Congenital myasthenic syndrome

Causes

This type of myasthenia doesn’t involve the immune system at all. It is caused by an inherited genetic fault.

Symptoms

As this is a genetic condition the mutation in a wide range of genes may give rise to the picture of congenital myasthenia. Symptoms can range from mild cases of droopy eyelids to the patient requiring wheelchair use. The condition is usually noticeable from birth although in some cases it may only become obvious in teens. People will have obvious weaknesses in facial movement. Infants may be slow in reaching milestones such as walking. There may be times when a child’s breathing becomes shallow (often as a result of an infection).

Diagnosis

Diagnosis is based on careful evaluation, EMG studies and DNA tests. Children may be referred to one of the specialist centres for assessment. These are in London, Newcastle and Oxford.

Treatment

Non-invasive ventilation: Some children with congenital myasthenia may need help with night time breathing difficulties. This might include non-invasive ventilation in bed.

Pyridostigmine: Some people can control their myasthenia with enzyme blocking drugs. The drug boosts the message from the nerve to the muscle.

Side effects: Stomach cramps, digestive problems and an urgent need to urinate Find out more

3,4-diamino-pyridine’ DAP: This works by boosting the feeble ACh release . It makes the electrical messages in the nerves last longer. DAP has to be used carefully; it is sometimes combined with pyridostigmine.

Side effects: DAP can cause short-term tingling around the mouth or in the fingers and toes. At high doses it can also affect the brain causing anxiety, over-excitement and even epileptic fits but this is very rare below 100 mg per day.

Ephedrine and salbutamol: these drugs can improve muscle strength. The effect of ephedrine is often delayed and the improvement occurs over a period of months.

Side effects: The most common side effects of both salbutamol and ephedrine are fine tremor, anxiety, headaches, muscle cramps, dry mouth and palpitations.

Quinidine or fluoxetine: these drugs may help the faulty AChRs to close in some patients.

Side effects: Careful monitoring is essential as there are risks of cardiac side effects as well as mood changes.

Drugs that can make myasthenia worse

Outcomes for people with CMS

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