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Galactosemia: GALT Gene Deletion/Duplication

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Condition Description

Galactosemia is an autosomal recessive disorder of galactose metabolism that often presents in the newborn period with poor suck, vomiting, diarrhea, bleeding diathesis, lethargy, jaundice, and sepsis. If left untreated, an individual may progress to irreversible liver disease and mental retardation. The prevalence of galactosemia is approximately 1 in 30,000 newborns. Most often galactosemia is caused by a deficiency of the galactose-1-phosphate uridyltransferase (GALT) enzyme, which catalyzes the conversion of the galactose-1-phosphate to glucose-1-phosphate. This is a critical step in the metabolism of galactose to glucose.

The GALT gene is encoded by 11 exons on chromosome 9p13. Galactosemia caused by mutations in the GALT gene is inherited in an autosomal recessive manner.

Family members of individuals with galactosemia are at risk to be carriers of the disorder. Biochemical and molecular screening is available to family members or partners of individuals with galactosemia using a combination of mutation analysis and enzyme activity.

Refer to the comprehensive galactosemia panel (GS) for a disease overview. Refer to the galactosemia carrier panel (GR).

Visit www.ThinkGenetic.com for patient-friendly information on galactosemia.

References:

Genes (1)

GALT

Indications

This test is indicated for individuals with biochemical diagnosis of a galactosemia or carrier status and a negative or unknown result from mutation analysis for common GALT gene mutations. This test is NOT recommended for galactosemia screening or diagnosis in persons with a positive newborn screen. Please refer to the Comprehensive Galactosemia Panel .

Methodology

DNA isolated from peripheral blood is hybridized to a CGH array to detect deletions and duplications. The targeted CGH array has overlapping probes which cover the entire genomic region.

Detection

Detection is limited to duplications and deletions. Array CGH will not detect point mutations or intronic mutations. Results of molecular analysis must be interpreted in the context of the patient's clinical and/or biochemical phenotype.

Specimen Requirements

Listed below are EGL's preferred sample criteria. For any questions, please call 470.378.2200 and ask to speak with a laboratory genetic counselor (eglgc@egl-eurofins.com).
Submit only 1 of the following specimen types
DNA, Isolated
DNA

Requirements
Microtainer
3µg
Isolation using the Perkin Elmer™Chemagen™ Chemagen™ Automated Extraction method or Qiagen™ Puregene kit for DNA extraction is recommended.
Collection and Shipping
Refrigerate until time of shipment in 100 ng/µL in TE buffer. Ship sample at room temperature with overnight delivery.
Whole Blood (EDTA)
WBP

Requirements
EDTA (Purple Top)
Infants and Young Children (<2 years of age): 2-3 ml
Children > 2 years of age to 10 years old: 3-5 ml
Older Children & Adults: 5-10 ml
Autopsy: 2-3 ml unclotted cord or cardiac blood
Collection and Shipping
Ship sample at room temperature for receipt at EGL within 72 hours of collection. Do not freeze.

Special Instructions

Submit copies of diagnostic biochemical test results with the sample. Sequence analysis is required before deletion/duplication analysis by targeted CGH array. If sequencing is performed outside EGL Genetics, please submit a copy of the sequencing report with the test requisition. Contact the laboratory if further information is needed.
  • Comprehensive GALT Analysis is the standard galactosemia test offered by EGL and includes GALT enzyme activity, isozyme pattern (phenotyping), and gal-1-p level.
  • Carrier Testing for Galactosemia is accomplished by looking at GALT and isozyme.
  • Prenatal testing may be available to couples who are confirmed carriers of galactosemia by molecular and biochemical analysis. Please contact the laboratory genetic counselor to determine the availability of prenatal testing.

How to Order

Requisition Forms