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Galactosemia Genetic Testing


DNA/RNA
Test performed by: LabPLUS - Dept. Diagnostic Genetics - Molecular Genetics


Referral Requirements

Important Note:

All tests referred through Metabolic or Genetic Services only.

Contact:

Genetic Health Service NZ can be contacted on 0800 476 123.


Specimen Collection
EDTA4 mL Paediatric EDTA Blood (Preferred)
EDTA8 mL Adult EDTA Blood

Note:

For paediatric samples a minimum of 0.5ml blood EDTA can be processed. (Microcollect)

Transport all bloods at room temperature within 24-48 hours. If necessary specimens can be refrigerated overnight for transport at room temperature the following day.

For testing of other sample types please contact the laboratory prior to sending.


Turnaround Time: 13 weeks
Contact Information

Contact Molecular Genetics via:

Lablink                                                     ext 22000

Mark Greenslade (Technical Head)   ext 22010

Pippa Grainger (Section leader)              ext 22014

Email: DGen@adhb.govt.nz




Background Information

Galactosemia is a disorder that affects how the body processes a simple sugar called galactose. A small amount of galactose is present in many foods. It is primarily part of a larger sugar called lactose, which is found in all dairy products and many baby formulas. The signs and symptoms of galactosemia result from an inability to use galactose to produce energy.

Several types of galactosemia have been identified. These conditions are each caused by mutations in a particular gene, and affect different enzymes involved in breaking down galactose. Classic galactosemia, also known as type I, is the most common and most severe form of the condition. Galactosemia type II (also called galactokinase deficiency) and type III (also called galactose epimerase deficiency) cause different patterns of signs and symptoms.

If infants with classic galactosemia are not treated promptly with a low-galactose diet, life-threatening complications appear within a few days after birth. Affected infants typically develop feeding difficulties, a lack of energy (lethargy), a failure to gain weight and grow as expected (failure to thrive), yellowing of the skin and whites of the eyes (jaundice), liver damage, and bleeding. Other serious complications of this condition can include overwhelming bacterial infections (sepsis) and shock. Affected children are also at increased risk of delayed development, clouding of the lens of the eye (cataract), speech difficulties, and intellectual disability. Females with classic galactosemia may experience reproductive problems caused by ovarian failure.

Galactosemia type II causes fewer medical problems than the classic type. Affected infants develop cataracts, but otherwise experience few long-term complications. The signs and symptoms of galactosemia type III vary from mild to severe and can include cataracts, delayed growth and development, intellectual disability, liver disease, and kidney problems.

Mutations in the GALE , GALK1 , and GALT genes cause galactosemia.

The GALE , GALK1 , and GALT genes provide instructions for making enzymes that are essential for processing galactose obtained from the diet. These enzymes break down galactose into another simple sugar, glucose, and other molecules that the body can store or use for energy.

Mutations in the GALT gene are responsible for classic galactosemia (type I). Most of these genetic changes almost completely eliminate the activity of the enzyme produced from the GALT gene, preventing the normal processing of galactose and resulting in the life-threatening signs and symptoms of this disorder. Another GALT gene mutation, known as the Duarte variant, reduces but does not eliminate the activity of the enzyme. People with the Duarte variant tend to have much milder features of galactosemia.

Galactosemia type II results from mutations in the GALK1 gene, while mutations in the GALE gene underlie galactosemia type III (Epimerase Deficiency Galactosemia). Like the enzyme produced from the GALT gene, the enzymes made from the GALK1 and GALE genes play important roles in processing galactose. A shortage of any of these critical enzymes allows galactose and related compounds to build up to toxic levels in the body. The accumulation of these substances damages tissues and organs, leading to the characteristic features of galactosemia.

Molecular genetic testing is available for GALT

For more information about the Molecular Genetics service:

Molecular Genetics information page


Last updated at 15:49:04 22/03/2021