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Description:Creatine deficiency syndromes are a newly described group of inborn errors caused by mutations in one of the three genes involved in creatine synthesis: arginine-glycine amidinotransferase (AGAT), guanidinoacetate methyltransferase (GAMT), and creatine transporter (CRTR). Measurement of guanidinoacetate in body fluids may discriminate GAMT (high concentration), AGAT (low concentration), and CRTR (normal concentration). The common clinical feature of creatine deficiency is mental retardation and epilepsy. In patients with CRTR deficiency, the urinary creatine excretion relative to the creatinine excretion is elevated, and the creatine/creatinine ratio can be used as a first biochemical diagnostic marker for CRTR deficiency. The CRTR is a sodium and chloride dependent transporter 1 (CT1), that belongs to the solute carrier family 6 member 8 (SLC6A8). The gene is located on the X-chromosome. Only a few mutations have been reported so far. Reasons for Referral:
Testing Methodology:A PCR-based assay is used to amplify all exons and the immediately adjacent intronic regions of the SLC6A8 gene. Direct sequence analysis of PCR products is performed in both the forward and reverse directions using automated fluorescent dideoxy sequencing methods. Specimen Requirements:Blood: EDTA (purple-top) tubes: Adult: 14 cc; Child: 6 cc; Infant: 2-3 cc Turnaround Time:Index: 4 weeks CPT Codes and Prices:Index: 83904x26, 83898x13, 83912, 83891,
83894x2 Shipping InformationForms:>> Gene Sequencing Requisition or Mitochondrial Requisition - Mitochondrial Diagnostic Checklist is included References:1.Stromberger C et al. (2003) Clinical characteristics and diagnostic clues in inborn errors of creatine metabolism. J. Inherit. Metab. Dis. 26: 299-308 Test Codes:Index: 3150 |