[Etiology, pathophysiology and clinical significance of hereditary fructose intolerance]

Due to repeatedly described incidents in patients with undiscovered hereditary fructose intolerance, the application of fructose and sorbit-containing parenteral solutions is a topic vehemently discussed. This paper presents a survey of the literature dealing with the inborn defect of fructose-1-phosphate aldolase. The physiology and pathophysiology of fructose metabolism are described as well as the clinical appearance and diagnostic possibilities. The acute course of a fructose incompatibility is determined by a threatening decrease in the blood glucose level, which is attributed to the inhibition of several enzymes of glycolysis and gluconeogenesis by an intracellular accumulation of fructose-1-phosphate. Within hours a global functional breakdown of organs, which normally have the enzyme, occurs. The impairment of the liver function finds expression in a severe coagulopathy, the damage of the kidney leads to anuria. In chronic oral fructose supply, damage of the liver and small intestinal mucosa with corresponding gastrointestinal symptoms determine the clinical course. Concerning diagnosis, contrary to the liver biopsy and the fructose tolerance test, the mucosal biopsy with determination of fructose-1-phosphate aldolase activity has the advantage of greater specificity and is better tolerated by the patient. A total abstinence to fructose and sorbitol-containing solutions is not considered to be necessary when the rarity of the illness is taken into account and certain precautions are taken. These include a specific anamnesis of nutrition as well as a total abstinence from fructose and sorbitol in infants and in the unconscious patient. For clinical routine a simple fructose tolerance test is suggested.