Which are the causes of Fructose Intolerance?

Hereditary Fructose Intolerance (HFI) is a metabolic disorder caused by a genetic deficiency of the enzyme aldolase B, which prevents the body from properly breaking down fructose. Unlike dietary fructose malabsorption, HFI is a serious, lifelong condition present from birth that requires strict avoidance of fructose, sucrose, and sorbitol to prevent liver and kidney damage.

What causes Hereditary Fructose Intolerance?

The primary cause of Hereditary Fructose Intolerance is a mutation in the ALDOB gene, located on chromosome 9. This gene provides instructions for producing the enzyme aldolase B, which is essential for metabolizing fructose in the liver, kidneys, and small intestine. When this enzyme is inactive, toxic byproducts (fructose-1-phosphate) accumulate, effectively "clogging" the cellular machinery and inhibiting the body's ability to release glucose, which can lead to severe hypoglycemia.

Is Hereditary Fructose Intolerance hereditary?

Yes, Hereditary Fructose Intolerance follows an autosomal recessive inheritance pattern. This means that an affected individual must inherit one defective ALDOB gene copy from each parent. Because parents are usually asymptomatic carriers, the condition often appears unexpectedly in families with no prior history of the disease.

What are the primary risk factors and triggers?

While the genetic mutation is the root cause, environmental triggers—specifically the introduction of dietary sugars—are what precipitate symptoms. Key factors include:

• Dietary Intake: The ingestion of fructose (found in fruits), sucrose (table sugar), or sorbitol (a common sugar substitute).


• Timing of Exposure: Symptoms typically emerge during infancy when a child transitions from breast milk or formula to solid foods containing fruits or sweetened cereals.


• Genetic Carriers: Having two parents who are both carriers of the ALDOB mutation, resulting in a 25% chance for each pregnancy to result in a child with Hereditary Fructose Intolerance.

What is the current state of research?

Scientists are currently investigating gene therapy and enzyme replacement strategies to restore aldolase B activity. While the genetic basis of Hereditary Fructose Intolerance is well-understood, researchers at DiseaseMaps.org and global institutes continue to study how environmental factors and gut microbiome composition might influence symptom severity among the 93 community members and others living with this condition.

Next steps

• Consult a metabolic specialist or a pediatric gastroenterologist for confirmatory genetic testing.


• Work with a specialized metabolic dietitian to create a fructose-free meal plan.


• Join the Hereditary Fructose Intolerance community at DiseaseMaps.org to connect with others who share your experience.

Medical disclaimer: This information is for educational purposes only and does not replace professional medical advice, diagnosis, or treatment.

References

• NIH Genetic and Rare Diseases Information Center (GARD): Hereditary Fructose Intolerance.


• Orphanet: Hereditary Fructose Intolerance (ORPHA:338).


• OMIM (Online Mendelian Inheritance in Man): Fructose Intolerance, Hereditary; HFI (#229600).


• Boston Children's Hospital: Hereditary Fructose Intolerance overview.