Myasthenia gravis is just a symptom; myasthenia gravis is the lack of strength in the muscles, resulting in impaired movement of the limbs. It can be caused by lesions of the cervical and lumbar spine, lesions of the spinal cord, intracranial lesions, or myasthenia gravis, etc. 1. Cervical spondylosis and lumbar disc herniation may lead to muscle weakness in the arms or lower limbs because of disc compression of the spinal cord and nerves. 2. Spondylitis, spinal cord tumors and other lesions that damage the spinal cord nerves can also lead to muscle atrophy and muscle weakness. 3. Patients with post-stroke symptoms, whether due to cerebral infarction or cerebral hemorrhage, may suffer from muscle weakness and hemiplegia due to the loss of muscle innervation by the brain, and muscle atrophy on the hemiplegic side may occur after a long period of time. 4. Myasthenia gravis is another common cause of muscle weakness, which is an autoimmune disease in which acetylcholine at the neuromuscular junction fails to bind normally to its receptors. Some patients have thymoma in combination. Patients with myasthenia gravis tend to fatigue easily after limb movement, and their muscle weakness is mild in the morning, with more severe symptoms starting in the afternoon. If muscle weakness occurs, it is recommended to seek medical treatment as soon as possible to clarify the cause of the disease and the severity of the disease under the guidance of a professional physician, so as to avoid delaying the condition.