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Myofibrillar Myopathy via the LDB3 (ZASP) 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
11447 LDB3 81406 81406,81479 $990 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
11447LDB381406 81406,81479 $990 Order Options and Pricing

Pricing Comments

Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.

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 platform).

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

The Sanger Sequencing method for this test is NY State approved.

For Sanger Sequencing click here.

Turnaround Time

3 weeks on average for standard orders or 2 weeks 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

Myofibrillar myopathy (MFM) refers to a genetically heterogeneous group of disorders sharing a homogeneous morphological pattern and, most often, onset of clinical symptoms in adulthood. Stained with trichome, abnormal muscle fibers are seen containing hyaline structures and vacuoles that contain membrane fragments from disintegrated sarcomeric Z disc and myofibrils (Selcen et al. Brain 127:439-451, 2004). With electron microscopy, affected muscle fibers reveal progressive degeneration of myofibrils beginning at the Z-disk. Immunohistochemical staining of the structurally abnormal fibers reveals abnormal expression and accumulation of several proteins, including myotilin, desmin, alpha-B crystalline, dystrophin, and β-amyloid precursor protein (Selcen et al. 2004). Clinically, patients present in adulthood with proximal and distal weakness and in some cases with cardiomyopathy. Patients with LDB3-related MFM (OMIM 609452) demonstrate distal more than proximal weakness, peripheral neuropathy, and sometimes cardiac involvement (Selcen and Engel. Ann Neurol 57:269-276, 2005).

Genetics

Myofibrillar myopathy and dilated cardiomyopathy related to LDB3 are inherited as autosomal dominant disorders. The LIM domain-binding protein-3, or Zasp, interacts with alpha-actinin and protein kinase C, and is an integral component of the Z-disc. All variants thus far reported cause amino acid substitutions. Other genes involved with MFM include DES, MYOT, FLNC, CRYAB, and BAG3.

The LIM domain-binding protein-3 is coded by exons 1 - 16 of the LDB3 gene on chromosome 10q23. Four isoforms result from alternative splicing of the 16 exons.

Clinical Sensitivity - Sequencing with CNV PGxome

Among a cohort of 80 MFM patients diagnosed at the Mayo Clinic, only 46% have been found to have variants in one of the six known causative genes (Selcen and Engel, GeneReviews 2010). The relative frequencies of variants found in the Mayo Clinic cohort was LDB3 (14%), MYOT (13%), DES (8%), FLNC (4%), BAG3 (4%), and CRYAB (3%). Thus, MFM appears to be a genetically heterogeneous disorder and the clinical sensitivity for testing any of the known genes is likely low. In a study of 100 probands with dilated cardiomyopathy, six patients were found to have LDB3 variants (Vatta et al. J Amer Coll Cardiol 42:2014-2027, 2003).

Testing Strategy

This test provides full coverage of all coding exons of the LDB3 gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other 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

Patients with clinical features consistent with myofibrillar myopathy, demonstrated autosomal dominant inheritance, and a muscle biopsy with characteristic immunohistochemical and ultrastructural features. Individuals with idiopathic cardiomyopathy.

Gene

Official Gene Symbol OMIM ID
LDB3 605906
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Myofibrillar Myopathy, ZASP-Related AD 609452

Citations

  • Duygu Selcen, Andrew G Engel (2010). "Myofibrillar Myopathy."
  • Selcen D, Ohno K, Engel AG. 2004. Myofibrillar myopathy: clinical, morphological and genetic studies in 63 patients. Brain 127(Pt 2): 439-451. PubMed ID: 14711882
  • Selcen, D., Engel, A. G. (2005). "Mutations in ZASP define a novel form of muscular dystrophy in humans." Ann Neurol 57(2): 269-76. PubMed ID: 15668942
  • Vatta, M., et.al. (2003). "Mutations in Cypher/ZASP in patients with dilated cardiomyopathy and left ventricular non-compaction." J Am Coll Cardiol 42(11): 2014-27. PubMed ID: 14662268

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

If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.


Specimen Types

Specimen Requirements and Shipping Details

PGxome (Exome) Sequencing Panel

PGnome (Genome) Sequencing Panel

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ORDER OPTIONS

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View Ordering Instructions

1) Select Test Method (Platform)


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.
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