Hereditary Fructose Intolerance

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Hereditary fructose intolerance is caused by mutations (changes) in the ALDOB gene. This gene is responsible for making an enzyme called aldolase B. This enzyme is mainly found in the liver and breaks down fructose into energy. Mutations in the ALDOB gene decrease the function of the enzyme, damaging its ability to metabolize (breakdown/absorb) fructose. This leads to a toxic build up of fructose-1-phosphate in the liver cells which over time will result in the death of liver cells.  

Hereditary fructose intolerance is estimated to affect 1 in 20,000 to 30,000 individuals each year worldwide.  

Symptoms are usually first seen after a baby starts eating food or formula. Early symptoms are similar to the symptoms of galactosemia (inability to use the sugar galactose) whereas later symptoms are more like liver disease.  

Symptoms of HFI include:  

• Excessive sleepiness 
• Irritability 
• Yellow tinge to the skin or whites of the eyes (jaundice) 
• Poor feeding and growth as a baby, failure to thrive 
• Problems after eating fruits and other foods that contain fructose or sucrose 
• Vomiting 
• Diarrhoea  
• Convulsions (spasms/shakings)  
• Abdominal pain  
• Reduced aldolase levels 
• Nausea  

Early diagnosis is very important as patients can live without symptoms when removing fructose from their diet.  

Physical examinations by a doctor may show an enlarged liver, enlarged spleen and jaundice (yellowish tinge to the skin and the whites of the eye). 

When clinical symptoms, nutritional and family history are suggestive towards HFI, a diagnosis of hereditary fructose intolerance can be confirmed through specialised DNA testing. In rare cases, when no mutation is found, a liver biopsy can be used to determine aldolase activity. A fructose tolerance test may also be used to confirm diagnosis.  

Hereditary fructose intolerance is treated through a restricted diet by cutting out fructose from the diet. All foods containing fructose, sucrose, and sorbitol should be avoided. Any dietary changes require specialist dietitian’s advice and monitoring. The clinical benefits of removing fructose from the diet are usually seen within a few days. You may also be prescribed with supplements, especially vitamin C and folates to replace the vitamins that may be lacking in the body. 

Hereditary fructose intolerance is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents.  

The pattern of inheritance of hereditary fructose intolerance is autosomal recessive. This means that carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with hereditary fructose intolerance are carriers.    

When both parents are carriers, the risk to the baby in each pregnancy is:

• 25% chance (1 in 4) of developing the condition  
• 50% chance (1 in 2) for the baby to be a carrier of the condition  
• 25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier  

Genetic counselling can be requested to get a full explanation.  

Hereditary Fructose Intolerance (HFI) UK

Raising awareness of HFI among healthcare and allied professionals, and support to individuals with HFI and their families.

Website: www.hfisupport.org.uk
Email: help@hfisupport.org.uk

References are available on request. Please contact us on 0800 652 3181 or by emailing contact@metabolicsupport.org.

Please note calls to 0800 numbers are free from UK landlines and mobiles. Calls from business lines may be charged – please check with your provider.

This information about metabolic diseases is provided by Metabolic Support UK and is intended for educational purposes only. It should not be used for diagnostic or treatment purposes.

Should you require more detailed information please contact Metabolic Support UK by email (contact@metabolicsupport.org) or by telephone ( 0800 652 3181). For specific medical information regarding a disorder or individual please contact your GP or Paediatrician. Metabolic Support UK accepts no responsibility for any errors or omissions nor does Metabolic Support UK assume any liability of any kind for the content of any information contained within this summary or any use that you may make of it.