Xanthinuria

An inherited metabolic disorder in which there is deficiency of an enzyme needed to process xanthine, a substance found in caffeine, theobromine, theophylline, and related substances. Unchecked, xanthinuria can lead to kidney stone formation and urinary tract disease (due to xanthine stones) and to muscle disease (due to deposits of xanthine in the muscle). Treatment is by avoiding foods and drinks containing xanthine derivatives, such as coffee, tea, and colas. The enzyme that is lacking in xanthinuria is xanthine dehydrogenase. The disorder is an autosomal recessive trait. The gene responsible for xanthinuria is on an autosome, a nonsex chromosome (chromosome 2p23-p22). Both parents of a child with xanthinuria are normal but carry one xanthinuria gene (the xanthinuria gene is recessive to the corresponding normal gene). Their affected child received both of their xanthinuria genes.

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1. Excretion of abnormally large amounts of xanthine in the urine. 2. A disorder [MIM*278300], characterized by urinary excretion of xanthine in place of uric acid, hypouricemia, and occasionally the formation of renal xanthine stones. There are two types: type I is due to xanthine dehydrogenase deficiency (XDH), and type II is due to deficiencies of both xanthine dehydrogenase and aldehyde oxidase. Autosomal recessive inheritance, caused by mutation in the XDH gene on chromosome 2p in some cases. SYN: xanthiuria, xanthuria. [xanthine + G. ouron, urine]

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n.

excess of the purine derivative xanthine in the urine, usually the result of an inborn defect of metabolism. It is both rare and symptomless.

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xan·thin·uria (zan″thin-uґre-ə) any of several disorders of purine metabolism in which deficiency of xanthine dehydrogenase (XDH) activity results in urinary secretion of excessive xanthine and a tendency to formation of xanthine calculi in the urinary tract. Xanthinuria type I is an autosomal recessive disorder caused by mutation in the XDH gene (locus 2p23-p22), which encodes xanthine dehydrogenase; xanthinuria type II is a combined deficiency of both xanthine dehydrogenase and aldehyde oxidase activity. Xanthinuria is also a feature of molybdenum cofactor deficiency (q.v.).