Molecular Test Listing

Molecular Requisition

WAARDENBURG SYNDROME , TYPE 2
MITF gene analysis

Approximately 1 in 1000 young children have a major hearing impairment (threshold >80dB). Significant hearing loss also occurs in about 1 in 25 people under age 45 and 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. Waardenberg syndrome (WS) is a major cause of syndromic, autosomal dominant hearing loss. However, variable expressivity may lead to underdiagnosis of this form of profound hearing loss. In Waardenburg Syndrome’s classical form the hearing loss is generally a result of mutations in the PAX3 gene associated with individuals with WS type 1 or 3. However, symptoms for WS type 2 has associated with another gene in this pathway, MITF (microphthalmia-associated transcription factor). Waardenberg Syndrome, type 2 has overlapping symptoms with WS 1 and 3 but in its classical format also leads to the loss of pigmentation in the eyes and skin as well as early onset deafness. The MITF protein also interacts with the PAX3 gene (see Waardenburg Syndrome, type 1 & 3) in an auditory-pigmentary developmental pathway. DNA sequencing the entire coding sequence of the MITF gene will detect greater than 98% of mutations in the coding sequence of the gene.

• To determine whether a hearing defect in a child is hereditary.
• To confirm the link between hypopigmentation and hearing loss into a single syndrome.
• To assess the risk of additional children with hearing loss in an affected family.
• Prenatal testing.

• Sequencing the entire coding sequence of the MITF gene will identify all published and unique familial mutations as well as examine the intron-exon borders.

• 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:      3 Weeks

CPT CODES: