Pentosuria

Pentosuria is a condition in which the pentose sugar L-xylulose appears in the urine in unusually high concentrations. It was characterized as an inborn error of carbohydrate metabolism in 1908 and is a component of Garrod's tetrad. It is associated with a deficiency of L-xylulose reductase, an enzyme needed for xylitol metabolism. Because L-xylulose is a reducing sugar, it can give a false indication of diabetes, although glucose metabolism is normal in people with pentosuria and they are not diabetic. Three forms are described: essential pentosuria, alimentary pentosuria acquired through fruits high in pentose, and drug-induced pentosuria. The defect is described as harmless and needing no cure.