Prader-Willi syndrome : (15q11q13) FISH Analysis

Test Information

This cytogenetic FISH analysis for Prader-Willi syndrome (15q11q13)is useful when a specific numerical or structural abnormality or microdeletion is suspected. FISH is also utilized to confirm microdeletions identified during high resolution chromosome analysis and to aid in identification of abnormal chromosomes. .

Turnaround Time

4 weeks

CPT Code(s)

88275, 88273, 88271, 88291

Cost

$584


Chromosomes

15q11q13

Clinical Information

Prader-Willi syndrome is characterized by significant infantile hypotonia and feeding difficulties. In early childhood this transitions into excessive eating and morbid obesity. Developmental delay and behavioral problems are common features. Physical characteristics include hypogonadism, short stature, small hands and feet, almond shaped eyes, and hypopigmentation. Prader-Willi syndrome is caused by the lack of expression of the paternally derived region of chromosome 15 (15q11.2-q13). This lack of expression can be caused by a deletion of the paternal chromosome, maternal uniparental disomy (UPD) of chromosome 15 or more rarely, a defect in the imprinting region. Angelman syndrome is characterized by significant developmental delay or intellectual disability, severe speech impairment, an ataxic gait, and inappropriate happy behavior including excessive laughing and smiling. Other physical concerns include microcephaly, seizures, wide mouth and a prominent mandible.

Indications

Fluorescence in situ hybridization is a molecular cytogenetic technique in which fluorescently labeled DNA probes are hybridized to metaphase spreads or interphase nuclei. Applications include identification of structurally abnormal chromosomes, including identification of marker chromosomes, detection of very small deletions (microdeletions), and rapid detection of Down syndrome and other numerical chromosome abnormalities; and the rapid detection of sex chromosomes and the SRY gene. FISH should be used in conjunction with G-banded chromosome analysis. FISH is performed upon request when a specific numerical or structural abnormality or microdeletion is suspected. FISH is also utilized to confirm microdeletions identified during high resolution chromosome analysis and to aid in identification of abnormal chromosomes.

Specimen Requirements

FISH can be performed on any tissue that can be cultured for chromosome analysis, including blood, fibroblasts, amniotic fluid, and chorionic villus sampling. Follow collection and transport guidelines specific for each tissue type. Studies requested should be indicated at the time of sample submission. Prenatal testing will be considered on a case-by-case basis as the lab would like to ensure there is an appropriate indication before accepting a prenatal specimen for testing. Appropriate indications include abnormal ultrasound findings, abnormal NIPT result, and/or family history with a known/identified genetic etiology. Contact the laboratory prior to sending a prenatal specimen to discuss your case with a lab genetic counselor.

Transport Instructions

Will vary depending on sample type: Blood: Specimen should be kept at room temperature; do not freeze or refrigerate. Specimen should be sent by courier or overnight mail to arrive at the laboratory the next day. Amniotic Fluid and CVS: Specimen should be kept at room temperature; do not freeze or refrigerate. Specimen should be sent by courier or overnight mail to arrive at the laboratory the next day. Solid Tissue(such as skin biopsy, products of conception, or fetal tissue): Specimen should be kept at room temperature if it will be transported immediately. If specimen is not being immediately transported to the laboratory, it may be refrigerated; do not freeze. Specimen should be sent by courier or overnight mail to arrive at the laboratory the next day.

Prenatal Testing Information

Considered on a case-by-case basis. Additional fees for cell culture and maternal cell contamination may apply. Maternal cell contamination studies are required for most prenatal testing. Contact the laboratory prior to sending a prenatal specimen.

Have Questions? Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Falecia Thomas, MS, CGC

Meet Reggie Roper

Reggie has been part of the GGC family for over 18 years. He has short stature, webbing of his hands, pulmonary stenosis, seizures and hydrocephalus along with developmental delay. He carried an initial diagnosis of cardiofaciocutaneous (CFC) syndrome; however, as genetic testing advanced, GGC made the diagnosis of Noon...

In The News