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Molecular Genetics Laboratory

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Carnitine Palmitoyltransferase 1A Deficiency (CPT1A1 Sequence Analysis)

  • LIS Mnemonic: MBCPTFS

    Collect

    Collect whole blood in a purple top (EDTA) tube (preferred). Extracted DNA is accepted.

    Volume Required

    6 ml whole blood or 6 ug DNA

    Minimum Required

    3 ml

    Transport

    Refrigerate sample until shipment. Send the sample at room temperature with overnight delivery for receipt Monday through Friday within 24 hours of collection.

    Stability

    Whole blood can be refrigerated until shipment.

    Unacceptable conditions

    Heparinized specimens, severely hemolyzed specimens, frozen, clotted or possibly commingled specimens, blood in non-sterile or leaky containers, mislabeled or inappropriately labeled specimens.

    Specimen Handling

    Do not heat, freeze or centrifuge blood before shipment. Refrigerate sample until shipment.

Days Performed

Mon - Fri 9:00am to 4:00pm

Reported

6-8 weeks

CPT

81406

Disease Information

Clinical Features:

Carnitine palmitoyltransferase 1A (CPT1A) deficiency is a disorder of long-chain fatty acid oxidation. Clinical symptoms usually occur in an individual with a concurrent febrile or gastrointestinal illness when energy demands are increased; onset of symptoms is usually rapid. The three recognized phenotypes are hepatic encephalopathy, in which individuals (typically children) present with hypoketotic hypoglycemia and sudden onset of liver failure; adult-onset myopathy, (seen in one individual of Inuit origin); and acute fatty liver of pregnancy, in which the fetus is homozygous for the CPT1A gene that causes CPT1A deficiency. A heterozygous female carrying a homozygous fetus is at risk for developing this obstetric complication.

Molecular Genetics:

CPT1A is the only gene associated with CPT1A deficiency. Mutations in the CPT1A gene result in reduced activity of CPT I, which prevents the entry of fatty acids in to the mitochondria for energy production. The result is a clinical and biochemical phenotype of fasting intolerance. The CPT1A gene spans more than 60 kb of genomic DNA, of which 18 exons (2-19) are transcribed. The CPT1A gene encodes a 773-amino acid polypeptide, which is expressed in liver, kidney, leukocytes, and skin fibroblasts. Missense, nonsense, insertion and deletion mutations have been reported (Bennett et al. 2004; Prasad et al. 2001; Stoler et al. 2004) and these mutations have been identified throughout the gene.

Test Methods:

We offer DNA sequence analysis of the entire coding region. PCR amplification and sequencing is performed on all coding exons including splice junctions. The patient’s gene sequence is then compared to a reference sequence. Sequence variants are classified as mutations, variants of unknown significance or benign variants unrelated to disease. Variants of unknown significance may warrant further studies in the patient and other family members. Large deletions, mutations in promoters, deep intronic regions and other regulatory regions will not be identified with this assay.

Detection Rate:

Point mutations in the CPT1A gene have been identified in about 90% of patients with CPT1 deficiency. The analytical sensitivity of this assay is close to a 100%.

Related Tests:

Known point mutation analysis is available to family members for mutations previously identified by sequence analysis. Prenatal testing is available to couples who are confirmed carriers of mutations. Please contact the laboratory director to discuss appropriate testing prior to collecting a prenatal specimen.

Results:

Test results with interpretation will be mailed and/or faxed to the referring physician or send out lab following completion of the test. Additional reports will be provided as requested.

Utility:

The clinical utility of the assay is in confirming the clinical diagnosis of CPT1A deficiency in these patients, assessing the risk to other first degree relatives and genotyping at risk family members.

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215-590-5221