Hereditary fructose intolerance

Alternative names:

disaccharide malabsorption; fructose intolerance; fructosemia

Definition:

A metabolic disease caused by the absence of an enzyme, 1-phosphofructaldolase.

Causes, incidence, and risk factors:

Fructose is a naturally occurring sugar and is used as a sweetener in many foods (including baby food) and drinks. Hereditary fructose intolerance is inherited as an autosomal recessive disease and characterized by profound hypoglycemia (low blood sugar) and progressive liver damage. In fructose-intolerant people, ingestion of fructose (fruit sugar) and sucrose (cane or beet sugar) produces complicated chemical changes that cannot be corrected because of the absence of the enzyme 1-phosphofructaldolase. The body is unable to convert its energy-storage material, glycogen, into glucose. Subsequently, the blood sugar falls. In addition, blocks in the metabolic pathway of fructose processing cause a build-up of substances that damage the liver.

Hereditary fructose intolerance can present as a relatively mild disease or as a very severe disease. In the severe form even eliminating fructose and sucrose from the diet may not prevent progressive liver disease.