Pentosuria

What is pentosuria?

Excretion of pentoses in urine is called pentosuria. The presence of pentose in urine was first described by Salkowski and Jastrowitz in 1892. This condition appears to be harmless to health. It is found exclusively in Jews and causes no decrease in life expectancy.

Sources of pentose

All the fruits are a source for pentose.

Inheritance

An autosomal recessive inherited disorder.

Enzyme defect

L-Xylitol dehydrogenase.

Metabolic block

L-Xylulose is converted to Xylitol in the presence of the enzyme L-Xylitol dehydrogenase. This reaction is blocked due to the deficient enzyme.

Due to inherited deficiency of the enzyme L-xylulose accumulates and is excreted in the urine.

Clinical significance

Oxalosis

Parenteral administration of xylitol may lead to oxalosis involving calcium oxalate deposition in brain and kidneys. This results from conversion of D-xylulose to oxalate. Other sources of oxalates are ascorbic acid and glycine.

Effect of other drugs

Various drugs markedly increase the rate at which glucose enters uronic acid pathway for example administration of barbital or chlorbutanol.

Symptoms

1. Excretion of xylulose in urine.

2.High levels of xylulose in blood.

Diagnosis

Loading Test

Administration of glucuronic acid to these subjects causes an increase in the quantity of xylulose excretion while administration of glucuronic acid to normal subject do not cause any increase.

Treatment

Avoid pentoses in the diet.