MedlinePlus Medical Encyclopedia: Hereditary fructose intolerance

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Hereditary fructose intolerance

Contents of this page:
Alternative names Definition Causes, incidence, and risk factors Symptoms Signs and tests	Treatment Expectations (prognosis) Complications Calling your health care provider Prevention

Alternative names

Fructosemia; Fructose intolerance; Fructose aldolase B-deficiency

Definition Return to top

Hereditary fructose intolerance is a metabolic disease caused by the absence of an enzyme, 1-phosphofructaldolase.

Causes, incidence, and risk factors Return to top

Fructose is a naturally-occuring fruit sugar. Man-made fructose is used as a sweetener in many foods (including baby food) and drinks. Hereditary fructose intolerance is an autosomal recessive disease. It may be as common as 1 in 20,000 in some European countries.

In fructose-intolerant people, ingestion of fructose (fruit sugar) and sucrose (cane or beet sugar, table sugar) produces complicated chemical changes that cannot be corrected because of the absence of the enzyme 1-phosphofructaldolase. Ingestion of fructose causes profound hypoglycemia (low blood sugar) and progressive liver damage. The body is unable to convert its energy storage material, glycogen, into glucose. Subsequently, the blood sugar falls (hypoglycemia). In addition, blocks in the metabolic pathway of fructose processing cause a build-up of substances that damage the liver.

Hereditary fructose intolerance can be relatively mild or very severe disease. In the severe form, even eliminating fructose and sucrose from the diet may not prevent progressive liver disease.

Symptoms Return to top

Onset of symptoms after starting an infant on food or formula
Poor feeding as a baby
Irritability
Increased or prolonged neonatal jaundice
Vomiting
Convulsions
Excessive sleepiness
Intolerance for fruits
Avoidance of fruits and fructose/sucrose-containing foods
Doing well after eating foods without fructose/sucrose

Note: The early symptoms of fructose intolerance may resemble those of galactosemia: irritability, jaundice, vomiting, convulsions and an enlarged liver and spleen. Later problems relate more to liver disease.

Signs and tests Return to top

Physical examination may also show:

Jaundice (yellow skin) or icterus (yellow eyes)
Hepatosplenomegaly (enlarged liver and spleen)

Tests that confirm the diagnosis include:

Positive urine test for reducing substances
Hypoglycemia (low blood sugar), especially after receiving fructose/sucrose
Excess uric acid in blood (hyperuricemia)
Failure of the kidney to work properly with abnormally high amounts of sugars, amino acids and salts appearing in urine
Liver failure shown with blood test
Bleeding tendency revealed by coagulation tests of blood
Liver biopsy
Enzyme studies

Genetic testing for fructose intolerance may be available

Treatment Return to top

Complete elimination of fructose and sucrose from the diet is an effective treatment for most patients. Treatment of individual complications follows mainstream medical guidelines. 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) Return to top

Absolute elimination of fructose and glucose produces good results in most children with fructose intolerance. A few children will go on to develop progressive liver disease. The prognosis depends on how soon the diagnosis is made and how soon fructose and sucrose can be eliminated from the baby's diet.

Complications Return to top

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 Return to top

Call your health care provider if your child has developed the above symptoms after you began feeding the child formula or solid food. The care of a medical specialist in Biochemical Genetics or Metabolism is strongly recommended if your child has this disorder.

Preliminary evidence suggests that parents of a child with this disorder (as well as other carriers of the mutant gene) may be at increased risk for gout (arthritis caused by excess uric acid in the body and uric acid crystals in the joints). Therefore, it is important to notify your physician if you have a family history of hereditary fructose intolerance.

Prevention Return to top

Genetic counseling may be of value to prospective parents with a family history of fructose intolerance. Most of the damaging effects of the disease can be prevented by strict adherence to a fructose-free diet.

Update Date: 8/19/2003

Updated by: Douglas R. Stewart, M.D., Division of Medical Genetics, Hospital of the University of Pennsylvania, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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