|
|
|||
|
The Kleberg Cytogenetics Laboratory offers a fluorescence in situ hybridization (FISH)-based assay for identifying the 1.5 Mb duplication associated with Charcot-Marie-Tooth disease type 1A (CMT1A) and the 1.5 Mb deletion associated with Hereditary Neuropathy with Liability to Pressure Palsies (HNPP). Clinical Features:CMT1A is an inherited peripheral neuropathy characterized by slowly progressive distal muscle wasting, weakness and decreased nerve conduction velocities. HNPP is characterized by periodic episodes of numbness and palsies that follow relatively minor compressions or trauma to the peripheral nerves. Severe cases of HNPP can have features that overlap those of CMT1A. Carpal tunnel syndrome and other entrapment neuropathies are frequent manifestations of HNPP and many patients with multifocal neuropathy have the deletion associated with HNPP. Reasons for Referral:FISH can be used to detect duplications/deletions in patients with a suspected diagnosis of an inherited peripheral neuropathy or in individuals with a positive family history. Although testing minors for adult onset disorders is not advised, children with neurological symptoms may be tested. For accurate interpretation of these results, the affected family member should have a duplication/deletion detected by the FISH assay in our laboratory. The Kleberg Cytogenetics Laboratory is not currently offering prenatal diagnosis for CMT1A or HNPP. Testing Methodology:FISH is the application of fluorescently labeled DNA molecules to 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. The majority (>98%) of CMT1A cases are caused by a DNA duplication of a 1.5 Mb region on 17p12 containing the PMP22 gene. The reciprocal product of the CMT1A duplication is a 1.5 Mb deletion that causes hereditary neuropathy with liability to pressure palsies (HNPP). Approximately 80% of patients with HNPP will have a deletion detectable by FISH. FISH for both CMT1A and HNPP is performed on interphase nuclei. In order for a result to be interpreted, at least 70% of the cells must show a consistent hybridization pattern. 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:9 days CPT Codes and Prices:88230, 88271, 88273, 88291 References:1. Lupski, et al. (1993) JAMA 270: 2326-2330. Forms: >> Cytogenetics
Requisition Test Code:8467 |