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Pediatrics - Cardiology

Houston, Texas

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Pediatrics - Cardiology
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SCN4B Mutation Analysis

SCN4B (sodium channel, voltage-gated, type IV, beta subunit) gene encodes one of several sodium channel beta subunits. These subunits interact with voltage-gated alpha subunits to change sodium channel kinetics. The encoded transmembrane protein SCN4B forms interchain disulfide bonds with SCN2A. Human SCN4B gene contains five exons spanning 19 kb of genomic distance that was mapped to chromosome 11q23.3. Multiple mutations in SCN4B are the cause of congenital long-QT syndrome type 10 (LQT10) and have been found in patients with sudden infant death syndrome (SIDS). SCN4B mutations demonstrate autosomal dominant inheritance with a broad range of clinical severity both within and between families. Definitive genotype/phenotype correlations have not been described.

The John Welsh Cardiovascular Diagnostic Laboratory offers molecular genetic testing for SCN4B mutations. Individuals are tested by automatic fluorescent DNA sequencing of the coding exons of the SCN4B gene. We strongly recommend initial testing of a clearly affected individual, if available, in order to provide the greatest test sensitivity and clearest interpretation of results for subsequent family members. Genetic counseling is recommended for all individuals.

Reasons for Referral

Molecular confirmation of the diagnosis of long-QT syndrome type 10 (LQT10) and sudden infant death syndrome (SIDS).

Methodology

Genomic DNA is analyzed for SCN4B mutations by automatic fluorescent DNA sequencing of the coding exons of the SCN4B gene, as well as the exon/intron junctions and a portion of the 5' and 3' untranslated region. Patient DNA is sequenced in both the forward and reverse orientations. If a mutation is identified, additional family members are analyzed only for the familial mutation by automatic fluorescent DNA sequencing.

Service Fees

Service Direct and Institutional Billing CPT Codes
Index Case (Full Gene) $750 per sample 81404, G0452
Additional Family Members $300 per sample; known familial mutation only 81403, G0452

Sensitivity

DNA Sequencing Analysis: Approximately 99 percent detection of mutations in coding exons 1-5 of SCN4B.

Specimen Requirements

Blood (preferred): EDTA (purple-top) tubes: Adult: 5 cc, Child: 5 cc, Infant: 2-3 cc
Tissue: Frozen (preferred), RNAlater, Formalin-fixed, Paraffin-embedded
Other Body Fluids: Call to inquire
Buccal Swabs: One swab from each cheek

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