Hereditary fructose intolerance

Hereditary fructose intolerance (HFI) or fructose poisoning is a hereditary condition caused by a deficiency of liver enzymes that metabolise fructose. It is also known as hereditary fructosemia.

Signs and symptoms
If fructose is ingested, other symptoms such as vomiting, hypoglycemia, jaundice, hemorrhage, hepatomegaly, hyperuricemia and eventually kidney failure will follow.

Cause
The deficient enzyme is aldolase-B, which converts fructose-1-phosphate to DHAP and glyceraldehyde. This means that the fructose cannot be further metabolised beyond fructose-1-phosphate. This traps phosphates, which are needed to phosphorylate glycogen phosphorylase, which functions to release units of glucose-1-phosphate from glycogen. (Glucose-1-phosphate is converted to glucose-6-phosphate and then dephosphorylated to form glucose).

In addition, Aldolase A plays an important role in gluconeogenesis, producing fructose-1,6-bisphosphate from glyceraldehyde-3-phosphate and DHAP. Though glucose may still be released through the breakdown of glycogen, it cannot be synthesized from gluconeogenesis. This causes severe hypoglycemia.

Common Traits

 * Refusal to eat or dislike of many fruits, vegetables, candies, and baked goods.
 * Love of dextrose-based candies.
 * Primary beverages are milk, water, unsweetened tea, and unsweetened coffee.
 * Feeling nauseated, sick, queasy, shaky, and/or foggy shortly after consuming fructose or sucrose.
 * Kidney pain, hypoglycemia, and weakness ensuing a few hours to a couple days after consuming fructose or sucrose.
 * Tendency to binge eat on "safe" foods after consuming fructose. Safe foods can include dairy, potato chips, pasta and rice.

Treatment
Treatment is with a fructose free diet, which if adhered to, is concordant with a good prognosis.

Fructose and sucrose eliminated from diet.

Related conditions
Hereditary fructose intolerance should not be confused with fructose malabsorption. The latter was formerly known as dietary fructose intolerance (DFI), a deficiency of fructose transporter protein in the enterocytes, which leads to abdominal bloating, diarrhea and/or constipation.