Hereditary Xanthinuria

MONDO:0018106 Pathograph 18 Show in embeddings browser inborn error of purine metabolism autosomal recessive disease

An autosomal recessive block at the last two steps of purine degradation. Xanthine oxidoreductase converts hypoxanthine to xanthine and xanthine to uric acid, and when it fails the patient has almost no uric acid and a great deal of xanthine. The paradox is that a disease of purine excess presents as hypouricemia. Xanthine is the least soluble purine, so it crystallises in the urine and forms radiolucent stones. Two forms exist: type I from biallelic XDH variants, and type II from biallelic MOCOS variants, which also costs the patient aldehyde oxidase because the sulfurase that activates the molybdenum cofactor serves both enzymes. Roughly a third of affected people are symptomatic. The rest are found by an incidental urate of nearly zero.

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1
Inheritance
7
Pathophys.
1
Histopath.
11
Phenotypes
18
Pathograph
2
Genes
5
Variants
3
Medical Actions
2
Subtypes
1
Trials
1
Models
5
References
1
Deep Research
👪

Inheritance

1
Autosomal recessive HP:0000007
Biallelic variants in XDH (type I) or in MOCOS (type II). Heterozygotes are unaffected.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Classical xanthinuria is a rare autosomal recessive metabolic disorder caused by variants in the XDH (type I) or MOCOS (type II) genes."
States the inheritance pattern and both causal genes.
◆

Subtypes

2
Type I (XDH deficiency) MONDO:0010209
XDH hgnc:12805 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in XDH (hgnc:12805). hgnc:12805 is a gene from the HUGO Gene Nomenclature Committee.
Isolated loss of xanthine oxidoreductase from biallelic XDH variants. Aldehyde oxidase is intact. OMIM 278300.
Show evidence (1 reference)
PMID:23203137 SUPPORT Human Clinical
"Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase."
Distinguishes the two types by which enzymes are lost.
Type II (MOCOS deficiency) MONDO:0011346
MOCOS hgnc:18234 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in MOCOS (hgnc:18234). hgnc:18234 is a gene from the HUGO Gene Nomenclature Committee.
Combined loss of xanthine oxidoreductase and aldehyde oxidase, because the molybdenum cofactor sulfurase that both enzymes depend on is defective. The renal disease is the same. What differs is drug handling, since aldehyde oxidase metabolises several xenobiotics. OMIM 603592.
Show evidence (1 reference)
PMID:23203137 SUPPORT Human Clinical
"Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase."
States the dual enzyme deficiency and its cause in this subtype.
⚙

Pathophysiology

7
Biallelic Loss of Xanthine Oxidoreductase Function
Frameshift, nonsense and missense variants in XDH abolish the enzyme. The functional work is unusually direct: p.Cys150Phe sits in the Fe/S-I cluster-binding site and stops the protein being built at all. The homodimer needs a molybdenum centre, an FAD and two iron-sulfur clusters, and a lesion in any of them ends catalysis.
XDH hgnc:12805 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves XDH (hgnc:12805). hgnc:12805 is a gene from the HUGO Gene Nomenclature Committee.
xanthine dehydrogenase activity GO:0004854 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves xanthine dehydrogenase activity (GO:0004854), qualified as loss of function. GO:0004854 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Downstream
Failure of Hypoxanthine and Xanthine Oxidation No enzyme, no reaction. The block is at the catalytic step itself.
Show evidence (2 references)
PMID:23203137 SUPPORT Human Clinical
"Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase."
Defines type I as XOR deficiency from a genetic defect in the enzyme itself.
PMID:34356852 SUPPORT In Vitro
"Heterologous protein expression studies revealed that the p.Cys150Phe variant within the Fe/S-I cluster-binding site impairs XDH biogenesis, the p.Thr349Ileu variant in the NifS-like domain of MOCOS affects protein stability and cysteine desulfurase activity, while the p.Pro591Ser and a..."
Functional expression data for the specific variants, including the Fe/S-cluster variant that prevents the protein being made.
Molybdenum Cofactor Sulfuration Failure
MOCOS inserts the terminal sulfur into the molybdenum cofactor. Without that sulfido group neither xanthine oxidoreductase nor aldehyde oxidase works, so a single gene takes out two enzymes. Expression studies place the variants in two functional classes: p.Thr349Ile destabilises the protein and its cysteine desulfurase activity, while p.Pro591Ser and p.Arg776Cys spoil cofactor binding.
MOCOS hgnc:18234 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves MOCOS (hgnc:18234). hgnc:18234 is a gene from the HUGO Gene Nomenclature Committee.
molybdenum cofactor sulfurtransferase activity GO:0008265 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves molybdenum cofactor sulfurtransferase activity (GO:0008265), qualified as loss of function. GO:0008265 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Downstream
Failure of Hypoxanthine and Xanthine Oxidation An unsulfurated cofactor leaves the oxidoreductase catalytically dead even though the XDH gene is intact.
Show evidence (2 references)
PMID:23203137 SUPPORT Human Clinical
"Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase."
States that type II is a dual deficiency caused by a defect in the sulfurase, which is what this node describes.
PMID:34356852 SUPPORT In Vitro
"Heterologous protein expression studies revealed that the p.Cys150Phe variant within the Fe/S-I cluster-binding site impairs XDH biogenesis, the p.Thr349Ileu variant in the NifS-like domain of MOCOS affects protein stability and cysteine desulfurase activity, while the p.Pro591Ser and a..."
Gives the functional classes of the MOCOS variants named here.
Failure of Hypoxanthine and Xanthine Oxidation
The two terminal hydroxylations of purine catabolism stop. Uric acid is no longer made, and xanthine and hypoxanthine accumulate. Hypoxanthine is largely salvaged back to IMP. Xanthine has no salvage route of consequence, so it goes to the urine.
purine nucleobase catabolic process GO:0006145 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased purine nucleobase catabolic process (GO:0006145). GO:0006145 is a biological process from the Gene Ontology. ↓ DECREASED urate biosynthetic process GO:0034418 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased urate biosynthetic process (GO:0034418). GO:0034418 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Hypouricemia with Xanthine and Hypoxanthine Accumulation The substrate accumulates and the product disappears, which is the biochemical signature of the disease.
Show evidence (1 reference)
PMID:23203137 SUPPORT Human Clinical
"Xanthine oxidoreductase (XOR) catalyzes the conversion of hypoxanthine to xanthine and xanthine to uric acid with concomitant reduction of either NAD+ or O(2)."
Names both reactions that fail at this node.
Hypouricemia with Xanthine and Hypoxanthine Accumulation
Serum and urinary urate fall to near zero and urinary xanthine and hypoxanthine rise. This is the finding that makes the diagnosis, and it is also how most asymptomatic patients are discovered, because a urate below the limit of detection is hard to ignore on a routine panel.
Downstream
Urinary Xanthine Supersaturation The excreted xanthine load is what drives the urine past the solubility of xanthine.
Show evidence (2 references)
PMID:20228523 SUPPORT Human Clinical
"In both patients, plasma and urinary concentrations of uric acid were low but xanthine and hypoxanthine concentrations were markedly elevated."
Documents the biochemical pattern in patients.
PMID:23203137 SUPPORT Human Clinical
"Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria, because of the excretion of xanthine in urine."
States that the urinary xanthine excretion is what the disease is named for.
Urinary Xanthine Supersaturation
Xanthine is the least soluble of the purines, and unlike uric acid its solubility barely moves with urine pH. That is the reason alkalinisation, which works for uric acid stones, is not established here. Dilution is what is left.
Downstream
Xanthine Crystal and Stone Formation Supersaturation is the thermodynamic driving force for crystallisation.
Show evidence (1 reference)
PMID:23203137 SUPPORT Human Clinical
"Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria, because of the excretion of xanthine in urine."
Establishes the high urinary xanthine that produces the supersaturated state this node names.
Xanthine Crystal and Stone Formation
Crystalluria and radiolucent calculi of pure xanthine. Radiolucent matters clinically: plain films miss them, so an unexplained stone in a child with a very low urate is the pattern that should prompt the diagnosis.
Downstream
Obstructive and Crystal-Induced Kidney Injury Stones obstruct, and obstruction plus crystal contact injures the tubule.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"The calculi consisted of pure xanthine."
Establishes the composition of the calculi this node names, in the second reported patient.
Obstructive and Crystal-Induced Kidney Injury
Hydronephrosis, hematuria, renal colic, infection, and in the worst cases a destroyed kidney. The mouse carrying an Xdh nonsense mutation shows what the human histology is inferred to be: intratubular casts, interstitial cellular infiltration, fibrosis, and tubular apoptosis. That model is the strongest evidence for the tubular injury limb, and it is a mouse.
epithelial cell of proximal tubule CL:0002306 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves epithelial cell of proximal tubule (CL:0002306). CL:0002306 is a cell type from the Cell Ontology.
Animal models
RENF mouse (Xdh nonsense mutation) Mouse partially recapitulates Reproduces the tubulointerstitial injury and the loss of renal function, and it carries the human biochemistry, since the mice have plasma uric acid below the limit of detection.
Show evidence (3 references)
PMID:20228523 SUPPORT Human Clinical
"However asymptomatic, and therefore undiagnosed, stones may invade the kidney and urinary tract, resulting in destruction of parenchyma, nephrectomy and renal failure."
The human clinical statement of this outcome.
PMID:23024809 SUPPORT Model Organism
"Histological analysis of RENF kidney sections revealed abnormal arrangement of glomeruli, intratubular casts, cellular infiltration in the interstitial space, and interstitial fibrosis."
Histology of the tubular and interstitial injury in the Xdh-nonsense mouse.
PMID:23024809 SUPPORT Model Organism
"TUNEL analysis of RENF kidney sections showed extensive apoptosis predominantly affecting the tubules."
Locates the apoptosis in the tubules in the same mouse model. Model-organism evidence, and the human tubular pathology is inferred from it.
✶

Histopathology

1
End-stage pyelonephritis
The renal parenchyma of a nephrectomy specimen from a child with xanthine calculi and a non-functioning kidney. This is the human counterpart of the tubulointerstitial injury that the entry otherwise carries on mouse histology, and it is the endpoint rather than the early lesion. No finding_term is bound, because NCIT:C34965 Pyelonephritis and HP:0012330 Pyelonephritis both exist but neither is reachable from the roots of the HistopathologyFindingTerm enum, which is restricted to morphology and cell-structure terms, so no accurate binding is available.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"Nephrectomy was performed, and histology revealed end-stage pyelonephritis."
Reports the histological finding in a resected kidney from a patient with this disease.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Hereditary Xanthinuria Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

11
Genitourinary 7
Xanthinuria OBLIGATE HP:0010934 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Xanthinuria (HP:0010934). HP:0010934 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23203137 SUPPORT Human Clinical
"Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria, because of the excretion of xanthine in urine."
States that the urinary xanthine excretion is the defining and name-giving feature.
Nephrolithiasis FREQUENT Xanthine nephrolithiasis HP:0000804 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Xanthine nephrolithiasis (HP:0000804). HP:0000804 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:34356852 SUPPORT Human Clinical
"The major clinical manifestation of xanthinuria is the formation of xanthine calculi in the urinary tract in about 40% of the affected individuals."
States the stone-specific proportion, about 40%, which places this phenotype in the FREQUENT band and identifies the calculi as xanthine.
PMID:20228523 SUPPORT Human Clinical
"It is an uncommon cause of stone formation in children."
Attributes paediatric stone formation to this disease in the case report from which the stone composition in the description is taken.
Hematuria HP:0000790 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hematuria (HP:0000790). HP:0000790 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"The first patient was an 8-year-old boy who presented with repeated episodes of hematuria evaluated with excretory urography, which demonstrated radio-lucent pelvic stone in the right kidney, causing hydronephrosis."
Documents hematuria as the presenting feature in a patient with this disease.
Hydronephrosis HP:0000126 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hydronephrosis (HP:0000126). HP:0000126 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"The first patient was an 8-year-old boy who presented with repeated episodes of hematuria evaluated with excretory urography, which demonstrated radio-lucent pelvic stone in the right kidney, causing hydronephrosis."
Documents the obstructing stone and the resulting hydronephrosis.
Crystalluria HP:0020074 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Xanthine crystalluria, annotated with Crystalluria (HP:0020074). HP:0020074 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Urolithiasis may present as hematuria, crystalluria, recurrent urinary tract infections, renal colic, acute renal failure that may lead to hydronephrosis, chronic renal failure and even death from uremia."
Names crystalluria among the ways the urolithiasis of this disease presents.
Recurrent Urinary Tract Infections HP:0000010 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent urinary tract infections (HP:0000010). HP:0000010 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Urolithiasis may present as hematuria, crystalluria, recurrent urinary tract infections, renal colic, acute renal failure that may lead to hydronephrosis, chronic renal failure and even death from uremia."
Names recurrent urinary tract infections among the presentations of the urolithiasis in this disease.
Renal Insufficiency VERY_RARE HP:0000083 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Renal insufficiency (HP:0000083). HP:0000083 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"However asymptomatic, and therefore undiagnosed, stones may invade the kidney and urinary tract, resulting in destruction of parenchyma, nephrectomy and renal failure."
States the progression to parenchymal destruction and renal failure, and calls it the exception to an otherwise benign course, which is the basis for the VERY_RARE band.
Metabolism 1
Hypouricemia OBLIGATE HP:0003537 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypouricemia (HP:0003537). HP:0003537 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"In both patients, plasma and urinary concentrations of uric acid were low but xanthine and hypoxanthine concentrations were markedly elevated."
Documents the low plasma and urinary urate in both reported patients.
Musculoskeletal 1
Arthropathy HP:0003040 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Arthropathy (HP:0003040). HP:0003040 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Less frequent manifestations are myopathy, arthropathy and duodenal ulcers."
Names arthropathy among the infrequent manifestations of this disease.
Constitutional 2
Renal Colic Flank pain HP:0030157 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Renal colic, annotated with Flank pain (HP:0030157). HP:0030157 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Urolithiasis may present as hematuria, crystalluria, recurrent urinary tract infections, renal colic, acute renal failure that may lead to hydronephrosis, chronic renal failure and even death from uremia."
Names renal colic among the presentations of the urolithiasis in this disease.
Myalgia HP:0003326 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Myalgia (HP:0003326). HP:0003326 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Less frequent manifestations are myopathy, arthropathy and duodenal ulcers."
Names myopathy among the infrequent manifestations, which is the muscle involvement this phenotype records.
🧬

Genetic Associations

2
XDH
Gene: XDH hgnc:12805 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is XDH (hgnc:12805). hgnc:12805 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Classical xanthinuria is a rare autosomal recessive metabolic disorder caused by variants in the XDH (type I) or MOCOS (type II) genes."
Assigns type I to XDH.
Variants (3)
XDH c.449G>T p.(Cys150Phe) Pathogenic
Missense variant in the Fe/S-I cluster-binding site. Expression studies show it impairs XDH biogenesis, so the protein is not built rather than built and inactive.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Among the 10 distinct variants identified, six were novel: c.449G>T (p.(Cys150Phe)), c.1434G>A (p.(Trp478*)), c.1871C>G (p.(Ser624*)) and c.913del (p.(Leu305fs*1)) in the XDH gene and c.1046C>T (p.(Thr349Ileu)) and c.1771C>T (p.(Pro591Ser)) in the MOCOS gene."
Reports the variant and its gene among those identified in the cohort.
XDH c.2473C>T p.(Arg825*) Pathogenic
Nonsense variant in exon 23, found by homozygosity testing in one family and previously reported in a Czech patient, which the authors read as a possibly old allele.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"SSCP screening followed by sequencing revealed a c.2473C>T (p.(Arg825*)) variant in exon 23 of the XDH gene that was previously reported in a Czech patient"
Reports the allele, its exon, and its prior independent observation.
XDH c.2164A>T p.(Lys825*) Pathogenic
Nonsense allele carried in compound heterozygosity in one family and shared as a founder variant across Arab and Turkmen families.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"The index case (V-15) and her two affected sibs were compound heterozygotes for c.1871C>G and a c.2164A>T (p.(Lys825*)) variant"
Records the allele and the compound-heterozygous genotype it was found in.
MOCOS
Gene: MOCOS hgnc:18234 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is MOCOS (hgnc:18234). hgnc:18234 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"For the MOCOS c.1046C>T variant found in the Yemenite-Jewish families F1, F3 and F8, a founder effect was demonstrated by haplotype analyses"
Establishes MOCOS as the type II gene in these families and the founder status of the recurring allele.
Variants (2)
MOCOS c.1046C>T p.(Thr349Ileu) Pathogenic
Missense variant in the NifS-like domain. Expression studies show it destabilises the protein and reduces cysteine desulfurase activity. Yemenite-Jewish founder allele.
Show evidence (1 reference)
PMID:34356852 SUPPORT In Vitro
"Heterologous protein expression studies revealed that the p.Cys150Phe variant within the Fe/S-I cluster-binding site impairs XDH biogenesis, the p.Thr349Ileu variant in the NifS-like domain of MOCOS affects protein stability and cysteine desulfurase activity, while the p.Pro591Ser and a..."
Reports the functional consequence of this variant in a heterologous expression system.
MOCOS c.1771C>T p.(Pro591Ser) Pathogenic
Missense variant in the C-terminal domain that impairs molybdenum cofactor binding.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Among the 10 distinct variants identified, six were novel: c.449G>T (p.(Cys150Phe)), c.1434G>A (p.(Trp478*)), c.1871C>G (p.(Ser624*)) and c.913del (p.(Leu305fs*1)) in the XDH gene and c.1046C>T (p.(Thr349Ileu)) and c.1771C>T (p.(Pro591Ser)) in the MOCOS gene."
Reports the variant and its gene among those identified in the cohort.
💊

Medical Actions

3
High Fluid Intake
Action: Fluid TherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Fluid Therapy (NCIT:C116537). NCIT:C116537 is a clinical intervention from the NCI Thesaurus. NCIT:C116537
Platform: Behavioral / lifestyle
Dilution of the urine, and the mainstay. Since xanthine solubility hardly changes with pH, lowering the concentration is the intervention with a mechanism behind it.
Mechanism Target:
INHIBITS Urinary Xanthine Supersaturation — More water in the urine lowers xanthine concentration and moves it back below saturation.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"Xanthine urolithiasis is usually a benign condition, easy to prevent or cure by appropriate alkalinization, forced hydration and restriction of dietary purines."
Names forced hydration among the measures that prevent or cure the stone disease.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Management includes high fluid intake and avoidance of purine and fructose-rich foods"
Names high fluid intake first among the management measures for this disease.
Dietary Purine Restriction
Action: Dietary InterventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dietary Intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. NCIT:C15447
Platform: Behavioral / lifestyle
Reducing purine intake reduces the xanthine that has to be excreted.
Mechanism Target:
MODULATES Hypouricemia with Xanthine and Hypoxanthine Accumulation — Less dietary purine means less substrate arriving at a blocked pathway.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"Xanthine urolithiasis is usually a benign condition, easy to prevent or cure by appropriate alkalinization, forced hydration and restriction of dietary purines."
Names dietary purine restriction among the measures that prevent the stone disease.
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Management includes high fluid intake and avoidance of purine and fructose-rich foods"
Names avoidance of purine-rich food among the management measures for this disease.
Surgical Stone Removal
Action: pyelolithotomyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is pyelolithotomy, annotated with Surgical Procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Platform: Surgery
Operative removal of an obstructing calculus. The cited case report describes pyelolithotomy for a pelvic stone, and nephrectomy for the kidney already destroyed by one. NCIT has no term for pyelolithotomy or for nephrolithotomy, so the binding is the generic surgical action and the specific operation is carried in preferred_term. Modern series use ureteroscopy, laser lithotripsy and percutaneous nephrolithotomy; those are not curated here because no source cached for this entry describes them in xanthinuria.
Mechanism Target:
INHIBITS Obstructive and Crystal-Induced Kidney Injury — Removing the calculus relieves the obstruction that drives the injury, without touching the metabolic block that produced it.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"The first patient was an 8-year-old boy who presented with repeated episodes of hematuria evaluated with excretory urography, which demonstrated radio-lucent pelvic stone in the right kidney, causing hydronephrosis."
Documents the obstructing stone and the hydronephrosis that the operation relieved.
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"He had pyelolithotomy, and the extracted stone consisted of pure xanthine."
Reports the operation performed and confirms the stone it removed was xanthine.
🔬

Diagnosis

2
Plasma and Urinary Purine Profile
Measurement of urate, xanthine and hypoxanthine in plasma and urine. A urate close to zero with raised xanthine is the pattern that makes the diagnosis, and it is usually reached from an incidental low urate rather than from a stone.
purine profile in plasma and urine NCIT:C17241 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:20228523 SUPPORT Human Clinical
"In both patients, plasma and urinary concentrations of uric acid were low but xanthine and hypoxanthine concentrations were markedly elevated."
States the biochemical pattern in plasma and urine on which the diagnosis rests.
Molecular Confirmation of XDH or MOCOS Variants
Sequencing to identify biallelic variants and to assign type I or type II, which the biochemical profile alone does not separate.
molecular genetic testing of XDH and MOCOS NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:34356852 SUPPORT Human Clinical
"Among the 10 distinct variants identified, six were novel: c.449G>T (p.(Cys150Phe)), c.1434G>A (p.(Trp478*)), c.1871C>G (p.(Ser624*)) and c.913del (p.(Leu305fs*1)) in the XDH gene and c.1046C>T (p.(Thr349Ileu)) and c.1771C>T (p.(Pro591Ser)) in the MOCOS gene."
Demonstrates variant identification in both genes as the route to a molecular diagnosis.
📊

Prevalence

1
Worldwide
Unknown Rare
The sources describe the disease as rare and concentrated in the Mediterranean and Middle East without giving a rate, so the qualitative band is used and no numeric estimate is asserted. The largest published series is 20 affected individuals from 13 kindred.
Show evidence (2 references)
PMID:34356852 SUPPORT Human Clinical
"Classical xanthinuria is a rare autosomal recessive metabolic disorder caused by variants in the XDH (type I) or MOCOS (type II) genes."
The source characterises the disease as rare without naming a measure or a rate, which is what the qualitative band records.
PMID:34356852 SUPPORT Human Clinical
"Classical xanthinuria occurs worldwide, yet more than two-thirds of cases are reported from the Mediterranean and Middle Eastern countries."
Supports the worldwide population and records the geographic concentration behind the founder effects in the genetic section.
🔬

Clinical Trials

1
NCT06092346 NOT_APPLICABLE RECRUITING
NIH/NHGRI prospective natural-history study of pyrimidine and purine metabolism disorders. The registry's own condition list names XDH / Xanthinuria Type 1 among the enrolling diagnoses, so this is an open observational study a patient with type I could enter. It is not xanthinuria-specific and not interventional, and that condition list is registry metadata that does not appear in the cached summary quoted below.
Show evidence (1 reference)
clinicaltrials:NCT06092346 SUPPORT Other
"Three types of participants are needed: people aged 1 month and older with DPPMs; their family members who do not have DPPMs; and healthy volunteers."
Establishes the enrolling population as people with purine and pyrimidine metabolism disorders, the class this disease belongs to. A registration record, not study evidence, hence OTHER.
🐁

Animal Models

1
RENF mouse (Xdh nonsense mutation)
An ENU mutagenesis screen for hereditary renal failure that recovered an Xdh nonsense allele. The authors present it as a model for xanthinuria in man.
Species
Mouse
Genotype
Xdh nonsense mutation at codon 26, homozygous (ENU-induced, designated RENF)
Publication
PMID:23024809
Pathograph links
Obstructive and Crystal-Induced Kidney Injury partially recapitulates fidelity: moderate observes: organism Reproduces the tubulointerstitial injury and the loss of renal function, and it carries the human biochemistry, since the mice have plasma uric acid below the limit of detection.
Limitations: The severity and timing do not match the human disease. RENF mice are in renal failure by four weeks with small, irregular kidneys, whereas human hereditary xanthinuria is usually benign and most affected people never reach renal failure at all. The cited abstract does not report xanthine calculi in these mice, so the stone-formation step that produces the human injury is not demonstrated in the model, and the mouse Xdh loss also removes renal COX-2 expression, which has no established counterpart in the human disease. This link is therefore evidence that losing XDH damages the kidney, not that it damages it by the route curated here.
Readouts
Renal histology
Direction: ALTERED
Interpretation: Structural correlate of the tubulointerstitial limb of this node.
Show evidence (1 reference)
PMID:23024809 SUPPORT Model Organism
"Histological analysis of RENF kidney sections revealed abnormal arrangement of glomeruli, intratubular casts, cellular infiltration in the interstitial space, and interstitial fibrosis."
Reports the histological measurement behind this readout.
Tubular apoptosis by TUNEL
Direction: INCREASED
Interpretation: Locates the cell death in the tubules rather than the glomeruli.
Show evidence (1 reference)
PMID:23024809 SUPPORT Model Organism
"TUNEL analysis of RENF kidney sections showed extensive apoptosis predominantly affecting the tubules."
Reports the apoptosis measurement and its tubular localisation.
Show evidence (2 references)
PMID:23024809 SUPPORT Model Organism
"Thus, we have established a mouse model for autosomal recessive early-onset renal failure due to a nonsense mutation in Xdh that is a model for xanthinuria in man."
The authors' own claim that this model is informative for human xanthinuria, which is what licenses linking it to this node.
+ 1 more reference
Show evidence (1 reference)
PMID:23024809 SUPPORT Model Organism
"DNA sequencing of the xanthine dehydrogenase (Xdh) gene revealed a nonsense mutation at codon 26 that co-segregated with affected RENF mice."
Establishes the genotype recorded for this model.
{ }

Source YAML

click to show 
name: Hereditary Xanthinuria
creation_date: '2026-09-05T17:15:00Z'
description: 'An autosomal recessive block at the last two steps of purine degradation. Xanthine oxidoreductase
  converts hypoxanthine to xanthine and xanthine to uric acid, and when it fails the patient has almost
  no uric acid and a great deal of xanthine. The paradox is that a disease of purine excess presents
  as hypouricemia. Xanthine is the least soluble purine, so it crystallises in the urine and forms
  radiolucent stones. Two forms exist: type I from biallelic XDH variants, and type II from biallelic
  MOCOS variants, which also costs the patient aldehyde oxidase because the sulfurase that activates
  the molybdenum cofactor serves both enzymes. Roughly a third of affected people are symptomatic.
  The rest are found by an incidental urate of nearly zero.'
categories:
- Inborn Error of Purine Metabolism
- Molybdenum Cofactor-Dependent Enzyme Deficiency
- Hereditary Urolithiasis
parents:
- inborn error of purine metabolism
- autosomal recessive disease
synonyms:
- classical xanthinuria
- xanthine oxidase deficiency
- xanthine dehydrogenase deficiency
- hereditary xanthinuria type I
- hereditary xanthinuria type II
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: Biallelic variants in XDH (type I) or in MOCOS (type II). Heterozygotes are unaffected.
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Classical xanthinuria is a rare autosomal recessive metabolic disorder caused by variants
      in the XDH (type I) or MOCOS (type II) genes.
    explanation: States the inheritance pattern and both causal genes.
has_subtypes:
- name: Type I
  display_name: Type I (XDH deficiency)
  subtype_term:
    preferred_term: xanthinuria type I
    term:
      id: MONDO:0010209
      label: xanthinuria type I
  description: Isolated loss of xanthine oxidoreductase from biallelic XDH variants. Aldehyde oxidase
    is intact. OMIM 278300.
  genes:
  - preferred_term: XDH
    term:
      id: hgnc:12805
      label: XDH
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type
      II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme
      similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase.
    explanation: Distinguishes the two types by which enzymes are lost.
- name: Type II
  display_name: Type II (MOCOS deficiency)
  subtype_term:
    preferred_term: xanthinuria type II
    term:
      id: MONDO:0011346
      label: xanthinuria type II
  description: Combined loss of xanthine oxidoreductase and aldehyde oxidase, because the molybdenum
    cofactor sulfurase that both enzymes depend on is defective. The renal disease is the same. What
    differs is drug handling, since aldehyde oxidase metabolises several xenobiotics. OMIM 603592.
  genes:
  - preferred_term: MOCOS
    term:
      id: hgnc:18234
      label: MOCOS
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type
      II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme
      similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase.
    explanation: States the dual enzyme deficiency and its cause in this subtype.
pathophysiology:
- name: Biallelic Loss of Xanthine Oxidoreductase Function
  biological_scale: MOLECULAR
  subtypes:
  - Type I
  description: 'Frameshift, nonsense and missense variants in XDH abolish the enzyme. The functional
    work is unusually direct: p.Cys150Phe sits in the Fe/S-I cluster-binding site and stops the protein
    being built at all. The homodimer needs a molybdenum centre, an FAD and two iron-sulfur clusters,
    and a lesion in any of them ends catalysis.'
  genes:
  - preferred_term: XDH
    term:
      id: hgnc:12805
      label: XDH
  molecular_functions:
  - preferred_term: xanthine dehydrogenase activity
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0004854
      label: xanthine dehydrogenase activity
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type
      II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme
      similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase.
    explanation: Defines type I as XOR deficiency from a genetic defect in the enzyme itself.
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Heterologous protein expression studies revealed that the p.Cys150Phe variant within
      the Fe/S-I cluster-binding site impairs XDH biogenesis, the p.Thr349Ileu variant in the NifS-like
      domain of MOCOS affects protein stability and cysteine desulfurase activity, while the p.Pro591Ser
      and a previously described p.Arg776Cys variant in the C-terminal domain affect Molybdenum cofactor
      binding.
    explanation: Functional expression data for the specific variants, including the Fe/S-cluster
      variant that prevents the protein being made.
  downstream:
  - target: Failure of Hypoxanthine and Xanthine Oxidation
    causal_link_type: DIRECT
    description: No enzyme, no reaction. The block is at the catalytic step itself.
    evidence:
    - reference: PMID:23203137
      reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
        hereditary xanthinuria in humans.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Xanthine oxidoreductase (XOR) catalyzes the conversion of hypoxanthine to xanthine
        and xanthine to uric acid with concomitant reduction of either NAD+ or O(2).
      explanation: Names the two reactions the lost enzyme catalyses, which is what the downstream
        node loses.
- name: Molybdenum Cofactor Sulfuration Failure
  biological_scale: MOLECULAR
  subtypes:
  - Type II
  description: 'MOCOS inserts the terminal sulfur into the molybdenum cofactor. Without that sulfido
    group neither xanthine oxidoreductase nor aldehyde oxidase works, so a single gene takes out two
    enzymes. Expression studies place the variants in two functional classes: p.Thr349Ile destabilises
    the protein and its cysteine desulfurase activity, while p.Pro591Ser and p.Arg776Cys spoil cofactor
    binding.'
  genes:
  - preferred_term: MOCOS
    term:
      id: hgnc:18234
      label: MOCOS
  molecular_functions:
  - preferred_term: molybdenum cofactor sulfurtransferase activity
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0008265
      label: molybdenum cofactor sulfurtransferase activity
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type
      II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme
      similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase.
    explanation: States that type II is a dual deficiency caused by a defect in the sulfurase, which
      is what this node describes.
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: Heterologous protein expression studies revealed that the p.Cys150Phe variant within
      the Fe/S-I cluster-binding site impairs XDH biogenesis, the p.Thr349Ileu variant in the NifS-like
      domain of MOCOS affects protein stability and cysteine desulfurase activity, while the p.Pro591Ser
      and a previously described p.Arg776Cys variant in the C-terminal domain affect Molybdenum cofactor
      binding.
    explanation: Gives the functional classes of the MOCOS variants named here.
  downstream:
  - target: Failure of Hypoxanthine and Xanthine Oxidation
    causal_link_type: DIRECT
    description: An unsulfurated cofactor leaves the oxidoreductase catalytically dead even though
      the XDH gene is intact.
    evidence:
    - reference: PMID:23203137
      reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
        hereditary xanthinuria in humans.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Type I xanthinuria involves XOR deficiency due to genetic defect of XOR, whereas type
        II xanthinuria involves dual deficiency of XOR and aldehyde oxidase (AO, a molybdoflavo enzyme
        similar to XOR) due to genetic defect in the molybdenum cofactor sulfurase.
      explanation: States that the sulfurase defect produces the XOR deficiency, which is this edge.
- name: Failure of Hypoxanthine and Xanthine Oxidation
  biological_scale: MOLECULAR
  description: The two terminal hydroxylations of purine catabolism stop. Uric acid is no longer made,
    and xanthine and hypoxanthine accumulate. Hypoxanthine is largely salvaged back to IMP. Xanthine
    has no salvage route of consequence, so it goes to the urine.
  biological_processes:
  - preferred_term: purine nucleobase catabolic process
    modifier: DECREASED
    term:
      id: GO:0006145
      label: purine nucleobase catabolic process
  - preferred_term: urate biosynthetic process
    modifier: DECREASED
    term:
      id: GO:0034418
      label: urate biosynthetic process
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Xanthine oxidoreductase (XOR) catalyzes the conversion of hypoxanthine to xanthine and
      xanthine to uric acid with concomitant reduction of either NAD+ or O(2).
    explanation: Names both reactions that fail at this node.
  downstream:
  - target: Hypouricemia with Xanthine and Hypoxanthine Accumulation
    causal_link_type: DIRECT
    description: The substrate accumulates and the product disappears, which is the biochemical signature
      of the disease.
    evidence:
    - reference: PMID:20228523
      reference_title: Xanthine urolithiasis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: In both patients, plasma and urinary concentrations of uric acid were low but xanthine
        and hypoxanthine concentrations were markedly elevated.
      explanation: 'Measures both halves of the step in two patients: urate low, xanthine and hypoxanthine
        high.'
- name: Hypouricemia with Xanthine and Hypoxanthine Accumulation
  biological_scale: ORGANISM
  description: Serum and urinary urate fall to near zero and urinary xanthine and hypoxanthine rise.
    This is the finding that makes the diagnosis, and it is also how most asymptomatic patients are
    discovered, because a urate below the limit of detection is hard to ignore on a routine panel.
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both patients, plasma and urinary concentrations of uric acid were low but xanthine
      and hypoxanthine concentrations were markedly elevated.
    explanation: Documents the biochemical pattern in patients.
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria,
      because of the excretion of xanthine in urine.
    explanation: States that the urinary xanthine excretion is what the disease is named for.
  downstream:
  - target: Urinary Xanthine Supersaturation
    causal_link_type: DIRECT
    description: The excreted xanthine load is what drives the urine past the solubility of xanthine.
    evidence:
    - reference: PMID:23203137
      reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
        hereditary xanthinuria in humans.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Human diseases associated with genetically determined dysfunction of XOR are termed
        xanthinuria, because of the excretion of xanthine in urine.
      explanation: Establishes the urinary xanthine excretion that this edge carries into the urine.
- name: Urinary Xanthine Supersaturation
  biological_scale: ORGANISM
  conforms_to: nephrolithiasis_crystal_nucleation#Urinary Supersaturation
  description: Xanthine is the least soluble of the purines, and unlike uric acid its solubility barely
    moves with urine pH. That is the reason alkalinisation, which works for uric acid stones, is not
    established here. Dilution is what is left.
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria,
      because of the excretion of xanthine in urine.
    explanation: Establishes the high urinary xanthine that produces the supersaturated state this
      node names.
  downstream:
  - target: Xanthine Crystal and Stone Formation
    causal_link_type: DIRECT
    description: Supersaturation is the thermodynamic driving force for crystallisation.
    evidence:
    - reference: PMID:20228523
      reference_title: Xanthine urolithiasis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: He had pyelolithotomy, and the extracted stone consisted of pure xanthine.
      explanation: The stone recovered from a patient was pure xanthine, which is the crystallisation
        product this edge asserts the supersaturated urine yields.
- name: Xanthine Crystal and Stone Formation
  biological_scale: TISSUE
  conforms_to: nephrolithiasis_crystal_nucleation#Crystal Nucleation and Growth
  description: 'Crystalluria and radiolucent calculi of pure xanthine. Radiolucent matters clinically:
    plain films miss them, so an unexplained stone in a child with a very low urate is the pattern
    that should prompt the diagnosis.'
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The calculi consisted of pure xanthine.
    explanation: Establishes the composition of the calculi this node names, in the second reported
      patient.
  downstream:
  - target: Obstructive and Crystal-Induced Kidney Injury
    causal_link_type: DIRECT
    description: Stones obstruct, and obstruction plus crystal contact injures the tubule.
    evidence:
    - reference: PMID:20228523
      reference_title: Xanthine urolithiasis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: However asymptomatic, and therefore undiagnosed, stones may invade the kidney and urinary
        tract, resulting in destruction of parenchyma, nephrectomy and renal failure.
      explanation: States the progression from silent stone to parenchymal destruction, nephrectomy
        and renal failure.
- name: Obstructive and Crystal-Induced Kidney Injury
  biological_scale: ORGANISM
  conforms_to: nephrolithiasis_crystal_nucleation#Crystal-Induced Tubular Injury and Inflammation
  description: 'Hydronephrosis, hematuria, renal colic, infection, and in the worst cases a destroyed
    kidney. The mouse carrying an Xdh nonsense mutation shows what the human histology is inferred
    to be: intratubular casts, interstitial cellular infiltration, fibrosis, and tubular apoptosis.
    That model is the strongest evidence for the tubular injury limb, and it is a mouse.'
  cell_types:
  - preferred_term: epithelial cell of proximal tubule
    term:
      id: CL:0002306
      label: epithelial cell of proximal tubule
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: However asymptomatic, and therefore undiagnosed, stones may invade the kidney and urinary
      tract, resulting in destruction of parenchyma, nephrectomy and renal failure.
    explanation: The human clinical statement of this outcome.
  - reference: PMID:23024809
    reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase nonsense
      mutation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Histological analysis of RENF kidney sections revealed abnormal arrangement of glomeruli,
      intratubular casts, cellular infiltration in the interstitial space, and interstitial fibrosis.
    explanation: Histology of the tubular and interstitial injury in the Xdh-nonsense mouse.
  - reference: PMID:23024809
    reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase nonsense
      mutation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: TUNEL analysis of RENF kidney sections showed extensive apoptosis predominantly affecting
      the tubules.
    explanation: Locates the apoptosis in the tubules in the same mouse model. Model-organism evidence,
      and the human tubular pathology is inferred from it.
phenotypes:
- category: Metabolic
  name: Hypouricemia
  frequency: OBLIGATE
  diagnostic: true
  description: Serum urate close to zero. The single most useful pointer to the diagnosis, and often
    an incidental finding.
  phenotype_term:
    preferred_term: Hypouricemia
    term:
      id: HP:0003537
      label: Hypouricemia
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both patients, plasma and urinary concentrations of uric acid were low but xanthine
      and hypoxanthine concentrations were markedly elevated.
    explanation: Documents the low plasma and urinary urate in both reported patients.
- category: Metabolic
  name: Xanthinuria
  frequency: OBLIGATE
  diagnostic: true
  description: Raised urinary xanthine, with hypoxanthine. The disease is named after it.
  phenotype_term:
    preferred_term: Xanthinuria
    term:
      id: HP:0010934
      label: Xanthinuria
  evidence:
  - reference: PMID:23203137
    reference_title: Mutations associated with functional disorder of xanthine oxidoreductase and
      hereditary xanthinuria in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Human diseases associated with genetically determined dysfunction of XOR are termed xanthinuria,
      because of the excretion of xanthine in urine.
    explanation: States that the urinary xanthine excretion is the defining and name-giving feature.
- category: Renal
  name: Nephrolithiasis
  frequency: FREQUENT
  description: Radiolucent calculi of pure xanthine, in about 40% of affected people. A separate
    figure from the same cohort paper, 7 of 20, counts people with xanthinuria-related symptoms of
    any kind rather than stones, so the two numbers measure different things and neither contradicts
    the other. Stones can be silent, which is how the disease reaches nephrectomy in the minority
    it damages.
  phenotype_term:
    preferred_term: Xanthine nephrolithiasis
    term:
      id: HP:0000804
      label: Xanthine nephrolithiasis
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The major clinical manifestation of xanthinuria is the formation of xanthine calculi
      in the urinary tract in about 40% of the affected individuals.
    explanation: States the stone-specific proportion, about 40%, which places this phenotype in the
      FREQUENT band and identifies the calculi as xanthine.
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: It is an uncommon cause of stone formation in children.
    explanation: Attributes paediatric stone formation to this disease in the case report from which
      the stone composition in the description is taken.
- category: Renal
  name: Hematuria
  description: Bleeding from stone passage or from stone-related injury. One of the two reported children
    presented with repeated hematuria, the other with gross hematuria and abdominal pain.
  phenotype_term:
    preferred_term: Hematuria
    term:
      id: HP:0000790
      label: Hematuria
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The first patient was an 8-year-old boy who presented with repeated episodes of hematuria
      evaluated with excretory urography, which demonstrated radio-lucent pelvic stone in the right
      kidney, causing hydronephrosis.
    explanation: Documents hematuria as the presenting feature in a patient with this disease.
- category: Renal
  name: Hydronephrosis
  description: Obstruction of the collecting system by a stone.
  phenotype_term:
    preferred_term: Hydronephrosis
    term:
      id: HP:0000126
      label: Hydronephrosis
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The first patient was an 8-year-old boy who presented with repeated episodes of hematuria
      evaluated with excretory urography, which demonstrated radio-lucent pelvic stone in the right
      kidney, causing hydronephrosis.
    explanation: Documents the obstructing stone and the resulting hydronephrosis.
- category: Renal
  name: Crystalluria
  description: Xanthine crystals in the urine, the step before a stone. HPO has crystalluria terms
    for orotic acid, leucine, calcium oxalate and calcium phosphate but none for xanthine, so the
    generic term is bound and the specificity is carried in preferred_term.
  phenotype_term:
    preferred_term: Xanthine crystalluria
    term:
      id: HP:0020074
      label: Crystalluria
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Urolithiasis may present as hematuria, crystalluria, recurrent urinary tract infections,
      renal colic, acute renal failure that may lead to hydronephrosis, chronic renal failure and
      even death from uremia.
    explanation: Names crystalluria among the ways the urolithiasis of this disease presents.
- category: Renal
  name: Recurrent Urinary Tract Infections
  description: Repeated infection of a tract that carries stones. A consequence of the calculi rather
    than of the metabolic block itself.
  phenotype_term:
    preferred_term: Recurrent urinary tract infections
    term:
      id: HP:0000010
      label: Recurrent urinary tract infections
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Urolithiasis may present as hematuria, crystalluria, recurrent urinary tract infections,
      renal colic, acute renal failure that may lead to hydronephrosis, chronic renal failure and
      even death from uremia.
    explanation: Names recurrent urinary tract infections among the presentations of the urolithiasis
      in this disease.
- category: Renal
  name: Renal Colic
  description: Colicky loin pain from a stone moving in the ureter. HPO has no renal colic term, so
    the binding is the broader Flank pain and the colicky, obstructive character is carried in the
    name and preferred_term rather than in the ontology.
  phenotype_term:
    preferred_term: Renal colic
    term:
      id: HP:0030157
      label: Flank pain
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Urolithiasis may present as hematuria, crystalluria, recurrent urinary tract infections,
      renal colic, acute renal failure that may lead to hydronephrosis, chronic renal failure and
      even death from uremia.
    explanation: Names renal colic among the presentations of the urolithiasis in this disease.
- category: Renal
  name: Renal Insufficiency
  frequency: VERY_RARE
  description: The worst outcome, reached through obstruction and crystal injury rather than through
    a primary glomerular lesion. One of the two reported children came to nephrectomy for an end-stage
    pyelonephritic kidney.
  phenotype_term:
    preferred_term: Renal insufficiency
    term:
      id: HP:0000083
      label: Renal insufficiency
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: However asymptomatic, and therefore undiagnosed, stones may invade the kidney and urinary
      tract, resulting in destruction of parenchyma, nephrectomy and renal failure.
    explanation: States the progression to parenchymal destruction and renal failure, and calls it
      the exception to an otherwise benign course, which is the basis for the VERY_RARE band.
- category: Musculoskeletal
  name: Myalgia
  description: Muscle pain attributed to xanthine deposition in muscle. The cohort paper calls myopathy
    a less frequent manifestation without quantifying it, so no frequency band is asserted.
  phenotype_term:
    preferred_term: Myalgia
    term:
      id: HP:0003326
      label: Myalgia
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Less frequent manifestations are myopathy, arthropathy and duodenal ulcers.
    explanation: Names myopathy among the infrequent manifestations, which is the muscle involvement
      this phenotype records.
- category: Musculoskeletal
  name: Arthropathy
  description: Joint disease, listed with myopathy among the infrequent manifestations. Not quantified
    in the sources used here, so no frequency band is asserted.
  phenotype_term:
    preferred_term: Arthropathy
    term:
      id: HP:0003040
      label: Arthropathy
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Less frequent manifestations are myopathy, arthropathy and duodenal ulcers.
    explanation: Names arthropathy among the infrequent manifestations of this disease.
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: RARE
  notes: The sources describe the disease as rare and concentrated in the Mediterranean and Middle
    East without giving a rate, so the qualitative band is used and no numeric estimate is asserted.
    The largest published series is 20 affected individuals from 13 kindred.
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Classical xanthinuria is a rare autosomal recessive metabolic disorder caused by variants
      in the XDH (type I) or MOCOS (type II) genes.
    explanation: The source characterises the disease as rare without naming a measure or a rate,
      which is what the qualitative band records.
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Classical xanthinuria occurs worldwide, yet more than two-thirds of cases are reported
      from the Mediterranean and Middle Eastern countries.
    explanation: Supports the worldwide population and records the geographic concentration behind
      the founder effects in the genetic section.
histopathology:
- name: End-stage pyelonephritis
  description: The renal parenchyma of a nephrectomy specimen from a child with xanthine calculi and
    a non-functioning kidney. This is the human counterpart of the tubulointerstitial injury that
    the entry otherwise carries on mouse histology, and it is the endpoint rather than the early
    lesion. No finding_term is bound, because NCIT:C34965 Pyelonephritis and HP:0012330 Pyelonephritis
    both exist but neither is reachable from the roots of the HistopathologyFindingTerm enum, which
    is restricted to morphology and cell-structure terms, so no accurate binding is available.
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Nephrectomy was performed, and histology revealed end-stage pyelonephritis.
    explanation: Reports the histological finding in a resected kidney from a patient with this disease.
genetic:
- name: XDH
  gene_term:
    preferred_term: XDH
    term:
      id: hgnc:12805
      label: XDH
  subtype: Type I
  relationship_type: CAUSATIVE
  notes: Biallelic XDH variants cause type I. The reported alleles are frameshift, nonsense
    and missense, and the functional consequence has been shown directly for several of them. A
    c.2164A>T nonsense allele recurs in Arab and Turkmen families as a founder variant.
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Classical xanthinuria is a rare autosomal recessive metabolic disorder caused by variants
      in the XDH (type I) or MOCOS (type II) genes.
    explanation: Assigns type I to XDH.
  variants:
  - name: XDH c.449G>T p.(Cys150Phe)
    description: Missense variant in the Fe/S-I cluster-binding site. Expression studies show it impairs
      XDH biogenesis, so the protein is not built rather than built and inactive.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:34356852
      reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from
        Germany: Molecular, Biochemical and Population Genetics Aspects.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: 'Among the 10 distinct variants identified, six were novel: c.449G>T (p.(Cys150Phe)),
        c.1434G>A (p.(Trp478*)), c.1871C>G (p.(Ser624*)) and c.913del (p.(Leu305fs*1)) in the XDH gene
        and c.1046C>T (p.(Thr349Ileu)) and c.1771C>T (p.(Pro591Ser)) in the MOCOS gene.'
      explanation: Reports the variant and its gene among those identified in the cohort.
  - name: XDH c.2473C>T p.(Arg825*)
    description: Nonsense variant in exon 23, found by homozygosity testing in one family and previously
      reported in a Czech patient, which the authors read as a possibly old allele.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:34356852
      reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from
        Germany: Molecular, Biochemical and Population Genetics Aspects.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: SSCP screening followed by sequencing revealed a c.2473C>T (p.(Arg825*)) variant in
        exon 23 of the XDH gene that was previously reported in a Czech patient
      explanation: Reports the allele, its exon, and its prior independent observation.
  - name: XDH c.2164A>T p.(Lys825*)
    description: Nonsense allele carried in compound heterozygosity in one family and shared as a
      founder variant across Arab and Turkmen families.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:34356852
      reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from
        Germany: Molecular, Biochemical and Population Genetics Aspects.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The index case (V-15) and her two affected sibs were compound heterozygotes for c.1871C>G
        and a c.2164A>T (p.(Lys825*)) variant
      explanation: Records the allele and the compound-heterozygous genotype it was found in.
- name: MOCOS
  gene_term:
    preferred_term: MOCOS
    term:
      id: hgnc:18234
      label: MOCOS
  subtype: Type II
  relationship_type: CAUSATIVE
  notes: Biallelic MOCOS variants cause type II. Because the sulfurase activates the molybdenum
    cofactor for both xanthine oxidoreductase and aldehyde oxidase, the loss is of two enzymes rather
    than one. c.1046C>T is a Yemenite-Jewish founder variant.
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: For the MOCOS c.1046C>T variant found in the Yemenite-Jewish families F1, F3 and F8,
      a founder effect was demonstrated by haplotype analyses
    explanation: Establishes MOCOS as the type II gene in these families and the founder status of
      the recurring allele.
  variants:
  - name: MOCOS c.1046C>T p.(Thr349Ileu)
    description: Missense variant in the NifS-like domain. Expression studies show it destabilises
      the protein and reduces cysteine desulfurase activity. Yemenite-Jewish founder allele.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:34356852
      reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from
        Germany: Molecular, Biochemical and Population Genetics Aspects.'
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: Heterologous protein expression studies revealed that the p.Cys150Phe variant within
        the Fe/S-I cluster-binding site impairs XDH biogenesis, the p.Thr349Ileu variant in the NifS-like
        domain of MOCOS affects protein stability and cysteine desulfurase activity, while the p.Pro591Ser
        and a previously described p.Arg776Cys variant in the C-terminal domain affect Molybdenum cofactor
        binding.
      explanation: Reports the functional consequence of this variant in a heterologous expression
        system.
  - name: MOCOS c.1771C>T p.(Pro591Ser)
    description: Missense variant in the C-terminal domain that impairs molybdenum cofactor binding.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:34356852
      reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from
        Germany: Molecular, Biochemical and Population Genetics Aspects.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: 'Among the 10 distinct variants identified, six were novel: c.449G>T (p.(Cys150Phe)),
        c.1434G>A (p.(Trp478*)), c.1871C>G (p.(Ser624*)) and c.913del (p.(Leu305fs*1)) in the XDH gene
        and c.1046C>T (p.(Thr349Ileu)) and c.1771C>T (p.(Pro591Ser)) in the MOCOS gene.'
      explanation: Reports the variant and its gene among those identified in the cohort.
treatments:
- name: High Fluid Intake
  therapeutic_modality: BEHAVIORAL
  description: Dilution of the urine, and the mainstay. Since xanthine solubility hardly changes with
    pH, lowering the concentration is the intervention with a mechanism behind it.
  treatment_term:
    preferred_term: Fluid Therapy
    term:
      id: NCIT:C116537
      label: Fluid Therapy
  target_mechanisms:
  - target: Urinary Xanthine Supersaturation
    treatment_effect: INHIBITS
    description: More water in the urine lowers xanthine concentration and moves it back below saturation.
    evidence:
    - reference: PMID:20228523
      reference_title: Xanthine urolithiasis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Xanthine urolithiasis is usually a benign condition, easy to prevent or cure by appropriate
        alkalinization, forced hydration and restriction of dietary purines.
      explanation: Names forced hydration among the measures that prevent or cure the stone disease.
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Management includes high fluid intake and avoidance of purine and fructose-rich foods
    explanation: Names high fluid intake first among the management measures for this disease.
- name: Dietary Purine Restriction
  therapeutic_modality: BEHAVIORAL
  description: Reducing purine intake reduces the xanthine that has to be excreted.
  treatment_term:
    preferred_term: Dietary Intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  target_mechanisms:
  - target: Hypouricemia with Xanthine and Hypoxanthine Accumulation
    treatment_effect: MODULATES
    description: Less dietary purine means less substrate arriving at a blocked pathway.
    evidence:
    - reference: PMID:20228523
      reference_title: Xanthine urolithiasis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Xanthine urolithiasis is usually a benign condition, easy to prevent or cure by appropriate
        alkalinization, forced hydration and restriction of dietary purines.
      explanation: Names dietary purine restriction among the measures that prevent the stone disease.
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Management includes high fluid intake and avoidance of purine and fructose-rich foods
    explanation: Names avoidance of purine-rich food among the management measures for this disease.
- name: Surgical Stone Removal
  therapeutic_modality: SURGERY
  description: Operative removal of an obstructing calculus. The cited case report describes pyelolithotomy
    for a pelvic stone, and nephrectomy for the kidney already destroyed by one. NCIT has no term
    for pyelolithotomy or for nephrolithotomy, so the binding is the generic surgical action and
    the specific operation is carried in preferred_term. Modern series use ureteroscopy, laser lithotripsy
    and percutaneous nephrolithotomy; those are not curated here because no source cached for this
    entry describes them in xanthinuria.
  treatment_term:
    preferred_term: pyelolithotomy
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_mechanisms:
  - target: Obstructive and Crystal-Induced Kidney Injury
    treatment_effect: INHIBITS
    description: Removing the calculus relieves the obstruction that drives the injury, without touching
      the metabolic block that produced it.
    evidence:
    - reference: PMID:20228523
      reference_title: Xanthine urolithiasis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: The first patient was an 8-year-old boy who presented with repeated episodes of hematuria
        evaluated with excretory urography, which demonstrated radio-lucent pelvic stone in the right
        kidney, causing hydronephrosis.
      explanation: Documents the obstructing stone and the hydronephrosis that the operation relieved.
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: He had pyelolithotomy, and the extracted stone consisted of pure xanthine.
    explanation: Reports the operation performed and confirms the stone it removed was xanthine.
diagnosis:
- name: Plasma and Urinary Purine Profile
  description: Measurement of urate, xanthine and hypoxanthine in plasma and urine. A urate close
    to zero with raised xanthine is the pattern that makes the diagnosis, and it is usually reached
    from an incidental low urate rather than from a stone.
  diagnosis_term:
    preferred_term: purine profile in plasma and urine
    term:
      id: NCIT:C17241
      label: Urinalysis
  evidence:
  - reference: PMID:20228523
    reference_title: Xanthine urolithiasis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: In both patients, plasma and urinary concentrations of uric acid were low but xanthine
      and hypoxanthine concentrations were markedly elevated.
    explanation: States the biochemical pattern in plasma and urine on which the diagnosis rests.
- name: Molecular Confirmation of XDH or MOCOS Variants
  description: Sequencing to identify biallelic variants and to assign type I or type II, which the
    biochemical profile alone does not separate.
  diagnosis_term:
    preferred_term: molecular genetic testing of XDH and MOCOS
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:34356852
    reference_title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany:
      Molecular, Biochemical and Population Genetics Aspects.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'Among the 10 distinct variants identified, six were novel: c.449G>T (p.(Cys150Phe)),
      c.1434G>A (p.(Trp478*)), c.1871C>G (p.(Ser624*)) and c.913del (p.(Leu305fs*1)) in the XDH gene
      and c.1046C>T (p.(Thr349Ileu)) and c.1771C>T (p.(Pro591Ser)) in the MOCOS gene.'
    explanation: Demonstrates variant identification in both genes as the route to a molecular diagnosis.
animal_models:
- name: RENF mouse (Xdh nonsense mutation)
  species: Mouse
  genotype: Xdh nonsense mutation at codon 26, homozygous (ENU-induced, designated RENF)
  publication: PMID:23024809
  description: An ENU mutagenesis screen for hereditary renal failure that recovered an Xdh nonsense
    allele. The authors present it as a model for xanthinuria in man.
  modeled_mechanisms:
  - target: Obstructive and Crystal-Induced Kidney Injury
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: Reproduces the tubulointerstitial injury and the loss of renal function, and it carries
      the human biochemistry, since the mice have plasma uric acid below the limit of detection.
    limitations: The severity and timing do not match the human disease. RENF mice are in renal failure
      by four weeks with small, irregular kidneys, whereas human hereditary xanthinuria is usually
      benign and most affected people never reach renal failure at all. The cited abstract does not
      report xanthine calculi in these mice, so the stone-formation step that produces the human injury
      is not demonstrated in the model, and the mouse Xdh loss also removes renal COX-2 expression,
      which has no established counterpart in the human disease. This link is therefore evidence that
      losing XDH damages the kidney, not that it damages it by the route curated here.
    readouts:
    - name: Renal histology
      target: Obstructive and Crystal-Induced Kidney Injury
      direction: ALTERED
      interpretation: Structural correlate of the tubulointerstitial limb of this node.
      evidence:
      - reference: PMID:23024809
        reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase
          nonsense mutation.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: Histological analysis of RENF kidney sections revealed abnormal arrangement of glomeruli,
          intratubular casts, cellular infiltration in the interstitial space, and interstitial fibrosis.
        explanation: Reports the histological measurement behind this readout.
    - name: Tubular apoptosis by TUNEL
      target: Obstructive and Crystal-Induced Kidney Injury
      direction: INCREASED
      interpretation: Locates the cell death in the tubules rather than the glomeruli.
      evidence:
      - reference: PMID:23024809
        reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase
          nonsense mutation.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: TUNEL analysis of RENF kidney sections showed extensive apoptosis predominantly affecting
          the tubules.
        explanation: Reports the apoptosis measurement and its tubular localisation.
    evidence:
    - reference: PMID:23024809
      reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase
        nonsense mutation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: Thus, we have established a mouse model for autosomal recessive early-onset renal failure
        due to a nonsense mutation in Xdh that is a model for xanthinuria in man.
      explanation: The authors' own claim that this model is informative for human xanthinuria, which
        is what licenses linking it to this node.
    - reference: PMID:23024809
      reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase
        nonsense mutation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: XDH mutations in man cause xanthinuria with undetectable plasma uric acid levels and
        three RENF mice had plasma uric acid levels below the limit of detection.
      explanation: Shows the model carries the defining human biochemistry, undetectable plasma urate,
        which is part of why it is treated as informative here. This sentence previously sat on the
        Hypouricemia phenotype graded HUMAN_CLINICAL; its human clause is background the paper restates
        rather than data it reports, so it belongs on the model, not on a human phenotype.
  evidence:
  - reference: PMID:23024809
    reference_title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase nonsense
      mutation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: DNA sequencing of the xanthine dehydrogenase (Xdh) gene revealed a nonsense mutation
      at codon 26 that co-segregated with affected RENF mice.
    explanation: Establishes the genotype recorded for this model.
clinical_trials:
- name: NCT06092346
  phase: NOT_APPLICABLE
  status: RECRUITING
  description: NIH/NHGRI prospective natural-history study of pyrimidine and purine metabolism disorders.
    The registry's own condition list names XDH / Xanthinuria Type 1 among the enrolling diagnoses,
    so this is an open observational study a patient with type I could enter. It is not xanthinuria-specific
    and not interventional, and that condition list is registry metadata that does not appear in the
    cached summary quoted below.
  evidence:
  - reference: clinicaltrials:NCT06092346
    supports: SUPPORT
    evidence_source: OTHER
    snippet: 'Three types of participants are needed: people aged 1 month and older with DPPMs; their
      family members who do not have DPPMs; and healthy volunteers.'
    explanation: Establishes the enrolling population as people with purine and pyrimidine metabolism
      disorders, the class this disease belongs to. A registration record, not study evidence, hence
      OTHER.
references:
- reference: PMID:20228523
  title: Xanthine urolithiasis.
- reference: PMID:23024809
  title: A mouse model of early-onset renal failure due to a xanthine dehydrogenase nonsense mutation.
- reference: PMID:23203137
  title: Mutations associated with functional disorder of xanthine oxidoreductase and hereditary xanthinuria
    in humans.
- reference: PMID:34356852
  title: 'Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany: Molecular,
    Biochemical and Population Genetics Aspects.'
- reference: clinicaltrials:NCT06092346
  title: Prospective Study of the Clinical, Genomic, Pharmacological, Laboratory, and Dietary Determinates
    of Pyrimidine and Purine Metabolism Disorders
disease_term:
  preferred_term: hereditary xanthinuria
  term:
    id: MONDO:0018106
    label: hereditary xanthinuria
notes: 'Allopurinol is not a treatment for this disease and is not listed as one. It inhibits the
  enzyme that is already missing, and its historical use as a diagnostic loading test to separate
  type I from type II should not be confused with therapy. Urinary alkalinisation is also not listed
  as a treatment: it is standard for uric acid stones, but xanthine solubility is close to pH-independent
  and the benefit here is disputed. The 2010 case report quoted in this entry does recommend alkalinisation,
  and that recommendation is not carried into the treatments section for that reason. Type II patients
  additionally lack aldehyde oxidase, which handles several drugs, so medication review is warranted;
  the strength of evidence differs by drug and no specific avoidance list is curated here.'
review_notes: 'The tubular-injury limb of the final node rests mainly on the Xdh-nonsense RENF mouse
  (PMID:23024809), now curated as an animal_models entry with a modeled_mechanisms link rather than
  only as evidence. All three items from that paper are graded MODEL_ORGANISM. The third was previously
  HUMAN_CLINICAL on the Hypouricemia phenotype; its quoted sentence names a human fact and a mouse
  result in one breath, and splitting it would produce two items quoting the same sentence with different
  evidence_source values, which check-snippet-grading gates, so the item is graded by the study rather
  than split. Human histology is now carried directly (PMID:20228523 nephrectomy specimen) instead
  of being inferred from the mouse alone. Three bindings are deliberate compromises, recorded here
  so they are not silently normalised later. Crystalluria uses the generic HP:0020074 because HPO
  has crystalluria terms for orotic acid, leucine, calcium oxalate and calcium phosphate but none
  for xanthine. Renal colic uses HP:0030157 Flank pain because HPO has no renal colic term. The end-stage
  pyelonephritis histopathology finding carries no finding_term at all, because NCIT:C34965 and HP:0012330
  both exist but neither is reachable from the HistopathologyFindingTerm enum roots. Two frequency
  bands were removed rather than re-justified. Myalgia previously carried VERY_RARE anchored to the
  cohort''s 7-of-20 figure, which counts symptoms of any kind and never mentions muscle; the replacement
  quote calls myopathy a less frequent manifestation without quantifying it, which supports no band.
  Arthropathy is added on the same clause and likewise carries none. Nephrolithiasis gained FREQUENT
  from a stone-specific figure of about 40% that was already in the cached source, and its binding
  moved from HP:0000787 to the more specific HP:0000804 Xanthine nephrolithiasis. Two errors found
  while curating are worth recording. The XDH allele c.2164A>T is written by the cited paper as
  p.(Lys825*), and this entry copies that, because a snippet never corrects the source it quotes.
  It is worth knowing that the annotation looks internally inconsistent: c.2164 falls in codon 722,
  not 825, and the deep-research report calls the same allele p.Lys722Ter. The paper separately
  reports a genuine p.(Arg825*) at c.2473C>T, which is a different allele and is curated separately
  here, so the two should not be merged on the shared residue number. Nothing in this entry asserts
  which protein-level annotation is correct. Separately, the MOCOS gene_term in the new genetic
  section was first written as hgnc:29506, which is SRCIN1; MOCOS is hgnc:18234, as the
  pathophysiology node already had it. just discover-datasets returned no GEO candidates, which is the expected result
  for a disorder this rare, so the entry carries no datasets block. Theobromine metabolites inhibit
  xanthine crystallisation in synthetic urine (PMID:30157195) and were left out of treatments because
  the evidence is in-vitro only and the authors ask for trials. Ureteroscopy, laser lithotripsy and
  percutaneous nephrolithotomy are not curated as treatments because no source cached for this entry
  describes them in xanthinuria; the surgical treatment records the pyelolithotomy that a cached case
  report does describe.'
📚

References & Deep Research

References

5
PMID:20228523
Xanthine urolithiasis.
No top-level findings curated for this source.
PMID:23024809
A mouse model of early-onset renal failure due to a xanthine dehydrogenase nonsense mutation.
No top-level findings curated for this source.
PMID:23203137
Mutations associated with functional disorder of xanthine oxidoreductase and hereditary xanthinuria in humans.
No top-level findings curated for this source.
PMID:34356852
Classical Xanthinuria in Nine Israeli Families and Two Isolated Cases from Germany: Molecular, Biochemical and Population Genetics Aspects.
No top-level findings curated for this source.
clinicaltrials:NCT06092346
Prospective Study of the Clinical, Genomic, Pharmacological, Laboratory, and Dietary Determinates of Pyrimidine and Purine Metabolism Disorders
No top-level findings curated for this source.

Deep Research

1

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (3)

Record review notes

The tubular-injury limb of the final node rests mainly on the Xdh-nonsense RENF mouse (PMID:23024809), now curated as an animal_models entry with a modeled_mechanisms link rather than only as evidence. All three items from that paper are graded MODEL_ORGANISM. The third was previously HUMAN_CLINICAL on the Hypouricemia phenotype; its quoted sentence names a human fact and a mouse result in one breath, and splitting it would produce two items quoting the same sentence with different evidence_source values, which check-snippet-grading gates, so the item is graded by the study rather than split. Human histology is now carried directly (PMID:20228523 nephrectomy specimen) instead of being inferred from the mouse alone. Three bindings are deliberate compromises, recorded here so they are not silently normalised later. Crystalluria uses the generic HP:0020074 because HPO has crystalluria terms for orotic acid, leucine, calcium oxalate and calcium phosphate but none for xanthine. Renal colic uses HP:0030157 Flank pain because HPO has no renal colic term. The end-stage pyelonephritis histopathology finding carries no finding_term at all, because NCIT:C34965 and HP:0012330 both exist but neither is reachable from the HistopathologyFindingTerm enum roots. Two frequency bands were removed rather than re-justified. Myalgia previously carried VERY_RARE anchored to the cohort's 7-of-20 figure, which counts symptoms of any kind and never mentions muscle; the replacement quote calls myopathy a less frequent manifestation without quantifying it, which supports no band. Arthropathy is added on the same clause and likewise carries none. Nephrolithiasis gained FREQUENT from a stone-specific figure of about 40% that was already in the cached source, and its binding moved from HP:0000787 to the more specific HP:0000804 Xanthine nephrolithiasis. Two errors found while curating are worth recording. The XDH allele c.2164A>T is written by the cited paper as p.(Lys825*), and this entry copies that, because a snippet never corrects the source it quotes. It is worth knowing that the annotation looks internally inconsistent: c.2164 falls in codon 722, not 825, and the deep-research report calls the same allele p.Lys722Ter. The paper separately reports a genuine p.(Arg825*) at c.2473C>T, which is a different allele and is curated separately here, so the two should not be merged on the shared residue number. Nothing in this entry asserts which protein-level annotation is correct. Separately, the MOCOS gene_term in the new genetic section was first written as hgnc:29506, which is SRCIN1; MOCOS is hgnc:18234, as the pathophysiology node already had it. just discover-datasets returned no GEO candidates, which is the expected result for a disorder this rare, so the entry carries no datasets block. Theobromine metabolites inhibit xanthine crystallisation in synthetic urine (PMID:30157195) and were left out of treatments because the evidence is in-vitro only and the authors ask for trials. Ureteroscopy, laser lithotripsy and percutaneous nephrolithotomy are not curated as treatments because no source cached for this entry describes them in xanthinuria; the surgical treatment records the pyelolithotomy that a cached case report does describe.

Review round: address ai4c-reviewer findings · 2026-09-06T18:42:39Z · View source

Addressed the CHANGES_REQUESTED review on PR #11191 (ai4c-reviewer, nine important findings and four suggestions). Every quote below was taken from the committed reference cache, not from the deep-research report. Important findings. 1. Nephrolithiasis now carries frequency FREQUENT, from a stone-specific figure already in the cached source: "The major clinical manifestation of xanthinuria is the formation of xanthine calculi in the urinary tract in about 40% of the affected individuals." The description now separates that from the cohort's 7-of-20 symptomatic figure, which counts symptoms of any kind. The binding also moved from HP:0000787 Nephrolithiasis to the more specific HP:0000804 Xanthine nephrolithiasis, which the same sentence supports directly. 2. The Myalgia snippet was the 7-of-20 sentence, which never mentions muscle. Replaced with "Less frequent manifestations are myopathy, arthropathy and duodenal ulcers." The VERY_RARE band was removed with it: its stated anchor was the 7-of-20 figure, and the replacement quote supports no band. 3. Added Crystalluria, Recurrent Urinary Tract Infections, Renal Colic and Arthropathy, all named in the cached line-44 paragraph. 4. Added subtype terms MONDO:0010209 and MONDO:0011346 with their OMIM numbers. The review named the slot disease_term; on Subtype the slot is subtype_term. 5. PMID:23024809 on Hypouricemia was graded HUMAN_CLINICAL. Splitting it was not available, because the human and mouse observations are in one sentence and two items quoting the same sentence with different evidence_source values is what check-snippet-grading gates. The second review argued that re-grading alone is also not enough, since the human clause is background the paper restates rather than data it reports, and PMID:20228523 already carries real human data for the same claim. Taken: the item was removed from the phenotype and the sentence moved onto the animal-model link, where it is evidence that the model carries the defining human biochemistry. 6. The definition sentence reused as a snippet three times was replaced with three distinct specifics from the same abstract: the pyelolithotomy stone composition on the supersaturation edge, "The calculi consisted of pure xanthine." on the crystal-formation node, and "It is an uncommon cause of stone formation in children." on the phenotype. 7. Added a genetic section for XDH (type I) and MOCOS (type II), each with representative pathogenic variants quoted from the cohort paper. 8. Added the RENF mouse as an animal_models entry with a modeled_mechanisms link to Obstructive and Crystal-Induced Kidney Injury, two histology readouts, and limitations recording that the mice are in renal failure by four weeks whereas the human disease is usually benign, and that the cited abstract reports no xanthine calculi in the model. 9. Added NCT06092346 as a clinical_trials entry, phase NOT_APPLICABLE, status RECRUITING, verified against the ClinicalTrials.gov v2 API. Suggestions taken: a diagnosis section (purine profile, molecular confirmation), a surgical stone-removal treatment grounded in the cached pyelolithotomy case rather than in modern techniques no cached source describes for this disease, a prevalence record (RARE / UNKNOWN measure), and the human nephrectomy histopathology. Second review round, taken in the same push: the mouse item moved off Hypouricemia (above); a second XDH nonsense allele, c.2473C>T p.(Arg825*), added from the cache; and the treatments section diversified, since one sentence from PMID:20228523 was the snippet on all four treatment evidence items. The two treatment-level items now quote "Management includes high fluid intake and avoidance of purine and fructose-rich foods" from PMID:34356852, leaving the older sentence on the target_mechanisms links. The allele annotations deserve care and are recorded in review_notes. Three different strings were in play for what looked like one variant: the deep-research report's p.Lys722Ter, the first review's repetition of it, and the second review's c.2473C>T p.(Arg825*). The cache resolves it: c.2164A>T is written by the paper as p.(Lys825*), and c.2473C>T p.(Arg825*) is a separate allele in a different family. Both are curated, separately. The paper's annotation of the first is copied as written even though c.2164 falls in codon 722 rather than 825, because a snippet never corrects its source; the entry asserts no view on which annotation is right. One error of mine: the new MOCOS gene_term was first written as hgnc:29506, which is SRCIN1; corrected to hgnc:18234. Three bindings are deliberate compromises and are recorded in review_notes so they are not normalised away later: Crystalluria on the generic HP:0020074 (HPO has no xanthine crystalluria term), Renal colic on HP:0030157 Flank pain (HPO has no renal colic term), and the histopathology finding with no finding_term at all, because NCIT:C34965 and HP:0012330 both exist but neither is reachable from the HistopathologyFindingTerm enum roots. Validation: just validate passes, snippets 57/57 verified against cached references (was 34/34), validate-terms passes with --labels, and check-entity-refs, check-causal-targets, check-duplicate-keys and check-enum-values are clean.

Create: Hereditary Xanthinuria · 2026-09-05T22:07:52Z · View source

New entry for hereditary xanthinuria (MONDO:0018106), curated from an Edison falcon deep-research report (research/Hereditary_Xanthinuria-deep-research-falcon.md) plus primary literature resolved from the report's DOIs through the PMC ID converter. Snippets were extracted programmatically as exact substrings of the cached references. The pathograph carries two parallel molecular entry points, biallelic XDH loss (type I) and molybdenum cofactor sulfuration failure from MOCOS loss (type II), converging on failure of hypoxanthine and xanthine oxidation, then hypouricemia with xanthine accumulation, urinary xanthine supersaturation, crystal and stone formation, and obstructive and crystal-induced kidney injury. Three nodes declare conforms_to against nephrolithiasis_crystal_nucleation (Urinary Supersaturation, Crystal Nucleation and Growth, Crystal-Induced Tubular Injury and Inflammation). Seven phenotypes, two behavioural treatments, two subtypes. The tubular-injury limb rests mainly on the Xdh-nonsense RENF mouse and both items from it are tagged MODEL_ORGANISM with the inference stated in the node text. Allopurinol and urinary alkalinisation are deliberately excluded from treatments and the reasons are recorded in notes; the case report cited in the entry does recommend alkalinisation, and that disagreement is stated rather than hidden. NCIT:C15325 was suggested for fluid therapy and is actually Skin Transplantation; term validation caught it and NCIT:C116537 is used. Validated with 'just validate': 34/34 snippets verified, terms clean. check-entity-refs, check-duplicate-keys pass; pytest -k conforms_to passes (2897). Compliance 98.8% global, 100.0% weighted; the gap is datasets, and just discover-datasets returned no GEO candidates.

Falcon ▸
Hereditary Xanthinuria: Comprehensive Disease-Characteristics Report
Edison Scientific Literature 35 citations 2026-09-05T17:26:35.987776

Hereditary Xanthinuria: Comprehensive Disease-Characteristics Report

Executive summary

Hereditary (classical) xanthinuria is a rare, lifelong, autosomal-recessive disorder of terminal purine catabolism. Type I results from biallelic XDH loss-of-function variants and isolated xanthine oxidoreductase deficiency; type II results from biallelic MOCOS variants and failure to sulfurate the molybdenum cofactor required by both xanthine oxidoreductase and aldehyde oxidase. Both forms cause profound hypouricemia and hypouricosuria with accumulation and urinary excretion of hypoxanthine and poorly soluble xanthine. Most patients are asymptomatic, but xanthine crystalluria and stones may cause hematuria, renal colic, obstruction, infection, hydronephrosis, acute kidney injury, chronic kidney disease, or—rarely—kidney failure. In the largest well-characterized cohort, 7/20 patients (35%) were symptomatic; broader case literature suggests disease-attributable symptoms or xanthine stones in approximately 40%. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 18-19)

A compact subtype comparison follows.

Domain Type I Type II Evidence/notes
Causal gene XDH MOCOS Biallelic loss-of-function variants cause classical hereditary xanthinuria (peretz2021classicalxanthinuriain pages 2-4, peretz2021classicalxanthinuriain pages 1-2)
OMIM disease ID 278300 603592 Current genetic-nephrolithiasis review confirms both subtype mappings (gefen2024reviewofchildhood pages 15-16)
Inheritance Autosomal recessive Autosomal recessive Consanguinity, homozygosity, and founder effects are frequent in reported families (peretz2021classicalxanthinuriain pages 18-19)
Enzyme defect Isolated xanthine dehydrogenase/xanthine oxidoreductase deficiency Combined xanthine dehydrogenase/xanthine oxidoreductase and aldehyde oxidase deficiency MOCOS normally sulfurates molybdenum cofactor required by both enzymes (peretz2021classicalxanthinuriain pages 2-4, ichida2012mutationsassociatedwith pages 1-3)
Core biomarkers Profound hypouricemia and hypouricosuria; increased urinary xanthine and hypoxanthine Same core biochemical profile Fractional urate excretion is generally normal or low; one type I case had serum urate <5.95 µmol/L and combined urinary xanthine/hypoxanthine of 108.35 µmol/mmol creatinine (abal2021identificationofa pages 1-2)
Principal complications Xanthine crystalluria and radiolucent urolithiasis; obstruction, hematuria, renal colic, urinary infection, hydronephrosis, and rarely kidney failure; occasional myopathy/arthropathy Similar renal and extra-renal phenotype, plus potential toxicity from drugs dependent on aldehyde oxidase metabolism Approximately 35% of a 20-patient cohort were symptomatic; historical series suggest stones or attributable symptoms in roughly 40% (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 18-19, cameron1993gouturicacid pages 6-8)
Diagnostic confirmation Biallelic pathogenic/likely pathogenic XDH variants Biallelic pathogenic/likely pathogenic MOCOS variants; aldehyde-oxidase functional/metabolite testing can distinguish type II Confirm biochemical suspicion with sequencing that covers coding regions, splice boundaries, and copy-number changes; historical allopurinol loading is now secondary to molecular testing (grases2018xanthineurolithiasisinhibitors pages 1-2, peretz2021classicalxanthinuriain pages 2-4)
Management High fluid intake; low-purine diet; reduce purine- and fructose-rich foods; monitor renal function and stone burden; remove obstructing stones when necessary Same measures, with added medication review for aldehyde-oxidase-dependent drugs No disease-specific pharmacotherapy is established. Urine alkalinization has uncertain or little benefit because xanthine solubility is relatively pH-independent; allopurinol is not routine therapy and may increase xanthine burden (grases2018xanthineurolithiasisinhibitors pages 1-2, peretz2021classicalxanthinuriain pages 2-4, cameron1993gouturicacid pages 1-2)

Table: Compact comparison of the genetic, biochemical, clinical, diagnostic, and management features of hereditary xanthinuria types I and II. Evidence notes identify established findings and important treatment cautions.

Evidence caveat. Disease-specific 2023–2024 primary literature is sparse. The current picture therefore rests on a 2024 genetic-nephrolithiasis review, a 2023 NIH natural-history protocol, the largest molecular cohort published in 2021, functional studies, and individual case reports. Population incidence, penetrance, quality-of-life effects, and long-term survival have not been established prospectively.

1. Disease information

Definition and classification

“Hereditary xanthinuria,” “classical xanthinuria,” “xanthine oxidoreductase deficiency,” and “xanthine dehydrogenase/oxidase deficiency” are commonly used names. The adjective classical generally covers types I and II and distinguishes them from generalized molybdenum-cofactor deficiency, sometimes historically called “type III.” The latter is a clinically distinct, usually severe neurodevelopmental disease caused by molybdenum-cofactor biosynthesis defects and should not be merged with XDH- or MOCOS-related classical xanthinuria. (abal2021identificationofa pages 1-2, gefen2024reviewofchildhood pages 15-16)

Identifiers supported by the retrieved sources

  • Parent disease: MONDO:0018106, as specified in the target template.
  • Xanthinuria type I: OMIM/MIM 278300.
  • Xanthinuria type II: OMIM/MIM 603592.
  • XDH gene entry cited in the NIH protocol: OMIM *607633.
  • No disease-specific ICD-10-CM or ICD-11 code was established in the retrieved literature; coding generally falls under broader disorders of purine/pyrimidine metabolism. A specific MeSH identifier was likewise not verified and should not be inferred. (abal2021identificationofa pages 1-2, gefen2024reviewofchildhood pages 15-16, NCT06092346 chunk 1)

The evidence is principally aggregated disease-level literature plus small patient cohorts and case reports, not EHR-derived population data. The major 2021 study combined molecular, biochemical, clinical, and genealogical data from Israeli and German families. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 5-8)

2. Etiology, risk, protection, and environment

Primary cause

The initiating cause is germline, biallelic loss of function in XDH or MOCOS. Type I is an isolated XDH/XOR defect. In type II, MOCOS deficiency leaves molybdenum cofactor in an inactive oxo form, disabling both XDH/XOR and aldehyde oxidase. These are monogenic disorders rather than infectious, toxic, occupational, or lifestyle-acquired diseases. (peretz2021classicalxanthinuriain pages 2-4, ichida2012mutationsassociatedwith pages 1-3)

Genetic risk factors

The principal risk factors are parental carrier status, consanguinity, endogamy, and founder alleles. In one family series, 70% of 17 parental couples were consanguineous and 18% were endogamous; most affected offspring were homozygous. More than two-thirds of published cases have originated from Mediterranean or Middle Eastern populations, probably reflecting ascertainment, consanguinity, and founder effects rather than biological restriction to those populations. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 18-19)

A likely founder XDH variant, c.2164A>T (p.Lys722Ter), was identified in Turkmen- and Arab-origin families. The estimated common ancestor was approximately 179 generations old, supporting broad dispersion across the Afro-Asian stone-forming belt. A Yemenite-Jewish MOCOS c.1046C>T (p.Thr349Ile) founder effect is also supported by affected families and carrier detection. (peretz2021classicalxanthinuriain pages 8-9)

No validated susceptibility loci, modifier genes, protective alleles, anticipation, or clinically important germline mosaicism have been established. The severe mouse–human difference implicates purine salvage and nucleobase transport—notably HPRT activity and species-specific SLC23A4 status—as plausible mechanistic modifiers, but this has not been demonstrated as a human modifier association. (terada2025pseudogenizationofthe pages 2-3, terada2025pseudogenizationofthe pages 1-2)

Environmental and protective factors

Diet does not cause the genetic defect, but purine intake, fructose-rich intake, low urine volume, and dehydration plausibly increase substrate delivery or urinary supersaturation and therefore modify stone risk. High fluid intake and reduction of purine-rich foods are the most consistently recommended protective measures; one cohort also recommends avoiding fructose-rich foods. Quantitative hydration or dietary targets have not been validated in trials. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 2-4, cameron1993gouturicacid pages 1-2)

There is no evidence that smoking, alcohol, pollution, radiation, occupational exposure, or infectious agents initiate classical xanthinuria. Alcohol may be discouraged as part of a low-purine stone-prevention diet, but this is management advice rather than evidence of causation. No vaccine or antimicrobial prevention applies.

3. Phenotypes

Phenotype Type and characteristics Frequency/course Suggested HPO term
Profound hypouricemia Laboratory abnormality; congenital biochemical trait, usually persistent Essentially defining; may be incidentally detected at any age Hypouricemia (HP:0003537)
Hypouricosuria Laboratory abnormality; very low/undetectable urinary urate, with normal or low fractional urate excretion Defining Decreased urinary urate excretion
Xanthinuria/hypoxanthinuria Laboratory abnormality; increased urinary xanthine and hypoxanthine Defining Xanthinuria; abnormal urinary purines
Xanthine crystalluria/urolithiasis Sign/manifestation; episodic, recurrent, variable severity; radiolucent stones About 40% in historical literature; variable between cohorts Nephrolithiasis (HP:0000787), Crystalluria
Hematuria and renal colic Symptom/sign secondary to stones Intermittent; subset of stone formers Hematuria (HP:0000790), Renal colic
Obstruction/hydronephrosis Structural complication Uncommon; may be acute Hydronephrosis (HP:0000126), Urinary-tract obstruction
Urinary infection Secondary complication Recurrent in some symptomatic patients Recurrent urinary-tract infections
AKI/CKD/kidney failure Organ complication from obstruction/crystal injury; severity highly variable Rare but documented, including ESKD Acute kidney injury, Renal insufficiency (HP:0000083)
Myalgia/myopathy Symptom attributed to xanthine deposition Minority/rare Myalgia (HP:0003326), Myopathy
Arthropathy Musculoskeletal manifestation Rare Arthropathy (HP:0003040)

The 2021 cohort found 7/20 affected persons symptomatic (35%). Among 11 adults, only 3 (27%) retrospectively reported urolithiasis symptoms, whereas 47% of children and young adults were symptomatic, suggesting ascertainment or age-related differences rather than a proven age-dependent penetrance model. Onset can be neonatal, pediatric, or adult, and many adults remain asymptomatic. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 18-19, peretz2021classicalxanthinuriain pages 19-20)

A quantitative type-I case had serum urate <5.95 µmol/L, urinary urate 12.15 µmol/mmol creatinine, and combined urinary xanthine/hypoxanthine 108.35 µmol/mmol creatinine; ultrasound showed 7- and 9-mm suspected renal calculi. (abal2021identificationofa pages 1-2)

There are no validated disease-specific EQ-5D, SF-36, PROMIS, behavioral, or psychiatric data. Quality-of-life impairment is expected mainly during renal colic, infection, repeated procedures, or kidney failure, but has not been quantified.

4. Genetic and molecular information

Causal genes and proteins

  • XDH, chromosome 2p23.1, transcript NM_000379.4, protein NP_000370.2, encodes a 1,333-amino-acid xanthine dehydrogenase/oxidoreductase. Each approximately 150-kDa subunit contains two [2Fe–2S] centers, an FAD-binding region, and a C-terminal molybdenum-cofactor-binding catalytic domain. (peretz2021classicalxanthinuriain pages 2-4, ichida2012mutationsassociatedwith pages 1-3)
  • MOCOS, chromosome 18q12.2, transcript NM_017947.1, protein NP_060417.4, encodes an 888-amino-acid molybdenum-cofactor sulfurase. Its N-terminal NifS-like, pyridoxal-phosphate-dependent cysteine-desulfurase domain supplies sulfur; its C-terminal domain binds Moco and generates active sulfido-Moco. (peretz2021classicalxanthinuriain pages 2-4)

Representative pathogenic variants

Reported XDH disease alleles include frameshift, nonsense, and missense variants: c.141insG p.Cys48LeufsTer12; c.449G>T p.Cys150Phe; c.641del p.Pro214GlnfsTer4; c.913del p.Leu305fsTer1; c.1434G>A p.Trp478Ter; c.1658insC p.Ala556SerfsTer67; c.1871C>G p.Ser624Ter; c.2164A>T p.Lys722Ter; and c.2473C>T p.Arg825Ter. Reported MOCOS alleles include c.1037insA p.Gln347AlafsTer33; c.1046C>T p.Thr349Ile; c.1088_1089del p.Leu363ProfsTer16 (ClinVar 1017655; rs761752580); c.1771C>T p.Pro591Ser; and c.2326C>T p.Arg776Cys. These are germline variants; somatic origin is not part of disease pathogenesis. Population allele frequencies were not available in the retrieved evidence and should be obtained directly from current gnomAD/ClinVar records before database ingestion. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 8-9)

Functional evidence is unusually strong for several missense alleles. XDH Cys150 lies in the Fe/S-I cluster-binding motif; the corresponding plant-protein substitution prevented detectable stable protein accumulation. MOCOS p.Thr349Ile markedly impaired protein stability, PLP binding, and cysteine-desulfurase activity; p.Pro591Ser and p.Arg776Cys reduced Moco/MPT binding to about 24% and 6% of wild type, respectively. These experiments used plant/yeast or bacterial heterologous systems rather than human renal cells. (peretz2021classicalxanthinuriain pages 14-16)

No recurrent chromosomal abnormality, disease-specific methylation signature, histone alteration, or validated epigenetic mechanism is known. Likewise, there are no established disease-specific single-cell, spatial-transcriptomic, proteomic, lipidomic, CRISPR-screen, or multi-omic patient datasets.

5–6. Mechanism and pathophysiology

Ordered causal chain

  1. Biallelic XDH loss of function leads to absent or markedly reduced XDH/XOR activity (type I).
  2. Alternatively, biallelic MOCOS loss of function leads to deficient sulfur insertion into Moco, which results in combined loss of XDH/XOR and aldehyde-oxidase activity (type II).
  3. Loss of XDH/XOR catalysis leads to failure of hypoxanthine → xanthine and xanthine → uric-acid oxidation.
  4. This block results in profound hypouricemia/hypouricosuria and accumulation of xanthine and hypoxanthine; much hypoxanthine is salvaged to IMP, whereas xanthine is excreted.
  5. High urinary xanthine plus its poor solubility leads to crystalluria and xanthine-stone nucleation.
  6. Crystal deposition or stones lead to tubular obstruction, epithelial injury, hematuria, renal colic, hydronephrosis, and infection.
  7. Persistent or severe obstruction/crystal injury leads to AKI, interstitial inflammation/fibrosis, CKD, and occasionally kidney failure; tubular apoptosis and fibrosis are demonstrated in mice but partly inferred in humans.
  8. Type-II aldehyde-oxidase deficiency additionally leads to impaired metabolism of selected xenobiotics, which can result in drug toxicity.

This is a metabolic enzyme-deficiency pathway, not a canonical Wnt/MAPK/mTOR signaling disorder. Mammalian XOR normally transfers electrons from the molybdenum catalytic center through Fe–S clusters to FAD and NAD+ or oxygen. It can also generate reactive oxygen species and participate in nitric-oxide biology; however, the contribution of reduced XOR-derived ROS or reduced urate antioxidant capacity to human xanthinuria phenotypes remains uncertain. (ichida2012mutationsassociatedwith pages 1-3)

Suggested ontology annotations: purine nucleobase catabolic process; xanthine catabolic process; hypoxanthine metabolic process; urate biosynthetic process; molybdenum-cofactor sulfuration; oxidoreductase activity; iron–sulfur cluster binding; FAD binding; molybdenum-ion binding. Relevant cells include renal tubular epithelial cells—especially proximal tubular epithelium—and hepatocytes, because liver is a major site of XDH and aldehyde-oxidase activity. Suggested CL labels are kidney proximal tubule epithelial cell and hepatocyte; suggested GO cellular components include cytosol, molybdenum-cofactor-containing enzyme complex, and iron–sulfur cluster-containing protein complex.

7. Anatomical structures affected

The primary clinically affected system is the urinary system: kidney, renal calyces/pelvis, ureters, and bladder can contain crystals or stones. Suggested UBERON labels are kidney, renal tubule, renal pelvis, ureter, and urinary bladder. Injury localizes principally to renal tubular lumina and epithelium, with downstream interstitium and whole-kidney involvement in severe disease. Stones may be unilateral or bilateral; no characteristic lateralization exists. (patil2025xanthinestonesin pages 2-4, piret2012amousemodel pages 4-8)

The liver is the major metabolic site of XDH/XOR and aldehyde oxidase but generally does not show a primary clinical lesion. Skeletal muscle and joints are rare secondary sites associated with myopathy or arthropathy. No consistent cardiovascular, respiratory, immune, endocrine, or nervous-system involvement characterizes classical types I/II. Neurologic disease should instead raise concern for generalized molybdenum-cofactor deficiency. (abal2021identificationofa pages 1-2, cameron1993gouturicacid pages 6-8)

8–9. Temporal development, inheritance, and population

The biochemical defect is congenital and lifelong. Clinical onset is highly variable—from neonatal stone disease to incidental adult hypouricemia—and the course may remain stable and asymptomatic or become episodic with recurrent stones. There is no accepted stage system, remission definition, anticipation, or predictable progression rate. Prevention before the first stone and rapid relief of obstruction are the main actionable windows. (peretz2021classicalxanthinuriain pages 18-19, peretz2021classicalxanthinuriain pages 19-20)

Inheritance is autosomal recessive. Penetrance of the biochemical phenotype appears high in biallelic loss of function, but penetrance of symptoms is incomplete and expressivity variable. For unrelated carrier parents, counseling uses the standard per-pregnancy probabilities: 25% affected, 50% carrier, and 25% unaffected/non-carrier. Carrier frequency and population incidence are unknown; published estimates vary too widely and are not supported by population screening. No reliable cases-per-100,000 prevalence or annual incidence can presently be supplied. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 18-19)

Both sexes are affected; no credible sex ratio has been established. Disease is worldwide, with apparent enrichment in Mediterranean, Middle Eastern, Arab, Jewish, and Turkmen families. That pattern is influenced by consanguinity, founder alleles, and publication bias. (peretz2021classicalxanthinuriain pages 1-2, peretz2021classicalxanthinuriain pages 8-9)

10. Diagnostics

Recommended workflow

  1. Recognize persistent profound hypouricemia. Repeat serum urate and exclude laboratory interference or urate-lowering medication.
  2. Determine underproduction versus renal wasting. Hereditary xanthinuria shows very low urinary urate and normal/low fractional urate excretion; renal hypouricemia usually has increased fractional excretion (>10% in a recent review/case definition).
  3. Measure urine and preferably plasma xanthine/hypoxanthine by HPLC or LC–MS/MS. Marked xanthinuria with hypouricosuria is the central biochemical signature.
  4. Analyze any stone by infrared spectroscopy or X-ray diffraction. Xanthine stones are typically radiolucent on plain radiography but detectable by ultrasound or CT.
  5. Confirm genetically with sequencing and deletion/duplication analysis of XDH and MOCOS. A monogenic nephrolithiasis/purine-metabolism panel is reasonable; WES/WGS is useful when targeted testing is negative or phenotype is atypical. CMA, karyotyping, FISH, mtDNA, and repeat-expansion testing are not first-line tests.
  6. Distinguish type I from type II. Genotype is preferred. Aldehyde-oxidase-dependent metabolite profiling can support type II. Historical liver biopsy and allopurinol-loading tests are now secondary and carry practical or safety disadvantages. (grases2018xanthineurolithiasisinhibitors pages 1-2, abal2021identificationofa pages 1-2, peretz2021classicalxanthinuriain pages 2-4)

A modern stone example illustrates imaging limitations: plain radiography was negative, whereas CT showed a 10-mm renal-pelvic stone and distal ureteral stones at approximately 352–427 HU; FT-IR/crystallography found 71% xanthine. This 2025 case is supportive but not a validated universal HU threshold. (patil2025xanthinestonesin pages 2-4)

Differential diagnosis

  • Renal hypouricemia due to SLC22A12/URAT1 or SLC2A9/GLUT9: low serum urate but high fractional urate excretion; exercise-induced AKI is characteristic.
  • Generalized molybdenum-cofactor deficiency due to MOCS1, MOCS2, GPHN or related genes: sulfite-oxidase deficiency, neonatal/infantile encephalopathy, seizures, abnormal tone and developmental impairment, plus xanthinuria.
  • Purine nucleoside phosphorylase deficiency, APRT deficiency/2,8-dihydroxyadenine stones, and other monogenic stone disorders.
  • Acquired hypouricemia from urate-lowering drugs, severe liver disease, malnutrition, SIADH, or proximal tubular dysfunction.
  • Iatrogenic xanthine stones during strong XOR inhibition, especially in high-purine-turnover states.

The 2024 pediatric review confirms XDH and MOCOS as xanthinuria genes and distinguishes MOCS1/MOCS2 molybdenum-cofactor deficiency, in which neurologic/systemic disease is expected. (gefen2024reviewofchildhood pages 15-16)

Population newborn screening is not established. Cascade biochemical and genetic testing of siblings and reproductive partners is appropriate after a molecular diagnosis.

11. Outcome and prognosis

Most diagnosed individuals have normal general development and can remain asymptomatic for decades. No disease-specific survival curve, 5- or 10-year survival statistic, life-expectancy estimate, mortality rate, validated prognostic model, or quality-of-life instrument exists. Prognosis is mainly determined by stone burden, obstruction, recurrent infection, and renal function. Rare severe outcomes include nephrectomy, CKD, ESKD, uremia, and death. (peretz2021classicalxanthinuriain pages 1-2, cameron1993gouturicacid pages 6-8)

A recent 2024 nephrolithiasis review recognizes that both types can progress to ESKD. Conversely, the 2021 family cohort reported no stone recurrence under conservative advice during available follow-up, although cohort size and follow-up preclude efficacy estimates. (peretz2021classicalxanthinuriain pages 19-20, gefen2024reviewofchildhood pages 15-16)

12. Treatment and current implementation

Conservative management

There is no approved enzyme replacement, substrate-reduction drug, gene therapy, RNA therapy, or disease-specific pharmacotherapy. Standard real-world care consists of:

  • high fluid intake to maintain dilute urine;
  • a low-purine diet and avoidance of excessive purine-rich food;
  • reduction of fructose-rich foods where advised;
  • periodic serum creatinine/eGFR, urinalysis, urinary metabolites, and renal imaging;
  • prompt treatment of urinary infection and urgent decompression/removal of obstructing stones. (peretz2021classicalxanthinuriain pages 2-4, abal2021identificationofa pages 1-2)

Suggested NCIt intervention labels include Dietary Modification, Fluid Therapy/Oral Hydration, Metabolic Monitoring, Ureteroscopy, Laser Lithotripsy, Percutaneous Nephrolithotomy, Ureteral Stent Placement, and Kidney Transplantation where clinically necessary.

Important therapeutic cautions

Allopurinol is not routine treatment for hereditary xanthinuria. It inhibits the already defective target and can increase xanthine burden in other clinical contexts. Its historical use as a diagnostic loading test should not be confused with chronic therapy. Type-II patients also lack aldehyde oxidase and may have altered handling/toxicity of AOX substrates; literature specifically flags allopurinol, azathioprine, cyclophosphamide, methotrexate, quinine, pyrazinamide, and related compounds, although the strength of clinical evidence differs by drug. Medication review with metabolic/pharmacology expertise is warranted. (cameron1993gouturicacid pages 6-8, cameron1993gouturicacid pages 1-2, salhen2013drosophilamelanogasteras pages 57-58)

Urinary alkalinization is not established: xanthine solubility is relatively pH-independent, and one experimental review states that alkalinization has no benefit, while some clinical reports call it controversial or possibly useful. It should not be represented as proven disease-modifying therapy. (grases2018xanthineurolithiasisinhibitors pages 1-2, policastro2018personalizedinterventionin pages 3-5)

Theobromine metabolites 3- and 7-methylxanthine inhibited xanthine crystallization in synthetic urine, but this is in-vitro evidence only; the authors explicitly called for clinical trials. It is not recommended therapy. (grases2018xanthineurolithiasisinhibitors pages 1-2)

Research study

NCT06092346, initiated 19 December 2023, is a recruiting NIH/NHGRI prospective observational natural-history study of purine and pyrimidine metabolism disorders, explicitly including XDH-associated xanthinuria type I. Planned enrollment is 999 participants aged ≥1 month, including affected people, family members, and healthy volunteers. It collects genomic, clinical, laboratory, pharmacological, imaging, microbiome, nutritional, quality-of-life, functional, hospitalization, and survival data at the NIH Clinical Center in Bethesda. It tests no treatment but is the most relevant current real-world research implementation. URL: https://clinicaltrials.gov/study/NCT06092346. (NCT06092346 chunk 1, NCT06092346 chunk 2)

13. Prevention

  • Primary prevention: the disease itself cannot be prevented after conception except through reproductive options following familial variant identification—carrier testing, prenatal diagnosis, or preimplantation genetic testing. Genetic counseling is indicated.
  • Secondary prevention: cascade testing and evaluation of unexplained persistent hypouricemia can identify presymptomatic relatives before stones occur.
  • Tertiary prevention: hydration, purine restriction, avoidance of dehydration, medication review—especially in type II—and surveillance for stones and renal dysfunction aim to prevent obstruction and kidney damage.
  • Vaccination, infectious prophylaxis, and population-wide screening have no disease-specific role. (abal2021identificationofa pages 1-2, peretz2021classicalxanthinuriain pages 2-4)

14. Natural disease in other species

Natural or inherited xanthinuria has comparative relevance in animals. A bovine MOCOS/MCS deletion, c.769_771delTAC (p.Tyr257del), causes type-II-like xanthinuria, urinary xanthine accumulation, growth arrest, and death at approximately six months. Drosophila rosy mutants disrupt the XDH ortholog and are useful for enzyme-domain and stress studies, but their prominent eye-pigment phenotype poorly models human renal stone disease. (salhen2013drosophilamelanogasteras pages 57-58)

Recent feline and canine reports exist in the search record, including familial Munchkin-cat xanthinuria and multiple canine XDH/MOCOS variants, but full text suitable for evidence extraction was unavailable; breed, VBO, exact variant, and frequency annotations should therefore be curated directly from those veterinary primary papers rather than inferred here. There is no zoonotic potential or cross-species transmission: these are inherited metabolic defects.

15. Model organisms and experimental systems

The ENU-derived RENF mouse carries homozygous Xdh p.Glu26Ter. By four weeks, mice have growth impairment, elevated urea/creatinine, small irregular kidneys, intratubular casts, interstitial inflammation and fibrosis, and extensive tubular apoptosis. The model reproduces biochemical xanthinuria and renal injury but is substantially more severe than typical human disease. (piret2012amousemodel pages 1-2, piret2012amousemodel pages 4-8)

A major translational advance published in 2025 showed why. Mice retain intestinal Slc23a4, whereas the human gene is pseudogenized. Combining high Hprt activity, Xdh knockout, and Slc23a4 knockout extended median survival to 191.8 days, versus 64.05 and 83.3 days on heterozygous and wild-type Slc23a4 backgrounds. Nevertheless, rescued mice had renal impairment, anemia, reproductive abnormalities, and urinary xanthine excretion approximately 20-fold greater than human type-I patients. A low-purine diet reduced urinary xanthine from 3.761 ± 0.299 to 1.520 ± 0.260 mol/mol creatinine. This is a useful adult model but not a faithful quantitative replica of human disease. (terada2025pseudogenizationofthe pages 2-3, terada2025pseudogenizationofthe pages 1-2)

Additional systems include Arabidopsis XDH expressed in Pichia pastoris and recombinant human MOCOS domains expressed in E. coli. They are valuable for variant-function classification but cannot model human stone formation, renal physiology, penetrance, or quality of life. (peretz2021classicalxanthinuriain pages 14-16)

Current expert assessment and research priorities

The strongest current interpretation is that hereditary xanthinuria is underdiagnosed because profound hypouricemia is often ignored and many affected people are asymptomatic. Persistent low serum urate combined with low urinary urate should prompt direct xanthine/hypoxanthine measurement and XDH/MOCOS testing. The major unmet needs are prospective natural-history data, population prevalence, standardized biochemical thresholds, systematic ClinVar/gnomAD variant curation, genotype–phenotype analysis, validated hydration/diet targets, type-II pharmacokinetic studies, and human-relevant renal organoid or cellular models. The NIH natural-history protocol is positioned to address several of these gaps. (abal2021identificationofa pages 1-2, NCT06092346 chunk 1, NCT06092346 chunk 2)

Representative abstract language

  • Peretz et al. (published 7 July 2021) reported: “Seven out of 20 affected individuals (35%) presented with xanthinuria-related symptoms of varied severity.” DOI/URL: https://doi.org/10.3390/biomedicines9070788. (peretz2021classicalxanthinuriain pages 1-2)
  • Abal et al. (published online 21 July 2021) concluded that hereditary xanthinuria is “an underdiagnosed pathology, often found in a routine analysis that shows hypouricemia.” DOI/URL: https://doi.org/10.1515/almed-2021-0018. (abal2021identificationofa pages 1-2)
  • The 2024 childhood-nephrolithiasis review identifies XDH and MOCOS as the genetic causes of autosomal-recessive xanthinuria types I and II and recognizes xanthine nephrolithiasis and possible ESKD. Published March 2024; DOI/URL: https://doi.org/10.3389/fgene.2024.1381174. (gefen2024reviewofchildhood pages 15-16)

PMIDs were not present in the retrieved full-text metadata for the principal sources and are therefore not fabricated here; DOI URLs provide persistent source resolution.

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