Summary

Fructose-1,6-diphosphatase (FDPase) deficiency is usually considered an inborn error of fructose metabolism, however, strictly speaking it is a defect of gluconeogenesis. The disorder is manifested by the appearance of hypoglycaemia, ketosis and lactic acidosis (neonatally or later during fasting or induced by fructose) and may also be life-threatening. FDPase deficiency can be suspected using simple bedside tests such as glucometer random blood sugar, Benedict's test, Rothera's test and Seliwanoff's test. We report our experience with two cases of FDPase deficiency and review the relevant literature. We also describe the fructosuria in these cases during the crises period, which has not been stressed in the literature.