Molecular Test Listing

Molecular Requisition

MATERNALLY INHERITED HEARING LOSS PANEL

About 1 in 1000 young children have a major hearing impairment (threshold >80dB). A mitochondrial form of inheritance appears to be responsible for deafness in a group of these children. This includes Aminoglycoside-induced (antibiotic) and nonsyndromic sensorineural deafness has been associated in some cases with an A1555G mutation in the mitochondria (12S DNA). This deafness can have both a congenital and late onset presentation and 70% of the affected individuals have not been exposed to the antibiotic. The significance of the mutation is not understood but aminoglycoside antibiotics in high concentrations have an ototoxic affect by damaging the auditory hair cells in the cochlea. In addition, other mitochondrial mutations have been discovered within the serine transfer RNA 1 gene (7512T-C, 7445A-G, 7472insC, 7510T-C and 7511T-C). In order to capture all these mutations and others that may exist at this locus of the mitochondria the region is analyzed by sequencing. The incidence of these mutations is not well known but may represent a small percentage of affected individuals that show no signs of connexin 26 defects. In maternally inherited forms of hearing loss the incidence of the mutations may approach 100%

• To determine whether a hearing defect in a child is hereditary.
• Evaluation of progressive hearing loss in adults in order to assess the potential genetic basis and modify therapy.
• To assess the risk of additional children with hearing loss in an affected family.

• PCR amplification of the mitochondrial DNA followed by mutation-specific restriction enzyme detection of the A1555G mutation and sequencing in the region of the mitochondrial serine tRNA 1 gene.
  

• Blood: EDTA (purple top) tubes
  Newborn: minimum 1-2 mL
  Child/Adult: prefer 2 tubes of 3-5mL blood
  
• Prenatal testing: Please contact the laboratory for instructions

TURNAROUND TIME:      15 Working days

CPT CODES: