Holoprosencephaly Panel

PLUSbpg-method Plus Analysis combines Sequence + Del/Dup (CNV) Analysis providing increased diagnostic yield in certain clinical conditions, where the underlying genetic defect may be detectable by either of the analysis methods. Results in 3–4 weeks. SEQbpg-method Our Sequence Analysis is based on a proprietary targeted sequencing method OS-Seq™ and offers panels targeted for genes associated with certain phenotypes. A standard way to analyze NGS data for finding the genetic cause for Mendelian disorders. Results in 3–4 weeks. DEL/DUPbpg-method Targeted Del/Dup (CNV) analysis is used to detect bigger disease causing deletions or duplications from the disease-associated genes. Results in 3–4 weeks.

Test code: MA0601

The Blueprint Genetics Holoprosencephaly Panel is a 12 gene test for genetic diagnostics of patients with clinical suspicion of holoprosencephaly.

The nonsyndromic forms of HPE that are best understood at a molecular genetic level are inherited in an autosomal dominant manner. This Panel is part of Comprehensive Skeletal / Malformation Syndrome Panel

About Holoprosencephaly

Holoprosencephaly (HPE) is the most common malformation of the forebrain in humans. It is a structural anomaly of the brain resulting from failed or incomplete forebrain division in the third to fourth weeks of gestation and frequently also affects facial features, including closely spaced eyes, small head size, and sometimes clefts of the lip and roof of the mouth, as well as other birth defects. In most cases of holoprosencephaly, the malformations are so severe that babies die before birth. In less severe cases, babies are born with normal or near-normal brain development and facial deformities that may affect the eyes, nose and upper lip. Typically HPE has been divided into the following types: Alobar HPE, Semilobar HPE, Lobar HPE, Middle interhemispheric fusion variant (MIHF/MIHV or syntelencephaly) and a septopreoptic type. This birth defect occurs soon after conception. It has a prevelance of 1/250 during early embryo development, and 1/10,000-20,000 at term.

30-40% of the HPE cases with positive family history have mutations in SHH gene. Approximately 18%-25% of individuals with HPE have a mutation in a single gene causing syndromic HPE. At least 25 different conditions in which HPE is an occasional finding have been described, such as Rubinstein-Taybi syndrome and Meckel syndrome (covered by our other panels Comprehensive Skeletal / Malformation Syndrome Panel, Comprehensive Short Stature Syndrome Panel and Meckel syndrome panel). Differential diagnosis includes anencephaly, severe congenital hydrocephalus, Walker-Warburg syndrome, large interhemispheric cyst, otocephaly and other midline defects. Although severely affected individuals do not reproduce, individuals with mild forms and microforms of autosomal dominant HPE may do so. A proband with autosomal dominant nonsyndromic HPE may have the disorder as the result of a de novo gene mutation. The proportion of cases caused by new gene mutations is estimated to be approximately 10%-30% for SHH, 70%-80% for ZIC2, and 10%-20% for SIX3.

Availability

Results in 3-4 weeks. We do not offer a maternal cell contamination (MCC) test at the moment. We offer prenatal testing only for cases where the maternal cell contamination studies (MCC) are done by a local genetic laboratory. Read more: http://blueprintgenetics.com/faqs/#prenatal

Like this:

Genes in the Holoprosencephaly Panel and their clinical significance
Gene Associated phenotypes Inheritance ClinVar HGMD
CDON Holoprosencephaly AD 7 10
FGF8 Hypogonadotropic hypogonadism AD/Digenic 10 28
FGFR1 Pfeiffer syndrome, Trigonocephaly, Hypogonadotropic hypogonadism, Osteoglophonic Dwarfism - Craniostenosis, Hartsfield syndrome AD/Digenic/Multigenic 41 232
FOXH1 Congenital heart malformations, Holoprosencephaly AD 32
GLI2 Culler-Jones syndrome AD 16 74
GLI3 Acrocallosal syndrome, Pallister-Hall syndrome, Grieg cephalopolysndactyly syndrome, Postaxial polydactyly type A, Preaxial polydactyly type 3, Preaxial polydactyly type 4 AD 49 221
NODAL Heterotaxy, visceral AD 4 23
PTCH1 Basal cell nevus syndrome AD 46 348
SHH Holoprosencephaly, Microphthalmia with coloboma AD 29 212
SIX3 Holoprosencephaly AD 11 82
TGIF1 Holoprosencephaly AD 7 27
ZIC2 Holoprosencephaly AD 10 112

*Some regions of the gene are duplicated in the genome leading to limited sensitivity within the regions. Thus, low-quality variants are filtered out from the duplicated regions and only high-quality variants confirmed by other methods are reported out. Read more.

Gene, refers to HGNC approved gene symbol; Inheritance to inheritance patterns such as autosomal dominant (AD), autosomal recessive (AR) and X-linked (XL); ClinVar, refers to a number of variants in the gene classified as pathogenic or likely pathogenic in ClinVar (http://www.ncbi.nlm.nih.gov/clinvar/); HGMD, refers to a number of variants with possible disease association in the gene listed in Human Gene Mutation Database (HGMD, http://www.hgmd.cf.ac.uk/ac/). The list of associated (gene specific) phenotypes are generated from CDG (http://research.nhgri.nih.gov/CGD/) or Orphanet (http://www.orpha.net/) databases.

Blueprint Genetics offers a comprehensive Holoprosencephaly Panel that covers classical genes associated with holoprosencephaly. The genes are carefully selected based on the existing scientific evidence, our experience and most current mutation databases. Candidate genes are excluded from this first-line diagnostic test. The test does not recognise balanced translocations or complex inversions, and it may not detect low-level mosaicism. The test should not be used for analysis of sequence repeats or for diagnosis of disorders caused by mutations in the mitochondrial DNA.

Analytical validation is a continuous process at Blueprint Genetics. Our mission is to improve the quality of the sequencing process and each modification is followed by our standardized validation process. Average sensitivity and specificity in Blueprint NGS Panels is 99.3% and 99.9% for detecting SNPs. Sensitivity to for indels vary depending on the size of the alteration: 1-10bps (96.0%), 11-20 bps (88.4%) and 21-30 bps (66.7%). The longest detected indel was 46 bps by sequence analysis. Detection limit for Del/Dup (CNV) analysis varies through the genome depending on exon size, sequencing coverage and sequence content. The sensitivity is 71.5% for single exon deletions and duplications and 99% for three exons’ deletions and duplications. We have validated the assays for different starting materials including EDTA-blood, isolated DNA (no FFPE) and saliva that all provide high-quality results. The diagnostic yield varies substantially depending on the used assay, referring healthcare professional, hospital and country. Blueprint Genetics’ Plus Analysis (Seq+Del/Dup) maximizes the chance to find molecular genetic diagnosis for your patient although Sequence Analysis or Del/Dup Analysis may be cost-effective first line test if your patient’s phenotype is suggestive for a specific mutation profile.

The sequencing data generated in our laboratory is analyzed with our proprietary data analysis and annotation pipeline, integrating state-of-the art algorithms and industry-standard software solutions. Incorporation of rigorous quality control steps throughout the workflow of the pipeline ensures the consistency, validity and accuracy of results. The highest relevance in the reported variants is achieved through elimination of false positive findings based on variability data for thousands of publicly available human reference sequences and validation against our in-house curated mutation database as well as the most current and relevant human mutation databases. Reference databases currently used are the 1000 Genomes Project (http://www.1000genomes.org), the NHLBI GO Exome Sequencing Project (ESP; http://evs.gs.washington.edu/EVS), the Exome Aggregation Consortium (ExAC; http://exac.broadinstitute.org), ClinVar database of genotype-phenotype associations (http://www.ncbi.nlm.nih.gov/clinvar) and the Human Gene Mutation Database (http://www.hgmd.cf.ac.uk). The consequence of variants in coding and splice regions are estimated using the following in silico variant prediction tools: SIFT (http://sift.jcvi.org), Polyphen (http://genetics.bwh.harvard.edu/pph2/), and Mutation Taster (http://www.mutationtaster.org).

Through our online ordering and statement reporting system, Nucleus, the customer can access specific details of the analysis of the patient. This includes coverage and quality specifications and other relevant information on the analysis. This represents our mission to build fully transparent diagnostics where the customer gains easy access to crucial details of the analysis process.

In addition to our cutting-edge patented sequencing technology and proprietary bioinformatics pipeline, we also provide the customers with the best-informed clinical report on the market. Clinical interpretation requires fundamental clinical and genetic understanding. At Blueprint Genetics our geneticists and clinicians, who together evaluate the results from the sequence analysis pipeline in the context of phenotype information provided in the requisition form, prepare the clinical statement. Our goal is to provide clinically meaningful statements that are understandable for all medical professionals, even without training in genetics.

Variants reported in the statement are always classified using the Blueprint Genetics Variant Classification Scheme modified from the ACMG guidelines (Richards et al. 2015), which has been developed by evaluating existing literature, databases and with thousands of clinical cases analyzed in our laboratory. Variant classification forms the corner stone of clinical interpretation and following patient management decisions. Our statement also includes allele frequencies in reference populations and in silico predictions. We also provide PubMed IDs to the articles or submission numbers to public databases that have been used in the interpretation of the detected variants. In our conclusion, we summarize all the existing information and provide our rationale for the classification of the variant.

A final component of the analysis is the Sanger confirmation of the variants classified as likely pathogenic or pathogenic. This does not only bring confidence to the results obtained by our NGS solution but establishes the mutation specific test for family members. Sanger sequencing is also used occasionally with other variants reported in the statement. In the case of variant of uncertain significance (VUS) we do not recommend risk stratification based on the genetic finding. Furthermore, in the case VUS we do not recommend use of genetic information in patient management or genetic counseling. For some cases Blueprint Genetics offers a special free of charge service to investigate the role of identified VUS.

We constantly follow genetic literature adapting new relevant information and findings to our diagnostics. Relevant novel discoveries can be rapidly translated and adopted into our diagnostics without delay. These processes ensure that our diagnostic panels and clinical statements remain the most up-to-date on the market.

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ICD & CPT codes

CPT codes

SEQ81479
DEL/DUP81479


ICD codes

Commonly used ICD-10 codes when ordering the Holoprosencephaly Panel

ICD-10 Disease
Q04.2 Holoprosencephaly

Accepted sample types

  • EDTA blood, min. 1 ml
  • Purified DNA, min. 5μg
  • Saliva (Oragene DNA OG-500 kit)

Label the sample tube with your patient’s name, date of birth and the date of sample collection.

Note that we do not accept DNA samples isolated from formalin-fixed paraffin-embedded (FFPE) tissue.

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