What is Galactosemia?

Dr. Yousef Elshrek

What is Galactosemia? • Galactosemia is a disorder that occurs

when the body is unable to break down a type of sugar called galactose that is found in milk and milk products.

• Instead of being changed into glucose, which the body uses for energy, galactose builds up and can cause damage to the brain, eyes, liver and kidneys.

• In another words , Galactosemia is a disorder that causes a certain kind of sugar to build up in the body.

• This sugar is called galactose.

• A modified diet will help prevent the disorder from harming your baby.

• Your baby cannot have food that has galactose in it.

• Most galactose comes from milk sugar.

• Milk sugar is called lactose.

• It is in all foods that have animal milk in them.

• It is in breast milk and many baby formulas.

• A baby with galactosemia doesn't have one of the enzymes that changes galactose into glucose.

• So galactose builds up in the body.

• This can cause damage to the brain, eyes, liver and kidneys.

• The damage can be reduced by taking galactose out of the diet.

• Those suffering from galactosemia cannot properly break down galactose as the result of a genetically inherited mutation in one of the enzymes in the Leloir pathway.

• These individuals cannot break down galactose properly, so the consumption of even small amounts of galactose is harmful to galactosemics.

Leloir pathway

• Galactose is a hexose sugar found in the disaccharide lactose.

• Galactose has six carbons like glucose and differs from glucose only in the stereochemistry of one carbon, C4. The enzymes of carbohydrate metabolism are specific enough that galactose must be changed to glucose before it can enter glycolysis. Dr. Luis Leloir won the 1970 Nobel Prize in part for his contribution to the understanding of galactose metabolism

• To convert galactose to glucose, it is first phosphorylated by galactokinase to produce galactose-1-phosphate.

• Galactose is then exchanged with the glucose group in UDP-glucose to create UDP-galactose and release glucose-1-phosphate.

• An epimerase enzyme changes the stereochemistry of C4 in UDP-galactose, creating UDP-glucose.

• In the next round of the transfer reaction, this glucose is released as glucose-1-phosphate.

• Once released, glucose-1-phosphate is converted to glucose-6-phosphate and can enter glycolysis to generate energy.

• Mutation of the kinase, the transferase or the epimerase can result in clinical deficiencies in galactose metabolism known as galactosemias.

• Galactosemias range in severity depending on the nature of the genetic change, and are usually treated through avoidance of galactose in the diet, primarily from lactose in dairy products.

Figure 1. Metabolic pathways of galactose assimilation. Solid arrows indicate the classical Leloir pathway of galactose disposal and subsequent oxidation to CO2. GALE, UDP-galactose 4 epimerase; GALK, galactokinase; GALT, Galactose-1-phosphate uridyltransferase. Empty arrows indicate the three known alternative pathways of galactose catabolism: galactose reduction to galactitol, galactose oxidation to galactonate and subsequent oxidation to CO2 and conversion of galactose-1-phosphate to UDP-galactose by UGP (UDP-glucose pyrophosphorylase) and subsequent conversion to glycogen and oxidation to CO2.

What Causes Galactosemia

• Galactosemia is inherited.

• A person with galactosemia inherited it

from both parents just as he or she inherited

hair, skin or eye color.

• This is not something person will outgrow.

• He will always have it.

• Therefore, he may have additional health

needs as she/he grows older.

• Galactosemia is not contagious. •

• That means you cannot “catch” it like a common cold.

• He cannot “give” it to another child. • He cannot eat foods that have galactose in them. • Most galactose comes from milk sugar called lactose. • It is in all foods that have animal milk in them. • It is in breast milk and many baby formulas. • A modified diet will help prevent this disorder. • Long term complication of galactosemia includes:

1. Speech deficits 2. Ataxia 3. Dysmetria 4. Diminished bone density 5. Premature ovarian failure 6. Cataract

How is galactosemia treated?

• The only way to treat galactosemia is through dietary restrictions.

• People with the disorder must stay away from foods and drinks containing galactose, including milk, cheese, and legumes (dried beans).

• Any other foods that contain milk or milk products.

• They must follow this diet for their entire lives.

• Galactosemia is treated with a modified diet.

• This diet is called the galactose restricted diet.

• It can help prevent severe damage from occurring to the brain, eyes, liver, and kidneys.

• Children who start the diet as infants and stay on the diet are less likely to have these problems.

Galactosemia causes eye cataract

How Can a person Make Sure Foods

Are Safe? • Read the label on all packaged foods.

• Many packaged and processed foods are unsafe.

• For example, "creamed corn" contains nonfat dry

milk, which is unsafe.

• Do not buy foods that list any of these

items:

1. milk, butter, cream, yogurt

2. cheese

3. nonfat dry milk or milk solids

4. whey or whey solids (milk proteins)

5. lactose (milk sugar)

6. casein (milk protein)

• If there is no label or the contents are not

listed, do not eat this food

• Not always.

• Lactose is often used as a "filler" in medicine, such as penicillin.

• Fillers are inactive ingredients and may not be listed on the container.

• Fillers may also be added to vitamin and mineral supplements .

• Laberls will list nutrients, but may not list fillers.

Are Medicines or Vitamins Safe?

• If a sugar is added, the type of sugar may not be shown.

• Remind your doctor that fillers cannot include lactose.

• Talk with your doctor, nutritionist or pharmacist before giving your child any medicines or food supplements. Your doctor may need to talk with the drug company to make sure the medicine is safe for your baby.

A Daily Guide for Young Children