GUANIDINOACETATE METHYLTRANSFERASE (GAMT) DEFICIENCY
GAMT Sequencing
MITOCHONDRIAL DNA ANALYSIS

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. Patients with GAMT deficiency exhibit a more complex clinical phenotype with dystonic hyperkinetic movement disorder and epilepsy that may be unresponsive to pharmacological treatment. GAMT deficiency is an autosomal recessive disorder. The gene contains 6 coding exons. Only a few mutations have been reported so far.

Reasons for Referral:

Confirmation of a clinical diagnosis
Carrier testing

Testing Methodology:

A PCR-based assay is used to amplify all exons and the immediately adjacent intronic regions of the GAMT 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: 3 weeks
Known Familial Mutation:2 weeks

CPT Codes and Prices:

Index case: 83904x12, 83898x6, 83912, 83891, 83894x2
Known Familial Mutation: 83904x4, 83898x2, 83912, 83891, 83894x2

Shipping Information

Forms:

>> Gene Sequencing Requisition or Mitochondrial Requisition - Mitochondrial Diagnostic Checklist is included
>> Prenatal Requisition

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: 3145
Known Familial Mutation: 3146
Prenatal: 3147