Overgrowth/Macrocephaly NGS Panel

Clinical Information

This panel consists of 16 genes associated with various syndromic forms of overgrowth and macrocephaly due to germline variants. 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.

Technical Information

This panel is performed by Next Generation Sequencing and covers the coding regions of the listed genes and the flanking intronic sequences. Promoter, 3′ untranslated sequences, and deep intronic sequences are also covered, but only known disease-causing variants in these regions will be reported. Variants identified on the panel are confirmed with Sanger sequencing if they do not meet certain quality thresholds.

Large deletions and duplications (CNVs) affecting the genes of the panel can be detected; however, due to defined settings in the analysis software, CNVs smaller than 2-kb may not be identified (for example, some small exonic level copy number changes may not be identified). Please note that certain types of genetic alterations including trinucleotide repeat expansions, methylation abnormalities, and balanced rearrangements (e.g., inversions, reciprocal translocations) may not be detected by the current analysis.

Specimen Requirements

• The preferred sample type is 3-4 ml of peripheral blood collected in an EDTA (purple top) tube. Extracted DNA and saliva are also accepted for this test. Blood and saliva kits are available by request.
• Send approximately 5µg of extracted DNA at a requested concentration of 90-130 ng/µl.
• If saliva is submitted, and the extracted DNA is below quality control, then you will be contacted to submit a blood sample or the panel can be completed on an exome backbone. Saliva samples must be submitted in an approved saliva kit.

Transport Instructions

• The blood 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.
• Extracted DNA should be sent at room temperature via overnight delivery.
• Saliva is stable at room temperature and can be delivered via overnight or ground shipping.