What Is Myasthenia Gravis?
Myasthenia gravis (or myasthenia) is a condition that causes weakness in the voluntary muscles (the muscles we can control). The weakness can come and go, and vary from mild to severe.
Myasthenia gravis (my-ess-THEE-nee-uh GRAV-iss) happens when connections between nerves and muscles get blocked. In children, the condition is called juvenile myasthenia gravis or JMG.
What Are the Signs & Symptoms of Myasthenia Gravis?
Myasthenia gravis is usually either ocular (eye) myasthenia or generalized myasthenia gravis.
Ocular Myasthenia Gravis
Ocular myasthenia gravis can affect one eye or both. It causes:
- ptosis (TOE-siss): a drooping eyelid
- double vision: when one eye is slower than the other
Ocular myasthenia gravis can spread and become generalized myasthenia gravis. This is less likely to happen if the ocular myasthenia is treated.
Generalized Myasthenia Gravis
Generalized myasthenia affects muscles all over the body. It often causes:
- frequent falls
- trouble speaking, chewing, or swallowing
Myasthenia gravis can be life-threatening if it affects:
- breathing muscles
- throat and tongue muscles that help keep the airway open from the nose and mouth to the lungs
This is called a myasthenic crisis. Some things can make symptoms worse and trigger a myasthenic crisis. These include illnesses, surgery, poor sleep, and some medicines, including common antibiotics.
What Causes Myasthenia Gravis?
The body's central nervous system sends signals through motor nerves that make muscles contract (move). Motor nerves reach muscles at points called neuromuscular junctions (NMJs). Motor nerves hold acetylcholine (ACh), a chemical that tells muscles to contract.
Myasthenia gravis is an autoimmune disease. Instead of fighting germs, the immune system makes antibodies that attack a muscle's nerve receptors. The antibodies stick to a muscle's NMJ, blocking the nerve's signal to the muscle.
Each muscle has many neuromuscular junctions. So some might not be blocked, letting the nerve's signal get through to a few areas of the muscle. The muscle contracts, but not at full strength.
Who Gets Myasthenia Gravis?
Myasthenia gravis can start at any age. A person is more likely to have the condition if a close family member has it or another autoimmune disease (such as rheumatoid arthritis, scleroderma, or lupus).
How Is Myasthenia Gravis Diagnosed?
If a child younger than age 2 has symptoms, and the muscle weakness comes and goes, doctors might suspect myasthenia gravis.
To find out, the doctor will do an exam and order tests such as:
- antibody titer: This blood test checks for antibodies that can stick to an NMJ.
- electromyography (EMG): This checks whether nerves are working well and whether the muscles are healthy.
- Tensilon test: Tensilon is medicine that slows down the normal breakdown of ACh, so there's more of it near the neuromuscular junction. If using Tensilon in this test restores some muscle strength, the problem is almost sure to be myasthenia gravis.
- stimulated single-fiber EMG: Doctors do this special EMG if other tests don't give them a clear answer.
How Is Myasthenia Gravis Treated?
Treatment for myasthenia gravis usually focuses on:
- making the immune system less active so it makes fewer antibodies
- helping the neuromuscular junction send signals from the nerve to the muscle
Making the immune system less active can be done in several ways. Sometimes these are used together. Doctors will adjust treatment so that a person gets the greatest amount of strength with the fewest side effects.
Immunosuppression treatments include:
- medicines that can be taken by mouth, such as prednisone
- supplemental antibodies from blood donors, called intravenous immunoglobulins (IVIG)
- plasmapheresis, which removes some antibodies from the blood
- surgery to remove the thymus (thymectomy). This gland helps the immune system develop. Removing it can make the immune system less active and ease myasthenia gravis symptoms.
Helping the NMJ
Medicines can keep more ACh near the neuromuscular junction. Then, when a nerve releases its ACh, the muscle is more likely to get the signal.
What Else Should I Know?
The treatment goal is complete remission. This means all myasthenia gravis symptoms go away and a person can stop taking medicines. But complete remission doesn't happen often.
Most children with the condition must continue treatment during their teen and adult years. Those who had a thymectomy might need less medicine and be more likely to have complete remission.
If your child has myasthenia gravis, tell any doctor caring for your child about the condition, even if a problem doesn't seem related to it.
It can help to talk with other parents who have a child with myasthenia. Ask your doctor to recommend a local support group, or look online at:
- Spinal Muscular Atrophy (SMA)
- Immune System
- Bones, Muscles, and Joints
- EMG (Electromyogram)
- Bell's Palsy
- Charcot-Marie-Tooth Disease (CMT)