Condition Description

CHARGEis a mnemonic that stands for coloboma, heart defects, choanal atresia, retarded growth and development, genital abnormalities, and earanomalies. CHARGE syndrome is characterized by unilateral or bilateral coloboma of the iris, retina-choroid, and/or disc with or without microphthalmos (80%-90% of individuals); unilateral or bilateral choanal atresia or stenosis (50%-60%); cranial nerve dysfunction resulting in hyposomia or anosmia,unilateral or bilateral facial palsy (40%), impaired hearing, and/or swallowing problems (70%-90%); abnormal outer ears, ossicular malformations, Mondini defect of the cochlea, and absent or hypoplastic semicircular canals; cryptorchidism in males and hypogonadotrophic hypogonadism in both males and females; developmental delay; cardiovascular malformations (75%-85%); growth deficiency (70%-80%); orofacial clefts (15%-20%); and tracheoesophageal fistula (15%-20%). Neonates with CHARGE syndrome often have multiple life-threatening medical conditions. Feeding difficulties are a major cause of morbidity in all age groups.

The diagnosis of CHARGE syndrome is based on clinical findings and temporal bone imaging. The CHD7 gene (8q12.1) is the only gene currently known to be associated with CHARGE syndrome; it encodes the chromodomain helicase DNA binding protein.Sequence analysis of the CHD7 coding region detects mutations in approximately 60%-65% of individuals with CHARGE syndrome. While one study suggested that individuals with CHARGE syndrome caused by a mutation in CHD7 were more likely to exhibit cardiovascular malformations, coloboma of the eye, and facial asymmetry, another study found no genotype-phenotype correlations in this cohort and noted that there were differences in clinical presentation even in sib pairs with identical mutations. Most individuals diagnosed with CHARGE syndrome represent simplex cases (i.e., a single occurrence in a family), although CHARGE syndromecaused by mutation of CHD7 can be inherited in an autosomal dominant manner. CHARGE syndrome has an estimated birth incidence of 1 in 10-12,000

Mutationsin CHD7 have also been shown to cause Kallmann syndrome-5, an allelic disorderwith a less severe but overlapping phenotype. Patients with anosmia and/or hypogonadotropichypogonadism, therefore, should be screened for additional clinical features ofCHARGE syndrome.

Click here for the GeneTests summary on this condition.

Genes (0)

Indications

This test is indicated for:

  • Confirmation of a clinical/biochemical diagnosis of CHARGE syndrome

Methodology

Next Generation Sequencing: In-solution hybridization of all coding exons is performed on the patient's genomic DNA. Although some deep intronic regions may also be analyzed, this assay is not meant to interrogate most promoter regions, deep intronic regions, or other regulatory elements, and does not detect single or multi-exon deletions or duplications. Direct sequencing of the captured regions is performed using next generation sequencing. The patient's gene sequences are then compared to a standard reference sequence. Potentially causative variants and areas of low coverage are Sanger-sequenced. Sequence variations are classified as pathogenic, likely pathogenic, benign, likely benign, or variants of unknown significance. Variants of unknown significance may require further studies of the patient and/or family members.

Detection

Clinical Sensitivity: 60-65%. Mutations in the promoter region, some mutations in the introns and other regulatory element mutations cannot be detected by this analysis. Large deletions will not be detected by this analysis. Results of molecular analysis should be interpreted in the context of the patient''''s biochemical phenotype.

Analytical Sensitivity: ~99%

Specimen Requirements

Listed below are EGL's preferred sample criteria. For any questions, please call 470.378.2200 and ask to speak with a laboratory genetic counselor (eglgc@egl-eurofins.com).
Submit only 1 of the following specimen types
Saliva
SLV

Requirements
Oragene™ Saliva Collection Kit
Orangene™ Saliva Collection Kit used according to manufacturer instructions. Please contact EGL for a Saliva Collection Kit for patients that cannot provide a blood sample.
Collection and Shipping
Please do not refrigerate or freeze saliva sample. Please store and ship at room temperature.
Whole Blood (EDTA)
WBP

Requirements
EDTA (Purple Top)
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Collection and Shipping
Ship sample at room temperature for receipt at EGL within 72 hours of collection. Do not freeze.
DNA, Isolated
DNA

Requirements
Microtainer
8µg
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Collection and Shipping
Refrigerate until time of shipment in 100 ng/µL in TE buffer. Ship sample at room temperature with overnight delivery.

Special Instructions

Submit copies of diagnostic biochemical test results with the sample, if appropriate. Contact the laboratory if further information is needed.


  • Custom diagnostic mutation analysis (KM) is available to family members if mutations are identified by targeted mutation testing or sequencing analysis.
  • Prenatal testing is available to individuals who are confirmed carriers of mutations. Please contact the laboratory genetic counselor to discuss appropriate testing prior to collecting a prenatal specimen.

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