Glycogen Storage Disease 1a
Glycogen Storage Disease 1a | | | |
| Number | | 511290 |
| CPT | | 83891; 83892; 83900; 83912; 83914 (x2) |
| Synonyms | | von Gierke Disease; Jewish Heritage Test |
| 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, 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 or hemolyzed specimen; quantity not sufficient for
analysis; improper container; wet buccal swab |
| 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. |
| Limitations | | This test only detects the R83C and Q347X mutations.
This procedure may be considered by Medicare and other
carriers as investigational and therefore, may not be
payable as a covered benefit for patients.
|
| Methodology | | Polymerase chain reaction (PCR) and primer extension |
| Additional Information | | Some infants that 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 mental retardation. 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 1/71, although it is seen in all ethnic
goups. 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 that are Ashkenazi
Jewish,2,3 and
approximately 60% of GSD1a carriers that 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. |
| Footnotes | |
1. Bali DS, Chen YT. Glycogen Storage Disease Type 1.
www.geneclinics.org, 2006.
2. Ekstein J, Rubin BY, Anderson SL, Weinstein DA,
Bach G, Abeliovich D, et al. Mutation frequencies for
glycogen storage disease Ia in the Ashkenazi Jewish
population. Am J Hum Genet. 2004; 129A:162-164.
3. Chou JY, Matern D, Mansfield BC, Chen YT. Type I
glycogen storage diseases: disorders of the
glucose-6-phosphatase complex. Curr Mol Med. 2002;
2:121-143.
4. Lei KJ, Chen YT, Ken H, Wong LJ, Liu JL,
McConkie-Rosell A, et al. Genetic basis of glycogen storage
disease type 1a: prevalent mutations at the
glucose-6-phosphatase locus. Am J Hum Genet. 1995;
57:766-771. |
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