Fructosemia
Key points
- Hereditary fructose intolerance is a metabolic disease caused by the absence of an enzyme, 1-phosphofructaldolase.
- Man-made fructose is used as a sweetener in many foods (including baby food) and drinks.
- Note: The early symptoms of fructose intolerance may resemble those of galactosemia: irritability, jaundice, vomiting, convulsions and an enlarged liver and spleen.
- Complete elimination of fructose and sucrose from the diet is an effective treatment for most patients.
Alternative names
Hereditary fructose intolerance; Fructose intolerance; Fructose aldolase B-deficiency
Definition
Hereditary fructose intolerance is a metabolic disease caused by the absence of an enzyme, 1-phosphofructaldolase.
Causes, incidence, and risk factors
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
- 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
Physical examination may also show:
- Jaundice (yellow skin) or icterus (yellow eyes)
- Hepatosplenomegaly (enlarged liver and spleen)
Tests that confirm the diagnosis include:
Written and revised by
Gerald Hurowitz, M.D.
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