|
The Kleberg Cytogenetics Laboratory offers a fluorescence in situ hybridization (FISH)-based assay for identifying the deletion on 15q11-q13 associated with Angelman syndrome. Clinical Features:Angelman syndrome is characterized by severe mental retardation, seizures, absent speech, outbursts of laughter, and ataxic gait. Reasons for Referral:Patients with clinical features suggestive of Angelman syndrome may be tested for deletions of 15q11-q13 by FISH simultaneously with high-resolution chromosomal analysis (if not previously performed). FISH may also be indicated when methylation studies have shown only an unmethylated contribution to further characterize the cause of Angelman syndrome in these patients. Prenatal diagnosis may be performed if an affected family member has been studied in our laboratory and shown to have a deletion detectable by FISH. Please call regarding all prenatal samples. Testing Methodology:FISH is the application of fluorescently labeled DNA molecules to metaphase chromosomes and interphase nuclei for the detection of chromosome abnormalities and alterations. It is a rapid, reliable and direct approach for identifying patients with microdeletions or microduplications. FISH analysis for Angelman syndrome is performed on metaphase chromosomes. The absence of a hybridization signal indicates a deletion. Approximately 70% of Angelman syndrome patients demonstrate a deletion of 15q11-q13. Interestingly, 3-5% of patients who do not demonstrate a deletion have inherited two copies of a paternal chromosome 15 and have failed to inherit a maternal chromosome 15. This phenomenon is termed paternal uniparental disomy (UPD). Recently, a methylation assay was developed to identify all deletion and UPD patients with Angelman syndrome, although methylation studies do not distinguish these two types. For individuals who have mental retardation and have not had a chromosome analysis, the current recommendations are routine cytogenetics and FISH, which can be performed simultaneously. For patients who have had a normal karyotype in the past, the methylation assay (see Angelman Syndrome DNA Methylation Analysis) can be used to detect most cases of Angelman syndrome). Specimen Requirements:Whole blood in sodium heparin (green-top) tubes: Shipping and Handling:All tubes must be labeled with the patient's testname and date of birth, and a completed requisition form must accompany each sample. If the laboratory is billing the patient's insurance, please enclose a copy of the insurance card. Ship specimens for overnight delivery at ambient temperature. Please notify the laboratory of incoming samples. Turnaround Time:7-10 days CPT Codes and Prices:88230, 88271, 88273, 88291 References:1. Kuwano, et al. (1992) Hum. Mol. Genet. 1: 417-425. Forms: >> Cytogenetics
Requisition Test Code:8459 |