The Invitae FG Syndrome Test analyzes the gene MED12, which is known to be associated with FG syndrome type 1 (FGS1). Previously, traditional testing strategies for MED12-related disorders included initial testing of exons 21 and 22 of the MED12 gene to evaluate for p.Arg961Trp (the recurring pathogenic variant for FGS1) and for other reported MED12 variants; when this initial testing was negative, sequence analysis of the remaining exons would have been considered. The Invitae FG Syndrome test analyzes the full coding region of the MED12 gene and eliminates the need for the former tiered-test approach.
Because FGS1 shares clinical findings with other MED12 spectrum disorders, the diagnosis of FGS1 relies on molecular genetic testing. Additionally, clinical findings associated with FGS1 are nonspecific, which may lead to clinical overdiagnosis. Identifying a genetic change related to FG syndrome can guide medical management, including early individualized education plans, early intervention for physical, occupational and speech therapy for developmental delays, and management of other clinical findings.
FG syndrome (FGS1) is a multisystemic developmental disorder and is one of the two most well-defined disorders within the spectrum of MED12-related disorders. MED12-related disorders are generally characterized by hypotonia, abnormalities of the corpus callosum, intellectual disability, and behavioral problems. Individuals with FG syndrome may also present with physical abnormalities including macrocephaly, distinctive facial features, anal abnormalities, broad thumbs, and big toes. Additional clinical findings may include heart defects, seizures, inguinal hernia, and undescended testes in males. The clinical presentation is variable; not all individuals with FG syndrome will present with every characteristic described above.
The clinical sensitivity for this test has not yet been determined.
FG syndrome is inherited in an X-linked pattern.
The penetrance of this disorder is presumed to be 100% in males. To date, the published variants in MED12 (p.Arg961Trp, p.Gly958Glu, and p.Asn1007Ser) have not been observed in unaffected males. The clinical presentation is variable. Female carriers for FGS1 are typically unaffected.
The prevalence of FGS1 is currently unknown.
Although formal diagnostic criteria have not been established for FGS1, the following clinical findings are suggestive of a clinical diagnosis: small ears, distinctive facial features (tall forehead; downslanted palpebral fissures; long, narrow face), congenital anomalies (heart or skeletal defects; abnormality of the corpus callosum), macrocephaly, low muscle tone, and a characteristic eager-to-please behavior.
Invitae is a College of American Pathologists (CAP)-accredited and Clinical Laboratory Improvement Amendments (CLIA)-certified clinical diagnostic laboratory performing full-gene sequencing and deletion/duplication analysis using next-generation sequencing technology (NGS).
Our sequence analysis covers clinically important regions of each gene, including coding exons, +/- 10 base pairs of adjacent intronic sequence, and select noncoding variants. Our assay provides a Q30 quality-adjusted mean coverage depth of 350x (50x minimum, or supplemented with additional analysis). Variants classified as pathogenic or likely pathogenic are confirmed with orthogonal methods, except individual variants that have high quality scores and previously validated in at least ten unrelated samples.
Our analysis detects most intragenic deletions and duplications at single exon resolution. However, in rare situations, single-exon copy number events may not be analyzed due to inherent sequence properties or isolated reduction in data quality. If you are requesting the detection of a specific single-exon copy number variation, please contact Client Services before placing your order.
|Gene||Transcript reference||Sequencing analysis||Deletion/Duplication analysis|