Hereditary Nonsyndromic Hearing Loss

CONNEXIN 26:

Approximately 1 in 1000 young children has a major hearing impairment (threshold >80dB). Significant hearing loss also occurs in about 1 in 25 people under age 45, and in 1 in 10 by age 60 (threshold >25dB). Most of the hearing loss is genetic with over 30 autosomal recessive (70-80%), dominant (23-30%) and X-linked (2-3%) forms. A large proportion (60-75%) of nonsyndromic hearing loss in children has been localized to defects in a single gene, Connexin 26 (Cx26) on chromosome 13q11-12. A variety of mutations have been described in this gene with a 35delG hotspot mutation representing over half of the defects in Caucasians.

This test may be ordered with Connexin 30 in a Connexin Hearing Loss Panel, or may be further combined with testing for mitochondrial hearing loss in a Nonsyndromic Hearing Loss Panel for the most efficient and economical diagnosis available.

REASONS FOR REFERRAL:

To determine whether a hearing defect in a child is hereditary.
Evaluation of progressive hearing loss in adults.
To determine the genetic basis for hearing loss in an affected individual, in order to modify therapy.
To evaluate the risk of having a child with hearing loss.
Individuals at risk who wish prenatal diagnosis.
This test is often included with testing for Connexin 30.

TESTING METHODOLOGY:

PCR amplification and DNA sequencing of the entire coding region of the Connexin 26 gene.

SPECIMEN REQUIREMENTS:

Blood EDTA (purple top) tubes:

Newborn: minimum 1-2 mL

Child/Adult: prefer 2 tubes of 3-5 mL

Prenatal testing: Please contact the laboratory for instructions.

A Molecular Genetics Laboratory Test Requisition must accompany the specimen. Contact the Molecular Laboratory at 918-502-1721 to obtain further information.

TURNAROUND TIME: 10 working days

CPT CODES: