PDHX Gene Analysis

The PDHX gene encodes the E3 binding protein component (formerly known as component X) of the pyruvate dehydrogenase complex (PDC). The E3 binding protein binds the E3 component (dihydrolipoamide dehydrogenase, encoded by the DLD gene) to the E2 component (dihydrolipoamide transacetylase, encoded by the DLAT gene), which is the core of the pyruvate dehydrogenase complex. Patients with PDHX mutations present with lactic acidosis, infantile encephalopathy, and reduced PDC activity in cultured skin fibroblasts, lymphocytes, or muscle. Mutations of PDHX (as well as PDHB and DLD) are more common in consanguineous families, since these disorders are autosomal recessive.

For patients with deficient PDC enzyme activity or strongly clinically suspected PDC deficiency, PDHA1 gene sequence analysis is recommended as the first step in mutation identification, since mutations of PDHA1 are most common. PDHX gene sequence analysis is available as a follow-up test or can be ordered as the initial test when clinically indicated. Sequence analysis of other genes in PDC complex including PDHB gene sequence analysis, DLD gene sequence analysis and DLAT gene sequence analysis are also available when clinically indicated.

PDHX known familial mutation analysis is available for family members when a mutation has been identified through analysis performed in this laboratory. PDHX prenatal diagnosis is also available for families who have had a mutation identified through analysis performed in this laboratory or by special arrangement in advance with the director.

Indications for Testing

  • Confirmation of a clinical/biochemical diagnosis of pyruvate dehydrogenase complex deficiency
  • Targeted mutation analysis for known familial mutations
  • Pregnancy known to be at risk for pyruvate dehydrogenase deficiency and a known PDHX familial mutation

OMIM #: 608769

Sample Requirements

  • Infants: two to three mL whole blood in purple top EDTA tube
  • Children (>2 years) and adults: five to seven mL whole blood in purple top EDTA tube
  • Amniotic fluid or cultured amniocytes
  • Chorionic villi or cultured chorionic villi

Contact laboratory genetic counselors or molecular director for specific sample requirements in advance.

Note: Maternal blood sample is also required for maternal cell contamination studies for prenatal samples. Send five mL in purple top EDTA tube along with prenatal sample.

Cultured skin fibroblasts, blood lymphocytes, and frozen tissue from fresh muscle or liver biopsies performed for enzyme analysis may also be used for DNA analysis. Cell line build up is available, as is DNA extraction and storage. Enzyme assay for PDC may be arranged directly with the Center for Inherited Disorders of Metabolism (CIDEM).

Sample Handling

Blood samples stored overnight should be refrigerated or kept cold. Blood samples should never be frozen. Specimens being sent from outside facilities should be packaged with a cold pack according to standard medical safety practices. The specimen should be shipped by overnight priority (scheduled to arrive by Friday morning at the latest).

Shipping Address

Center for Human Genetics Laboratory
10524 Euclid Ave, Sixth Floor
Cleveland, OH 44106
216-983-1134

For local samples, please call Client Service (216-844-5227) to arrange for sample pick-up.

Turnaround Time

PDHX Sequencing – 3 weeks
PDHX Known Familial Mutation analysis – 1 week
PDHX Prenatal Diagnosis – 1 week

CPT Codes

PDHX Gene Sequencing: 81406
PDHX Prenatal Analysis: 81404
PDHX Known Familial Mutation Analysis: 81403

Please submit a completed Prenatal and Postnatal Cytogenetics and Molecular specimens requisition for each sample.

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