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XANTHINE urolithiasis is uncommon in dogs, with case series giving a prevalence of between 0.07 and 0.46 per cent (Houston and Moore 2009, Osborne and others 2009, Low and others 2010). The most common cause of canine xanthinuria is iatrogenic when allopurinol is administered, inhibiting xanthine dehydrogenase (XDH) (Bartges and Kirk 2008).
In human beings, primary xanthinuria may be caused by enzyme deficiency or a cofactor abnormality. XDH deficiency may be isolated (type I), due to a missense mutation in the encoding gene for XDH, or in association with aldehyde oxidase deficiency, due to a missense mutation of the MCSU gene. Both are inherited in an autosomal recessive manner (Levartovsky and others 2000, Ichida and others 2001). Human beings with these defects may be asymptomatic with incidental hypouricaemia (Holmes and others 1974). Clinical signs, when they occur, are related to muscle deposition of xanthine causing myopathy, or renal dysfunction due to renal deposition (Nyhan 2005). A final cause of primary xanthinuria is an abnormality of the molybdenum cofactor required by xanthine oxidase, aldehyde oxidase and sulphite oxidase. Sulphite oxidase deficiency results in dramatic clinical signs of neonatal seizures and ophthalmic abnormalities (Wadman and others 1983).
Xanthine uroliths appear uncommon in cats, with a prevalence of 0.1 per cent reported in uroliths submitted to the Minnesota Urolith Center, USA (Osborne and others 2004). There are case reports of xanthinuria in two domestic shorthair cats and one Himalayan cat (White and others 1997, Tsuchida and others 2007, Schweighauser and others 2009). Single nucleotide polymorphism analysis of the XDH gene in a xanthinuric Himalayan cat suggested that it had …