Hereditary Fructose Intolerance (HFI) is a rare genetic disorder
of fructose metabolism due to a deficiency of the enzyme, aldolase
B that finishes the conversion of partially converted fructose (fructose-1-phosphate)
Fructose is the sugar found in fruit.
Hereditary Fructose Intolerance (HFI) should not be confused with Fructose Malabsorption. They are two different conditions but with some similar symptoms. In HFI fructose is not properly metabolised due to a deficiency of the enzyme, aldolase B. Normally, once fructose is absorbed it is transformed into fructose-1-phosphate by an enzyme called fructose-1-phosphate aldolase. Aldolase B in turn finishes the partially converted fructose to glucose (for energy). Lack of aldolase B results in the accumulation of fructose-1-phosphate in the liver, kidneys and intestine. This inhibits glycogen breakdown and glucose synthesis, thereby causing severe hypoglycaemia (low sugar levels) following ingestion of fructose.
Clinical symptoms include severe abdominal pain, vomiting, and hypoglycemia following ingestion of fructose or other sugars metabolized through fructose-1-phosphate. Prolonged fructose ingestion in infants leads ultimately to hepatic and/or renal failure and death. Patients develop a strong distaste for sweet food, and can avoid a recurrence of symptoms chronic course of the disease by remaining on a fructose free diet.
HFI may be relatively mild or a very severe disease. In the severe form, even eliminating fructose and sucrose from the diet may not prevent progressive liver disease.
- Onset of symptoms after starting an infant on food or formula
- Poor feeding as a baby
- Increased or prolonged neonatal jaundice
- Excessive sleepiness
- Intolerance for fruits
- Avoidance of fruits and fructose/sucrose-containing foods
- Doing well after eating foods without fructose/sucrose
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.
Fructose is the sugar found naturally in fruits. Man-made fructose is used as a sweetener in many foods, including baby food and drinks. The worldwide incidence rate of HFI remains unknown due to the difficulty of HFI diagnosis. The condition is widespread, however, most cases have been reported in Europe and North America. It may be as common as 1 in 20,000.
Signs & Tests
Physical examination may also show:
- Jaundice (yellow skin) or icterus (yellow eyes)
- Hepatosplenomegaly (enlarged liver and spleen)
Enzyme studies and Liver function Tests are the main tests that confirm the diagnosis. Others 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
- Bleeding tendency revealed by coagulation tests of blood
- Liver biopsy
Genetic testing for fructose intolerance may be available.
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.
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.
- Illness due to eating fructose- or sucrose-containing foods
- Strong avoidance of fructose-containing foods due to noxious effects
- Liver failure
Calling your health care provider
Call your health care provider if your child 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.
Genetic counselling 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