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Carbohydrate Metabolism Disorders

Carbohydrates are the body's sugar source. Sugars used to provide energy for the body include glucose , sucrose , fructose among many others. Some sugars need to be broken down, usually by enzymes , before they can be used by the body. If the enzymes needed are not present (usually due to an inherited disorder), these sugars can build up and cause problems. The type of problem depends on the sugar involved.
The following is a run down of the main carbohydrate metabolism disorders :

  1. Galactosemia . Galactosemia is an inherited autosomal recessive trait that affects the way the sugar galactose is broken down, due to the lack of the enzyme galactose-1-phosphate uridyl transferase. Galactose can be found on its own in food or is the result of lactose (milk sugar) being broken down into galactose and glucose. The body uses glucose for energy. In galactosemia, galactose then builds up and becomes toxic. In reaction to this build up of galactose the body makes some abnormal chemicals. The build up of galactose and the other chemicals can cause serious health problems like a swollen and inflamed liver, kidney failure, ovarian failure in girls, stunted physical and mental growth, and cataracts in the eyes.
    If the condition is not treated there is a 70% chance that the child could die. About 1 out of 50,000 to 70,000 babies is born without this enzyme. During pregnancy an amniocentesis test may detect if the infant has Galactosemia.
    Galactosemia is not lactose intolerance. Galactosemia is more serious because it will cause permanent damage if left untreated.
    The treatment for galactosemia is to restrict galactose and lactose from the diet for life. With a restricted diet the child with galactosemia may have less severe symptoms. There is no chemical or drug substitute that can be taken for the missing enzyme. Click here for a list of foods/food labels that indicate the presence of galactose or lactose.
    For more comprehensive information on this topic contact the source for this info. [ 1 ]
  2. Glycogen storage diseases or glycogenoses are a group of disorders due to a lack of one or more enzymes needed to break down glucose into its storage form, glycogen, and back from glycogen to glucose when the body requires it. Glucose is a critical source of energy for the brain and is the initial source of energy for muscles. Thus it must be stored in an easily releasable form. The liver serves as the glycogen (and therefore glucose) depot for the brain, while muscles maintain a glycogen supply of their own. There are at least 10 well recognised varieties of glycogen storage diseases (list here ), all of which are autosomal recessive disorders . In each, glycogen accumulates in the liver or muscles and sometimes in the kidneys. [ 2 ]
  3. Hereditary fructose intolerance (HFI) . Also known as Fructose-1-Phosphate Aldolase Deficiency , Fructosemia Disorder. An inherited inability to digest fructose (fruit sugar) or its precursors (sugar, sorbitol and brown sugar). This is due to a deficiency of activity of the enzyme fructose-1-phosphate aldolase , resulting in an accumulation of fructose-1-phosphate in the liver, kidney, and small intestine. People with HFI usually develop a strong dislike for sweets and fruit. After eating foods containing fructose, they may experience such symptoms as severe abdominal pain, vomiting, and hypoglycaemia (low blood sugar levels; treated with glucose tablets). Early diagnosis is important because, while most people who have HFI can lead normal lives if they adopt a fructose-free diet, the condition can lead to permanent physical harm, including serious liver and kidney damage, if left untreated. [ 3 ]
  4. Fructosuria. Also referred to as Essential Fructosuria , Hepatic Fructokinase Deficiency , Levulosuria Disorder . Fructosuria is a very rare, harmless, inherited metabolic disorder. It is characterised by the excretion of fruit sugar (fructose) in the urine. Normally, no fructose is excreted in the urine. This condition is caused by a deficiency of the enzyme fructokinase in the liver. This enzyme is needed for the synthesis of glycogen (the body's form of stored energy) from fructose. The presence of fructose in the blood and urine can sometimes lead to an incorrect diagnosis of Diabetes Mellitus. About 1 out of 130,000 people in the general population has fructosuria. No treatment is necessary. [ 3 ]
  5. Pentosuria. A benign inborn error of metabolism due to a defect in the activity of the enzyme l-xylulose, resulting in high levels of the sugar l-xylulose in the urine. A harmless condition. Occurs almost exclusively in Ashkenazim Jews of Polish-Russian extraction. [ 4 ]

The information in this page is presented in summarised form and has been taken from the following source(s):
1. Texas Department of Health Newborn Screening (NBS) Program:
2. The Encycloædia Britannica© Online:
3. United States National Organization for Rare Disorders, Inc:
4. Online Mendelian Inheritance in Man, OMIM, National Center for Biotechonology Information:

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Carbohydrate Metabolism
Carbohydrate Disorders
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Contact Last modified: Oct 20 2004