Fructosemia
Fructosemia, also known as hereditary fructose intolerance, is a rare genetic disorder characterized by the body's inability to properly metabolize fructose due to a deficiency in the enzyme fructose-1-phosphate aldolase B. This autosomal recessive condition can lead to severe health issues when foods containing fructose, sucrose, or sorbitol are consumed. Symptoms may include vomiting, low blood glucose levels, and in severe cases, lead to failure to thrive or even coma. The impact of fructosemia can vary widely, with some individuals experiencing mild symptoms while others face life-threatening complications.
Management of fructosemia is strictly dietary, necessitating the complete elimination of fructose-containing foods and ingredients, which extend beyond fruits to include honey, sugar, and certain artificial sweeteners. Awareness and careful reading of food labels are crucial for those affected to avoid potential health risks. Cases of fructosemia have been documented since the mid-20th century, and contemporary approaches include genetic counseling for affected individuals considering parenthood. Overall, with diligent dietary management, individuals with fructosemia can lead healthy lives.
Fructosemia
Anatomy or system affected: Gastrointestinal system, intestines, kidneys, liver
Definition: An inborn error of metabolism in which eating foods containing fructose or sucrose will result in high blood fructose levels.
Causes: Genetic enzyme deficiency
Symptoms: Variable; may include vomiting, low blood glucose, failure to thrive, and coma if foods containing fructose, sucrose, or sorbitol are eaten
Duration: Chronic
Treatments: Avoidance of foods containing fructose, sucrose, or sorbitol
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.
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