Myasthenia gravis is an autoimmune disease that disrupts communication between nerves and muscles, weakening neuromuscular connections, especially those affecting vision, chewing and swallowing, and breathing, as well as those in the arms and legs. When properly diagnosed and treated, myasthenia gravis does not shorten life expectancy or prevent people from living relatively normal lives. This rare disorder affects 20 out of 100,000 people worldwide, with women typically developing symptoms before age 40 and men after age 60; symptoms may worsen over time for both men and women.
What Are the Symptoms?
Myasthenia gravis is characterized by muscle weakness that worsens when affected muscles are active and improves when muscles are at rest. Common symptoms include eyelid drooping, double vision, slurred or low volume speech, difficulty chewing and swallowing, changes in facial expression, shortness of breath, and weakness in the neck, arms, hands, and leg muscles that may interfere with walking or holding up the head. Symptoms can be exacerbated by fatigue, stress, illness, pregnancy, or a course of medication, including some antibiotics.
What Are the Causes?
The immune system is designed to attack intruders such as pathogens and cancer cells, but in people with autoimmune diseases, it mistakenly attacks the body itself. With myasthenia gravis, the immune system’s antibodies interfere with, block, or destroy neurotransmitters (such as acetylcholine and other muscle-specific proteins) that allow nerves to communicate with muscles. The thymus gland, which ordinarily produces healthy white blood cells to fight infection and disease, can malfunction and contribute to the disease. Less frequently, myasthenia gravis is caused by a different set of antibodies that interfere with other neurotransmitters. It is also possible for a woman with the disease to give birth to a baby with neonatal myasthenia gravis, which is typically treated successfully within months of birth.
How Is It Diagnosed?
A neurologic exam by a physician assesses reflexes, muscle function, balance, coordination, and vision. The doctor may also order blood tests to check for abnormal antibody activity; nerve stimulation to assess neuromuscular communication and muscle fatigue; a CT or MRI scan to assess the thymus and look for possible tumors; and other targeted tests.
What Treatments Are Available?
Medications known as anticholinesterase agents, such as pyridostigmine (Mestinon), can slow the breakdown of the neurotransmitter acetylcholine and improve neuromuscular communication. This can provide temporary relief of some symptoms but does not actually change the course of the disease. Drugs that suppress the immune system, including prednisone and azathioprine (Imuran), can improve muscle function by suppressing the antibodies that attack acetylcholine and other neurotransmitters. Eculizumab (Soliris), which was approved by the US Food and Drug Administration in 2017, specifically targets the process of acetylcholine antibodies injuring the neuromuscular junction. For more severe cases, intravenous injections of immunoglobulin target antibodies in blood plasma and can relieve symptoms for a period of weeks or months between treatments. A thymectomy, which entails surgical removal of the thymus gland, may be recommended for some individuals. Removing the thymus gland can reduce symptoms and, in some cases, appears to eliminate symptoms entirely.
What Research Is Being Done?
In the last three decades, researchers have identified the neuromuscular processes at work in myasthenia gravis and potential therapies to manage them. Recent studies focus on the thymus gland and the effectiveness of surgically removing it, on increasingly targeted medications that inhibit the breakdown of neurotransmitters, and on the use of computer technology to map and model the progression and management of the disease more accurately.
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