Estimating the Prevalence of Xanthinuria by Laboratory Screening

A population phenotyping study of three drug‐metabolizing enzymes in Kyushu, Japan, with use of the caffeine test

“…28,43,48,49 In this respect, we anticipate that latent xanthinuria among Japanese persons may be more common than expected and that genetically determined polymorphism of xanthine oxidase may exist in healthy Japanese populations, such as our subjects. One of the 20 putative poor metabolizers showed the lowest urinary uric acid concentration of 2.5 mg/dL (comparable to the value reported from Japanese subjects with asymptomatic xanthinuria 27,28 ) and that subject had no symptoms. Further studies are obviously required to elucidate the genetic, environmental, and physiologic significance of the regulation of xanthine oxidase and xanthine dehydrogenase and to assess whether asymptomatic xanthinuria would be a rather common genetic phenomenon among Japanese persons.…”

“…However, most caffeine phenotyping studies have reported no bimodal distribution, and 2% to 10% of the study subjects appeared to have low xanthine oxidase activity (and therefore apparently poor metabolizers). 6,8,9,11,17 Nevertheless, xanthinuria is thought to be a rare disease, 27,41 whereas only one third of the persons with low xanthine oxidase activity have clinical symptoms referable to deficiency of xanthine oxidase or xanthine dehydrogenase. 27,41 Three mutations in the human xanthine dehydrogenase gene responsible for classic xanthinuria have been identified, 28,43 and other genotypical abnormalities have been reported for atypical type I xanthinuria or type II xanthinuria.…”

“…6,8,9,11,17 Nevertheless, xanthinuria is thought to be a rare disease, 27,41 whereas only one third of the persons with low xanthine oxidase activity have clinical symptoms referable to deficiency of xanthine oxidase or xanthine dehydrogenase. 27,41 Three mutations in the human xanthine dehydrogenase gene responsible for classic xanthinuria have been identified, 28,43 and other genotypical abnormalities have been reported for atypical type I xanthinuria or type II xanthinuria. 48,49 All of those subjects with xan-thinuria were Japanese persons with low serum uric acid levels (0.1 to 1 mg/dL; 0.6 to 5.9 mol/L) but without referable symptoms.…”

“…Moreover, the uric acid concentration in one of the 20 putative poor metabolizers was 2.5 mg/dL (147 mol/L), which was comparable to the value for asymptomatic xanthinuria reported previously in Japanese subjects. 27,28…”