Autoimmune Myasthenia Gravis in Children

Autoimmune myasthenia gravis (MG) is a complex, autoimmune disorder in which antibodies destroy neuromuscular connections. This causes problems with the nerves that communicate with muscles, resulting in weakness of the skeletal muscles. MG affects the voluntary muscles of the body, especially the eyes, mouth, throat, and limbs.

Patients can be seen by Texas Children's experts in Neurology.

Causes & Risk Factors

There are different forms of myasthenia gravis.  Autoimmune myasthenia gravis is not inherited as a rare genetic disease or contagious, but it may be acquired through immune proteins or antibodies to babies born to mothers with MG, or the disorder may develop spontaneously later in childhood.  Rare forms of myasthenia gravis are related to underlying genetic defects inherited from the parents.

Symptoms & Types

There are three types of MG in children, including the following:

  • Congenital MG. This is a very rare nonimmune form of MG that is most often inherited as an autosomal recessive disease. This means that both males and females are equally affected and that 2 copies of the gene, one inherited from each parent, are necessary to have the condition. Symptoms of congenital MG usually begin in the baby's first year and are lifelong.
  • Transient neonatal MG. Babies born to mothers with autoimmune MG may have a temporary form of MG. This 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 Autoimmune MG. This autoimmune disorder develops typically in female adolescents--especially Caucasian females. Rarely, it may develop in children under the age of 10 years. It is potentially a lifelong condition that may go in and out of remission. About 10% of MG cases are juvenile-onset.

What are the symptoms of myasthenia gravis?

The following are the most common symptoms of myasthenia gravis. However, each child may experience symptoms differently. Symptoms may include:

  • Babies with neonatal MG may be weak with a poor suck, and may have respiratory difficulty. A few babies may need the help of a mechanical breathing machine if their respiratory muscles are too weak to breathe on their own. Symptoms go away as the maternal antibodies disappear over time.
  • Congenital MG symptoms may begin in the first year, with generalized weakness in the arms and legs, and delays in motor skills such as crawling, sitting, and walking. Babies may have difficulty feeding and may have weak eyelids and poor head control.
  • Juvenile MG symptoms may begin gradually over weeks or months. The child may become excessively tired after very little activity, and begin to have problems chewing and swallowing. Drooping eyelids and lazy eye movements can cause vision problems.
  • Patients with myasthenia gravis can have attacks of increased weakness, even if they are receiving treatment. Such attacks require emergent medical evaluation.

The symptoms of myasthenia gravis may resemble other conditions. Always consult your child's doctor for a diagnosis.

Diagnosis & Tests

The diagnosis of myasthenia gravis is made after the sudden or gradual onset of specific symptoms and after diagnostic testing. During the physical examination, the doctor obtains a complete medical history of the child and may also ask if there is a family history of any medical problems.

A mainstay of the diagnosis of MG is through the performance of an electromyogram/nerve conduction study (EMG/NCS), which is a test that measures the electrical activity of a muscle or a group of muscles.   In addition, patients have a blood test for the antibodies associated with autoimmune MG.  An EMG/NCS can detect abnormal electrical muscle activity due to diseases and neuromuscular conditions. The diagnosis of MG may be confirmed with a Tensilon or Edrophonium test. With this test, a small amount of medicine (Tensilon or edrophonium chloride) is injected through an IV. If the child has MG, an immediate, but brief, increase in muscle strength is noted.

Other diagnostic tests that may be performed to help confirm the diagnosis of myasthenia gravis include:

  • Blood tests
  • Genetic tests. Diagnostic tests that evaluate for conditions that have a tendency to run in families.

Treatment & Care

Specific treatment for myasthenia gravis will be determined by your child's doctor based on:

  • Your child's age, overall health, and medical history
  • The extent of the condition
  • Your child's tolerance for specific medications, procedures, or therapies
  • Expectations for the course of the condition
  • Your opinion or preference

There is no cure for MG, but the symptoms can sometimes be controlled. Myasthenia gravis can be a lifelong medical condition, and the key to medically managing MG is early detection.

The goal of treatment is to alleviate signs and symptoms of weakness and to minimize the possibility of acute attacks of increased weakness, which can affect swallowing and breathing.

Treatment may include:

  • Medications (cholinesterase inhibitors, steroids, and immunosuppressants)
  • Thymectomy. This is the surgical removal of the thymus gland. The role of the thymus gland in MG is not fully understood, and the thymectomy may or may not improve a child's symptoms.
  • High-dose intravenous immune globulin
  • Plasmapheresis. A procedure that removes abnormal antibodies from the blood and replaces the child's blood with normal antibodies through donated blood.

The extent of the problems is dependent on the severity of the condition and the presence of other problems that could affect the child. In severe attacks, a breathing machine may be required to help the child breathe easier.

The health care team educates the family after evaluation and diagnosis on how to best care for their child at home and outlines specific clinical problems that require immediate medical attention by their doctor. A child with MG requires frequent medical evaluations throughout his life.

It is important to allow the child as much independent function and self care, especially with juvenile MG, as possible and to promote age-appropriate activities to ensure a sense of normalcy.