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Study Description

NMD are rare ion channel disorders. The optimal management and treatment of these disorders are not known. This multi-center proposal will allow the prospective collection of standardized data from a critical number of patients to help better define the clinical features of NDM. The data will also be used to establish clinically relevant endpoints for use in therapeutic trials. The identification and genetic characterization of patients will facilitate recruitment of participants for future therapeutic trials. Ultimately, the information gained will lead to the improvements in the treatment and management of NMD with an associated reduction in morbidity and improvement in patient quality of life.

  • Study Type: Longitudinal
  • Number of study subjects that have individual level data available through Authorized Access: 95

Authorized Access
Publicly Available Data (Public ftp)

Connect to the public download site. The site contains release notes and manifests. If available, the site also contains data dictionaries, variable summaries, documents, and truncated analyses.

Study Inclusion/Exclusion Criteria

Inclusion Criteria (Participants must meet 1,2,3,4,5;or1,2,3,4,6):

  1. At least 6 years of age.
  2. Clinical symptoms or signs suggestive of myotonic disorders.
  3. Presence of myotonic potentials on electromyography (EMG).
  4. Persistence of symptoms and signs after discontinuation of medications that produce myotonia:
    • a. Fibrate acid derivatives
    • b. Hydroxymethylglutaryl CoA reductase inhibitors
    • c. Chloroquine
    • d. Colchicine
  5. Absence of features suggestive of myotonic dystrophy 1
    • a. Ptosis
    • b. Temporal wasting
    • c. Mandibular weakness
    • d. Cataracts occurring before age 50
    • e. Evidence of multisystem defects (cardiac conduction defects, hypogonadism)
  6. Or negative genetic test for DM1 (CTG repeat < 100) if patient has clinical feature/s as in criteria 5.

Exclusion Criteria

  1. Inability or unwillingness to provide informed consent.
  2. Other neurologic conditions that might affect the assessment of the study measurements.
  3. Genetically confirmed DM1 (CTG repeat >100).

Study History

The myotonic muscle disorders represent a heterogeneous group of clinically similar diseases sharing the feature of myotonia: delayed relaxation of muscle after voluntary contraction (action myotonia) or mechanical stimulation (percussion myotonia). In classic myotonia, the myotonia improves as muscles warm up, whereas in paradoxical myotonia (paramyotonia) it worsens with repeated muscle contractions. Electrophysiologically, myotonia is characterized by the repetitive electrical activity of muscle fibers.

Nondystrophic types of myotonia can be identified by their clinical features and molecular defect. The nondystrophic myotonias are clinically heterogeneous and have been traditionally divided into three categories: hyperkalemic periodic paralysis, paramyotonia congenita, and myotonia congenita.

Selected publications
Diseases/Traits Related to Study (MESH terms)
Links to Related Resources
Authorized Data Access Requests
Study Attribution