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Congenital Disorders of Glycosylation, Type Ii (CDG Ii) via the ALG2 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
8969 ALG2 81479 81479,81479 $990 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
8969ALG281479 81479,81479 $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

  • Hongjie Chen

Clinical Features and Genetics

Clinical Features

Congenital disorders of glycosylation (CDGs) are a clinically heterogeneous group of inborn errors of metabolism that are characterized by defects in protein or lipid glycosylation, a form of post-translational modification. Consequently, the majority of these disorders demonstrate multi-system involvement. These disorders can be further differentiated into several categories depending upon what part of the glycosylation pathway has been disrupted: protein N-linked protein glycosylation defects, which are the most common; O-linked protein glycosylation defects; glycolipid and glycosylphosphatidylinositol (GPI) anchor defects; or multi-pathway defects (Brasil et al. 2018. PubMed ID: 29702557; Jaeken. 2017. PubMed ID: 28484880; Scott et al. 2014. PubMed ID: 24831587).

Fewer than 10 cases of CDG Ii, an N-linked glycosylation defect, have been reported in the literature to date (Cossins et al. 2013. PubMed ID: 23404334; Thiel et al. 2003. PubMed ID: 12684507; Asteggiano et al. 2018. PubMed ID: 30397276). Three probands presented with a multisystem disorder characterized by developmental and intellectual disability, bilateral iris colobomas, unilateral cataract, infantile spasms, and hypsarrhythmia (Thiel et al. 2003. PubMed ID: 12684507; Asteggiano et al. 2018. PubMed ID: 30397276). Two of these individuals also presented with additional features, including severe microcephaly, dysmorphism, bilateral epicanthus, bilateral convergent strabismus, and abnormal MRI findings such as hyperintensity in the basal ganglia and periventricular white matter in addition to thinning of the corpus callosum (Asteggiano et al. 2018. PubMed ID: 30397276).

Affected individuals from two other families, however, presented predominantly with a congenital myasthenic syndrome characterized by delayed motor milestones, hypotonia (primarily proximal muscle weakness), mild facial weakness, contractures of the knees, distal joint laxity, bilateral pes planus, and high arched palate (Cossins et al. 2013. PubMed ID: 23404334). Most of the patients never achieved ambulation. In addition, a muscle biopsy taken from one proband exhibited a severe reduction in ALG2 protein.

Genetics

Congenital disorder of glycosylation type Ii is inherited in an autosomal recessive manner. Most of the causative variants reported in this gene to date are missense; however, one small single basepair deletion and one in-frame indel have been described (HGMD; Asteggiano et al. 2018. PubMed ID: 30397276).

The ALG2 gene encodes a mannosyltransferase that catalyzes the transfer of mannose residues onto Man1GlcNAc2-PP-dolichol (Thiel et al. 2003. PubMed ID: 12684507).

Clinical Sensitivity - Sequencing with CNV PGxome

Due to the low incidence of this disorder clinical sensitivity cannot be estimated. All coding and non-coding regions of the ALG2 gene that harbor causative variants reported in the Human Gene Mutation Database (HGMD; http://www.hgmd.cf.ac.uk/) as of 08/05/2019 are covered in this test.

Testing Strategy

This test provides full coverage of all coding exons of the ALG2 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

Candidates for this test include individuals with clinical symptoms consistent with CDG Ii or individuals with a CDG-I pattern upon isoelectric focusing of serum transferrin, particularly after more common forms of CDG-I have been ruled out (particularly PMM2 gene sequencing) (Thiel et al. 2003. PubMed ID: 12684507). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in ALG2.

Gene

Official Gene Symbol OMIM ID
ALG2 607905
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Related Test

Name
Congenital Disorders of Glycosylation (CDG) Panel (Types Id, Ie, If, Ig, Ih, Ii)

Citations

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

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View Ordering Instructions

1) Select Test Method (Platform)


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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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