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Congenital Myopathy via the MYO18B Gene

Summary and Pricing

Test Method

Exome Sequencing with CNV Detection
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
7229 MYO18B 81479 81479,81479 $890 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
7229MYO18B81479 81479,81479 $890 Order Options and Pricing

An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.

Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing backbone).

Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing backbone).

Turnaround Time

18 days on average for standard orders or 13 days on average for STAT orders.

Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.

Targeted Testing

For ordering sequencing of targeted known variants, go to our Targeted Variants page.

EMAIL CONTACTS

Genetic Counselors

Geneticist

  • Angela Gruber, PhD

Clinical Features and Genetics

Clinical Features

Congenital myopathy (CM) refers to a genetically and clinically heterogeneous group of disorders characterized by muscle weakness and hypotonia at birth or in infancy. Five forms of congenital myopathy are recognized by the International Standards of Care Committee for Congenital Myopathies (North et al. 2014. PubMed ID: 24456932): nemaline myopathy, core myopathy, centronuclear myopathy, myosin storage myopathy, and congenital fiber type disproportion. The clinical course of congenital myopathy is typically static or slowly progressive. Lower facial weakness leading to an open mouth is often the first sign of congenital myopathy in the newborn. Ptosis and ophthalmoplegia are also common. See North et al. (2014) for diagnostic strategies and a comprehensive review of the congenital myopathies.

MYO18B-related congenital myopathies have been reported in at least 6 individuals to date, with 4 of these 6 also presenting with Klippel-Feil anomaly. All cases have been homozygous or compound heterozygous for loss of function variants in MYO18B (Alazami et al. 2015. PubMed ID: 25748484; Malfatti et al. 2015. PubMed ID: 27858739; Schieffer et al. 2019. PubMed ID: 31195167; Brunet et al. 2020. PubMed ID: 32184166; Mihaylova et al. 2020. PubMed ID: 32637634). Klippel-Feil syndrome is characterized by fusion of the cervical spine which can result in scoliosis but can also include limited neck mobility and low posterior hairline. All reported patients presented with congenital myopathy and dysmorphic features; however, Klippel-Feil anomaly was not present in all cases (See Table in Mihaylova et al. 2020. PubMed ID: 32637634; Malfatti et al. 2015. PubMed ID: 27858739). Clinical features include generalized muscle weakness, hypotonia, feeding problems, delayed motor milestones, facial weakness, dysmorphic features, and, in some cases, cardiac findings. One case presented on prenatal ultrasound with micrognathia, cleft palate, and bilateral clinodactyly (Brunet et al. 2020. PubMed ID: 32184166).

Genetic testing may aid in establishing a differential diagnosis and may assist reproductive planning.

Genetics

Pathogenic variants in the MYO18B gene are associated with autosomal recessive congenital myopathy with or without Klippel-Feil anomaly. Established pathogenic variants include nonsense and small, frameshifting deletions and duplications. Missense variants have been reported; however, evidence for pathogenicity of these variants is limited at this time. All reported variants have been inherited from a carrier parent. No structural variants have been reported. Of note, a frameshift variant in the last exon that results in a truncated protein has been reported in a patient with nemaline myopathy and cardiomyopathy while other reported patients do not present with cardiac findings (Malfatti et al. 2015. PubMed ID: 27858739). 

MYO18B encodes a non-conventional myosin that is predominantly expressed in skeletal and cardiac muscle. MYO18B protein localizes at the sacromeric Z-line and implies a possibly role in muscle contractile function. Knockout of MYO18B in zebrafish results in disrupted sarcomeric assembly in skeletal muscles (Gurung et al. 2017. PubMed ID: 27879346). MYO18B has been cited as a non-essential gene for growth of human tissue culture cells (Online Gene Essentiality).

Clinical Sensitivity - Sequencing with CNV PGxome

The clinical sensitivity is difficult to estimate, as to date, a limited number of cases have been described in the literature. Analytical sensitivity should be high as all pathogenic variants reported to date are detectable by sequencing and NGS copy number variant analysis.

Testing Strategy

This test is performed using Next-Gen sequencing with additional Sanger sequencing as necessary.

This test provides full coverage of all coding exons of the MYO18B gene plus 10 bases flanking noncoding DNA in all available transcripts in addition to non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as ≥20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).

Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).

Indications for Test

Candidates for this test are patients with clinical features consistent with a congenital myopathy and Klippel-Feil anomaly. Targeted testing is indicated for family members of patients who have known pathogenic variants in MYO18B. This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in MYO18B.

Gene

Official Gene Symbol OMIM ID
MYO18B 607295
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Citations

  • Alazami et al. 2015. PubMed ID: 25748484
  • Brunet et al. 2020. PubMed ID: 32184166
  • Gurung et al. 2017. PubMed ID: 27879346
  • Malfatti et al. 2015. PubMed ID: 27858739
  • Mihaylova et al. 2020. PubMed ID: 32637634
  • North et al. 2014. PubMed ID: 24456932
  • Online GEne Essentiality Database (OGEE).
  • Schieffer et al. 2019. PubMed ID: 31195167

Ordering/Specimens

Ordering Options

We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.

myPrevent - Online Ordering

  • The test can be added to your online orders in the Summary and Pricing section.
  • Once the test has been added log in to myPrevent to fill out an online requisition form.
  • PGnome sequencing panels can be ordered via the myPrevent portal only at this time.

Requisition Form

  • A completed requisition form must accompany all specimens.
  • Billing information along with specimen and shipping instructions are within the requisition form.
  • All testing must be ordered by a qualified healthcare provider.

For Requisition Forms, visit our Forms page


Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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ORDER OPTIONS

View Ordering Instructions

1) Select Test Method (Backbone)


1) Select Test Type


2) Select Additional Test Options

STAT and Prenatal Test Options are not available with Patient Plus.

No Additional Test Options are available for this test.

Note: acceptable specimen types are whole blood and DNA from whole blood only.
Total Price: $
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