Mayo Clinic discovers cause of a frequently fatal myasthenic syndrome affecting children

Rochester, MN -- A Mayo Clinic study published in today’s edition of the Proceedings of the National Academy of Sciences has identified a gene mutation in children who suffer from congenital myasthenic syndromes (CMS) associated with episodic respiratory distress and apnea.

The gene mutation affects the enzyme that produces acetyl choline, the chemical that transmits impulses from nerve to muscle, so that the mutated enzyme becomes inefficient or is not produced in adequate amounts.

While this form of CMS is rare, it often results in sudden death in the affected children. Confirming this condition in children who show other risk factors (including a family history) allows physicians and parents to provide treatments that will prevent the attacks.

Congenital myasthenic syndromes with episodic apnea cause patients, most often young children, to experience episodes in which they have a sudden loss of ability to breathe or swallow. Episodes are often preceded by undue exertion, fever or excitement but also can occur spontaneously or during the night. As children grow older, the episodes become less frequent and milder, and are rarely fatal after age 15. The condition is hereditary and more than one child in a family can have the condition.

"What we have developed is a way at the molecular level to confirm a diagnosis that a child has this condition," says Andrew Engel, M.D., a Mayo Clinic neurologist and researcher. "This is not a routine screening test, but rather a test that confirms what is suggested by a careful clinical history, neurologic evaluation, and clinical electrophysiologic studies. It will be another tool to assist physicians and families in caring for young CMS children.

NOTE: Copies of the study may be obtained from the Proceedings of the National Academy of Sciences by calling 202-334-3741.

Dr. Engel will be available to respond to inquiries beginning on Monday, Feb. 12, 2001.

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e-mail: newsbureau@mayo.edu