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| The Kleberg Cytogenetics Laboratory offers a fluorescence in situ hybridization (FISH)-based assay for identifying the microdeletions on 8q24.1 associated with Langer-Giedion syndrome (LGS) and trichorhinophalangeal syndrome (TRPSI). Both syndromes exhibit significant phenotypic variability and most likely represent a contiguous gene deletion syndrome, with the deletion causing LGS including a gene for multiple exostoses (EXT1). The deletion causing trichorhinophalangeal syndrome includes the gene, TRPSI. Clinical Features:Langer-Giedion syndrome is characterized by unusual facial features, mental retardation and multiple exostoses. Trichorhinophalangeal syndrome is limited to the facial features and cone-shaped epiphyses seen in LGS. Most TRPSI patients do not have mental retardation or exostoses. Reasons for Referral:FISH can be used to detect deletions in patients with a suspected diagnosis of LGS or TRPS1. 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 LGS/TRPSI is performed on metaphase chromosomes. The absence of a hybridization signal indicates a deletion. Due to the clinical variability of both LGS and TRPSI, this laboratory uses a combination of probes in order to maximize detection of both disorders. For patients suspected of having LGS, the FISH-based assay utilizes two probes in order to detect the presence or absence of the EXT1 and TRPSI contiguous genes. Most patients with LGS will demonstrate deletions in both regions. Patients suspected of having TRPSI are only tested with the TRPSI probe, however; only a small number of patients with TRPSI will demonstrate deletions by the FISH assay. See trichorhinophalangeal syndrome (TRPSI) for testing information. 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, 88271x3, 88273, 88291, 88280 References:1. Ahn, et al. (1995) Nat. Genet. 11: 137-143. Forms: >> Cytogenetics
Requisition Test Code:8430 |