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 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. If both parents carry an abnormal gene, each of their children has a 25% chance of being affected. The condition may be as common as 1 in 20,000 people 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

Exams and Tests

Physical examination may show:

Enlarged liver and spleen (hepatosplenomegaly)
Yellow skin or eyes

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

Removing fructose and sucrose from the diet is an effective treatment for most patients. Complications are treated. For example, some patients can take medication 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

Avoidance of fructose-containing foods due to their effects
Bleeding
Death
Gout
Illness from eating foods containing fructose or sucrose
Liver failure
Low blood sugar (hypoglycemia)
Seizures

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 sticking to a fructose-free diet.