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Pritchard EC, Haase B, Wall MJ, O’Brien CR, Gowan R, Mizzi K, Kicinski A, Podadera J, Boland LA. Xanthinuria in a familial group of Munchkin cats and an unrelated domestic shorthair cat. J Feline Med Surg 2024; 26:1098612X241241408. [PMID: 38717789 PMCID: PMC11156243 DOI: 10.1177/1098612x241241408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
CASE SERIES SUMMARY Four confirmed cases of xanthinuria in cats, and one suspected case based on pedigree analysis, were identified. Clinical presentations varied and included haematuria, pollakiuria, dysuria, and urethral and ureteral obstruction. All cats had upper urinary tract uroliths. Diagnosis was obtained through infrared mass spectrometry of uroliths or urine. Clinical signs commenced at 3-8 months of age and reduced in all cats in the medium to long term after the introduction of a protein-restricted diet. Four cats were castrated males and one was a spayed female. Cases consisted of four Munchkin pedigree cats and one unrelated domestic shorthair cat. All four affected Munchkin pedigree cats were related, with three cases full siblings and the fourth case a half-sibling. No connection to the Munchkin pedigree could be established for the domestic shorthair cat. A candidate causative genetic variant (XDH p.A681V) proposed for this cat was excluded in the Munchkin family. RELEVANCE AND NOVEL INFORMATION All affected cats presented diagnostic challenges and routine urinalysis was insufficient to obtain a diagnosis. Cases of feline xanthinuria may be underdiagnosed due to situations where uroliths cannot be retrieved for analysis and there is an inability to make a diagnosis using crystal morphology alone on routine urinalysis. Metabolic screening of urine may provide an effective mechanism to confirm xanthinuria in suspected cases where uroliths are inaccessible or absent. In this case series, male cats were more common. Their anatomy may increase the risk of lower urinary tract signs and urethral obstruction developing secondary to xanthine urolithiasis. A protein-restricted diet appears to reduce clinical signs as part of long-term management. PLAIN LANGUAGE SUMMARY Four closely related Munchkin cats and one domestic shorthair cat were found with a suspected genetic disease causing high levels of xanthine in their urine. The case series looks at similarities and differences in their clinical signs, as well as difficulties experienced in obtaining a correct diagnosis. All cats had upper urinary tract stones and required metabolic testing of the stones or urine to diagnose. All cats were young when their clinical signs started and were on a high-protein diet. Four cats were desexed males and one was a desexed female. A genetic variant that may have caused the disease in the domestic shorthair cat was ruled out in the Munchkin family. Cases of high xanthine levels in feline urine may be underdiagnosed as the stones may not be accessed for testing. In this case series, male cats were more common. Their anatomy may increase the risk of lower urinary tract signs. A protein-restricted diet appears to reduce clinical signs as part of long-term management.
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Affiliation(s)
- Emily C Pritchard
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
| | - Bianca Haase
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
| | | | | | | | - Kim Mizzi
- Ringwood Veterinary Clinic, Melbourne, VIC, Australia
| | | | - Juan Podadera
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
| | - Lara A Boland
- Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Sydney, NSW, Australia
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Gonçalves PL, Diniz H, Tavares I, Dória S, Dong J, Kyriss M, Fairbanks L, Oliveira JP. Kidney Failure Secondary to Hereditary Xanthinuria due to a Homozygous Deletion of the XDH Gene in the Absence of Overt Kidney Stone Disease. Nephron Clin Pract 2024; 148:578-583. [PMID: 38527446 DOI: 10.1159/000536248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Accepted: 01/08/2024] [Indexed: 03/27/2024] Open
Abstract
Hereditary xanthinuria (HXAN) is a rare metabolic disorder that results from mutations in either the xanthine dehydrogenase (XDH) or the molybdenum cofactor sulfurase genes (MOCOS), respectively defining HXAN type I and type II. Hypouricemia, hypouricosuria, and abnormally high plasma and urine levels of xanthine, causing susceptibility to xanthine nephrolithiasis and deposition of xanthine crystals in tissues, are the metabolic hallmarks of HXAN. Several pathogenic variants in the XDH gene have so far been identified in patients with HXAN type I, but the clinical phenotype associated with the whole deletion of the human XDH gene is unknown. Herein, we report the case of a woman diagnosed with HXAN, whose molecular genetic testing revealed a homozygous microdeletion involving the XDH gene. Distinctive features of her medical history were the diagnosis of arterial hypertension and microalbuminuria at 22 years of age; a single pregnancy at the age of 25, complicated by proteinuria and transient kidney function deterioration in the third trimester; unexplained severe hypouricemia incidentally discovered during pregnancy; inability to breastfeed her newborn daughter due to primary agalactia; chronic kidney disease (CKD) stage 3 diagnosed at age 35; and progression to end-stage kidney disease over the next 12 years. Protocol noninvasive laboratory and imaging investigation was not informative as to the cause of CKD. This is the first description of the clinical phenotype associated with a natural knockout of the human XDH gene. Despite the lack of kidney histopathology data, the striking similarities with the phenotypes exhibited by comparable murine models validate the latter as useful sources of mechanistic insights for the pathogenesis of the human disease, supporting the hypothesis that the absence of xanthine dehydrogenase activity might represent a susceptibility factor for chronic tubulointerstitial nephritis, even in patients without kidney stones.
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Affiliation(s)
| | - Hugo Diniz
- Department of Nephrology, São João University Hospital Centre, Porto, Portugal
| | - Isabel Tavares
- Department of Nephrology, São João University Hospital Centre, Porto, Portugal
- Group of Research and Development in Nephrology and Infectious Diseases, i3S - Institute for Health Research and Innovation, University of Porto, Porto, Portugal
- Department of Medicine, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Sofia Dória
- Unit of Genetics, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal
| | - Juan Dong
- PreventionGenetics, LLC, an Exact Sciences Co., Marshfield, Wisconsin, USA
| | - McKenna Kyriss
- PreventionGenetics, LLC, an Exact Sciences Co., Marshfield, Wisconsin, USA
| | - Lynette Fairbanks
- Purine Research Laboratory, Viapath, St Thomas' Hospital, London, UK
| | - João Paulo Oliveira
- Group of Research and Development in Nephrology and Infectious Diseases, i3S - Institute for Health Research and Innovation, University of Porto, Porto, Portugal
- Unit of Genetics, Department of Pathology, Faculty of Medicine, University of Porto, Porto, Portugal
- Service of Medical Genetics, São João University Hospital Centre, Porto, Portugal
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Association of Mutations Identified in Xanthinuria with the Function and Inhibition Mechanism of Xanthine Oxidoreductase. Biomedicines 2021; 9:biomedicines9111723. [PMID: 34829959 PMCID: PMC8615798 DOI: 10.3390/biomedicines9111723] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 11/16/2021] [Accepted: 11/16/2021] [Indexed: 01/07/2023] Open
Abstract
Xanthine oxidoreductase (XOR) is an enzyme that catalyzes the two-step reaction from hypoxanthine to xanthine and from xanthine to uric acid in purine metabolism. XOR generally carries dehydrogenase activity (XDH) but is converted into an oxidase (XO) under various pathophysiologic conditions. The complex structure and enzymatic function of XOR have been well investigated by mutagenesis studies of mammalian XOR and structural analysis of XOR-inhibitor interactions. Three XOR inhibitors are currently used as hyperuricemia and gout therapeutics but are also expected to have potential effects other than uric acid reduction, such as suppressing XO-generating reactive oxygen species. Isolated XOR deficiency, xanthinuria type I, is a good model of the metabolic effects of XOR inhibitors. It is characterized by hypouricemia, markedly decreased uric acid excretion, and increased serum and urinary xanthine concentrations, with no clinically significant symptoms. The pathogenesis and relationship between mutations and XOR activity in xanthinuria are useful for elucidating the biological role of XOR and the details of the XOR reaction process. In this review, we aim to contribute to the basic science and clinical aspects of XOR by linking the mutations in xanthinuria to structural studies, in order to understand the function and reaction mechanism of XOR in vivo.
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