Prader-Willi Syndrome by FISH

Test name:
FISH, Prader-Willi syndrome

Order name:
Prader-Willi by FISH request

Specimen requirements:
Sodium heparin peripheral blood

Minimum volume:
1mL. 4 mL preferred

Storage and stability information:
Room temperature 3 days

Test performed:
Once per week

Methodology:
Fluorescence in situ hybridization

Reference range:
See lab report

Clinical significance:
Seventy percent of patients with Prader-Willi syndrome have an interstitial deletion of chromosome 15.  Twenty to 30% of patients with Prader-Willi syndrome have been described who do not have the cytogenetic deletion, but instead have two copies of the 15q11.2q13 critical region that are inherited from the mother.  This form of inheritance is known as maternal uniparental disomy.  The remaining 2 to 5% of patients have evidence of normal biparental inheritance of chromosome 15, but with an imprinting mutation.  DNA methylation studies can be performed to detect these defects.

CPT codes:
88368 x 4