Test code: MA0401
The Blueprint Genetics Polymicrogyria Panel is a 14 gene test for genetic diagnostics of patients with clinical suspicion of polymicrogyria.
Polymicrogyria in all its forms collectively is a fairly common brain malformation, however, each individual disorder in which it can be observed is rare. Most forms of polymicrogyria are inherited in autosomal recessive manner, but autosomal dominant and X-linked inheritance have also been suggested in some forms. This panel is part of Comprehensive Skeletal / Malformation Syndrome Panel.
Polymicrogyria (PMG) is a heterogenous group of cerebral cortical malformations. It is characterized by excessive cortical folding and abnormal cortical layering that, depending on its topographic distribution, presents with variable combinations of neurological symptoms of varying severity such as epilepsy, developmental delay, intellectual disability, motor dysfunction (e.g. spasticity), and pseudobulbar palsy. The mildest form, unilateral focal polymicrogyria, may have minimal neurologic manifestations. In more severe forms, focal, motor, sensory, visual, or cognitive problems may be present, depending on the brain region affected. In the most widespread form, bilateral generalized polymicrogyria, severe intellectual disability, cerebral palsy, and refractory epilepsy may be present.
Polymicrogyria can result from both genetic and environmental causes and can occur as an isolated finding with no other systemic involvement or as part of a syndrome with multisystem involvement. ADGRG1 gene (coding G protein-coupled receptor 56 protein) has been identified as the cause of GPR56-related bilateral frontoparietal polymicrogyria which is inherited in autosomal recessive manner. The majority of families with bilateral frontoparietal polymicrogyria (BFPP) studied to identify the gene in which mutation is causative (ADGRG1) were consanguineous families from the Middle East, although mutations have been identified in families from other ethnic groups as well. Bilateral frontal polymicrogyria and bilateral generalized polymicrogyria are also thought to be inherited in an autosomal recessive manner. Perisylvian polymicrogyria appears to be genetically heterogeneous with a number of families suggesting autosomal dominant, autosomal recessive, or X-linked inheritance.
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.
|ADGRG1||Polymicrogyria, bilateral frontoparietal, Polymicrogyris, bilateral perisylvian||AR||22|
|CHD7||Isolated gonadotropin-releasing hormone deficiency, CHARGE syndrome||AD||128||746|
|FH||Hereditary leiomyomatosis and renal cell cancer||AD||89||161|
|GPSM2||Deafness, Chudley-McCullough syndrome||AR||10||11|
|KIF1BP||Goldberg-Shprintzen megacolon syndrome||AR||5|
|NSDHL||Congenital hemidysplasia with ichthyosiform erythroderma and limb defects (CHILD syndrome), CK syndrome||XL||15||28|
|SRPX2||Rolandic epilepsy, mental retardation, and speech dyspraxia||XL||1||3|
|TUBA8||Polymicrogyria with optic nerve hypoplasia||AR||1||1|
|TUBB3*||Fibrosis of extraocular muscles, congenital, Cortical dysplasia, complex, with other brain malformations||AD/AR||18||23|
- * 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 Polymicrogyria Panel that covers classical genes associated with polymicrogyria. 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
Commonly used ICD-10 codes when ordering the Polymicrogyria Panel
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.