Identification of a xanthinuria type I case with mutations of xanthine dehydrogenase in an Afghan child.

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Xanthinuria due to xanthine dehydrogenase (XDH ) deficiency is a rare genetic disorder characterized by hypouricemia and the accumulation of xanthine in the urine . We have identified an Afghan girl whose xanthinuria could be classified as type I xanthinuria based on an allopurinol loading test . Three mutations were identified in the XDH gene , 141 insG , C 2 729 T (T 910 M ) and C 3 886 T (R 1296 W ). Site-directed mutagenesis followed by expression analysis in Escherichia coli revealed that not only the frame shift mutation 141 insG impairs XDH activity , but also the missense mutation C 2 729 T , while C 3 886 T resulted in major residual activity of about 50 % of the wild type . In this report , a case of xanthinuria type I with mutations of XDH was identified and characterized by expression studies .