What is Galactose ?
Galactose is a simple sugar, less sweet than glucose or fructose. It is mainly found in dairy products. Galactose contributes directly to vital information processing in the body and is an important substance in cell and cell wall.
What is Galactosemia?
Galactosemia is a genetic condition (inherited as Autosomal recessive) wherein excessive galactose and its products accumulate in the body.
When we consume lactose (dairy products like milk, cheese, butter), our body breaks lactose into glucose and galactose. Glucose is needed as energy source by the body. Galactose is then converted to glucose by certain enzymes in the body.
In Galactosemia these enzymes that convert galactose to glucose are absent, therefore cause galactose to stock up. This excess galactose is poison for the body. It has serious effects on liver, kidney, brain, eyes.
How does classic Galactosemia present?
Classic Galactosemia is caused by deficiency (absence) of enzyme Galactose 1 phosphate uridyl tranferase (GALT). Absence of this enzyme causes accumulation of Gal-1 phosphate.
The child presents in first week of life itself with
- Low sugars
- Yellowish discolouration / jaundice
- Reduced activity/ lethargy
- Feeding problems
- Irritability/ excessive crying
- Inability to gain weight
- Cataracts / white opacity in eye
- Distension of abdomen
- Infections (especially by organism E. coli)
If this is not diagnosed early, it can have deleterious effects on major vital organs. The patients may also succumb to liver, kidney failure and infections.
What are other types of Galactose metabolism defects?
Two other types are due to deficient Galactokinase (GALK), epimerase enzymes.
These are less common than Classic type.
How is Galactosemia inherited?
A person unaffected by galactosemia (neither carrier nor galactosemic) inherits two ‘normal' genes for the production of the GALT enzyme. This person's genotype would be N/N and their enzyme activity would be normal.
A person who is a carrier of classic galactosemia inherits one normal gene from one parent and one gene containing the error that leads to classic galactosemia from the other parent. This person's genotype would be G/N and their enzyme activity would be less than normal, but not so much so as to cause medical complications or require dietary management.
A person who is classic galactosemic inherits two genes with the error, one from each of his/her parents. This person's genotype would be G/G and their enzyme activity would be essentially zero.
This is called Mendelian Autosomal recessive inheritance.
How is Galactosemia diagnosed?
1. Demonstrating presence of reducing sugar (galactose) in urine of the child when on lactose containing feeds.
2. RBC enzyme assays showing low/ absent levels of the enzyme
3. Increased levels of galactose and its products in blood.
Testing for Galactosemia is done routinely in Newborn Screening Tests.
How is Galactosemia treated?
Galactosemia cannot be cured. However steps can be taken to minimize the symptoms and the complications.
It is a condition where any lactose containing products is harmful for the child and therefore treatment is essentially LACTOSE FREE DIET (so will be Galactose free as well). Various lactose free formulas are available for newborns and infants.
Eliminating lactose from the diet reverses growth failure, liver and kidney failure and cataracts regress
However this is a lifetime disease and dietary elimination continues lifelong.
What are the complications expected in the long run?
Though lactose free diet prevents major organ damages, in the long term complications may still occur such as:
- Poor growth
- Learning difficulties
- Speech disorders
- Menstrual irregularities
- Instability in gait (balance)
What are the foods which need to be avoided in Galactosemia?
- Nonfat Milk
- Nonfat Dry Milk
- Milk Chocolate
- Buttermilk Solids
- Nonfat Dry Milk Solids
- Milk Derivatives
- Dried Cheese
- Milk Solids
- Sour Cream
- Dry Milk
- Whey and Whey Solids
- Dry Milk Protein
- Organ Meats (liver, heart, kidney brains, sweetbreads, pancreas)
- Sodium Caseinate
- Calcium Caseinate
- Tragacanth Gum
- Dough Conditioners
- Hydrolyzed Protein
- MSG (Monosodium Glutamate)
- Soy Sauce
Important articles on Galactosemia:
1. Literature review and outcome of classic galactosemia diagnosed in the neonatal period.
Karadag N, Zenciroglu A, Eminoglu FT, Dilli D, Karagol BS, Kundak A, Dursun A, Hakan N, Okumus N.
Clin Lab. 2013;59(9-10):1139-46. Review.
2. Etiology, clinical spectrum and outcome of metabolic liver diseases in children.
Roy A, Samanta T, Purkait R, Mukherji A, Ganguly S.
J Coll Physicians Surg Pak. 2013 Mar;23(3):194-8. doi: 03.2013/JCPSP.194198.
3. Circumstances when breastfeeding is contraindicated.
Lawrence RM.Pediatr Clin North Am. 2013 Feb;60(1):295-318. doi: 10.1016/j.pcl.2012.09.012. Epub 2012 Oct 30.
4. Galactosemia: when is it a newborn screening emergency?
Berry GT.Mol Genet Metab. 2012 May;106(1):7-11. doi: 10.1016/j.ymgme.2012.03.007. Epub 2012 Mar 21.
5. Galactosemia presenting as recurrent sepsis.
Rathi N, Rathi A.J Trop Pediatr. 2011 Dec;57(6):487-9. doi: 10.1093/tropej/fmr018. Epub 2011 Feb 14.
6. Classic Galactosemia and Clinical Variant Galactosemia.
Berry GT.In: Pagon RA, Adam MP, Ardinger HH, Bird TD, Dolan CR, Fong CT, Smith RJH, Stephens K, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2014. 2000 Feb 04 [updated 2014 Apr 03].