Inherited abnormalities of fructose metabolism, which include three known autosomal recessive types: hepatic fructokinase deficiency (essential fructosuria), hereditary fructose intolerance, and hereditary fructose-1,6-diphosphatase deficiency. Essential fructosuria is a benign asymptomatic metabolic disorder caused by deficiency in fructokinase, leading to decreased conversion of fructose to fructose-1-phosphate and alimentary hyperfructosemia, but with no clinical dysfunction; may produce a false-positive diabetes test.