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Hereditary fructose intolerance (HFI) is a condition in which the body lacks a substance called aldolase B needed to process fructose, a common sugar found in fruit and many other foods. When a person with HFI consumes fructose, the result is low blood sugar (hypoglycemia) and a buildup of toxic substances in the liver.
Infants or children with the disease who consume the sugars fructose and sucrose or the sugar substitute sorbitol typically experience symptoms after eating, including vomiting, convulsions, irritability, and/or sleepiness. Many infant formulas are made with the sugar lactose, although some also contain fructose and sucrose, as do many baby foods. Infants or children with HFI may show a yellowing of the skin and whites of the eyes (jaundice) and have an enlarged liver and spleen. If unrecognized and untreated, these children will fail to grow at a normal rate.
If the disease is not detected and treated, HFI can lead to serious liver disease, hypoglycemic shock, seizures, gout, bleeding, and kidney or liver failure. In extreme cases, it can be fatal. For this reason, early detection is critical.
A strict diet free from fructose, sucrose, and sorbitol allows most people with HFI to live normal, symptom-free lives, although those with a severe course of the disease may develop serious liver disease later in life, even with a careful diet.
Symptoms of the disease can vary from mild to severe. People with HFI often show an aversion to sweets and fruit, and thus those with a mild case may be protected from some of the symptoms they would otherwise experience.
The exact prevalence of HFI is unknown, but several studies have placed the number of affected people in the U.S. and Europe at 1 in 20,000. A recent U.K. study placed the figure at 1 in 12,000 to 58,000.
The key to treating people with HFI is to strictly control their diet, eliminating all fructose, sucrose, and sorbitol. On this careful diet, people with HFI can be symptom-free, though symptoms will quickly return upon consuming fructose, sucrose, or sorbitol.
In cases where liver disease has progressed to a life-threatening stage, liver transplantation is a possible treatment.
Without a careful monitoring of the diet—elimination of all fructose, sucrose, and sorbitol—HFI can be life-threatening, causing serious liver disease, hypoglycemic shock, or liver or kidney failure.
With a careful diet, however, people with HFI may be symptom free and able to live normal lives. The earlier the condition is diagnosed and the diet corrected, the less damage is done to the liver and kidneys and the better the overall prognosis. Early detection and diet modification is also important so that children can grow to normal height. Within three to four weeks of adopting a fructose-free diet, people with HFI can be symptom-free.
In a minority of people who have a severe form of the disease, liver disease may still develop, despite a careful diet.
The informational website of a laboratory in the biology department at Boston University specializing in hereditary fructose intolerance.
A database of articles that brings together information from the National Library of Medicine, the National Institutes of Health, and other government and health-related organizations.
A catalog of human genes and genetic disorders authored by staff at Johns Hopkins University and elsewhere and published by the National Institutes of Health's National Center for Biotechnology Information. Please note that this information is written in highly technical language.