Diagnostic Test Directory

Molecular Genetics Laboratory

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Early Infantile Epileptic Encephalopathy (STXBP1)

    Collect

    Collect whole blood in a purple top (EDTA) tube (preferred). Extracted DNA is also acceptable.

    Volume Required

    5 ml whole blood or 6 up extracted DNA

    Minimum Required

    3 ml whole blood

    Transport

    Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.

    Stability

    Whole blood can be refrigerated until shipment.

    Unacceptable conditions

    Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.

    Specimen Handling

    Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.

Days Performed

Mon - Fri 9:00am to 4:00pm

Reported

4-6 weeks

CPT

Sequence analysis- 81406; Known mutation- 81403

Disease Information

Clinical Features:

Early Infantile Epileptic Encephalopathy (EIEE) is a severe age-related epileptic encephalopathy which is also known as Ohtahara syndrome. The characteristics of EIEE syndrome are: onset in early infancy (neonatal period through the first few months of life); tonic spasms associated with suppression bursts EEG pattern; medically intractable seizures and severe psychomotor retardation. Mutations in at least 4 genes have been identified in EIEE individuals including ARX (EIEE-1), CDKL5 (EIEE-2), SLC25A22(EIEE-3), and STXBP1 (EIEE-4).

Molecular Genetics:

Early infantile epileptic encephalopathy-4 (EIEE4) is an autosomal dominant condition that is caused by mutations in the STXBP1 gene. Mutations in the STXBP1 may account for up to 30% of individuals with EIEE and upto10% of individuals with early onset epileptic encephalopathy (5/49) that do not fit the phenotype of Ohtahara or West syndrome. Missense, nonsense, frameshift, splicing mutations and deletions have been identified in EIEE patients.

Test Methods:

PCR amplification and sequence analysis is performed on the coding exon including splice junctions. The patient’s gene sequence is compared to a reference sequence. Sequence variants are classified as mutations, variants of unknown significance or benign variants unrelated to disease. Variants of unknown significance may warrant further studies in the patient and other family members. Mutations in promoters, deep intronic regions and other regulatory regions will not be identified with this assay. Sensitivity: This assay has greater than 99.7% sensitivity for detecting substitution variants and indels. Reference Range: Copy number variations and mutations within the promoter regions, deep intronic regions or regulatory elements would also not be detected by this assay.

Detection Rate:

Mutations in the STXBP1 may account for up to 30% of individuals with EIEE and upto10% of individuals with early onset epileptic encephalopathy (5/49) that do not fit the phenotype of Ohtahara or West syndrome.

Related Tests:

Early Infantile Epileptic Encephalopathy Panel – ARX, CDKL5, MEF2c, STXBP1, SLC25A22, SRPX2 Early Infantile Epileptic Encephalopathy (Sequence) – SLC25A22 Rolandic Epilepsy (Sequence) – SRPX2 Atypical Rett Syndrome (Sequence and MLPA) – CDKL5 Infantile Spasms (Sequence) – ARX MEF2C Related Mental Retardation, Stereotypic Movements, Epilepsy, and/or Cerebral Malformations (Sequence and MLPA) – MEF2C

Results:

Test results with interpretation will be mailed and/or faxed to the referring physician or send out lab following completion of the test. Additional reports will be provided as requested.

Utility:

The clinical utility of the assay is to support a clinical diagnosis of the disease, facilitate genetic counseling, and assess the risk to other first degree relatives and to facilitate testing of at - risk family members.

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