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Simpson-Golabi-Behmel Syndrome via the GPC3 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
9981 GPC3 81479 81479,81479 $640 Order Options and Pricing
Test Code Test Copy Genes Test CPT Code Gene CPT Codes Copy CPT Code Base Price
9981GPC381479 81479,81479 $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

  • Hannah Cox, PhD

Clinical Features and Genetics

Clinical Features

Simpson-Golabi-Behmel syndrome (SGBS, OMIM 312870) is characterized clinically by pre- and postnatal overgrowth, distinct craniofacial and skeletal findings, and variable mental retardation. Craniofacial findings include macrocephaly, down-slanting palpebral fissures, ocular hypertelorism, epicanthal folds, broad and flat nasal bridge with short nose, low-set and posteriorly rotated ears, and large mouth and tongue. Skeletal and limb abnormalities include postaxial polydactyly of hands, syndactyly of the second and third fingers and toes, short and webbed neck, fusion of vertebrae, and pectus excavatum. Language delay is common, and mental retardation varies from mild to severe, although individuals with normal intelligence have been reported. Structural CNS findings, including agenesis of the corpus callosum, Chiari malformation, and hydrocephalus, have been reported (Young et al. Ped Neurol 34:139-142, 2006). Other findings include cardiac conduction defects, supernumerary nipples, and increased risk of embryonal tumors (Li et al. Am J Med Genet 102:161-168, 2001). Female carriers may exhibit some features of SGBS, and skewed X-inactivation has been reported to correlate with clinical features in females (Yano et al. Clin Genet doi:10.1111, 2010).

Genetics

Simpson-Golabi-Behmel syndrome is inherited as an X-linked recessive disorder with marked inter- and intrafamilial variable expression. Variants in the GPC3 gene (OMIM 300037) were found to cause SGBS (Pilia et al. Nat Genet 12:241-247, 1996) and, to date, are the only known cause of this disorder. Penetrance in males is thought to be complete (James et al. GeneReviews, 2006). Penetrance in female carriers is unknown, although carriers can manifest some clinical features (Golabi and Rosen Am J Med Genet 17:345-348, 1984; Rodriguez-Criado Am J Med Genet 138A:272-277, 2005). Nearly fifty GPC3 variants have been reported. The great majority of these variants are deletions of one or more exons. Other variant types include missense, nonsense, and splicing defects that presumably result in loss of function. Gonadal mosaicism has been documented for GPC3 variants (Pilia et al. 1996; Romanelli et al. Clin Genet 72:384-386, 2007).

Clinical Sensitivity - Sequencing with CNV PG-Select

Because most causative GPC3 variants are deletions of single or multiple exons, clinical sensitivity of GPC3 sequencing is expected to be low. For example, Li et al. (2001) failed to identify any individuals with point variants among a group of 45 patients. Seven patients in this study were found to have deletions. In another study, however, six individuals were found to have GPC3 point variants among a cohort of 25 patients (Veugelers et al. Hum Mol Genet 9:1321-1328, 2000). Of these 25 patients, ten had a clinical diagnosis of SGBS, and the remaining were diagnosed with other overgrowth syndromes or were classified as undiagnosed overgrowth.

Testing Strategy

This test provides full coverage of all coding exons of the GPC3 gene, plus ~10 bases of flanking noncoding DNA. We define full coverage as >20X NGS reads or Sanger sequencing.

Indications for Test

A child with pre- and post-natal overgrowth and characteristic craniofacial and skeletal features.

Gene

Official Gene Symbol OMIM ID
GPC3 300037
Inheritance Abbreviation
Autosomal Dominant AD
Autosomal Recessive AR
X-Linked XL
Mitochondrial MT

Disease

Name Inheritance OMIM ID
Simpson-Golabi-Behmel Syndrome XL 312870

Related Test

Name
Perlman Syndrome via the DIS3L2 Gene

Citations

  • Aaron James, et.al. (2006). "Simpson-Golabi-Behmel Syndrome."
  • Golabi, M., Rosen, L. (1984). "A new X-linked mental retardation-overgrowth syndrome." Am J Med Genet 17(1): 345-58. PubMed ID: 6538755
  • Li, M., et.al. (2001). "GPC3 mutation analysis in a spectrum of patients with overgrowth expands the phenotype of Simpson-Golabi-Behmel syndrome." Am J Med Genet 102(2): 161-8. PubMed ID: 11477610
  • Pilia, G., et.al. (1996). "Mutations in GPC3, a glypican gene, cause the Simpson-Golabi-Behmel overgrowth syndrome." Nat Genet 12(3): 241-7. PubMed ID: 8589713
  • Rodriguez-Criado, G., et.al. (2005). "Clinical and molecular studies on two further families with Simpson-Golabi-Behmel syndrome." Am J Med Genet A 138A(3): 272-7. PubMed ID: 16158429
  • Romanelli, V., et.al. (2007). "Germinal mosaicism in Simpson-Golabi-Behmel syndrome." Clin Genet 72(4): 384-6. PubMed ID: 17850639
  • Veugelers, M., et.al. (2000). "Mutational analysis of the GPC3/GPC4 glypican gene cluster on Xq26 in patients with Simpson-Golabi-Behmel syndrome: identification of loss-of-function mutations in the GPC3 gene." Hum Mol Genet 9(9): 1321-8. PubMed ID: 10814714
  • Yano, S., et.al. (2010). "Familial Simpson-Golabi-Behmel syndrome: studies of X-chromosome inactivation and clinical phenotypes in two female individuals with GPC3 mutations." Clin Genet. PubMed ID: 20950395
  • Young, E. L., et.al. (2006). "Expanding the clinical picture of Simpson-Golabi-Behmel syndrome." Pediatr Neurol 34(2): 139-42. PubMed ID: 16458828

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.
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