Congenital myasthenic syndromes are hereditary (genetic) conditions resulting from a defect at the junction where your nerve stimulates muscle activity that results in muscle weakness.

Congenital myasthenic syndromes may affect your nerve cells (presynaptic), your muscle cells (postsynaptic), or the space between your nerve and muscle cells (synaptic).

  • Expertise and experience. Mayo Clinic doctors have extensive experience in diagnosing and treating congenital myasthenic syndromes, although they are rare conditions. Congenital myasthenic syndromes are estimated to occur in 2.5 to 12.5 out of 1,000,000 people. Mayo Clinic doctors evaluate and treat about 10 people with congenital myasthenic syndromes each year.
  • Teamwork. Mayo Clinic doctors trained in nervous system conditions (neurologists), genetic conditions (medical geneticists), musculoskeletal conditions (orthopedic surgeons), eye conditions (ophthalmologists), anesthesiology (anesthesiologists) and other areas work together to evaluate and treat people with congenital myasthenic syndromes.
  • Research. Mayo Clinic doctors study genes involved in congenital myasthenic syndromes and develop therapies to treat congenital myasthenic syndromes.
  • Individualized treatment. Your doctors will work with you to create an individualized treatment plan to help you manage your condition.
  • Efficiency. In Mayo Clinic's system, your testing and treatment usually can be done in days, not weeks.

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Mayo Clinic doctors trained in nervous system conditions (neurologists) and other areas diagnose congenital myasthenic syndromes.

Congenital myasthenic syndromes may be difficult to diagnose. Symptoms vary and may be similar to those of myasthenia gravis and other conditions. Doctors at Mayo Clinic have experience diagnosing congenital myasthenic syndromes.

To diagnose congenital myasthenic syndromes, your doctor will review your medical history and your family medical history. Your doctor will perform a thorough physical and neurological examination and review your signs and symptoms, including signs of muscle weakness with repeated activity.

Your doctor and other specialists may also conduct several tests to diagnose congenital myasthenic syndromes and rule out other conditions.

Tests may include:

  • Blood tests. A blood test checks to see if abnormal antibodies may be blocking your muscle receptors from nerve signals and causing your symptoms.
  • Electromyography (EMG). Electromyography (EMG) measures electrical activity within muscles or individual muscle fibers (single-fiber EMG).
  • Nerve conduction studies. Nerve conduction studies measure the strength of muscle contraction by stimulating nerves with a small electrical impulse applied to your skin. The application of repeat impulses can reveal specific muscle weakness.
  • Genetic testing. Your doctor may recommend genetic testing for the mutation present in congenital myasthenic syndromes and for other neurological conditions with similar symptoms.

Mayo Clinic doctors trained in nervous system conditions (neurologists) and other areas treat congenital myasthenic syndromes.

Your doctor will provide you or your child with individualized care to help you manage your symptoms. Your treatment may vary depending on the type of congenital myasthenic syndrome.

Treatment may include:

  • Medications. Depending on the type of congenital myasthenic syndrome, your treatment may include pyridostigmine (Regonol, Mestinon), 3,4-diaminopyridine (amifampridine phosphate), quinidine sulfate, fluoxetine (Sarafem, Prozac), ephedrine or other medications. These medications may help improve signals between your nerves and muscles.
  • Physical therapy. You may have physical therapy to help manage your symptoms.
  • Follow-up care and support. Doctors will coordinate your follow-up care with your primary doctor. You may work with a genetic counselor.

Mayo Clinic works with hundreds of insurance companies and is an in-network provider for millions of people. In most cases, Mayo Clinic doesn't require a physician referral. Some insurers require referrals or may have additional requirements for certain medical care. All appointments are prioritized on the basis of medical need.

Specialists in neurology care for adults who have congenital myasthenic syndromes at Mayo Clinic in Arizona.

For appointments or more information, call the Central Appointment Office at 800-446-2279 (toll-free) 8 a.m. to 5 p.m. Mountain Standard Time, Monday through Friday or complete an online appointment request form.

Specialists in neurology care for adults who have congenital myasthenic syndromes at Mayo Clinic in Florida.

For appointments or more information, call the Central Appointment Office at 904-953-0853 8 a.m. to 5 p.m. Eastern time, Monday through Friday or complete an online appointment request form.

Specialists in neurology and pediatric neurology care for children and adults with congenital myasthenic syndromes at Mayo Clinic in Minnesota.

Doctors in the Neuromuscular Disease Group evaluate and treat people with neuromuscular disorders and conduct research.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

Pediatric specialists in neurology, orthopedic surgery, ophthalmology and other areas treat children with congenital myasthenic syndromes.

For appointments or more information, call the Central Appointment Office at 507-538-3270 7 a.m. to 6 p.m. Central time, Monday through Friday or complete an online appointment request form.

See information on patient services at the three Mayo Clinic locations, including transportation options and lodging.

Mayo Clinic researchers in nervous system conditions (neurologists), hereditary conditions (medical geneticists) and other areas conduct research in congenital myasthenic syndromes.

Doctors conduct ongoing research studying prevention, genetics, diagnostic techniques and treatment options for congenital myasthenic syndromes. Learn more about research in neuromuscular diseases and ALS on the neurology research website.

See a list of publications by Mayo Clinic authors on congenital myasthenic syndromes on PubMed, a service of the National Library of Medicine.

Feb. 24, 2014