Hereditary fructose Intolerance

A rare genetic disorder of fructose malabsorption, Hereditary Fructose Intolerance (HFI) occurs due to a deficiency of the enzyme that converts fructose into glucose.

Normally, once fructose is absorbed after ingestion, it is transformed to glucose for energy. A lack of the enzyme responsible for this process results in the accumulation of fructose-1-phosphate in the liver, kidneys and intestines. This inhibits glycogen breakdown and glucose synthesis, causing severe hypoglycaemia (low blood sugar levels).

While HFI shouldn't be confused with Fructose malabsorption, the symptoms are sometimes similar (severe abdominal pain, vomiting). When infants with HFI ingest fructose after prolonged periods this may lead to hepatic and/or renal failure and death. A strong distaste for sweet food often develops and remaining on a fructose-free diet can avoid recurrence of symptoms and thus, chronic development of the disease.

HFI varies from relatively mild to severe. When severe, even eliminating fructose and sucrose won't prevent progressive liver disease.

What to look out for:

• onset of symptoms after putting an infant on food or formula
• poor feeding as a baby
• irritability
• prolonged neonatal jaundice (yellow skin) or icterus (yellow eyes)
• convulsions
• excessive sleepiness
• intolerance for fruit
• doing well after eating foods without fructose

Physical examination may also show an enlarged liver and spleen.

Several tests may be employed to confirm diagnosis and genetic testing is also available.

Absolute elimination of fructose and glucose will improve circumstances for most children with HFI, however some may develop progressive liver disease. Prognosis depends on how soon fructose sources are eliminated from the baby's/child's diet.