Galactosemia

Galactosemia

Galactosemia is an inborn error of metabolism. Because of energy barriers, essentially none of the chemical reactions that take place in living things could occur at any measurable rate without the presence of a catalyst. Most catalysts in living things are enzymes that depend on their structure to be able to function. Their structure is determined by their coding on DNA. Inborn errors of metabolism, like the one seen in galactosemia, are caused by defective genes.

Galactosemia is an inherited metabolic disorder in which the transformation of galactose to glucose is blocked, allowing galactose to increase to toxic levels in the body (Chung 1997). Galactose epimerase, the enzyme in the liver that is required to break down galactose, is deficient in galactosemia patients (“Galactosemia” 1995 and Wohlers, Christacos, and Harreman 1999). This enzyme works as a catalyst to speed up the breakdown of galactose. When there is a deficiency of this enzyme, the body cannot metabolize galactose as quickly as needed, causing a toxic buildup (Olendore, Jenyan, and Bayden 1999).

This disease is inherited in an autosomal recessive manner, this means that galactosemia is only present in individuals with two defective copies of any one of the three genes that causes it (Chung 1997). These genes are the genes that code for the three enzymes, galactosemia-1-phosphate-uridyl transferase (GALT), galactokinase (GALK), and uridyl disphosphogalactose-4-epimerase (Olendore, Jenyan, and Bayden 1999). Although carriers have less than normal enzyme activity, carriers of the disease are unaware that they are carrying a defective gene since no symptoms are evident (Chung 1997). If two carriers of the same defective gene have children, the chance of their child getting galactosemia by having two copies of the same defective gene is 25% for each pregnancy (Elsas 1999). Every cell nucleus has two copies of each gene, therefore, if only one of the two copies is defective, enough of the enzyme is made and the pathway of galactose metabolism is not blocked (Olendore, Jenyan, and Bayden 1999).

Most states have now included testing for galactosemia in newborn screening programs (“Galactosemia” 1995). However, if galactosemia is not found in a screening program, some symptoms appear within the...

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...al of death (“Galactosemia” 1995).

Unfortunately, many children are born each year with galactosemia and there is no medication that can treat it (Chung 1997). However, galactosemia is manageable and the symptoms can be greatly reduced by taking a few precautions. First of all, babies whose GALT activity is less than 10% need to have all their milk products replaced by formula such as Isomil or Prosobee, which are free of lactose. Soy products contain other sugars such as sucrose, fructose, and non-galactose polycarbohydrates, which supply the needed energy to the baby. All lactose containing foods such as dairy products, tomato sauces, candies, and medicines should be avoided fro the remainder of the patients life (Elsas 1999). Finally, legumes, organ meats, and processed meats also contain galactose and should be avoided (Olendore, Jenyan, and Bayden 1999). Management of the diet becomes less important after infancy and early childhood because milk products are no longer the primary source of energy (Elsas 1999). So, although galactosemia can be fatal, it is highly treatable and a patient can live a normal life with only a few changes in their diet.