Congenital myasthenic syndrome with episodic apnea

Overview

A disorder characterized by muscular weakness.

Symptoms

* Fluctuating ptosis
* Poor infant sucking
* Weak infant cry
* Infant feeding difficulties
* Secondary respiratory infections
* Weakness after 10 years
* Fatigue

Causes

Myasthenia gravis causes a failure in transmission of nerve impulses at the neuromuscular junction. Theoretically, such impairment may result from an autoimmune response, ineffective acetylcholine release, or inadequate muscle fiber
response to acetylcholine. (See Impaired transmission in myasthenia gravis.)

Myasthenia gravis affects 3 of every 10,000 people at any age, but it’s more common in young women and older men. About 20% of neonates born to mothers with myasthenia gravis have transient (or occasionally persistent) myasthenia. This disease may coexist with immunologic and thyroid disorders; about 15% of patients with myasthenia gravis have thymomas. Remissions occur in about 25% of patients.

Prognosis

Prognosis of Congenital myasthenic syndrome with episodic apnea: condition often improves with age

Treatment

Treatment is symptomatic. Anticholinesterase drugs, such as neostigmine and pyridostigmine, counteract fatigue and muscle weakness and allow about 80% of normal muscle function. However, these drugs become less effective as the disease worsens. Corticosteroids may relieve symptoms. Immunosuppressants are also used. Plasmapheresis is used in severe myasthenic exacerbation.

Patients with thymomas require thymectomy, which may cause remission in some cases of adult-onset myasthenia. Acute exacerbations that cause severe respiratory distress necessitate emergency treatment. Tracheotomy, positive-pressure ventilation, and vigorous suctioning to remove secretions usually produce improvement in a few days. Because anticholinesterase drugs aren’t effective in myasthenic crisis, they’re stopped until respiratory function improves. Myasthenic crisis requires immediate hospitalization and vigorous respiratory support.