Health Encyclopedia

Hereditary fructose intolerance

Definition

Hereditary fructose intolerance is a disorder of metabolism in which a person lacks the protein needed to break down fructose. Fructose is a fruit sugar that naturally occurs in the body. Man-made fructose is used as a sweetener in many foods, including baby food and drinks.

Alternative Names

Fructosemia; Fructose intolerance; Fructose aldolase B-deficiency; Fructose 1, 6 bisphosphate aldolase deficiency

Causes, incidence, and risk factors

This condition occurs when the body is missing a substance called aldolase B. This substance is needed to break down fructose.

If a person without this substance eats fructose and sucrose (cane or beet sugar, table sugar), complicated chemical changes occur in the body. The body cannot change its energy storage material, glycogen, into glucose. As a result, the blood sugar falls and dangerous substances build up in the liver.

Hereditary fructose intolerance is inherited, which means it is passed down through families. It may be as common as 1 in 20,000 in some European countries.

Symptoms

Symptoms can be seen after a baby starts eating food or formula.

The early symptoms of fructose intolerance are similar to those of galactosemia. Later symptoms relate more to liver disease.

Symptoms may include:

Convulsions
Excessive sleepiness
Irritability
Jaundice
Poor feeding as a baby
Problems after eating fruits and fructose/sucrose-containing foods
Vomiting

Signs and tests

Physical examination may show:

Yellow skin or eyes
Hepatosplenomegaly (enlarged liver and spleen)

Tests that confirm the diagnosis include:

Blood clotting tests
Blood sugar test
Enzyme studies
Genetic testing
Kidney function tests
Liver function tests
Liver biopsy
Uric acid blood test
Urinalysis

Blood sugar will be low, especially after receiving fructose or sucrose. Uric acid levels will be high.

Treatment

Complete elimination of fructose and sucrose from the diet is an effective treatment for most patients. Individual complications are treated as appropriate. For example, some patients can take medication to lower the level of uric acid in their blood and thereby decrease their risk for gout.

Expectations (prognosis)

Hereditary fructose intolerance may be relatively mild or a very severe disease.

Complete avoidance of fructose and sucrose produces good results in most children with this condition. A few children will go on to develop severe liver disease.

In the severe form, even eliminating fructose and sucrose from the diet may not prevent severe liver disease.

How well a person does depends on how soon the diagnosis is made and how soon fructose and sucrose can be eliminated from the diet.

Complications

Hypoglycemia
Illness due to eating fructose- or sucrose-containing foods
Strong avoidance of fructose-containing foods due to noxious effects
Seizures
Bleeding
Gout
Liver failure
Death

Calling your health care provider

Call your health care provider if your child develops symptoms of this condition after feeding starts. If your child has this condition, experts recommend seeing a doctor who specializes in biochemical genetics or metabolism.

Prevention

Couples with a family history of fructose intolerance who wish to have a baby may consider genetic counseling.

Most of the damaging effects of the disease can be prevented by strict adherence to a fructose-free diet.

Review Date:5/2/2007
Reviewed By:Brian Kirmse, MD, Mount Sinai School of Medicine, Department of Human Genetics, New York, NY. Review provided by VeriMed Healthcare Network.

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