Nondystrophic Myotonia NGS Panel

  • Panel Description
  • Test Description
  • CPT Codes
  • Resources

Panel Description

Nondystrophic Myotonia
Myotonia Congenita
Hyperkalemic Periodic Paralysis
Paramyotonia Congenita

Nondystrophic myotonias are a group of disorders characterized by skeletal muscle excitability leading to failure of muscle relaxation after activation or contraction leading to stiffness. Individuals with these conditions may experience periodic cramping followed by weakness, stiffness, and fatigue. Temporary paralysis may occur in some cases. Triggers may include cold, stress, or exercise. These symptoms often appear early in life between infancy and childhood, but onset may be in adulthood in rare cases. Unlike its counterpart, dystrophic myotonia, nondystrophic myotonias are not usually progressive and most often do not involve other organ systems.

Nondystrophic myotonias are often linked to pathogenic variants in the SCN4A or CLCN1 genes. Our panel also includes evaluation of genes associated with related conditions such as rippling muscle disease, periodic paralysis, and Schwartz-Jampel syndrome, a syndromic condition characterized by myotonia.

This panel may be appropriate for anyone with a personal or family history of nondystrophic myotonia. Patients exhibiting symptoms of myotonia without any signs of progressive muscle-weakening can also benefit from this test. Nondystrophic myotonia should be a consideration particularly when the associated symptoms are triggered by cold temperatures, exercise, viral infection, eating certain foods, or fasting.

Nondystrophic myotonia is extremely rare and there are no FDA-approved therapeutic treatments for it at this time. This also makes it harder to diagnose as it is frequently overlooked. Genetic testing is useful not only for assisting with diagnoses but also for identifying the specific type of nondystrophic myotonia present and developing an appropriate treatment plan.

Genetic testing for nondystrophic myotonia can:
  • Establish or confirm the appropriate diagnosis
  • Identify risks for additional related symptoms
  • Connect patients to relevant resources & support
  • Result in more personalized treatment and symptom management
  • Inform family members about their own risk factors
  • Provide options for family planning

Test Description

  • Sequencing
  • Del/Dup
  • Rush / STAT
  • Exclude VUS
  • MCC
  • Duo/Trio
3-5 weeks
Call for details
96% at 20x
Blood (two 4ml EDTA tubes, lavender top) or Extracted DNA (3ug in EB buffer) or Buccal Swab or Saliva (kits available upon request)
All sequencing technologies have limitations. This analysis is performed by Next Generation Sequencing (NGS) and is designed to examine coding regions and splicing junctions. Although next generation sequencing technologies and our bioinformatics analysis significantly reduce the contribution of pseudogene sequences or other highly-homologous sequences, these may still occasionally interfere with the technical ability of the assay to identify pathogenic variant alleles in both sequencing and deletion/duplication analyses. Sanger sequencing is used to confirm variants with low quality scores and to meet coverage standards. If ordered, deletion/duplication analysis can identify alterations of genomic regions which include one whole gene (buccal swab specimens and whole blood specimens) and are two or more contiguous exons in size (whole blood specimens only); single exon deletions or duplications may occasionally be identified, but are not routinely detected by this test. Identified putative deletions or duplications are confirmed by an orthogonal method (qPCR or MLPA). This assay will not detect certain types of genomic alterations which may cause disease such as, but not limited to, translocations or inversions, repeat expansions (eg. trinucleotides or hexanucleotides), alterations in most regulatory regions (promoter regions) or deep intronic regions (greater than 20bp from an exon). This assay is not designed or validated for the detection of somatic mosaicism or somatic mutations.

CPT Code 81185, 81479x2

NOTE:  The CPT codes listed on the website are in accordance with Current Procedural Terminology, a publication of the American Medical Association. CPT codes are provided here for the convenience of our clients. Clients who bill for services should make the final decision on which codes to use.


Nondystrophic Myotonia