannot fully recover after rest. Most cases last for several years to decades and are maintained by medication. A few cases may resolve spontaneously.