People with myasthenia gravis (MG) have muscle weakness that worsens throughout the day. This autoimmune disease affects the neuromuscular system. Drooping eyelids are often the first sign. Eventually, you may find it difficult to control your neck and limbs. Medications and surgery can help relieve the symptoms of this lifelong illness.
Myasthenia gravis (MG) is an autoimmune disease, meaning the body’s immune system mistakenly attacks its own parts. MG affects the communication between nerves and muscles (the neuromuscular junction).
People with MG lose the ability to control muscles voluntarily. They experience muscle weakness and fatigue of various severity. They may not be able to move muscles in the eyes, face, neck and limbs. MG is a lifelong neuromuscular disease. There isn’t a cure, but treatments can help and some patients may achieve remission.
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MG affects about 20 out of every 100,000 people. Experts estimate that 36,000 to 60,000 Americans have this neuromuscular disease. The actual number of people affected may be higher, as some people with mild cases may not know they have the disease.
MG mostly affects women aged 20 to 40 and men aged 50 to 80. About one in 10 cases of MG occur in teenagers (juvenile MG). The illness can affect people of all ages but is rare in children.
These factors increase risk:
Autoimmune MG is the most common form of this neuromuscular disease. Autoimmune MG may be:
In rare instances, pregnancy brings on MG symptoms for the first time. If you already have MG, symptoms may worsen during the first trimester or immediately after childbirth. In some patients, MG symptoms improve during pregnancy.
Certain MG treatments are not safe during pregnancy or breastfeeding. Your healthcare provider can guide you through this time, ensuring a healthy pregnancy.
In general, autoimmune MG isn’t inherited. It’s rare for more than one member of the same family to receive a diagnosis of autoimmune MG. The non-autoimmune form of MG (also called congenital myasthenic syndrome) can affect more than one member of the same family.
A pregnant woman cannot pass MG to her infant. However, about one in 10 babies born to women with MG develop a temporary condition called neonatal myasthenia. These infants may have weak cries or sucking reflexes at birth. These symptoms go away in a few weeks. This condition doesn’t increase a child’s risk of developing MG in the future.
MG is an autoimmune disease. For unknown reasons, the body’s immune system attacks itself.
In someone with a healthy immune system, nerves and muscles communicate a bit like a tiny baseball game:
In a healthy person, nerves signal muscles work effortlessly, like one ballplayer catching a ball and throwing it to a teammate.
But people with MG have antibodies that destroy the receptor sites, blocking nerve-muscle communication. The “catcher” can’t catch the ball, and communication becomes sluggish or doesn’t work at all.
Many people with MG have thymus gland conditions that may bring on MG. The thymus is a small organ in the upper chest that is part of the lymphatic system. It makes white blood cells that fight infections. Two-thirds of young people with MG have overactive thymic cells (thymic hyperplasia). About one in 10 people with MG have thymus gland tumors called thymomas, which may be benign (not cancer) or cancerous.
Initial symptoms of MG often come on suddenly. The neuromuscular disease causes your muscles to get weaker when you’re active. Muscle strength returns when you rest.
The intensity of muscle weakness often changes from day to day. Most people feel strongest at the start of the day and weakest at the end of the day.
Symptoms of MG include:
Your healthcare provider will perform a physical exam and assess your symptoms. You may undergo these tests:
Up to one in five people with MG experience a myasthenic crisis or severe respiratory muscle weakness. They may need a respirator or other treatments to help them breathe. This is a life-threatening medical emergency. Weak muscles, infections, fevers and reactions to medications can cause a crisis.
Myasthenia gravis is a treatable disease and most patients will live a relatively normal life with treatment.
Treatments for MG focus on improving symptoms. Treatments include:
Healthcare providers don’t know what triggers autoimmune diseases like MG. There isn’t anything you can do to prevent it.
If you have MG, these steps can ease fatigue and boost muscle strength:
With treatment, most people with MG lead full, active lives. Symptoms tend to reach their peak in severity within one to three years of initial diagnosis. For 15% of people with MG, the disease only affects the eyes and face (ocular MG).
You should call your healthcare provider if you experience:
You may want to ask your healthcare provider:
A note from Cleveland Clinic
It’s challenging to live with a chronic illness like MG. Although there isn’t a cure, most people with MG lead productive, active lives. Severe disabilities from MG are extremely rare. Treatments and lifestyle changes can ease symptoms. Your healthcare provider can suggest ways to manage symptoms so you can continue to enjoy life.
Last reviewed by a Cleveland Clinic medical professional on 04/07/2021.
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