Cerebral Creatine Disorders

Creatine Transporter Deficiency

Creatine transporter deficiency is a recently described X-linked syndrome resulting from mutations in the SLC6A8 gene localized to Xq28. Affected males present with moderate to severe mental retardation, severe speech and language delays, seizures, and epilepsy. Behavioral disturbances and autistic features have also been noted in a majority of patients. Some carrier females may have a history of learning disabilities. Studies in urine from affected males show an elevated creatine/creatinine ratio which is diagnostic for the disorder.

Specimen requirements: Urine (at least 500ul) is requested for the analysis. A fasting sample or first morning urine is preferred in males under 10 years of age.

Transport: Samples must be frozen and shipped on dry ice by overnight delivery services.

Standard of analysis: Analysis will be done by tandem mass spectrometry (MS-MS) with quantitation of creatine and creatinine.

Turn around time: Analysis will be complete within ten days.

Special request: Any type of special request must be made directly to the laboratory at the time the specimen is submitted.

Report: Written reports with interpretation will be mailed and, when abnormalities exist, the report will be made by telephone. Results may be sent by fax when requested.

Creatine Biosynthesis Disorders

Lab studies request form

CPT Codes/Price List (PDF)

Recently, three disorders have been identified that are caused by defects in creatine synthesis and transport- AGAT (L-arginine:glycine amidinotransferase) deficiency, GAMT (guanidinoacetate methyltransferase) deficiency, and creatine transporter deficiency. All three disorders are characterized by mental retardation, speech delay and epilepsy. GAMT deficiency can also present with a dystonic hyperkinetic movement disorder. Creatine transporter deficiency shows X-linked inheritance while GAMT and AGAT deficiencies are autosomal recessive. The three disorders can be separated based on urine testing for guanidinoacetate (GAA) and creatine. Patients with AGAT deficiency show a low urinary GAA level while patients with GAMT have an elevated GAA level. Males with the creatine transporter deficiency have an elevated urinary creatine/creatinine ratio.

Specimen requirements: Urine (at least 500ul) is requested for the analysis. A fasting sample or first morning urine is preferred in males under 10 years of age.

Transport: Urine samples must be frozen and shipped on dry ice by overnight delivery services.

Standard of analysis: Analysis will be done by tandem mass spectrometry (MS-MS) with quantitation of creatine, GAA, and creatinine.

Turn around time: Analysis will be complete within ten days.

Special request: Any type of special request must be made directly with the laboratory at the time the specimen is submitted.

Report: Written reports with interpretation will be mailed and, when abnormalities exist, the report will be made by telephone. Results may be sent by fax when requested.