Two previously unreported inborn errors of metabolism occur in the reversible part of the pentose phosphate pathway. Deficiency of ribose-5-phosphate isomerase has been described in one patient who suffered from a progressive leukoencephalopathy and developmental delay. ransaldolase deficiency has been diagnosed in five unrelated families (eight patients) in which the proband presented in the newborn or antenatal period with epatosplenomegaly, liver function problems, hepatic fibrosis and hemolytic anemia.
In recent years, two new inborn errors affecting pentose metabolism have been discovered: ribose-5-phosphate isomerase deficiency and transaldolase deficiency. Unlike essential pentosuria, these defects do not segregate in persons of Ashkenazi Jewish origin. Ribose-5-phosphate isomerase deficiency has been diagnosed in a Caucasian patient. Transaldolase deficiency has been diagnosed in five families (eight patients), the parents being related in all cases. Both disorders appear as autosomal recessive. Whereas essential pentosuria is a defect in the glucuronic acid pathway, the two newly discovered defects are in the reversible part of the pentose phosphate pathway.