Hereditary fructose intolerance

  • Definition
    • Hereditary fructose intolerance is a disorder 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
    • This condition occurs when the body is missing an enzyme called aldolase B. This substance is needed to break down fructose.

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

      Hereditary fructose intolerance is inherited, which means it can be passed down through families. If both parents carry a nonworking copy of the adolase B gene, each of their children has a 25% (1 in 4) chance of being affected.

  • 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 (inability to use the sugar galactose). Later symptoms relate more to liver disease.

      Symptoms may include:

      • Convulsions
      • Excessive sleepiness
      • Irritability
      • Yellow skin or whites of the eyes (jaundice)
      • Poor feeding as a baby
      • Problems after eating fruits and other foods that contain fructose or sucrose
      • Vomiting
  • Exams and Tests
  • Treatment
    • Removing fructose and sucrose from the diet is an effective treatment for most people. Complications may be treated. For example, some people can take a medicine to lower the level of uric acid in their blood and decrease their risk for gout.

  • Outlook (Prognosis)
    • Hereditary fructose intolerance may be mild or severe.

      Avoiding fructose and sucrose helps most children with this condition.

      A few children with a severe form of the disease will develop severe liver disease. Even removing fructose and sucrose from the diet may not prevent severe liver disease in these children.

      How well a person does depends on:

      • How soon the diagnosis is made
      • How soon fructose and sucrose can be removed from the diet
      • How well the enzyme works in the body
  • Possible Complications
    • These complications may occur:

      • Avoidance of fructose-containing foods due to their effects
      • Bleeding
      • Gout
      • Illness from eating foods containing fructose or sucrose
      • Liver failure
      • Low blood sugar (hypoglycemia)
      • Seizures
      • Death
  • When to Contact a Medical Professional
    • 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 decreasing fructose and sucrose intake.

  • References
    • Ghishan FK. Inborn errors of metabolism that lead to permanent liver injury. In: Boyer TD, Manns MP, Sanyal AJ, eds. Zakim & Boyer's Hepatology: A Textbook of Liver Disease. 6th ed. Philadelphia, PA: Elsevier Saunders, 2012:chap 66.

      Steinmann B, Santer R. Disorders of Fructose Metabolism. In: Saudubray JM, van den Berghe G, Walter JH, eds. Inborn Metabolic Diseases: Diagnosis and Treatment. 5th ed. New York, NY: Springer; 2012:chap 9.