Fructose intolerance

What’s measured

Fructose known as fruit sugar

Fructose, also known as fruit sugar, occurs naturally in fruits, honey, and certain vegetables. A synthetic version of fructose is also utilised as a sweetener in food products. Hereditary fructose intolerance stems from a mutation in the gene responsible for the enzyme aldolase B, which metabolises the fruit sugar fructose. Congenital fructose intolerance arises from mutations in the ALDOB gene, leading to decreased activity of the enzyme aldolase B and consequently impairing the body's capacity to metabolise fructose. A deficiency in the enzyme aldolase B results in the buildup of fructose 1-phosphate within liver cells, leading to their severe damage. 

Genetic testing for fructose intolerance reveals it to be an autosomal recessive condition, wherein the patient carries two mutant alleles of the ALDOB gene [1]. 

Testing includes

The test monitors for the presence of genes associated with fructose intolerance, it detects four mutations in the aldolase B gene (del4E4, A149P, A174D, and N334K).

Instructions before collection

The result of the genetic test is not affected by adherence to a fructose-free diet. Peripheral blood collection does not need to be performed while fasting and can be performed at any time of the day. The result of the test is not affected by the use of any medications, diets or smoking.

Sources

[1] Ali M, Rellos P, Cox TM. Hereditary fructose intolerance. J Med Genet 1998; 35:353. Kim AY, Hughes JJ, Pipitone Dempsey A, et al. Pitfalls in the Diagnosis of Hereditary Fructose Intolerance. Pediatrics 2020; 146.