Disorders of the Pentose Phosphate Pathway

Abstract

Three inborn errors in the pentose phosphate pathway are known. In glucose-6-phosphate dehydrogenase deficiency, there is a defect in the first, irreversible step of the pathway. As a consequence NADPH production is decreased, making erythrocytes vulnerable to oxidative stress. Drug-and fava bean-induced haemolytic anaemia is the main presenting symptom of this defect. As this is a haematological disorder it is not discussed further.

Deficiency of ribose-5-phosphate isomerase has been described in one patient who suffered from a progressive leucoencephalopathy and developmental delay.

Transaldolase deficiency has been diagnosed in three unrelated families. All patients presented in the newborn period with liver problems. One of the patients died soon after birth from liver failure and cardiomyopathy, whereas another patient is now 15 years old and suffers from liver cirrhosis. Her neurological and intellectual development has been normal.

Essential pentosuria, due to a defect in the enzyme xylitol dehydrogenase, affects the related glucuronic acid pathway. Whereas the pentose phosphate pathway involves D stereoisomers, glucuronic acid gives rise to L-xylulose which is subsequently converted into xylitol and D-xylulose. Affected individuals excrete large amounts of L-xylulose in urine. This is a benign disorder and not discussed further.