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Congenital Disorders of Glycosylation, Type Ic (CDG Ic) via the ALG6 Gene

Summary and Pricing

Test Method

Sequencing and CNV Detection via NextGen Sequencing using PG-Select Capture Probes
Test Code Test Copy GenesTest CPT Code Gene CPT Codes Copy CPT Codes Base Price
ALG6 81479 81479,81479 $990
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
7863ALG681479 81479,81479 $990 Order Options and Pricing

Pricing Comments

Testing run on PG-select capture probes includes CNV analysis for the gene(s) on the panel but does not permit the optional add on of exome-wide CNV analysis. Any of the NGS platforms allow reflex to other clinically relevant genes, up to whole exome or whole genome sequencing depending upon the base platform selected for the initial test.

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

This test is also offered via a custom panel (click here) on our exome or genome backbone which permits the optional add on of exome-wide CNV or genome-wide SV analysis.

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.


Genetic Counselors


  • 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: 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).

CDG Ic, an N-linked glycosylation defect, is the second-most prevalent CDG after CDG Ia (PMM2 deficiency), and generally results in a milder clinical course (Haeuptle et al. 2009. PubMed ID: 19862844; Morava et al. 2016. PubMed ID: 27287710). Approximately 90 cases have been reported in the literature to date (Morava et al. 2016. PubMed ID: 27287710; Medrano et al. 2019. PubMed ID: 30653653). Affected individuals commonly present in infancy or early childhood with a combination of developmental delay, hypotonia (predominantly proximal muscle weakness), speech disability, and epilepsy, while other features such as failure to thrive, ataxia, nystagmus, strabismus, gastrointestinal disturbances, progressive microcephaly, coagulopathy, dysmorphic features, behavioral abnormalities (autistic behavior and/or severe mood swings), abnormal fat distribution, and elevated liver transaminases may be variable (Morava et al. 2016. PubMed ID: 27287710). MRI findings (including vermis hypoplasia and/or cerebellar atrophy) have been described in a subset of patients, as well as skeletal abnormalities such as brachydactyly or arachnodactyly (Morava et al. 2016. PubMed ID: 27287710; Hanefeld et al. 2000. PubMed ID: 10832578; Ichikawa et al. 2013. PubMed ID: 23044053; Drijvers et al. 2010. PubMed ID: 20447155).


Congenital disorder of glycosylation type Ic is inherited in an autosomal recessive manner. Most of the causative variants reported in this gene to date are missense; however, one nonsense variant, three splicing variants, three small in-frame deletions, two single basepair duplications, and one large deletion have also been described (Human Gene Mutation Database). Several in-frame deletions reported in independent patients lead to the removal of the same critical p.Ile299 residue (p.Ile299del) (Haeuptle et al. 2009. PubMed ID: 19862844).

The recurrent p.Ala333Val pathogenic variant has been described in individuals of European, Japanese, and Indian ancestry, and is speculated to have arisen as a founder mutation from an isolated White population (Vuillaumier-Barrot et al. 2005. PubMed ID: 15771971; Dercksen et al. 2013. PubMed ID: 23430515; Ichikawa et al. 2013. PubMed ID: 23044053; Newell et al. 2003. PubMed ID: 12855228). In one study, this common pathogenic variant (p.Ala333Val) was found in the homozygous state in eight of eleven CDG Ic patients, while other pathogenic variants in ALG6 were identified in the remaining three patients (Imbach et al. 2000. PubMed ID: 10914684; Imbach et al. 1999. PubMed ID: 10359825). Another recurrent pathogenic variant is the c.167+5G>A splice site pathogenic variant (Westphal et al. 2000. PubMed ID: 10924277; Imbach et al. 2000. PubMed ID: 10914684; Drijvers et al. 2010. PubMed ID: 20447155; Posey et al. 2017. PubMed ID: 27959697; Dercksen et al. 2013. PubMed ID: 23430515).

The ALG6 gene encodes a glucosyltransferase that catalyzes the transfer of the first glucose (Glc) residue onto the dolichol-linked oligosaccharide precursor for N-linked glycosylation (Haeuptle et al. 2009. PubMed ID: 19862844).

Clinical Sensitivity - Sequencing with CNV PG-Select

Due to the low incidence of this disorder, clinical sensitivity is difficult to estimate. All of the reported variants in the Human Gene Mutation Database (HGMD; http://www.hgmd.cf.ac.uk/) should be covered in this test, including one gross deletion.

Testing Strategy

This test provides full coverage of all coding exons of the ALG6 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.

Indications for Test

Candidates for this test include individuals with clinical symptoms consistent with CDG Ic or individuals with a CDG-I pattern upon isoelectric focusing of serum transferrin, particularly after the most common form of CDG-I has been ruled out (PMM2 gene) (Morava et al. 2016. PubMed ID: 27287710). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in ALG6.


Official Gene Symbol OMIM ID
ALG6 604566
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT


Name Inheritance OMIM ID
Congenital Disorder Of Glycosylation Type 1C AR 603147

Related Test

Congenital Disorders of Glycosylation (CDG) Panel (Types Ia, Ib, and Ic)


  • Brasil et al. 2018. PubMed ID: 29702557
  • Dercksen et al. 2013. PubMed ID: 23430515
  • Drijvers et al. 2010. PubMed ID: 20447155
  • Haeuptle et al. 2009. PubMed ID: 19862844
  • Hanefeld et al. 2000. PubMed ID: 10832578
  • Human Gene Mutation Database (Biobase).
  • Ichikawa et al. 2013. PubMed ID: 23044053
  • Imbach et al. 1999. PubMed ID: 10359825
  • Imbach et al. 2000. PubMed ID: 10914684
  • Jaeken. 2017. PubMed ID: 28484880
  • Medrano et al. 2019. PubMed ID: 30653653
  • Morava et al. 2016. PubMed ID: 27287710
  • Newell et al. 2003. PubMed ID: 12855228
  • Posey et al. 2017. PubMed ID: 27959697
  • Scott et al. 2014. PubMed ID: 24831587
  • Vuillaumier-Barrot et al. 2005. PubMed ID: 15771971
  • Westphal et al. 2000. PubMed ID: 10924277


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

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