Test Directory

• WBS, 7q11.23
• 7cen, D7Z1, 7p11.1-q11.1

Williams syndrome (WS) is a genetic disorder that occurs in 1/20,000 to 1/50,000 live births. Although WS is typically a sporadic disorder, familial cases have been reported. WS is a contiguous gene deletion syndrome, caused by deletion of several genes on chromosome 7q. One gene that often is deleted in WS is the elastin gene, which causes supravalvular aortic stenosis (SVAS) and other cardiovascular disease in these patients. The elastin gene (ELN) has been mapped to 7q11.23 (Williams syndrome chromosome region) and is reportedly hemizygous in up to 96% of patients with WS. The deletion of an elastin gene locus cannot be detected by conventional high-resolution chromosome analysis in the vast majority of cases due to the small size of this deletion.

The use of high-resolution chromosome studies and fluorescence in situ hybridization (FISH) for Williams syndrome chromosome region should diagnose about 96% of Williams syndrome patients and, at the same time, identify any other chromosome anomalies.

Specimen: Peripheral Blood

Collection Container: Green Top (Sodium Heparin)

Desired Specimen Volume: 2 - 5 mL

Minimum Acceptable Volume: 1 mL

• Lithium heparin is not acceptable.
• Specimens must be collected in a sterile collection container.

Each specimen must be accompanied by a requisition form, script, electronic order or physician note. Each order must indicate the reason for testing (diagnosis).

• Transport to the laboratory at room temperature.
• Store specimen as whole blood, in original tube, at room temperature and deliver to lab within 24 hours.
• If specimen cannot be delivered within 24 hours, store in refrigerator. Do not freeze specimen.
• Specimens collected on the weekends must be refrigerated upon arrival at HNL Lab Medicine.

• Specimen frozen
• Specimen arriving without any form of patient identification (unlabeled)
• Specimen with attached needles
• Specimen arriving with broken or leaking collection tube
• Unfixed specimen treated with fixative

In a normal cell, the expected signal pattern is two red signals and two green signals. In an abnormal cell containing the deletion, the expected signal pattern is one red signal and two green signals. In an abnormal cell containing a duplication, the expected signal pattern is three red signals and two green signals.

• FISH Williams-Beuren Syndrome
• WBS
• 7q11.23

Probes used for metaphase and interphase FISH (PWS/AS, DGS or WBS region DNA probes) are labelled with fluorophores and analyzed under fluorescence microscopy. This test will detect the cryptic rearrangements involving 7q11.23 that is not demonstrated by conventional chromosome studies.