Glycogen Storage Disease 1a

CPT 81250
Synonyms
  • Jewish Heritage Test
  • von Gierke Disease

Test Details

Use

Glycogen storage disease type 1a (GSD1a), also called von Gierke disease (OMIM 232200), is a recessive inherited disorder characterized by an enlarged liver and kidneys due to the accumulation of glycogen and fat.

Special Instructions

If cultured cells are needed, an additional 7-12 days may be required. Additional culture fee may be included.

Limitations

This test only detects the R83C and Q347X mutations.

Methodology

Polymerase chain reaction (PCR) and primer extension

References

Monaghan KG, Feldman GL, Palomaki GE, Spector EB, Ashkenazi Jewish Reproductive Screening Working Group; Molecular Subcommittee of the ACMG Laboratory Quality Assurance Committee. Technical standards and guidelines for reproductive screening in the Ashkenazi Jewish population. Genet Med. 2008 Jan;10(1):57-72.18197058

Additional Information

Some infants who are untreated develop severe hypoglycemia (low blood sugar).1,2 Long-term complications of untreated GSD1a include short stature, osteoporosis, delayed puberty, kidney disease, liver disease, seizures and intellectual disability. This condition is caused by a deficiency of the enzyme D-glucose-6-phosphatase (G6Pase), and can be treated by making dietary changes and maintaining normal levels of glucose to prevent hypoglycemia. Individuals who are treated can be expected to have normal growth and many live into adulthood.1 The disease has elevated prevalence among Ashkenazi Jews, with a carrier rate of 1 in 71, although it is seen in all ethnic groups. Carriers of GSD1a do not exhibit symptoms that would lead one to suspect their carrier status. When both parents are carriers of GSD1a, there is a 25% chance with each pregnancy to have a child with the disease. Prenatal diagnosis is available.1 Molecular genetic testing for GSD1a encompasses two mutations in the gene encoding D-glucose-6-phosphatase (G6Pase, OMIM 611045). Testing for these two mutations identifies 99% of GSD1a carriers who are Ashkenazi Jewish,2,3 and approximately 60% of GSD1a carriers who are non-Ashkenazi Jewish Caucasian.4 Biochemical analysis of liver biopsy specimens can be performed for diagnostic purposes but does not determine carrier status.2 A negative test result decreases the likelihood that a person is a carrier, but cannot completely eliminate the possibility. The presence of a rare mutation cannot be ruled out. DNA test results must be combined with clinical information for the most accurate interpretation.

Specimen Requirements

Information on collection, storage, and volume

Specimen

Whole blood, amniotic fluid, chorionic villus sample (CVS), or Labcorp buccal swab kit (buccal swab collection kit contains instructions for the use of a buccal swab)

Volume

7 mL whole blood, 10 mL amniotic fluid, 20 mg CVS, or Labcorp buccal swab kit

Minimum Volume

3 mL whole blood, 5 mL amniotic fluid, 10 mg CVS, or two buccal swabs

Container

Lavender-top (EDTA) tube, yellow-top (ACD) tube, sterile plastic conical tube or two confluent T-25 flasks for fetal testing, or Labcorp buccal swab kit

Storage Instructions

Maintain specimen at room temperature or refrigerate at 4°C.

Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; wet buccal swab