Xanthine oxidase deficiency

Hypouricemia and increased excretion of hypoxanthine and xanthine are associated with xanthine oxidase deficiency due to a genetic defect or to severe liver damage. Patients with a severe enzyme deficiency may exhibit xanthinuria and xanthine lithiasis. 

B-5) Xanthine oxidase deficiency. The inability to change xanthine to urate results in xanthinuria with decreased blood and urine urate levels. Sometimes urinary xanthine stones may form. The absent enzyme may be confirmed on liver biopsy. 

In 2010, a baby girl was diagnosed with molybdenum cofactor deficiency at 6 days old. After treatment with purified cyclic pyranopterin monophosphate (cPMP), the precursor of MoCo whose synthesis was defective, starting at 36 days old, all urinary metabolites of sulfite oxidase and xanthine oxidase deficiency returned to almost normal values and has remained constant for more than one year. 

Hereditary sulfite oxidase deficiency can occur alone or with xanthine oxidase deficiency. Both enzymes contain molybdenum (Chapter 27). Patients with sulfite oxidase deficiency exhibit mental retardation, major motor seizures, cerebral atrophy, and lens dislocation. Dietary deficiency of molybdenum (Chapter 37) can cause deficient activity of sulfite and xanthine oxidases. 

Mercaptopurine is partially metabolized to 6-thiouric acid (which lacks antitumor activity) by xanthine oxidase. Allopurinol, a xanthine oxidase inhibitor used in the treatment of gout, potentiates the action of 6-mercaptopurine by preventing its conversion to 6-thiouric acid. This effect is taken into consideration in treatment. Mercaptop-urines are also inactivated by S-methylation carried out by thiopurine S-methyltransferase (TPMT), particularly in hematopoietic tissues which lack xanthine oxidase. Deficiency of TPMT due to polymorphisms causes profound toxicity with the regular therapeutic regime. This is another example of the use of pharmacogenomics. 

Xanthinuria low uric acid excretion in urine Xanthine oxidase deficiency Ayvazian, J.H., and Skupp, S. The study of purine utilization and excretion in a Xanthinuric man. J. Clin. Invest. 44, 1248-1260 (1965)... 

CLINICOBIOCHEMICAL ANALYSIS OF FOUR CASES OF XANTHINE OXIDASE DEFICIENCY... 

Among these urines, the peak of allopurinol was not detected by HPLC. These data suggested that the xanthinuria of these patients was caused by xanthine oxidase deficiency. 

Xanthinuria has been thought to be a rare hereditary disease involving xanthine oxidase deficiency. A summary of clinical and chemical features from 42 cases of xanthinuria worldwide was reported by Seegmiller. 

In this Japanese study series, two cases had clinical involvement and the other were without any clinical problems. Two cases with clinical problems did not relate directly to xanthine oxidase deficiency. 

Arthritis, a muscle symptom of cramps, was not found in any of the cases. The clinical course of the patients with xanthine oxidase deficiency is benign and symptoms are silent. This is one of the reasons why it is difficult to investigate this disorder. 

Cases 3 and 4 involved hereditary xanthine oxidase deficiency, but in Case 1, her younger sister s xanthine oxidase was 12% of normal activity and serum uric acid level was 2.4 mg/dl. 

Yamanaka H., Nishioka K. Allopurinol Metabolism in a Patient with Xanthine Oxidase Deficiency. Annals of Rheumatic Diseases, in press. 

From our study and from the results of BRADFORD Cl968) on the important daily turnover of hypoxanthine in xanthine oxidase deficiency, we would like to say that deficiency ( or inhibition by alio or oxipurinol ) of xanthine oxidase activity should be an important factor in the regulation of de novo biosynthesis of uric acid, (over productor with normal HGPRT activity). 

X component of pyruvate dehydrogenase complex deficiency Xanthine dehydrogenase deficiency Xanthine oxidase deficiency X-linked adrenoleukodystrophy... 

Table II. Serum and urine urate and urine oxypurine excretion in heterozygotes for xanthine oxidase deficiency.

Sperling, 0., Liberman, U.A., DeVries, A., Frank, M. Xanthinuria An additional case with demonstration of xanthine oxidase deficiency. A.J.C.P. 55 351-54, 1971. 

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