Galactokinase deficiency

Definition

Galactosemia is the inability of the body to use (metabolize) the simple sugar galactose, causing the accumulation of galactose 1-phosphate in the body. This causes damage to the liver, central nervous system, and other body systems.

Alternative Names

Causes

Galactosemia is an inherited enzyme disorder (transmitted as an autosomal recessive trait). It occurs in approximately 1 out of every 60,000 births among Caucasians, while the rate is different for other groups.

There are 3 forms of the disease: galactose-1 phosphate uridyl transferase deficiency (classic galactosemia, the most common and most severe form), deficiency of galactose kinase, and deficiency of galactose-6-phosphate epimerase.

People with galactosemia are unable to fully break down the simple sugar galactose. Galactose makes up half of lactose, the sugar found in milk. Lactose is called a disaccharide (di meaning 2 and saccharide meaning sugar) because it is made up of two sugars, galactose and glucose, bound together.

If an infant with galactosemia is given milk, derivatives of galactose build up in the infant's system, causing damage to the liver, brain, kidneys, and eyes. Individuals with galactosemia cannot tolerate any form of milk (human or animal) and must carefully watch intake of other galactose-containing foods. Exposure to milk products may result in liver damage, mental retardation, cataract formation, and kidney failure.

After drinking milk for a few days, a newborn with galactosemia will refuse to eat and develop jaundice, vomiting, lethargy, irritability, and convulsions. The liver will be enlarged and the blood sugar may be low. Continued feeding of milk products to the infant leads to cirrhosis of the liver, cataract formation in the eye (which may result in partial blindness), and mental retardation

Symptoms

• Jaundice (yellowish discoloration of the skin and the whites of the eyes)
• Vomiting
• Poor feeding (baby refusing to drink milk-containing formula)
• Poor weight gain
• Lethargy
• Irritability
• Convulsions

Exams and Tests

• Hepatomegaly (enlarged liver)
• Hypoglycemia (low blood sugar)
• Aminoaciduria (amino acids are present in the urine and/or blood plasma)
• Cirrhosis
• Ascites (fluid collects in the abdomen)
• Mental retardation
• Cataract formation

Tests include:

• Prenatal diagnosis by direct measurement of the enzyme galactose-1-phosphate uridyl transferase 
• The presence of "reducing substances" in the infant's urine with normal or low blood sugar while the infant is being fed breast milk or a formula containing lactose. A simple test on the urine indicates the presence of a reducing substance, and a specific enzymatic study on the urine can prove the substance to be galactose.
• Presence of chemicals, called ketones, in the urine
• Measurement of enzyme activity in the red blood cells
• Blood culture for bacteria infection (E. coli sepsis)

Treatment

Once the disease is recognized, treatment consists of strictly avoiding all milk, milk-containing products, and other foods that contain galactose. The infant can be fed with soy formula, meat-base formula, or Nutramigen (a protein hydrolysate formula), or other lactose-free formula.

The condition is lifelong and requires abstinence from milk, milk products, and galactose-containing foods for life. Calcium supplements are recommended.

Parents need to take care and educate the child to avoid not only milk and milk products, but also those foods that contain dry milk products. For this reason, it is essential to read product labels and be an informed consumer.

Support Groups

Parents of Galactosemic Children, Inc.

www.galactosemia.org

Outlook (Prognosis)

If diagnosis is made early and milk products are strictly avoided, the prognosis is for a relatively normal life. Despite strict avoidance of galactose, mild intellectual impairment may still develop.

Possible Complications

• Cataracts
• Cirrhosis
• Severe infection with bacteria (E. coli sepsis)
• Delayed speech development
• Severe mental retardation
• Irregular menstrual cycles, decreased function of ovaries, leading to ovarian failure
• Tremors and uncontrollable motor functions
• Death, if diet is not adhered to

When to Contact a Medical Professional

• If your infant shows a combination of galactosemia symptoms
• If you have a family history of galactosemia and are considering having children.

Prevention

A personal knowledge of family history is helpful. If there is a family history of galactosemia, genetic counseling will help prospective parents make decisions about pregnancy and prenatal testing. Once the diagnosis of galactosemia is made, genetic counseling is recommended for other members of the family.

Many states have mandatory screening of newborns for galactosemia. Parents may receive a call from a health care provider that says the screening test indicates possible galactosemia. At that time, the parents should promptly stop milk products and have a blood test done for galactosemia through their doctor.