Overgrowth/Macrocephaly Sequencing Panel

Test Information

This panel of 16 genes intended for patients with a diagnosis of Overgrowth/Macrocephaly and is performed by Next Generation Sequencing (NGS).

Turnaround Time

8-10 weeks

CPT Code(s)

81479

Cost

$3,000

Genes

  • BRWD3
  • CDKN1C
  • CUL4B
  • DNMT3A
  • EED
  • EZH2
  • GLI3
  • GPC3
  • MED12
  • NFIX
  • NSD1
  • PHF6
  • PTCH1
  • PTEN
  • RNF135
  • UPF3B

Clinical Information

This panel consists of 16 genes associated with various syndromic forms of overgrowth and macrocephaly due to germline mutations. Many of these disorders can present similarly making it difficult to pinpoint the specific diagnosis. Overgrowth may be present in neonates at birth or develop at a later age. In some cases, the patient's growth may normalize as they get older. Additional features for many of the conditions on the panel include intellectual disability, congenital anomalies, or an increased risk for tumors.

Indications

For patients with a specific suspected disorder, individual gene sequencing should be considered first. Molecular testing is useful to confirm the diagnosis and to identify the disease causing mutations within a family to allow for carrier testing and prenatal diagnosis.

Methodology

Next Generation Sequencing

Detection

The current design of this panel covers all genes and the flanking intronic sequences. This method allows for analysis of greater than 98% of the targeted sequence for the detection of nucleotide substitutions and small deletions and duplications. Large deletions and duplications will not be detected by this panel. Mutations and variants identified on the panel are confirmed with Sanger sequencing. All novel and apparently pathogenic changes are reported when found within the coding region as well as within 10 basepairs of each intron/exon boundary for each gene. Promoter and 3' untranslated sequences are not included in the current analysis. It should be noted that the current protocol is not specifically designed to detect copy number alterations and single exon deletions may require additional follow-up to determine whether or not they represent technical artifacts. We recommend further array-based testing to more accurately address the concerns of dosage alterations. The Cytogenetic Laboratory at GGC offers a high resolution whole genome SNP microarray. The GGC Diagnostic Laboratory Directors are available for further consultation regarding the limitations of the NGS and array testing procedures.

Specimen Requirements

5 to 7 ml of peripheral blood collected in an EDTA (lavender top) tube is the preferred specimen type. The minimal blood needed for reliable DNA isolation is 3 ml. Extracted DNA and saliva are also accepted for this test. Saliva samples must be submitted in an approved saliva kit. Contact the lab to receive a saliva kit or to have one sent to your patient.

Transport Instructions

The specimen should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.

Prenatal Testing Information

If the pathogenic mutation(s) are identified in an affected individual using this panel, prenatal diagnosis is available for future pregnancies. Sanger sequencing will be used for prenatal diagnosis when there is a known familial mutation. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for all prenatal molecular tests. Contact the laboratory prior to sending a prenatal specimen.

Have Questions? Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Falecia Thomas, MS, CGC

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