KidsMD Health Topics

Myasthenia Gravis

  • Overview

    Juvenile myasthenia gravis (JMG) is the childhood form of myasthenia gravis (MG), and is an autoimmune disease in which a child’s body produces antibodies that attack the acetylcholine receptor and sometimes other proteins at the neuromuscular junction. Acetylcholine is a neurotransmitter that plays a key role in muscle contractions. Not having enough receptor sites for acetylcholine causes a child’s muscles to weaken over time.

    Here’s what you need to know about JMG:

    • JMG should not be confused with congenital myasthenicsyndrome or neonatal myasthenia gravis.  Congenital myasthenic syndrome is a similar but different disease of the neuromuscular junction that is genetic rather than autoimmune in origin. Neonatal myasthenia gravis is a transient (temporary) condition in infants born to mothers with symptomatic or subclinical myasthenia gravis. However, treatment is important because these infants may be quite ill for several weeks.
    • In post-pubertal patients, females are more likely to have JMG than males. In pre-pubertal patients, JMG affects both genders equally.
    • Although JMG can affect people of any age, the disease is relatively rare in children.
    • JMG causes a child’s muscles, especially his eyes, mouth, throat and limbs, to weaken after periods of activity. The weakness usually subsides after a period of rest.
    • Most children with JMG experience symptoms on and off, but the degree of muscle weakness can fluctuate in severity during the “on” times. 
    • In some cases, JMG may be a life threatening condition. However, most people with the disease improve over time if they receive effective treatment.

     

    How Children’s Hospital Boston approaches JMG:

    Since 1977, thousands of children have been successfully diagnosed and treated at the Neuromuscular Program where they are evaluated and treated by a team of world-renowned experts in child neurology, orthopedics and genetics.

    The Department of Ophthalmology and the Ophthalmology Program at Children’s also uses both medical and surgical approaches to treat a wide range of eye conditions caused by neurological disorders such as myasthenia gravis. We use the most advanced diagnostic and treatment methods available and incorporate minimally invasive techniques whenever possible.

    Our teams will work together with your family to develop treatment plans that meet your child's unique needs and provide him with the best possible quality of life.

    Myasthenia gravis: Reviewed by Peter Kang, MD © Children’s Hospital Boston, 2011

  • In-Depth

    A diagnosis of juvenile myasthenia gravis (JMG) comes with a lot of questions and uncertainty about your child’s health, like:

    • What is it?
    • What should I do when my child is diagnosed?
    • What treatments are available?
    • What’s the long-term outlook for my child?

    At Children’s Hospital Boston, we know how important it is for parents and families to understand their child’s medical concerns. We’ve provided answers to many commonly asked questions about JMG in the following pages, and when you meet with our team of doctors, they’ll be able to explain your child’s condition and treatment options fully.

    What is JMG?

    • In the most common type of JMG, the immune system creates antibodies that attack receptor sites for acetylcholine, a neurotransmitter that actives muscle movement.
    • When these receptor sites are damaged or destroyed, the affected muscles do not receive enough acetylcholine.
    • Without acetylcholine to stimulate movement, the muscles become weak and tired after a period of activity.
    • A child with JMG will experience fluctuating muscle weakness that may last throughout their lives. The degree of muscle weakness and the muscles that are affected will vary form person to person.
    • With treatment, symptoms usually become more sporadic, and some children go into remission for long periods of time before needing another treatment intervention.
    • Some people with JMG experience a myasthenic crisis, a life threatening condition in which the muscles used for breathing become very weak and cause severe breathing problems.

    What are the different types of MG?

    There are two types of MG in children:

    Transient neonatal MG

    • Between 10 and 25 percent of babies born to mothers with MG may have this temporary form of the condition, which occurs when antibodies common in MG cross the placenta to the developing fetus.
    • Neonatal MG usually lasts only a few weeks and babies are not at greater risk for developing MG later in life.

    Juvenile MG (JMG)

    • It is a life-long condition that may go in and out of remission (symptom-free periods).
    • This type of MG accounts for 10-15 percent of all cases of MG.
    • Congenital myasthenic syndrome (CMS) is a very genetic disease of the neuromuscular junction. Both males and females are equally affected and that two copies of the gene, one inherited from each parent, are necessary to have the condition.
    • Symptoms of CMS usually begin in infancy or early childhood; this is generally a lifelong condition.

    How serious is JMG?

    People who receive effective treatment for JMG can significantly improve their muscle strength, experience long periods of remission and lead normal lives. However, not receiving treatment for JMG can have serious consequences.  A child with significant muscle weakness may injure himself during activities such as walking down a flight of stairs or riding a bike.

    The most serious complication of JMG is myasthenic crisis; this generally occurs when patients have symptoms throughout their body (generalized myasthenia) as opposed to patients who only have symptoms in their eyes (ocular myasthenia).

    • Myasthenic crisis is a life threatening complication in which the muscles used for breathing become weak and cause severe respiratory problems. Potential triggers for myasthenic crisis include stress, acute illnesses, surgery, or an overdose of certain medications.  Myasthenic crisis requires immediate medical attention.

    Is JMG curable?

    There is no cure for JMG yet. However, effective treatment can significantly improve a child’s muscle strength and may increase the duration of symptom-free periods. 

     

    Causes

    What causes JMG?

    JMG occurs in the following way:

    • Neurotransmitters are chemicals in the brain, spinal cord, and neuromuscular junction that send electrical signals from one neuron to another, or from a neuron to a muscle fiber. Different neurotransmitters control and regulate various bodily functions and emotions. The neurotransmitter that connects neurons to muscle fibers is called acetylcholine.
    • Normally, acetylcholine is released from the end of a neuron and travels across the synapse before binding to special receptor sites on the muscle fiber.
    • In the case of JMG, the immune system creates antibodies that damage or destroy the acetylcholine receptors. When these antibodies bind to the receptors, they prevent the neuron from sending signals to initiate muscle contraction.  This causes the muscle weakness that is associated with JMG.

     

    Symptoms

    What are the symptoms of JMG?

    JMG is characterized by muscle weakness that typically gets worse later in the day or after a period of activity.  However, symptoms of JMG may be difficult to detect because they usually fluctuate. They may also resemble those of other conditions, and may be overlooked. If you observe the following signs in your child, you may want consult your child’s doctor to get an accurate diagnosis:

    • drooping eyelids or double vision
    • dysarthria (difficulty speaking)
    • dysphasia (difficulty swallowing)
    • fatigue
    • muscles that become progressively weaker after periods of activity or as the day progresses
    • weak neck muscles
    • problems walking
    • lopsided facial expressions

    The severity of symptoms and the pattern of muscles affected vary from person to person. Every person with JMG doesn’t experience all of these symptoms, and a person’s clinical picture can change over time.

    Symptoms of JMG can worsen due to :

    • alcohol use
    • fatigue and sleep deprivation
    • taking certain medications, especially penicillamine or interferons
    • certain antibiotics or cardiovascular drugs (in certain cases, these drugs may be used in patients with JMG, but the prescribing physician must be aware of the JMG and monitor the patient closely.)

     

    Questions to ask your doctor

    You will probably have a lot of questions on your mind before meeting with your child’s doctor. At the appointment, it can be easy to be overwhelmed with information and forget the questions you wanted to ask.

    A lot of parents find it helpful to jot down questions beforehand. That way, when you talk to your child’s clinician, you can be sure that all your concerns are addressed. Remember that physicians are open to learning from families too. Attend conferences, read up on updated materials and don’t be afraid to share what you have learned.

    Some questions you might ask include:

    • How should I talk to my child about this condition and his health?
    • Do I need to restrict my child’s physical activity?
    • Do I need to make any other changes to my child’s home and school routines?
    • How will JMG affect my child’s vision?
    • What does his long-term treatment plan involve?
    • What resources can you point me to for more information?
  • Tests

    At Children’s Hospital Boston, we know that the first step in treating your child’s juvenile myasthenia gravis (JMG) is to form an accurate and complete diagnosis. Our Neuromuscular Program uses a number of different tests to help us accurately diagnose your child’s disorder and evaluate his condition.

    How is Juvenile Myasthenia Gravis diagnosed?

    There will be a physical exam, during which your child's physician will take your child’s complete medical history, and may also ask if there is a family history of any medical problems.

    The diagnostic tests your child might require include:

    • antibody titer tests measure the presence of antibodies that are attacking the child’s neuromuscular system. If the titers are positive, this strongly suggests that your child has JMG.
    • Repetitive nerve stimulation is a useful way of diagnosing JMG and is performed during an electromyography study (EMG). The technique involves the stimulating specific nerves and examining abnormal muscle movements.
    • Tensilon tests are sometimes used to confirm a diagnosis of JMG.  During this test, your child will get an injection of a small amount of a medicine called Tensilon. If JMG is present, the diagnostician will notice an immediate, brief increase in muscle tone.
    • Stimulated single fiber EMG (SSFEMG) is a specialized test that is also performed in the EMG Laboratory.  It is sometimes used when other diagnostic tests for JMG are negative or inconclusive and the clinical suspicion is high.
    • Genetic tests, which evaluate the likeliness that congenital myasthenic syndrome (CMS) is present based on your child's genes.  Genetic testing is not used for the diagnosis of JMG

    How Children’s Hospital Boston approaches JMG:

    Since 1977, thousands of children have been successfully diagnosed and treated at the Neuromuscular Program where they are evaluated and treated by a team of world-renowned experts in child neurology, orthopedics and genetics.

    The Department of Ophthalmology and the Ophthalmology Program at Children’s also uses both medical and surgical approaches to treat a wide range of eye conditions caused by neurological disorders such as myasthenia gravis. We use the most advanced diagnostic and treatment methods available and incorporate minimally invasive techniques whenever possible.

    Our teams will work together with your family to develop treatment plans that meet your child's unique needs and provide him with the best possible quality of life.

  • A diagnosis of juvenile myastheniagravis (JMG) can be worrisome. You are probably wondering where to go from here and how to make sure your child receives the best possible care.

    All of the members of the Neuromuscular Program at Boston Children's Hospital are here to help. Our specialists are dedicated to anticipating any complications that your child may experience from his disease and developing the best therapeutic plans to manage them.

    What treatments are available?

    Although JMG can't be cured, there are several treatment options that are effective in strengthening muscles, managing symptoms and prolonging symptom-free periods.

    Depending on his specific needs, your child may receive one or a combination of a few different treatments:

    Medicine

    • acetylcholinesterase inhibitors, especially pyridostigmine, are standard drugs that increase acetylcholine neurotransmitter levels. These work well for some children with mild symptoms.
    • immunomodulatory therapy, which are treatments that reduce the quantity of harmful antibodies in the body. They include:
    • Plasmapheresis: This is used to remove antibodies from the blood. First, blood is removed from your child's body through an intravenous catheter. Plasma containing abnormal antibodies is then separated from the rest of his blood and discarded. Finally, his own cleaned blood is returned to his body through another intravenous catheter.  The discarded antibodies may be replaced by albumin or, in certain cases, plasma from blood donors.
    • Intravenous immunoglobin (IVIG): This works by decreasing the amount of antibodies produced by the immune system, much like plasmopheresis. However, it's easier to administer than plasmopheresis because you only need one, relatively small IV. IVIG is usually effective at helping calm the autoimmune reaction caused by JMG.
    • Steroids: While steroids drugs are usually effective, they have significant side effects. 
    • Less common immunosuppressive drugs can be used in cases where the traditional treatment methods don't work. However, these drugs carry significant side effects and should only be used when other options have been exhausted or are inadvisable.

    What are the side effects of steroids?

    Children who are on steroids should be carefully monitored by a physician. They may experience:

    • weight gain
    • slow height growth
    • temporary moodiness or other behavioral changes
    • increases in blood pressure and blood sugar
    • calcium deficiency
    • change in facial appearance

    Surgery

    Thymectomy is the surgicalremoval of the thymus gland in the chest.  The thymus has been associated with production of the harmful antibodies, though the exact mechanism by which the thymus promotes this is unclear.

    • A thymectomy needs to be performed when a child has a thymoma, a rare tumor of the thymus.
    • Thymectomy may be used on children with generalized JMG who are not responding to medical treatments, or those who would be heavily dependent on medication in the long term.  Thymectomy is usually not indicated in cases of pure ocular myasthenia (myasthenia that only affects the eyes).
    • This procedure can work very well in some, though not all cases. Based on a number of retrospective studies, it can produce remission from MG, increase strength and reduce the need for medication.

    Will my child need surgery?

    Children with generalized myasthenias who are not responding to medical treatments, or who are heavily dependent on medication, maybe eligible for a thymectomy (surgical removal of the thymus). In some cases, children who undergo the procedure improve significantly.

    Coping and Support

    If your child has just been diagnosed with JMG, this is certainly a stressful time for your family. You are being given lots of new information and are probably feeling overwhelmed. It's normal and acceptable to go through a range of emotions. Fortunately, there is a lot of help available to you.

    This list outlines some of our resources at Children's and in the wider community that may be helpful to you:

    Resources for families:

    • Children's Center for Familiesis dedicated to helping families locate the information and resources they need to better understand their child's particular condition and take part in their care. All patients, families and health professionals are welcome to use the Center's services at no extra cost. The center is open Monday through Friday from 8 a.m. to 7 p.m., and on Saturdays from 9 a.m. to 1 p.m. Please call 617-355-6279 for more information.
    • The Medical Coping Team at Boston Children's Hospital works with teens and their families to help them adjust to the stress caused by chronic illness. Our experienced team of pediatric psychologists, psychiatrists and other mental health professionals provide effective, compassionate evaluation, education, counseling and therapy to help teens cope.

    Outside resources:

    Please note that neither Boston Children's Hospital nor the Neuromuscular Program at Children's unreservedly endorses all of the information found at the sites listed below.

    • The Muscular Dystrophy Association provides information about muscular dystrophies as well as many other neuromuscular diseases at their website. The site also gives a lot of information about services, support for your family and research.
    • The Myasthenia Gravis Foundation of America (MGFA) is focused on advocating optimal diagnosis and treatment for individuals affected by MG.  The MGFA website offers educational resources, community support and opportunities for volunteer work. 
  • Research & Innovation

    The pace at which our understanding of the immune system—and, along with it, autoimmune diseases like myasthenia gravis (MG)—has increased dramatically in the past few decades. So, too, has the pace of diagnostics and treatment.

    Searching for better therapies

    Established in 1977 the Neuromuscular Program at Children’s Hospital Boston was of the first clinics providing comprehensive care for patients with neuromuscular diseases. Today, we continue to offer the highest level of diagnostic and treatment services. Experts in our program closely tie clinical care to the latest developments in research.

    A great deal of this research is going on right here at Children’s:

    • Our physicians also have strong ties to research laboratories at Children’s that are finding the molecular underpinnings of neuromuscular diseases and developing potential treatments.
    • The Immune Disease Institute, a non-profit research and educational institution, is working in collaboration with Children’s Hospital Boston to accelerate groundbreaking research in immunology and inflammation and to translate basic discoveries into the clinical setting. Their work on autoimmunity centers on discovering what controls the interaction of immune cells with each other and understanding how genetic variation contributes to autoimmunity.
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