What is fructosemia?

Causes and Symptoms

Fructosemia may also be called hereditary fructose intolerance; it literally means “fructose in the blood.” Fructosemia occurs as a result of a hereditary lack of an enzyme called fructose-1-phosphate aldolase B. This autosomal recessive disease is rare, although some researchers suspect that more people have the disorder than are diagnosed. These individuals may naturally avoid fructose after becoming ill following the consumption of fructose-containing foods. The infant, child, or adult with undiagnosed fructosemia will be normal unless foods containing fructose, sucrose, or sorbitol are eaten. If foods containing these carbohydrates are eaten, then fructose levels will increase in the patient’s blood and urine and the person will become ill. Symptoms include vomiting and low blood glucose and may progress to failure to thrive and/or coma. The severity of the disease appears to be variable, being rather mild in some individuals and causing death in others. In severe cases, the liver, kidneys, and
intestines may be affected, although this damage usually reverses with the elimination of dietary fructose.

Treatment and Therapy

Treatment for this disorder is entirely dietary. Foods containing fructose, sucrose, or sorbitol must be eliminated from the diet. Fructose is often thought of as “fruit sugar,” but far more foods than fruits and juices must be eliminated. Honey contains fructose, for example. Because half of sucrose becomes fructose when sucrose is metabolized, all foods containing sucrose (sugar) must be eliminated as well. This includes all sugar, whether from cane, beets, or sorghum. Sucrose is also part of maple syrup. Sorbitol metabolism also produces fructose, and so this sugar substitute must be avoided as well. Some infant formulas and baby foods may contain fructose, and many sweetened fruit beverages do. Reading food labels and being familiar with the ingredients of restaurant food is imperative for those with fructosemia.

Perspective and Prospects

Cases of fructosemia were first described in the mid-1950s. Soon after, the biochemical pathway defect was discovered. Today, genetic counseling may be of benefit to those who have fructosemia and want to have children, although strict avoidance of the three carbohydrates fructose, sucrose, and sorbitol will prevent symptoms.

Bibliography:

Ali, M., et al. “Hereditary Fructose Intolerance.” Journal of Medical Genetics 35, no. 5 (May, 1998): 353–365.

Cox, T. M. “Aldolase B and Fructose Intolerance.” FASEB Journal 8, no. 1 (January, 1994): 62–71.

Haldeman-Englert, Chad, and David Zieve. "Hereditary Fructose Intolerance." MedlinePlus, May 15, 2011.

"Hereditary Fructose Intolerance." Genetics Home Reference, May 13, 2013.

Sanders, Lee M. "Disorders of Carbohydrate Metabolism." Merck Manual Home Health Handbook, Feb. 2009.

Steinmann, Beat, René Santer, and Georges van den Berghe. “Disorders of Fructose Metabolism.” In Inborn Metabolic Diseases: Diagnosis and Treatment, edited by Jean-Marie Saudubray, et al. 5th ed. New York: Springer, 2012.