Description

Congenital myasthenic syndromes are a group of rare inherited diseases caused by a change in the gene that results in muscle weakness that worsens with physical activity. Any muscles that are used for the movement can be affected, including the muscles that control speech, chewing and swallowing, the view and the blinking, breathing, and walking.

There are many types of congenital myasthenic syndromes, depending on which gene is affected. The mutation also determines many of the signs and symptoms and the severity of the condition.

Congenital myasthenic syndromes are usually identified at birth or in early childhood and permanent conditions.

There is No cure for the congenital myasthenic syndromes. The medications usually are an effective treatment for the symptoms of muscle weakness. That drug depends on which gene is identified as the cause of congenital myasthenic syndrome. In rare cases, some children may have a mild form that does not need treatment.

Symptoms

Congenital myasthenic syndromes are usually identified at birth. But if the signs and symptoms are mild, the condition of not being identified until the child, or, rarely, at the beginning of adulthood.

Depending on the type of congenital myasthenic syndrome, the severity of the signs and symptoms vary greatly, ranging from a minor weakness in the inability to move. Some of the symptoms can be life-threatening.

Common to all of the congenital myasthenic syndromes is muscle weakness that worsens with physical activity. Any muscles that are used for the movement may be affected, but the most commonly affected muscles are those that control the movement of the eyelids and the eyes, and chewing and swallowing.

During infancy and early childhood, the progressive loss of the essential voluntary muscle activity occurs with the use of the muscles. Deterioration of the muscle weakness can result in:

  • The droopy eyelids and poor eye control, often with the double vision.
  • Difficulty chewing and swallowing.
  • Weakness of the facial muscles.
  • A weak cry.
  • Slurred or nasal speech.
  • Delayed crawling and walking.
  • Delay in the development of the wrist, hand and finger skills, such as brushing your teeth or combing your hair.
  • Difficulties to support the head in a vertical position.
  • Trouble breathing, shortness of breath and have short pauses in breathing, sometimes aggravated by infection, fever, or stress.

Depending on the type of congenital myasthenic syndrome, other signs and symptoms may include:

  • Skeletal deformities, such as the joints, the spine or foot deformities.
  • Unusual Facial features, such as the narrow jaw or wide eyes.
  • The hearing loss.
  • Weakness, numbness and pain, usually in hands and feet.
  • Seizures.
  • Kidney problems.
  • The cognitive impairment, which is rarely.

When to see a doctor

Talk with your doctor if you observe any signs that appear earlier in the child or if you have any concerns about your own signs or symptoms.

Causes

Caused by any of more than 30 genes identified, the type of congenital myasthenic syndrome depends on which gene is affected.

Congenital myasthenic syndromes are classified by the site of which is affected in the neuromuscular junction ― the area that provides signals (impulses) between nerve cells and muscle cells to trigger the movement (synapses). Disrupts the signals that cause the loss of muscle function can occur in different places:

  • The nerve cells where the impulse is initiated (presynaptic).
  • Space between the nerve and muscle cells (synaptic).
  • Muscle cells, where the impulse is received (postsynaptic), the most common location.

Some types of congenital myasthenic syndromes are the result of congenital disorders of glycosylation. Glycosylation is a complex chemical process that plays a role in the regulation of the communication between the cells. Glycosylation defects can affect the transmission of signals from the nerve cells to the muscles.

Congenital myasthenic syndromes are most commonly inherited in an autosomal recessive pattern. That means that both parents must be carriers, but often do not show signs of the disease. The child inherits two copies of the abnormal gene — one from each parent. If children inherit only one copy, which will not develop the syndrome, but they are going to be carriers and possibly transmit the gene to their own children.

Rarely, congenital myasthenic syndromes can be inherited in an autosomal dominant pattern, which means that only one parent passes on the gene affected. In some cases, the affected gene occurs randomly and is not inherited. In other cases, there is no gene can be identified.

Risk factors

A child is at risk of a congenital myasthenic syndrome, if both parents are carriers of a gene known to cause the syndrome. The child inherits two copies of the gene. Children who inherit only one copy of the gene from one parent usually will not develop the syndrome, but will be carriers.

Diagnosis

Your doctor will do a physical exam, including a neurological examination and review of symptoms and medical history to check if there are signs of a congenital myasthenic syndrome. Your doctor may also order tests to exclude other conditions with similar symptoms.

The following tests can help to diagnose a congenital myasthenic syndrome and to determine the severity of the disorder.

  • Blood tests. A blood test can reveal the presence of abnormal antibodies that disrupt signals between nerves and muscles. Other blood tests may be useful to rule out other conditions that can have similar symptoms.
  • Electromyography (EMG). The EMG is a diagnostic procedure to assess the health of muscles and the nerve cells that control them, called motor neurons. EMG results can reveal nerve dysfunction, muscle dysfunction or problems with the transmission of signals between the nerves and the muscles.
  • Repetitive nerve stimulation. In this nerve conduction study, electrodes are placed on the skin over the muscles to be tested. Small pulses of electricity are sent through the electrodes to measure the ability of the nerve to send a signal to the muscle. The nerve is tested several times to see if their ability to send signals worsens with fatigue.
  • The genetic testing. This may identify the specific affected gene that is responsible for the congenital myasthenic syndrome, and that treatments may be beneficial.
  • Cholinesterase test challenge. Cholinesterase inhibitor drugs, such as pyridostigmine, is given to determine if the improvement in muscle fatigue occurs with repetitive movement.
  • Other tests. These may include pulmonary function tests to assess the breathing and oxygenation, a sleep study to assess the breathing and apnea during sleep, or a muscle biopsy to look at the muscle fibers.

Genetic testing

Genetic testing involves examining your DNA, the chemical database that carries instructions for your body's functions. Genetic testing can reveal changes, sometimes called mutations in the genes that cause congenital myasthenic syndromes. Genetic testing may also be recommended to family members.

Talk with your doctor, a medical geneticist or a genetic counselor about why the test is being done and how the results may affect you is an important step in the process of genetic testing.

Treatment

In rare cases, some children with mild congenital myasthenic syndromes may not need treatment.

Medicine

The medications are not a cure, but it can enhance the muscle contraction and muscle strength in people with congenital myasthenic syndromes. What drugs are effective depends on the type of affected gene. The medications that are effective for a type of down syndrome may be ineffective for another type, so that genetic testing is recommended before starting medications.

Medication treatment options may include:

  • Acetazolamide
  • 3,4-diaminopyridine (3,4-DAP), marketed as amifampridine (Firdapse, Ruzurgi)
  • Albuterol
  • Ephedrine
  • Fluoxetine (Prozac)
  • Neostigmine (Bloxiverz)
  • Pyridostigmine (Mestinon, Regonol)

Supportive treatments

Supportive treatments depend on the type and severity of the congenital myasthenic syndrome. The options may include:

  • Therapies. Physical, speech and occupation therapy can help to maintain the function. The therapy may also offer supportive devices, such as wheelchairs, walkers, and of the hand and the arm support.
  • Respiratory support. Some congenital myasthenic syndromes can result in pauses in breathing is called sleep apnea. The use of an apnea monitor can be recommended. Noninvasive positive pressure ventilation such as continuous positive airway pressure (CPAP) mask and the machine, it can be used to support the breathing and oxygenation. In some cases, intubation and the use of mechanical ventilation may be necessary.
  • Support for breastfeeding. Problems with chewing and swallowing may require a supplement of nutrition. Enteral nutrition, also known as tube feeding, is a way of delivering nutrition directly into the stomach or the small intestine. Your doctor may recommend a procedure for placing a tube through the skin into the abdomen and into the stomach (gastrostomy) or in the small intestine (jejunostomy).
  • Surgery. For serious orthopaedic deformities, as in the spine or feet, surgical correction may be necessary.

Course of care

Regular follow-up appointments with a team of medical professionals provides continuing care, and can help prevent some complications. Your health care team can link you with the appropriate support, for home, school or work.

The pregnancy can worsen the symptoms of the congenital myasthenic syndromes, so close monitoring during and after pregnancy is necessary.

Coping and support

The care of a child or family member with a congenital myasthenic syndrome can be stressful and tiring. You may not know what to expect, and you may worry about your ability to provide the necessary care.

Please keep in mind these steps to prepare yourself:

  • Learn about the disorder. Learn as much as you can about congenital myasthenic syndromes. Then you can make the best decisions and to be an advocate for you or your child.
  • To find a team of trusted professionals. You will have to make important decisions about care. Medical centers with the expertise of the teams can offer information on the disorder, to coordinate your care among specialists, help you evaluate options and provide treatment.
  • Search for other families. Talking with people who are dealing with similar issues can provide information and emotional support. Ask your doctor about support groups in your community. If a group is not for you, maybe your doctor can put you in contact with a family who has dealt with the disorder. Or you may be able to find an individual or support group online.
  • Consider the possibility of support for caregivers. Ask for or accept help in the care of your loved one when needed. Additional options of support could include the question about the sources of respite care, asking for the support of family and friends, and take the time for their own interests and activities. Counseling with a mental health professional can help with the adaptation and coping.

Preparing for your appointment

Make an appointment with your doctor if you notice signs or symptoms common to congenital myasthenic syndromes. After the initial evaluation, you may be referred to a physician trained in the evaluation and treatment of these conditions.

Here's some information to help you prepare for your appointment, as well as what to expect from your doctor.

What you can do

You may want to prepare the answers to these questions:

  • What are the symptoms of notice?
  • When did the symptoms begin?
  • Is there something that the symptoms better or worse?
  • Have someone in your family had a congenital myasthenic syndrome?

What to expect from your doctor

After obtaining detailed information about the symptoms and the medical history of your family, your doctor may order tests to help with diagnosis and treatment plan.

Symptoms and treatment of the Congenital myasthenic syndromes