Congenital Disorders of Glycosylation, Type Ia (CDG-Ia) via the PMM2 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
7913 PMM2 81479 81479,81479 $640 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
7913PMM281479 81479(x2) $640 Order Options and Pricing

Pricing Comments

This test is also offered via our exome backbone with CNV detection (click here). The exome-based test may be higher priced, but permits reflex to the entire exome or to any other set of clinically relevant genes.

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

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

  • Kym Bliven, PhD

Clinical Features and Genetics

Clinical Features

Congenital disorders of glycosylation (CDG) are a genetically heterogeneous group of disorders caused by defective synthesis of asparagine (N)-linked glycans. Abnormalities in these glycoconjugates result in disturbed metabolism, cell recognition, cell adhesion, protease resistance, host defense, cell migration, and antigenicity (Marquardt and Denecke. Eur J Pediat 162:359-379, 2003). Consequently, clinical presentations are characterized by multisystem involvement. Individuals with CDG Ia (OMIM 212065) have cerebellar hypoplasia, dysmorphic facies, coagulopathy, strabismus, psychomotor retardation, and sometimes unusual fat distribution and inverted nipples (de Lonlay et al. J Med Genet 38:14-19, 2001; Sparks and Krasnewich GeneReviews 2008). Presentation and clinical course can be highly variable, and three stages have been delineated. The infantile multisystem stage is characterized by failure to thrive secondary to vomiting, diarrhea, and feeding problems; hypotonia and hyporeflexia; high nasal bridge; prominent jaw and ears; and unusual fat distribution over the buttocks. Some patients who present in this stage exhibit fatal neurological and multi-organ involvement, while others present with a non-fatal neurological form lacking visceral organ involvement (de Lonlay et al. J Med Genet 38:14-19, 2001). The late-infantile and childhood ataxia-mental retardation stage is characterized by developmental delay, (especially language and motor skills), ataxia, joint contractures, and skeletal deformities. During the adult stable disability stage, premature aging is observed along with stable mental capacity, progressive skeletal deformities, and hypogonadism (Drouin-Garraud et al. Am J Med Genet 101: 46-49, 2001).

Genetics

All CDGs exhibit autosomal recessive inheritance. Thirteen forms of CDG have been characterized at the molecular level, but only three (CDG Ia, CDG Ib, and CDG Ic) have been reported in more than a few individual patients. CDG Ia is the most common form with ~400 cases reported worldwide, followed by CDG 1b and CDG Ic, each with approximately 20 cases. The PMM2 gene (OMIM 601785) codes for phosphomannomutase-2, an enzyme involved in the synthesis of GDP-mannose. Variants in PMM2 are distributed throughout the coding region, and missense variants are the most common type.

Clinical Sensitivity - Sequencing with CNV PG-Select

In cases with demonstrated reduced activity of phosphomannomutase and diagnostic serum transferrin glycoforms, PMM2 sequencing is nearly 100% sensitive (Sparks and Krasnewich, GeneReviews 2008). Among 56 patients with proven enzyme deficiency Matthijs et al. found variants on 99% of the affected alleles, and one variant (p.Arg141His) accounted for almost 40% of all causative variants  (Matthijs et al. Am J Hum Genet 62:542-550, 1998). The p.Arg141His homozygous genotype has never been observed, presumably because it is embryonic lethal (Matthijs et al. Molec Genet Metab 68:220-226, 1999). The relatively common European p.Arg141His/p.Phe119Leu and p.Arg141His/p.Asp188Gly genotypes are associated with severe phenotypes, including a high mortality rate for the latter.

Testing Strategy

This test provides full coverage of all coding exons of the PMM2 gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.

Indications for Test

Individuals with clinical symptoms consistent with CDG Ia. Individuals with diagnostic serum transferrin isoform results (decreased tetrasialotransferrin and increased asailotransferrin and disialotransferrin). This test may also be considered for the reproductive partners of individuals who carry pathogenic variants in PMM2.

Gene

Official Gene Symbol OMIM ID
PMM2 601785
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Congenital Disorder Of Glycosylation Type 1A AR 212065

Related Test

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

Citations

  • de Lonlay, P., et.al. (2001). "A broad spectrum of clinical presentations in congenital disorders of glycosylation I: a series of 26 cases." J Med Genet 38(1): 14-9. PubMed ID: 11134235
  • Drouin-Garraud, V., et.al. (2001). "Neurological presentation of a congenital disorder of glycosylation CDG-Ia: implications for diagnosis and genetic counseling." Am J Med Genet 101(1): 46-9. PubMed ID: 11343337
  • Matthijs, G., et.al. (1998). "Lack of homozygotes for the most frequent disease allele in carbohydrate-deficient glycoprotein syndrome type 1A." Am J Hum Genet 62(3): 542-50. PubMed ID: 9497260
  • Matthijs, G., et.al. (1999). "Phosphomannomutase deficiency: the molecular basis of the classical Jaeken syndrome (CDGS type Ia)." Mol Genet Metab 68(2): 220-6. PubMed ID: 10527672
  • Susan E Sparks, Donna M Krasnewich (2008). "Congenital Disorder of Glycosylation Type 1a."
  • Susan E Sparks, Donna M Krasnewich (2008). "Congenital Disorders of Glycosylation Overview."

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

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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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