Waardenburg Syndrome, Type 2 – MITF Gene

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WAARDENBURG SYNDROME, TYPE 2 - MITF GENE

Gene Symbol: MITF

Chromosomal Locus: 3p14-p13
 
Protein: Microphthalmia-Associated Transcription Factor
 
Pseudonyms: WS2
 
TURNAROUND TIME: 4 weeks
   
TESTING METHODOLOGY: Polymerase chain reaction (PCR) and DNA Sequencing of all 9 exons, and their intron- exon borders.
 
SPECIMEN REQUIREMENTS:
  • Collect: Prefer two 5ml whole blood EDTA (lavender top) tube.
  • Min. Collection: 0.7 ml whole blood EDTA.
  • Transport: blood EDTA at Room Temp shipped regular next day air (No Saturday delivery; store specimen at 40°C and ship Monday).
  • Stability: Ambient: up to 7 days; Refrigerated: 2 weeks. Frozen: unacceptable
  • Unacceptable Conditions: Serum. Frozen or severely hemolyzed blood. Clotted blood.
  • Prenatal testing: Direct: 5ml direct unspun amniotic fluid or 15mg CVS tissue with a backup flask growing. Culture: confluent T25 flask. Maternal blood sample is required for maternal cell contamination studies.
A Molecular Genetics Laboratory Test Requisition must accompany the specimen. Contact the Molecular Laboratory at 918-502-1721 to obtain further information.
Note: Counseling and informed consent are recommended for genetic testing. A consent form is available as a resource but not required.
 
INTERPRETATIVE DATA:
 
Incidence: Estimates range from 1:10,000 to 1:40,000
 
Inheritance: Autosomal dominant
 
Disease Characteristics: Congenital sensorineural hearing loss and pigmentary abnormalities of the iris, hair, and skin. The hearing loss is typically non-progressive, sensorineural, and may be either unilateral or bilateral. Symptoms are highly variable even within families.
Molecular Genetic Mechanism: A variety of missense, nonsense and insertion/deletion mutations have been described in the gene.
 
 
Clinical Sensitivity: MITF mutations have been described in 10-20% of individuals with Waardenburg syndrome.
 
Analytical Sensitivity: 99%
 
Test Limitations: Mutations outside of the tested region will not be detected. Rare diagnostic errors can occur due to primer or probe site mutations or rare polymorphisms.
 
INDICATIONS FOR USE:
• To determine whether a hearing defect in a child is hereditary.
• To confirm the link between hypopigmentation and hearing loss into a single syndrome.
• Individuals at risk who wish prenatal diagnosis.
 
ADDITIONAL REFERENCES:
OMIM - Waardenburg Syndrome Type 2: www.omim.org/entry/193510
Genetics Home Reference: www.ghr.nlm.nih.gov/gene/MITF