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| The Kleberg Cytogenetics Laboratory offers a fluorescence in situ hybridization (FISH)-based assay for identifying the duplication of the proteolipid protein (PLP) gene associated with Pelizaeus-Merzbacher disease (PMD). Clinical Features:Pelizaeus-Merzbacher Disease (PMD) is an X-linked, dysmyelinating disorder of the central nervous system. The phenotype is variable, however, most affected males present with nystagmus in infancy or early childhood, hypotonia and cognitive impairment. PMD manifests mainly in males, but carrier females may also have neurologic symptoms. Reasons for Referral:Patients with clinical features suggestive of PMD may be tested for a duplication of PLP. Carrier testing is available for female relatives if the affected male has been tested previously in our laboratory and has been shown to have a duplication. 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. In most cases, (60-70%) PMD is caused by a duplication of the proteolipid protein (PLP) gene, located on Xq22. Many of the remaining cases (~30%) have point mutations or other mutations in the PLP gene, not detected by FISH. The FISH assay for PMD 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 at ambient temperature. Please notify the laboratory of incoming samples. Turnaround Time:9 days CPT Codes and Prices:88230, 88273, 88271, 88291 References:1. Inoue, et al. (1999) Ann. Neuro. 45: 624-632. Forms:Test Code:8475 |