Pentosuria

At a glance

Disorder of carbohydrate metabolism. Benign anomaly of the metabolism of glucuronic acid.

Synonyms

Essential Pentosuria; L-Xylulosuria; Xylitol Dehydrogenase Deficiency; L-Xylulose Reductase Deficiency.

History

First postulated to be an inborn error of metabolism by Archibald E. Garrod, an English physician, in the Croonian lectures in 1908.

Incidence

1:40,000 to 1:50,000 in the US population; the frequency in Ashkenazi Jews may be as high as 1:2,500 and is 1:5,000 in Israeli Jews. In the vast majority of cases, antecedents have been traced to Eastern Europe.

Genetic inheritance

Autosomal recessive.

Pathophysiology

Inborn error of metabolism in which between 1 and 4 g L-xylulose is excreted in the urine each day. It is a benign metabolic disturbance, which occurs almost exclusively in Ashkenazi Jews of Polish-Russian extraction. Caused by homozygous mutation in the DCXR gene on chromosome 17q25. Essential pentosuria is the result of a partial deficiency of L-xylulose reductase in the glucuronic acid oxidation pathway. The basic fault concerns nicotinamide adenine dinucleotide phosphate (NADP)-linked xylitol dehydrogenase.

Diagnosis

L-Xylose dehydrogenase converts L-xylose to xylitol. Xylitol is converted to D-xylose, which becomes D-xylose-5-phosphate and enters the pentose phosphate shunt. Deficiency of this enzyme leads to increased concentration of L-xylose in the blood and urine. No therapy is required. Red cells from pentosuric patients contain only the minor L-xylulose reductases isozyme (normally major and minor).

Clinical aspects

Affected individuals cannot degrade L-xylulose derived from glucuronic acid. It is a benign condition that is of clinical significance only when confused with diabetes mellitus. Blood sugar is normal. The pentose (urine) does not react with glucose oxidase test papers.

Anesthetic considerations

There are no considerations for this pathology, only those associated with the surgical procedure involved.

Other condition to be considered

• Alimentary Pentosuria: Arabinose or xylose is found in the urine of normal people following the ingestion of very large quantities of fruits such as cherries, grapes, and fruit juices. Large quantities of D-ribose may be found in the urine of some patients with muscular dystrophy, probably as a result of breakdown of ribose-containing nucleotides in degenerating muscle.

References