Renal Coloboma Syndrome

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Classifications

Harrison's Part

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Inheritance

1

Autosomal dominant HP:0000006

Autosomal dominant. Expressivity is highly variable, including between monozygotic twins and between family members carrying the same allele: a parent may carry the variant and have only albuminuria or FSGS while the child has bilateral cystic hypodysplasia. About 65% of probands have a negative family history, explained by de novo variants, unrecognised mild disease in a parent, or parental germline mosaicism - both maternal and paternal germline mosaicism have been documented.

Autosomal dominant inheritance Expressivity: VARIABLE

Show evidence (6 references)

PMID:20301624 SUPPORT Human Clinical

"Approximately 65% of probands with a documented PAX2 pathogenic variant have a negative family history."

Quantifies the proportion of apparently sporadic presentations.

PMID:20301624 SUPPORT Human Clinical

"Both maternal and paternal germline mosaicism, with unaffected parents having more than one affected child with a pathogenic variant, have been reported."

Documents germline mosaicism, which changes the recurrence risk quoted to apparently unaffected parents.

PMID:41278353 SUPPORT Human Clinical

"Full penetrance for a kidney phenotype, but variable expressivity was observed in our 10 carriers of a PAX2 LOF variant, including parents who were not necessarily affected by CAKUT but by albuminuria or FSGS."

Supports full penetrance for some kidney phenotype alongside markedly variable expressivity within families.

+ 3 more references

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Mechanistic Hypotheses

1

PAX2 nephropathy as a second, postnatal podocyte disease

podocyte_fitness_pathway EMERGING

Evidence balance 1 support

The conventional model treats PAX2 kidney disease as purely developmental: fewer nephrons, then hyperfiltration, then chronic kidney disease. An emerging model adds a second arm in which PAX2 variants reduce the resilience of mature podocytes and parietal epithelial cells, producing albuminuria out of proportion to the structural lesion and, in some families, FSGS with no malformation at all. The clinical observation that motivates it is the excess albuminuria in PAX2 carriers relative to stage-matched CAKUT controls; the experimental support is patient-derived iPSC podocytes whose vulnerability to injury is corrected by repairing the variant. It matters therapeutically because the developmental arm is fixed at birth while podocyte injury might be modifiable.

Show evidence (1 reference)

PMID:41278347 SUPPORT Other

"PAX2 nephropathy may be an exception, because podocyte injury might be partially modifiable, raising the prospect of prolonging nephron survival in patients with milder dysplasia."

States the therapeutic consequence that makes the two-pathway model worth distinguishing; phrased by the authors as a prospect, not a result.

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Pathophysiology

8

PAX2 Haploinsufficiency

A heterozygous loss-of-function variant in PAX2 - most often a frameshift, nonsense or canonical splice-site change, with the recurrent c.76dupG (p.Val26Glyfs*28) in exon 2 the commonest single allele - halves the dose of a paired-box transcription factor that is required in the nephric duct, ureteric bud, metanephric mesenchyme, optic stalk and otic vesicle. The resulting phenotypes are dosage effects in tissues where PAX2 is transcriptionally rate-limiting, which is why one gene produces an apparently unrelated kidney-plus-eye combination. Mechanistically PAX2 does not act alone: it recruits a PTIP-MLL H3K4 methyltransferase complex to its target loci, so halving PAX2 halves the delivery of an activating chromatin mark to the developmental programmes it licenses.

Genetic context PAX2 hgnc:8616 variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Most pathogenic alleles are predicted loss of function. A dominant-negative contribution has been proposed for the recurrent c.76dupG allele, whose transcript escapes nonsense-mediated decay, and for some FSGS-associated missense alleles that enhance PAX2 repressor activity.

PAX2 paired-domain DNA-binding transcription factor activity GO:0003700 ↓ DECREASED

Downstream

Increased Ureteric Bud Apoptosis and Reduced Branching Reduced PAX2 dosage removes a survival signal in the developing ureteric bud epithelium.

Failure of Optic Fissure Closure PAX2 is expressed at the apposing edges of the optic fissure, and its loss prevents fissure closure.

Otic Vesicle Patterning Failure PAX2 is expressed in the otic primordium, and its loss prevents formation of the auditory parts of the inner ear.

Reduced Podocyte Fitness A second, postnatal arm in which PAX2 variants compromise the resilience of podocytes and parietal epithelial cells in nephrons that formed normally.

Show evidence (5 references)

PMID:7795640 SUPPORT Human Clinical

"We have conducted a mutational analysis of PAX2 in a family with optic nerve colobomas, renal hypoplasia, mild proteinuria and vesicoureteral reflux. We report a single nucleotide deletion in exon five, causing a frame-shift of the PAX2 coding region in the octapeptide domain."

The founding report linking a truncating PAX2 allele to the combined ocular and renal phenotype in a segregating family.

PMID:10466411 SUPPORT Human Clinical

"Optic nerve coloboma combined with renal disease, also called renal-coloboma syndrome ( # 120330 in McKusick's Mendelian Inheritance in Man Online, OMIM), a relatively recently characterized syndrome, results from autosomal dominant mutations in the PAX2 gene."

States the causal relationship and the dominant mode, anchoring PAX2 variation as the initiating lesion of the entry.

PMID:41278353 SUPPORT Human Clinical

"Severe kidney anomalies, that is, cystic KHD or agenesis, were significantly more frequent in patients carrying the NM_000278.5(PAX2):c.76dupG variant in exon 2 with a possible dominant-negative effect than in patients with nonsense or frameshift variants in exon 3 to 7."

Supports the note that the recurrent c.76dupG allele may act beyond simple haploinsufficiency; the dominant-negative mechanism is proposed, not shown.

+ 2 more references

Increased Ureteric Bud Apoptosis and Reduced Branching

One of the normal functions of PAX2 in kidney development is suppression of apoptosis in the ureteric bud epithelium. At half dosage, apoptotic cell death rises during fetal kidney development and the ureteric bud undergoes fewer branching generations, so fewer nephron-inducing tips are ever generated.

ureteric bud cell CL:4030066

branching involved in ureteric bud morphogenesis GO:0001658 ↓ DECREASED apoptotic process in the developing ureteric bud GO:0006915 ↑ INCREASED

ureteric bud UBERON:0000084

Animal models

Pax2 null mouse (homozygous) Mouse partially recapitulates In the homozygous null the ureteric bud is absent altogether, so kidney development never begins - the extreme of the branching defect rather than the graded reduction seen in patients.

Pax2 1Neu heterozygous mouse Mouse recapitulates Heterozygous fetal kidneys show the increased apoptosis and reduced branching that the node asserts, at the correct gene dosage.

Downstream

Reduced Nephron Endowment and Renal Hypodysplasia Fewer ureteric-bud tips induce fewer nephrons, and the kidney that results is small and maldeveloped.

Show evidence (2 references)

PMID:22213154 SUPPORT Human Clinical

"There is evidence that one important role of PAX2 during renal development may be suppression of apoptosis in the developing ureteric bud."

Names apoptosis suppression in the ureteric bud as the relevant normal PAX2 function, which is the function lost at this node.

PMID:10587573 SUPPORT Model Organism

"Heterozygous 1Neu mice showed increased apoptotic cell death during fetal kidney development"

Measures the apoptotic increase in a heterozygous model carrying the mouse equivalent of the commonest human allele.

Reduced Nephron Endowment and Renal Hypodysplasia

The kidney is built with fewer nephrons than normal and with disordered architecture - small kidneys with poor corticomedullary differentiation, cortical cysts and, at the severe end, multicystic dysplasia or agenesis. The same disturbance of nephric-duct and ureteric-bud development produces the ureterovesical junction defects underlying vesicoureteral reflux.

nephron development GO:0072006 ↓ DECREASED

kidney UBERON:0002113

Downstream

Glomerular Hyperfiltration and Progressive Nephron Loss A reduced nephron endowment forces the surviving nephrons to hyperfilter.

Renal hypoplasia

Cystic renal dysplasia

Multicystic kidney dysplasia Reported at the severe end of the structural spectrum; the route from PAX2 loss to a multicystic dysplastic kidney is not established, and early ureteric obstruction has been proposed as an intermediate.

Vesicoureteral reflux Reflux accompanies the renal malformation in PAX2 families; the specific ureterovesical-junction lesion has not been resolved.

Show evidence (3 references)

PMID:10587573 SUPPORT Human Clinical

"In a total of 29 patients, renal hypoplasia was the most common congenital renal abnormality."

Establishes renal hypoplasia as the dominant human structural lesion; the quoted sentence reports the patient series, not the mouse work in the same paper.

PMID:41278353 SUPPORT Human Clinical

"In 104 pediatric carriers of a PAX2 LOF variant with CAKUT, hallmark kidney manifestations were (cystic) KHD (97% vs. 59% in patients with CAKUT and wildtype PAX2, P < 0.0001)"

Shows kidney hypoplasia/dysplasia is the hallmark structural lesion of PAX2 loss of function, against a CAKUT comparison group.

PMID:21654726 SUPPORT Human Clinical

"Histologically, kidneys exhibit fewer than the normal number of glomeruli and these glomeruli are enlarged, a finding called oligomeganephronia."

The histological statement of this node: a reduced nephron count with compensatory glomerular enlargement.

Glomerular Hyperfiltration and Progressive Nephron Loss

With too few nephrons for body size, single-nephron filtration rises, the remaining glomeruli hypertrophy, and the resulting haemodynamic stress drives proteinuria, hypertension and a steady loss of the nephrons that are left. This is the route by which a congenital, non-progressive malformation becomes progressive chronic kidney disease.

glomerular filtration GO:0003094 ↑ INCREASED

renal glomerulus UBERON:0000074

Downstream

Chronic kidney disease

Proteinuria

Hypertension

Show evidence (2 references)

PMID:39994403 SUPPORT Human Clinical

"During kidney development, PAX2 suppresses apoptosis in the developing ureteric bud; therefore, PAX2 pathogenic variants increase apoptosis during the development of the kidneys and urinary tract, which may underlie the decreased nephron number, hypertrophy of the remaining nephrons, and RHD"

Connects the reduced nephron number to compensatory hypertrophy of the remaining nephrons, the haemodynamic state this node describes.

PMID:21654726 SUPPORT Human Clinical

"Consequences of the renal hypodysplasia include hypertension, proteinuria and renal insufficiency that frequently progresses to end-stage kidney disease."

Names the three downstream outcomes this node feeds and attributes them to the hypodysplasia rather than to a separate lesion.

Reduced Podocyte Fitness

A second mechanistic arm, distinct from the developmental one. PAX2 is normally silenced in the mature podocyte, and variant carriers whose nephrons formed normally still show podocytes that are unusually vulnerable to injury, together with disturbed nuclear maintenance in parietal epithelial cells and reduced regenerative capacity under stress. This arm explains the albuminuria that is disproportionate to the CKD stage, and the families in whom adult-onset FSGS is the whole phenotype.

podocyte CL:0000653 parietal epithelial cell CL:1000452

renal glomerulus UBERON:0000074

Experimental models

Patient-derived iPSC podocytes carrying PAX2 p.G189R IPSC DERIVED MODEL Podocyte motility was altered in patient-derived cells and restored by correcting the variant, isolating PAX2 as the cause of the podocyte phenotype.

Downstream

Focal segmental glomerulosclerosis

Albuminuria

Show evidence (2 references)

PMID:41278347 SUPPORT Other

"Cunanan et al.5 recently showed in a murine model that Pax2 variants impair nuclear maintenance in parietal epithelial cells and disrupt podocyte homeostasis, thus reducing regenerative capacity under stress."

Describes the parietal-epithelial and podocyte defect this node asserts; the quote is a commentary's report of a murine result, not the primary paper.

PMID:24676634 SUPPORT Human Clinical

"Thus, mutations in PAX2 may contribute to adult-onset FSGS in the absence of overt extrarenal manifestations."

Establishes that a PAX2 allele can produce podocyte disease with no developmental malformation, which is what makes this a separate arm.

Failure of Optic Fissure Closure

In the developing eye PAX2 expression is concentrated at the apposing edges of the optic fissure and falls as the fissure closes. Where PAX2 dosage is insufficient, the fissure margins fail to appose and fuse and the basement membrane between them is not dissolved, leaving a ventral gap at the optic stalk.

closure of optic fissure GO:0061386 ↓ DECREASED

optic fissure UBERON:0005412

Animal models

Pax2 null mouse (homozygous) Mouse recapitulates The null mouse fails to close the optic fissure and develops coloboma, which is the same developmental step that fails in patients.

Downstream

Optic Nerve Head Dysplasia

Retinal coloboma A gap left in the retina and choroid where the fissure margins did not fuse, the same lesion expressed at a different point along the fissure.

Show evidence (3 references)

PMID:8951055 SUPPORT Model Organism

"Our results identify Pax2 as a major regulator of patterning during organogenesis of the eye and inner ear and indicate its function in morphogenetic events required for closure of the optic fissure and neural tube."

Assigns Pax2 the morphogenetic role in optic-fissure closure that this node loses.

PMID:22213154 SUPPORT Human Clinical

"In the optic cup and stalk, PAX2 expression is most evident at the closing edges of the optic fissure."

Places PAX2 expression precisely at the fissure margins, which is why a dosage defect acts on this step.

PMID:22213154 SUPPORT Model Organism

"The ocular phenotype is characterized by a failure of closure of the optic fissure and failed basement membrane dissolution."

Adds failed basement-membrane dissolution to the fissure-closure defect; the sentence describes the homozygous mutant mouse phenotype.

Optic Nerve Head Dysplasia

The clinical lesion at the optic nerve head - a wide, excavated disc with peripapillary atrophy and anomalous vessels emerging from the disc periphery rather than a central retinal artery. Whether to call this a coloboma or a dysplasia has been disputed since the 1990s, which is the source of the competing "renal coloboma" and "papillorenal" disease names.

optic disc UBERON:0001783

Downstream

Optic disc coloboma

Reduced visual acuity

Retinal detachment

Show evidence (3 references)

PMID:20301624 SUPPORT Human Clinical

"Ophthalmologic abnormalities are typically described as optic nerve coloboma or dysplasia."

Names the lesion and preserves the coloboma-versus-dysplasia ambiguity that this node records.

PMID:22213154 SUPPORT Model Organism

"Ocular findings in heterozygous mice again are reminiscent of the human phenotype with optic nerve dysplasia, abnormal vessels that emerge from the periphery of the optic disc, and thinning of the retina"

Describes the disc morphology this node asserts; the observation is in heterozygous mutant mice rather than patients.

PMID:21654726 SUPPORT Human Clinical

"The eye anomalies consist of a wide and sometimes excavated dysplastic optic disc with the emergence of the retinal vessels from the periphery of the disc, frequently called optic nerve coloboma or morning glory anomaly."

The human description of the same disc morphology, including the peripheral vessel emergence that distinguishes it from an ordinary coloboma.

Otic Vesicle Patterning Failure

The third organ arm. PAX2 is expressed in the otic primordium, and reduced dosage disturbs patterning of the auditory portion of the inner ear. In the mouse null the cochlea and spiral ganglion are absent outright; in human carriers the corresponding lesion is subtle and presents as high-frequency sensorineural loss rather than deafness, so the human severity is not established at the same resolution.

inner ear morphogenesis GO:0042472 ⚠ ABNORMAL

cochlea UBERON:0001844

Downstream

Sensorineural hearing impairment

Show evidence (2 references)

PMID:8951055 SUPPORT Model Organism

"During gestation, the paired box-containing gene Pax2 is expressed in the mid-hindbrain area, developing eye and inner ear."

Establishes inner-ear expression, which is the precondition for a dosage effect at this site.

PMID:10466411 SUPPORT Human Clinical

"some patients are affected with vesico-ureteral reflux (VUR), high frequency hearing loss, central nervous system (CNS) anomalies, and/or genital anomalies, consistent with the expression of PAX2 in these tissues during development"

Makes the same expression-to-phenotype argument in patients, and names high-frequency hearing loss as the auditory outcome.

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Histopathology

2

Oligomeganephronia

Fewer glomeruli than normal, each enlarged. The histological signature of a reduced nephron endowment with compensatory hypertrophy, and the tissue-level expression of the developmental arm of the disorder.

Show evidence (1 reference)

PMID:21654726 SUPPORT Human Clinical

"Histologically, kidneys exhibit fewer than the normal number of glomeruli and these glomeruli are enlarged, a finding called oligomeganephronia."

States the finding and names it.

Focal segmental glomerulosclerosis on biopsy

Segmental sclerosis of some glomeruli on kidney biopsy, seen both in carriers with structurally normal kidneys and in those with hypodysplasia.

Show evidence (1 reference)

PMID:31538321 SUPPORT Human Clinical

"Abdominal ultrasound showed no renal and urinary tract malformations and kidney biopsy showed FSGS."

A biopsy-proven FSGS lesion in a PAX2 carrier whose imaging showed no malformation, which is the podocyte arm presenting alone.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

20

Cardiovascular 1

Hypertension HP:0000822

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Ongoing treatment of hypertension and/or vesicoureteral reflux"

GeneReviews lists hypertension as a manifestation requiring ongoing treatment, so it is a recognised feature of the disorder.

Ear 1

Sensorineural hearing impairment OCCASIONAL HP:0000407

Show evidence (2 references)

PMID:20301624 SUPPORT Human Clinical

"Additional clinical findings include high-frequency sensorineural hearing loss, soft skin, and ligamentous laxity."

Names the auditory phenotype and its high-frequency character.

PMID:22213154 SUPPORT Human Clinical

"The most common findings reported in this series were abnormal renal structure or function (92% of individuals), ophthalmological abnormalities (77% of individuals), and hearing loss (7% of individuals)."

The 7% figure supports the OCCASIONAL band (5-29%).

Eye 5

Optic disc coloboma FREQUENT HP:0000588

Show evidence (2 references)

PMID:20301624 SUPPORT Human Clinical

"Ophthalmologic abnormalities are typically described as optic nerve coloboma or dysplasia."

Names the typical ocular lesion of the syndrome.

PMID:22213154 SUPPORT Human Clinical

"The most common findings reported in this series were abnormal renal structure or function (92% of individuals), ophthalmological abnormalities (77% of individuals), and hearing loss (7% of individuals)."

Supports the FREQUENT band (30-79%). The 77% figure is for ophthalmological abnormalities as a class, of which optic nerve coloboma or dysplasia is the typical form; a coloboma-specific denominator is not published.

Reduced visual acuity HP:0007663

Show evidence (2 references)

PMID:20301624 SUPPORT Human Clinical

"Ophthalmologic abnormalities may significantly impair vision in some individuals, while others have subtle changes only noted after detailed ophthalmologic examination."

Establishes both that vision loss occurs and that it is variable.

PMID:21654726 SUPPORT Human Clinical

"Consequences of the ocular malformations include decreased visual acuity and retinal detachment."

Attributes reduced acuity to the structural ocular malformation rather than to a separate process.

Retinal detachment HP:0000541

Show evidence (2 references)

PMID:20301624 SUPPORT Human Clinical

"Use of protective eyewear to prevent retinal detachment."

GeneReviews lists prevention of retinal detachment as a management goal, which establishes it as a recognised complication of this disorder.

PMID:21654726 SUPPORT Human Clinical

"Consequences of the ocular malformations include decreased visual acuity and retinal detachment."

Names retinal detachment directly as a consequence of the ocular malformation.

Retinal coloboma HP:0000480

Show evidence (1 reference)

PMID:21654726 SUPPORT Human Clinical

"Associated findings may include a small corneal diameter, retinal coloboma, scleral staphyloma, optic nerve cyst and pigmentary macular dysplasia."

Lists retinal coloboma among the associated ocular findings; the phrasing establishes occurrence, not frequency.

Microcornea HP:0000482

Show evidence (1 reference)

PMID:21654726 SUPPORT Human Clinical

"Associated findings may include a small corneal diameter, retinal coloboma, scleral staphyloma, optic nerve cyst and pigmentary macular dysplasia."

Names a small corneal diameter among the associated ocular findings.

Genitourinary 10

Renal hypoplasia HP:0000089

Sequelae: Chronic kidney disease

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"The disorder was originally referred to as renal coloboma syndrome and characterized by renal hypodysplasia and abnormalities of the optic nerve"

Names renal hypodysplasia as one of the two defining features of the syndrome.

Cystic renal dysplasia HP:0000800

Show evidence (1 reference)

PMID:41278353 SUPPORT Human Clinical

"Heterozygous inherited or de novo PAX2 LOF variants were detected in 7 of 301 patients (2.3%), all presenting with bilateral (cystic) kidney hypoplasia/dysplasia/hypodysplasia (KHD)."

Every variant carrier in this cohort had bilateral cystic kidney hypoplasia/dysplasia.

Multicystic kidney dysplasia HP:0000003

Show evidence (1 reference)

PMID:16049068 SUPPORT Human Clinical

"The first presentation of multicystic dysplastic kidney in this syndrome is reported."

Reports the phenotype in a molecularly confirmed family; a single family, so this is a rare rather than typical finding.

Vesicoureteral reflux HP:0000076

Show evidence (1 reference)

PMID:10466411 SUPPORT Human Clinical

"some patients are affected with vesico-ureteral reflux (VUR), high frequency hearing loss, central nervous system (CNS) anomalies, and/or genital anomalies, consistent with the expression of PAX2 in these tissues during development"

Lists reflux among the recurring features of the syndrome in a review of reported patients.

Chronic kidney disease HP:0012622

Course: PROGRESSIVE

Sequelae: Stage 5 chronic kidney disease

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"In most individuals, clinically significant renal insufficiency / renal failure is reported."

GeneReviews states that clinically significant renal impairment is the usual course.

Stage 5 chronic kidney disease HP:0003774

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"End-stage renal disease requiring renal transplant is not uncommon."

Confirms that progression to kidney failure is a common outcome.

Proteinuria HP:0000093

Show evidence (1 reference)

PMID:7795640 SUPPORT Human Clinical

"We have conducted a mutational analysis of PAX2 in a family with optic nerve colobomas, renal hypoplasia, mild proteinuria and vesicoureteral reflux."

Records proteinuria as part of the phenotype in the founding kindred.

Albuminuria HP:0012592

Show evidence (1 reference)

PMID:41278353 SUPPORT Human Clinical

"albuminuria (significantly more severe than in patients with (cystic) KHD and wildtype PAX2, P < 0.0001), suggesting a proteinuric effect of PAX2 LOF variants"

Quantifies the excess albuminuria relative to a matched structural-disease comparison group.

Focal segmental glomerulosclerosis HP:0000097

Show evidence (2 references)

PMID:24676634 SUPPORT Human Clinical

"Here, exome sequencing in members of an index family with dominant FSGS revealed a nonconservative, disease-segregating variant in the PAX2 transcription factor gene."

Segregation of a PAX2 allele with dominant FSGS in an index family.

PMID:20301624 SUPPORT Human Clinical

"PAX2 pathogenic variants have been identified in multiple sporadic and familial cases of nonsyndromic renal disease including renal hypodysplasia and focal segmental glomerulosclerosis."

Places FSGS inside the accepted PAX2 phenotypic spectrum.

Uric acid nephrolithiasis HP:0000791

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Uric acid nephrolithiasis has been reported."

GeneReviews records the finding; the phrasing establishes occurrence, not frequency.

Integument 1

Soft skin HP:0000977

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Additional clinical findings include high-frequency sensorineural hearing loss, soft skin, and ligamentous laxity."

Lists soft skin among the additional clinical findings.

Metabolism 1

Hyperuricemia HP:0002149

Sequelae: Uric acid nephrolithiasis

Show evidence (1 reference)

PMID:35087773 SUPPORT Human Clinical

"sensorineural hearing loss, central nervous system (CNS) malformation, hyperuricemia, soft skin, and joint laxity"

Lists hyperuricemia among the extrarenal, extraocular features of the disorder.

Musculoskeletal 1

Joint hypermobility HP:0001382

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Additional clinical findings include high-frequency sensorineural hearing loss, soft skin, and ligamentous laxity."

Lists ligamentous laxity among the additional clinical findings.

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Genetic Associations

1

PAX2 (Renal coloboma syndrome / PAX2-related disorder)

Gene: PAX2 hgnc:8616 relationship_type: CAUSATIVE

Show evidence (6 references)

PMID:22213154 SUPPORT Human Clinical

"Mutations in the paired-box gene, PAX2, have been identified in approximately half of individuals with classic findings of renal hypoplasia/dysplasia and abnormalities of the optic nerve."

Establishes PAX2 as the causal gene and gives the diagnostic yield in clinically classic cases.

PMID:11730657 SUPPORT Human Clinical

"The causal relationship between PAX2 gene mutations and renal-coloboma syndrome is further supported by this novel mutation."

An independent de novo case supporting causality rather than linkage alone.

PMID:23756089 SUPPORT Human Clinical

"Large genomic deletions of PAX2 have been identified in 3/90 known RCS families, accounting for approximately (3%) of RCS cases."

Quantifies the copy-number contribution referenced in the notes.

+ 3 more references

💊

Medical Actions

9

Antihypertensive and Antiproteinuric Therapy

Action: Pharmacotherapy NCIT:C15986

Agent: antihypertensive agent NCIT:C270

Platform: Small molecule

Ongoing pharmacological control of blood pressure, with antiproteinuric measures, to slow loss of an already reduced nephron mass. There is no PAX2-specific pharmacotherapy; management follows general chronic kidney disease practice, and the 2025 CAKUT cohort specifically recommends antiproteinuric measures in PAX2 variant carriers.

Mechanism Target:

Glomerular Hyperfiltration and Progressive Nephron Loss — Lowering glomerular pressure and proteinuria is aimed at the hyperfiltration injury rather than at the malformation, which is fixed.

Show evidence (2 references)

PMID:20301624 SUPPORT Human Clinical

"Ongoing treatment of hypertension and/or vesicoureteral reflux"

GeneReviews management section names ongoing hypertension treatment; it does not name a drug class, so the agent binding is left at the class level.

PMID:41278353 SUPPORT Human Clinical

"In patients with CAKUT and PAX2 LOF variants, close monitoring and antiproteinuric measures should be considered, and PAX2 variant testing is recommended in living related donors."

A recommendation specific to PAX2 carriers; it is the authors' conclusion from an observational cohort, not a trial result.

Dialysis

Action: Dialysis NCIT:C15221

Platform: Device

Renal replacement therapy for kidney failure, often required in childhood or early adulthood.

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"renal replacement therapy (dialysis and/or renal transplantation) for end-stage renal disease"

GeneReviews names dialysis as management for end-stage renal disease in this disorder.

Kidney Transplantation

Action: Kidney Transplantation NCIT:C15265

Platform: Surgery

Definitive treatment for kidney failure. Because carrier relatives may have only albuminuria or FSGS, PAX2 testing is recommended before accepting a living related donor.

Show evidence (2 references)

PMID:20301624 SUPPORT Human Clinical

"End-stage renal disease requiring renal transplant is not uncommon."

Establishes transplantation as a routine outcome of the disorder's course.

PMID:41278353 SUPPORT Human Clinical

"PAX2 variant testing is recommended in living related donors."

Supports the donor-screening caveat attached to this treatment.

Low Vision Aids

Action: low vision aids Ontology label: Supportive Care NCIT:C15747

Platform: Device

Optical and educational adaptation for significant visual impairment from optic nerve dysplasia.

Target Phenotypes: Reduced visual acuity HP:0007663

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"low vision aids for significant visual impairment"

GeneReviews management recommendation. NCIT has no clinical-action term for low vision aids, so the action is bound at Supportive Care and the specificity is carried in preferred_term.

Protective Eyewear

Action: protective eyewear Ontology label: Supportive Care NCIT:C15747

Platform: Device

Preventive measure against retinal detachment in eyes with colobomatous or dysplastic discs.

Target Phenotypes: Retinal detachment HP:0000541

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Use of protective eyewear to prevent retinal detachment."

GeneReviews lists this under prevention of secondary complications.

Genetic Counseling and Cascade Testing

Action: Genetic Counseling NCIT:C15240

Platform: Other

Counselling for 50% recurrence risk, with molecular testing offered to at-risk relatives and clinical evaluation where no familial variant is known. Germline mosaicism means apparently unaffected parents of a child with a de novo variant are not at zero recurrence risk.

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Offer molecular genetic testing if a PAX2 pathogenic variant has been identified in an affected family member."

GeneReviews cascade-testing recommendation.

Nephrology Surveillance

Category: Monitoring Action: monitoring of renal function and blood pressure Ontology label: Renal Function Test NCIT:C74972

Periodic nephrology follow-up measuring renal function and blood pressure. The developmental nephron deficit is fixed at birth, so surveillance watches the hyperfiltration injury that follows it, which is the modifiable arm. It does not itself act on that node: it detects rising creatinine, blood pressure and albuminuria early enough for the antiproteinuric therapy above to do so.

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Follow up by a nephrologist to monitor renal function and blood pressure and an ophthalmologist to monitor vision, with periodic audiometric evaluations."

GeneReviews surveillance recommendation; this entry covers its nephrology clause.

Ophthalmologic Surveillance

Category: Monitoring Action: monitoring of vision Ontology label: Eye Examination NCIT:C38060

Ophthalmology follow-up to monitor vision. GeneReviews pairs it with protective eyewear against retinal detachment, which this entry records as a separate treatment; it does not state an interval, and none is asserted here.

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Follow up by a nephrologist to monitor renal function and blood pressure and an ophthalmologist to monitor vision, with periodic audiometric evaluations."

GeneReviews surveillance recommendation; this entry covers its ophthalmology clause.

Periodic Audiometric Evaluation

Category: Monitoring Action: periodic audiometric evaluation Ontology label: Audiometric Test NCIT:C38036

Audiometry measuring the high-frequency sensorineural hearing loss that follows the otic patterning defect; it detects that phenotype rather than acting on it. GeneReviews recommends it periodically rather than as a single assessment; it does not state a starting age or interval, and none is asserted here.

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"Follow up by a nephrologist to monitor renal function and blood pressure and an ophthalmologist to monitor vision, with periodic audiometric evaluations."

GeneReviews surveillance recommendation; this entry covers its audiometry clause, which is what the hearing-loss arm of this entry is monitored by.

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Diagnosis

4

PAX2 molecular genetic testing (Positive)

The diagnosis is established by finding a heterozygous pathogenic PAX2 variant in a proband with characteristic renal and/or eye findings. Sequencing of the coding exons is the primary test; copy-number analysis adds the roughly 3% of cases caused by whole-gene deletion.

Show evidence (4 references)

PMID:20301624 SUPPORT Human Clinical

"The diagnosis of PAX2-related disorder is established in a proband with the characteristic renal and/or eye findings by the identification of a heterozygous pathogenic variant in PAX2 by molecular genetic testing."

States the diagnostic standard.

PMID:20301624 SUPPORT Human Clinical

"Among individuals with apparently nonsyndromic renal hypodysplasia and in families with autosomal dominant isolated focal segmental glomerulosclerosis, pathogenic variants in PAX2 have been identified in approximately 8% and 4%, respectively."

Gives the diagnostic yield in the two non-syndromic presentations where PAX2 testing is worth doing.

PMID:37123577 SUPPORT Human Clinical

"It has been estimated that approximately 10% of children with hypoplastic kidneys may have renal coloboma syndrome."

A pre-test probability for the commonest presenting finding; the review reports it as an estimate rather than a measured yield.

+ 1 more reference

Dilated ophthalmologic examination (Positive)

Dilated fundoscopy for optic nerve head dysplasia and retinal coloboma. GeneReviews includes it in the battery used to assess an at-risk relative in whom no PAX2 pathogenic variant has been found. The ocular finding is what makes a renal presentation syndromic, which is the distinction this entry's differential diagnoses turn on.

dilated ophthalmologic examination NCIT:C38060

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"perform dilated ophthalmologic examination, renal ultrasound examination, tests of renal function, uric acid levels, and urinalysis; measure blood pressure."

GeneReviews names dilated ophthalmologic examination in the evaluation of an at-risk relative in whom no PAX2 pathogenic variant has been found.

Renal ultrasonography (Positive)

Ultrasound assessment of kidney size, echogenicity and cystic change, which is how renal hypodysplasia is detected in a relative who has no symptoms.

renal ultrasound examination NCIT:C159885

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"perform dilated ophthalmologic examination, renal ultrasound examination, tests of renal function, uric acid levels, and urinalysis; measure blood pressure."

GeneReviews names renal ultrasound examination in the same at-risk-relative evaluation.

Renal function, uric acid and urinalysis (Abnormal)

Biochemical assessment of the kidney: serum creatinine and estimated GFR for excretory function, urinalysis for the albuminuria that is disproportionate in this disorder, and serum uric acid. Blood pressure is measured alongside. This entry separately records hyperuricemia and uric acid nephrolithiasis as phenotypes; GeneReviews does not state why uric acid is in the panel.

tests of renal function NCIT:C74972

Markers: serum creatinine, estimated GFR, serum uric acid, urinalysis, blood pressure

Show evidence (1 reference)

PMID:20301624 SUPPORT Human Clinical

"perform dilated ophthalmologic examination, renal ultrasound examination, tests of renal function, uric acid levels, and urinalysis; measure blood pressure."

GeneReviews names tests of renal function, uric acid levels, urinalysis and blood pressure in the at-risk-relative evaluation. The uric acid clause is why this entry carries hyperuricemia and uric acid nephrolithiasis.

📈

Progression

1

Progression to kidney failure

Kidney function declines over childhood and young adulthood. In a Korean cohort of 27 PAX2 variant carriers, kidney failure developed in 52% at a median age of 14.5 years; the accompanying literature review of 328 cases found faster progression in carriers of predicted loss-of-function variants.

Show evidence (3 references)

PMID:39994403 SUPPORT Human Clinical

"Kidney failure developed in 52% of Korean patients at a median age of 14.5 years, with no difference in kidney survival between variant types."

Quantifies the rate and timing of progression to kidney failure in a genetically confirmed cohort.

PMID:39994403 SUPPORT Human Clinical

"the literature review indicated faster progression to kidney failure in patients with pLoF variants (11.0 vs. 24.0 years; pLoF, n = 138 vs. non-pLoF, n = 71; P = 0.002)"

Supports variant-type dependence of the progression rate across the pooled published cases.

PMID:31538321 SUPPORT Human Clinical

"In previous reports describing PAX2 mutations with FSGS, affected individuals with missense PAX2 mutations developed ESKD in adulthood, whereas one case with truncating PAX2 mutations developed ESKD in childhood similar to the current case."

Supports the same genotype-timing gradient within the FSGS arm specifically; the observation is a single case set against a literature review, not a cohort comparison.

📊

Prevalence

1

Worldwide

Cases In Literature Unknown

No population-based prevalence or incidence estimate exists. The largest published census is the PAX2 locus-specific database, which by 2011 held 173 mutation-positive individuals from 86 families worldwide, and 272 individuals from 136 families by 2022. A separate denominator is available for ascertainment through paediatric CAKUT: PAX2 loss-of-function variants were found in 7 of 301 unselected paediatric CAKUT patients (2.3%).

Show evidence (3 references)

PMID:22213154 SUPPORT Human Clinical

"Review of published cases and the collective diagnostic experience of three laboratories in the United States, France, and New Zealand identified 55 unique mutations in 173 individuals from 86 families."

Gives the published case census behind the CASES_IN_LITERATURE measure; it counts reported individuals, not a population rate.

PMID:41278353 SUPPORT Human Clinical

"Heterozygous inherited or de novo PAX2 LOF variants were detected in 7 of 301 patients (2.3%), all presenting with bilateral (cystic) kidney hypoplasia/dysplasia/hypodysplasia (KHD)."

Supplies the diagnostic yield of PAX2 testing within a paediatric CAKUT cohort, which is the closest thing to a denominator in the literature.

PMID:35087773 SUPPORT Human Clinical

"At the time of publication, only 272 affected individuals from 136 different families are documented in the updated database of PAX2 mutations"

Updates the locus-specific-database census a decade after Bower et al., still a count of reported individuals rather than a population rate.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Renal Coloboma Syndrome:

Isolated congenital anomalies of the kidney and urinary tract

Overlapping Features CAKUT without ocular findings. PAX2 loss-of-function variants are found in a small but non-trivial fraction of such patients, so absence of an eye finding does not exclude PAX2.

Distinguishing Features

Cystic kidney hypodysplasia combined with albuminuria disproportionate to the CKD stage should prompt PAX2 testing even without ocular findings.

Show evidence (1 reference)

PMID:41278347 SUPPORT Other

"Clinically, the combination of cystic dysplasia and albuminuria disproportionate to chronic kidney disease stage should prompt consideration of PAX2 testing."

Gives the testing trigger that separates PAX2 nephropathy from undifferentiated CAKUT.

🧫

Experimental Models

1

Patient-derived iPSC podocytes carrying PAX2 p.G189R IPSC_DERIVED_MODEL

Induced pluripotent stem cells from a member of a family with adult-onset autosomal dominant FSGS carrying the PAX2 p.G189R octapeptide-domain variant, differentiated into podocytes. CRISPR-Cas9 correction of the point mutation provides an isogenic control, making this the cleanest available test of whether the variant itself causes the podocyte defect.

Organism

human NCBITaxon:9606

Publication

PMID:30998089

Pathograph links

Reduced Podocyte Fitness rescues fidelity: moderate Podocyte motility was altered in patient-derived cells and restored by correcting the variant, isolating PAX2 as the cause of the podocyte phenotype.

Limitations: The readout is motility in culture, not albuminuria or glomerular sclerosis, and the model carries a single missense allele from one family rather than the loss-of-function alleles typical of the syndromic presentation.

Readouts

Podocyte motility

Direction: RESTORED

Interpretation: Correction of the variant restores the cellular behaviour that the variant altered.

Show evidence (1 reference)

PMID:30998089 SUPPORT In Vitro

"Editing the PAX2 p.G189R mutation restored podocyte motility, which was altered in podocytes derived from patient iPSCs."

Reports the measurement and its direction in the isogenic comparison.

Show evidence (1 reference)

PMID:30998089 SUPPORT In Vitro

"Here, we efficiently corrected this point mutation in patient-derived induced pluripotent stem cells (iPSCs) by means of CRISPR-Cas9-based homology-directed repair."

Establishes the isogenic-correction design that makes this model informative for the podocyte node.

🐁

Animal Models

2

Pax2 null mouse (homozygous)

The germline knockout is anephric and shows the ocular counterpart of the human lesion, which is what established PAX2 as required for both organ programmes. Homozygous loss is more severe than any human genotype, so the model demonstrates the requirement rather than reproducing the disease.

Species

Mouse

Genotype

Pax2 homozygous null

Publication

PMID:8575306

Pathograph links

Increased Ureteric Bud Apoptosis and Reduced Branching partially recapitulates fidelity: moderate In the homozygous null the ureteric bud is absent altogether, so kidney development never begins - the extreme of the branching defect rather than the graded reduction seen in patients.

Limitations: Human disease is heterozygous and produces a small maldeveloped kidney, not agenesis; the homozygous model overshoots the human lesion.

Show evidence (1 reference)

PMID:8575306 SUPPORT Model Organism

"We report here that Pax-2 homozygous mutant newborn mice lack kidneys, ureters and genital tracts."

Establishes the absolute requirement for Pax-2 in ureter and kidney formation, upstream of the branching step this node describes.

Failure of Optic Fissure Closure recapitulates fidelity: high The null mouse fails to close the optic fissure and develops coloboma, which is the same developmental step that fails in patients.

Show evidence (1 reference)

PMID:8951055 SUPPORT Model Organism

"Furthermore, Pax2 mutants show extension of the pigmented retina into the optic stalks and failure of the optic fissure to close resulting in coloboma."

Directly reports failed fissure closure and coloboma in the model.

Show evidence (1 reference)

PMID:8575306 SUPPORT Model Organism

"Mesenchyme of the nephrogenic cord fails to undergo epithelial transformation and is not able to form tubules in the mesonephros."

Supports treating the null mouse as informative for PAX2-dependent nephric development, the process disrupted in the human disorder.

Pax2 1Neu heterozygous mouse

An ENU-derived allele carrying the guanine insertion equivalent to the recurrent human c.76dup. The heterozygous state matches the human genotype, which makes this the closest available model of the renal arm.

Species

Mouse

Genotype

Pax2(1Neu) heterozygous

Publication

PMID:10587573

Pathograph links

Increased Ureteric Bud Apoptosis and Reduced Branching recapitulates fidelity: high Heterozygous fetal kidneys show the increased apoptosis and reduced branching that the node asserts, at the correct gene dosage.

Readouts

Apoptotic cell death in fetal kidney

Direction: INCREASED

Interpretation: Direct measurement of the cell-death increase this mechanism node claims.

Show evidence (1 reference)

PMID:10587573 SUPPORT Model Organism

"Heterozygous 1Neu mice showed increased apoptotic cell death during fetal kidney development"

Reports the apoptosis measurement in the heterozygous fetal kidney.

Fetal kidney size and nephron number at E15

Direction: DECREASED

Interpretation: Structural correlate of reduced branching, measured at the stage when branching is active.

Show evidence (1 reference)

PMID:10587573 SUPPORT Model Organism

"At E15, heterozygous mutant kidneys were approximately 60% of the size of wild-type littermates, and the number of nephrons was strikingly reduced."

Quantifies both readouts in the same animals.

Show evidence (1 reference)

PMID:10587573 SUPPORT Model Organism

"These findings support the notion that heterozygous mutations of PAX2 are associated with increased apoptosis and reduced branching of the ureteric bud, due to reduced PAX2 dosage during a critical window in kidney development."

The authors' own statement that the model speaks to this mechanism at human-equivalent gene dosage.

{ }

Source YAML

click to show

name: Renal Coloboma Syndrome
creation_date: "2026-09-09T00:00:00Z"
category: Genetic
disease_term:
  preferred_term: PAX2-related disorder
  term:
    id: MONDO:0007352
    label: renal coloboma syndrome
description: >-
  An autosomal dominant developmental disorder caused by heterozygous
  loss-of-function variants in PAX2, in which one transcription-factor dosage
  defect disrupts two separate organogenesis programmes: ureteric-bud outgrowth
  and branching in the developing kidney, and closure of the optic fissure at
  the optic stalk. The result is renal hypodysplasia with a reduced nephron
  endowment, vesicoureteral reflux and progressive chronic kidney disease
  alongside optic nerve coloboma or dysplasia. GeneReviews now titles the entry
  PAX2-related disorder, because molecular testing has widened the phenotype
  beyond the classic renal-plus-optic-nerve pairing to include isolated CAKUT
  and adult-onset focal segmental glomerulosclerosis (FSGS type 7); renal
  coloboma syndrome and papillorenal syndrome are the older names for the
  syndromic core.
synonyms:
- PAX2-related disorder
- papillorenal syndrome
- renal-coloboma syndrome
- coloboma of optic nerve with renal disease
- optic coloboma, vesicoureteral reflux and renal anomalies
notes: >-
  Naming: this entry keeps the MONDO binding and file slug assigned by the
  curation queue (MONDO:0007352, renal coloboma syndrome) while using the
  current GeneReviews term, PAX2-related disorder, as the preferred display
  term. Whether the optic nerve lesion is a true coloboma or a dysplasia has
  been argued since the 1990s and is the reason both "renal coloboma" and
  "papillorenal" names persist; Bower et al. record the dispute explicitly.
  Related entries: Renal_Agenesis carries PAX2 as a syndromic CAKUT gene row
  and Familial_Vesicoureteral_Reflux names PAX2 among syndromic VUR genes.
  Both are cross-references, not subtype relationships - this is a leaf disease
  entry with a single causal gene.
  Four phenotypes are deliberately left off the pathograph because no source
  here supports a mechanism for them: microcornea, soft skin, joint
  hypermobility, and hyperuricemia's own upstream cause. They are reported
  associations of PAX2-related disorder, not steps anyone has traced, and an
  unconnected node is the honest representation of that.
  Scoped out deliberately: CNS/corpus callosum anomalies, genital anomalies and
  cataract are listed in the deep-research report but are not curated here. The
  report itself qualifies them as occurring "in some families" and as "less
  common findings", and gives no frequency, cohort or denominator that could be
  quoted, so there is nothing to attach an evidence snippet to. Two of the three
  CURIEs the report offers for them are also wrong in the way described below:
  HP:0002190, offered for corpus callosum anomalies, is Choroid plexus cyst, and
  HP:0000083, offered for genital anomalies, is Renal insufficiency. Only
  HP:0000518 (Cataract) is named correctly. Adding these would need a primary
  source with a frequency, not the report.
  Provenance caveat on the deep-research input: the Perplexity report's citations
  all resolved (22/22), but its term validation was unreliable - 29 of the 56
  CURIE labels it offered named a different term than the report claimed, among
  them HP:0000588/HP:0000589 inverted, UBERON:0001626 offered as "optic nerve"
  when UBERON calls it left coronary artery, and HGNC:8619 offered as PAX2 when
  that identifier is PAX5. Every ontology binding in this entry was therefore
  re-derived with OAK against the configured adapters and none was lifted from
  the report. The report also cites "PMID:8787321" for a 2022 Frontiers in
  Pediatrics review; that is a PMC identifier written as a PMID, and PMID:8787321
  is an unrelated 1995 French paper on inguinal hernia repair. The intended
  article is PMID:35087773, which this entry cites instead.
classifications:
  harrisons_chapter:
  - classification_value: KIDNEY_URINARY_TRACT
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
references:
- reference: PMID:20301624
  title: PAX2-Related Disorder.
  tags:
  - GeneReviews
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: UNKNOWN
  notes: >-
    No population-based prevalence or incidence estimate exists. The largest
    published census is the PAX2 locus-specific database, which by 2011 held
    173 mutation-positive individuals from 86 families worldwide, and 272
    individuals from 136 families by 2022. A separate denominator is available
    for ascertainment through paediatric CAKUT: PAX2 loss-of-function variants
    were found in 7 of 301 unselected paediatric CAKUT patients (2.3%).
  evidence:
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Review of published cases and the collective diagnostic experience of
      three laboratories in the United States, France, and New Zealand
      identified 55 unique mutations in 173 individuals from 86 families.
    explanation: >-
      Gives the published case census behind the CASES_IN_LITERATURE measure;
      it counts reported individuals, not a population rate.
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Heterozygous inherited or de novo PAX2 LOF variants were detected in 7 of
      301 patients (2.3%), all presenting with bilateral (cystic) kidney
      hypoplasia/dysplasia/hypodysplasia (KHD).
    explanation: >-
      Supplies the diagnostic yield of PAX2 testing within a paediatric CAKUT
      cohort, which is the closest thing to a denominator in the literature.
  - reference: PMID:35087773
    reference_title: "PAX2 Mutation-Related Renal Hypodysplasia: Review of the Literature and Three Case Reports."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At the time of publication, only 272 affected individuals from 136
      different families are documented in the updated database of PAX2
      mutations
    explanation: >-
      Updates the locus-specific-database census a decade after Bower et al.,
      still a count of reported individuals rather than a population rate.
progression:
- phase: Progression to kidney failure
  notes: >-
    Kidney function declines over childhood and young adulthood. In a Korean
    cohort of 27 PAX2 variant carriers, kidney failure developed in 52% at a
    median age of 14.5 years; the accompanying literature review of 328 cases
    found faster progression in carriers of predicted loss-of-function
    variants.
  evidence:
  - reference: PMID:39994403
    reference_title: Genotype of PAX2-related disorders correlates with kidney and ocular manifestations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Kidney failure developed in 52% of Korean patients at a median age of
      14.5 years, with no difference in kidney survival between variant types.
    explanation: >-
      Quantifies the rate and timing of progression to kidney failure in a
      genetically confirmed cohort.
  - reference: PMID:39994403
    reference_title: Genotype of PAX2-related disorders correlates with kidney and ocular manifestations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the literature review indicated faster progression to kidney failure in
      patients with pLoF variants (11.0 vs. 24.0 years; pLoF, n = 138 vs.
      non-pLoF, n = 71; P = 0.002)
    explanation: >-
      Supports variant-type dependence of the progression rate across the
      pooled published cases.
  - reference: PMID:31538321
    reference_title: A novel truncating PAX2 mutation in a boy with renal coloboma syndrome with focal segmental glomerulosclerosis causing rapid progression to end-stage kidney disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In previous reports describing PAX2 mutations with FSGS, affected
      individuals with missense PAX2 mutations developed ESKD in adulthood,
      whereas one case with truncating PAX2 mutations developed ESKD in
      childhood similar to the current case.
    explanation: >-
      Supports the same genotype-timing gradient within the FSGS arm
      specifically; the observation is a single case set against a literature
      review, not a cohort comparison.
pathophysiology:
- name: PAX2 Haploinsufficiency
  description: >-
    A heterozygous loss-of-function variant in PAX2 - most often a frameshift,
    nonsense or canonical splice-site change, with the recurrent c.76dupG
    (p.Val26Glyfs*28) in exon 2 the commonest single allele - halves the dose of
    a paired-box transcription factor that is required in the nephric duct,
    ureteric bud, metanephric mesenchyme, optic stalk and otic vesicle. The
    resulting phenotypes are dosage effects in tissues where PAX2 is
    transcriptionally rate-limiting, which is why one gene produces an apparently
    unrelated kidney-plus-eye combination. Mechanistically PAX2 does not act
    alone: it recruits a PTIP-MLL H3K4 methyltransferase complex to its target
    loci, so halving PAX2 halves the delivery of an activating chromatin mark to
    the developmental programmes it licenses.
  role: trigger
  biological_scale: MOLECULAR
  molecular_functions:
  - preferred_term: PAX2 paired-domain DNA-binding transcription factor activity
    term:
      id: GO:0003700
      label: DNA-binding transcription factor activity
    modifier: DECREASED
  genetic_context:
    gene:
      preferred_term: PAX2
      term:
        id: hgnc:8616
        label: PAX2
    zygosity: HETEROZYGOUS
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Most pathogenic alleles are predicted loss of function. A dominant-negative
      contribution has been proposed for the recurrent c.76dupG allele, whose
      transcript escapes nonsense-mediated decay, and for some FSGS-associated
      missense alleles that enhance PAX2 repressor activity.
  evidence:
  - reference: PMID:7795640
    reference_title: Mutation of the PAX2 gene in a family with optic nerve colobomas, renal anomalies and vesicoureteral reflux.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We have conducted a mutational analysis of PAX2 in a family with optic
      nerve colobomas, renal hypoplasia, mild proteinuria and vesicoureteral
      reflux. We report a single nucleotide deletion in exon five, causing a
      frame-shift of the PAX2 coding region in the octapeptide domain.
    explanation: >-
      The founding report linking a truncating PAX2 allele to the combined
      ocular and renal phenotype in a segregating family.
  - reference: PMID:10466411
    reference_title: "Renal-coloboma syndrome: a multi-system developmental disorder caused by PAX2 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Optic nerve coloboma combined with renal disease, also called
      renal-coloboma syndrome ( # 120330 in McKusick's Mendelian Inheritance in
      Man Online, OMIM), a relatively recently characterized syndrome, results
      from autosomal dominant mutations in the PAX2 gene.
    explanation: >-
      States the causal relationship and the dominant mode, anchoring PAX2
      variation as the initiating lesion of the entry.
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Severe kidney anomalies, that is, cystic KHD or agenesis, were
      significantly more frequent in patients carrying the
      NM_000278.5(PAX2):c.76dupG variant in exon 2 with a possible
      dominant-negative effect than in patients with nonsense or frameshift
      variants in exon 3 to 7.
    explanation: >-
      Supports the note that the recurrent c.76dupG allele may act beyond simple
      haploinsufficiency; the dominant-negative mechanism is proposed, not shown.
  - reference: PMID:37628926
    reference_title: PAX2 Gene Mutation in Pediatric Renal Disorders-A Narrative Review.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The PAX2 gene is involved in the definitive kidney formation, which is
      present in the caudal intermediate mesoderm and is also expressed in the
      ureteric bud (UB) and the metanephric mesenchyme (MM)
    explanation: >-
      Places PAX2 expression in the three compartments whose development fails
      here; a narrative review's synthesis rather than a primary observation.
  - reference: PMID:37628926
    reference_title: PAX2 Gene Mutation in Pediatric Renal Disorders-A Narrative Review.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      In this process, PAX2 recruits a histone H3K4 methyltransferase PAX
      interacting protein 1-mixed-lineage leukemia (PTIP-MLL) complex as a
      response to inductive signals
    explanation: >-
      Supports the chromatin-level account of how PAX2 acts on its targets, and
      so why dosage matters; a narrative review's synthesis rather than a
      primary observation.
  downstream:
  - target: Increased Ureteric Bud Apoptosis and Reduced Branching
    causal_link_type: DIRECT
    description: >-
      Reduced PAX2 dosage removes a survival signal in the developing ureteric
      bud epithelium.
    evidence:
    - reference: PMID:10587573
      reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        These findings support the notion that heterozygous mutations of PAX2
        are associated with increased apoptosis and reduced branching of the
        ureteric bud, due to reduced PAX2 dosage during a critical window in
        kidney development.
      explanation: >-
        States the causal step from reduced PAX2 dosage to ureteric-bud
        apoptosis and reduced branching, which is exactly this edge.
  - target: Failure of Optic Fissure Closure
    causal_link_type: DIRECT
    description: >-
      PAX2 is expressed at the apposing edges of the optic fissure, and its loss
      prevents fissure closure.
    evidence:
    - reference: PMID:8951055
      reference_title: Pax2 contributes to inner ear patterning and optic nerve trajectory.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Furthermore, Pax2 mutants show extension of the pigmented retina into
        the optic stalks and failure of the optic fissure to close resulting in
        coloboma.
      explanation: >-
        Links loss of Pax2 directly to failed optic-fissure closure and the
        resulting coloboma in the mouse null.
  - target: Otic Vesicle Patterning Failure
    causal_link_type: DIRECT
    description: >-
      PAX2 is expressed in the otic primordium, and its loss prevents formation of
      the auditory parts of the inner ear.
    evidence:
    - reference: PMID:8951055
      reference_title: Pax2 contributes to inner ear patterning and optic nerve trajectory.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        In the inner ear, Pax2 mutants show agenesis of the cochlea and the
        spiral ganglion, i.e., the parts of the organ responsible for auditory
        function and in whose primordium Pax2 is expressed.
      explanation: >-
        Ties loss of Pax2 to failure of the specific inner-ear structures whose
        maldevelopment this node describes.
  - target: Reduced Podocyte Fitness
    causal_link_type: DIRECT
    description: >-
      A second, postnatal arm in which PAX2 variants compromise the resilience of
      podocytes and parietal epithelial cells in nephrons that formed normally.
    evidence:
    - reference: PMID:41278347
      reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        By contrast, PAX2 loss-of-function variants are frequently associated
        with podocyte damage, albuminuria, and FSGS
      explanation: >-
        Attributes podocyte damage to PAX2 loss of function as a mechanism
        distinct from the developmental arm; the source is an invited commentary
        synthesising clinical and experimental work rather than primary data.
- name: Increased Ureteric Bud Apoptosis and Reduced Branching
  description: >-
    One of the normal functions of PAX2 in kidney development is suppression of
    apoptosis in the ureteric bud epithelium. At half dosage, apoptotic cell
    death rises during fetal kidney development and the ureteric bud undergoes
    fewer branching generations, so fewer nephron-inducing tips are ever
    generated.
  role: mechanism
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: ureteric bud cell
    term:
      id: CL:4030066
      label: ureteric bud cell
  biological_processes:
  - preferred_term: branching involved in ureteric bud morphogenesis
    term:
      id: GO:0001658
      label: branching involved in ureteric bud morphogenesis
    modifier: DECREASED
  - preferred_term: apoptotic process in the developing ureteric bud
    term:
      id: GO:0006915
      label: apoptotic process
    modifier: INCREASED
  locations:
  - preferred_term: ureteric bud
    term:
      id: UBERON:0000084
      label: ureteric bud
  evidence:
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      There is evidence that one important role of PAX2 during renal development
      may be suppression of apoptosis in the developing ureteric bud.
    explanation: >-
      Names apoptosis suppression in the ureteric bud as the relevant normal
      PAX2 function, which is the function lost at this node.
  - reference: PMID:10587573
    reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Heterozygous 1Neu mice showed increased apoptotic cell death during fetal
      kidney development
    explanation: >-
      Measures the apoptotic increase in a heterozygous model carrying the mouse
      equivalent of the commonest human allele.
  downstream:
  - target: Reduced Nephron Endowment and Renal Hypodysplasia
    causal_link_type: DIRECT
    description: >-
      Fewer ureteric-bud tips induce fewer nephrons, and the kidney that results
      is small and maldeveloped.
    evidence:
    - reference: PMID:10587573
      reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        At E15, heterozygous mutant kidneys were approximately 60% of the size
        of wild-type littermates, and the number of nephrons was strikingly
        reduced.
      explanation: >-
        Measures both the size reduction and the nephron-number reduction that
        this edge asserts, in the same heterozygous fetal kidneys.
- name: Reduced Nephron Endowment and Renal Hypodysplasia
  description: >-
    The kidney is built with fewer nephrons than normal and with disordered
    architecture - small kidneys with poor corticomedullary differentiation,
    cortical cysts and, at the severe end, multicystic dysplasia or agenesis.
    The same disturbance of nephric-duct and ureteric-bud development produces
    the ureterovesical junction defects underlying vesicoureteral reflux.
  role: mechanism
  biological_scale: TISSUE
  biological_processes:
  - preferred_term: nephron development
    term:
      id: GO:0072006
      label: nephron development
    modifier: DECREASED
  locations:
  - preferred_term: kidney
    term:
      id: UBERON:0002113
      label: kidney
  evidence:
  - reference: PMID:10587573
    reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a total of 29 patients, renal hypoplasia was the most common congenital
      renal abnormality.
    explanation: >-
      Establishes renal hypoplasia as the dominant human structural lesion; the
      quoted sentence reports the patient series, not the mouse work in the same
      paper.
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In 104 pediatric carriers of a PAX2 LOF variant with CAKUT, hallmark
      kidney manifestations were (cystic) KHD (97% vs. 59% in patients with
      CAKUT and wildtype PAX2, P < 0.0001)
    explanation: >-
      Shows kidney hypoplasia/dysplasia is the hallmark structural lesion of
      PAX2 loss of function, against a CAKUT comparison group.
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Histologically, kidneys exhibit fewer than the normal number of glomeruli
      and these glomeruli are enlarged, a finding called oligomeganephronia.
    explanation: >-
      The histological statement of this node: a reduced nephron count with
      compensatory glomerular enlargement.
  downstream:
  - target: Glomerular Hyperfiltration and Progressive Nephron Loss
    causal_link_type: DIRECT
    description: >-
      A reduced nephron endowment forces the surviving nephrons to hyperfilter.
    evidence:
    - reference: PMID:41278347
      reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        a developmental pathway, in which impaired kidney morphogenesis,
        particularly defective nephron formation, results in CAKUT and reduced
        nephron endowment, predisposing to hyperfiltration and progressive
        chronic kidney disease
      explanation: >-
        States the step from reduced nephron endowment to hyperfiltration and
        progressive CKD, which is this edge.
  - target: Renal hypoplasia
    causal_link_type: DIRECT
  - target: Cystic renal dysplasia
    causal_link_type: DIRECT
  - target: Multicystic kidney dysplasia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reported at the severe end of the structural spectrum; the route from
      PAX2 loss to a multicystic dysplastic kidney is not established, and early
      ureteric obstruction has been proposed as an intermediate.
    evidence:
    - reference: PMID:16049068
      reference_title: Multicystic dysplastic kidney and variable phenotype in a family with a novel deletion mutation of PAX2.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The finding of multicystic dysplastic kidney in renal coloboma syndrome
        could suggest that PAX2 may play a role in early ureteric obstruction
        and subsequent renal maldevelopment.
      explanation: >-
        Reports the association and offers the proposed intermediate, phrased by
        the authors as a suggestion, which is why the link is typed as indirect.
  - target: Vesicoureteral reflux
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reflux accompanies the renal malformation in PAX2 families; the specific
      ureterovesical-junction lesion has not been resolved.
    evidence:
    - reference: PMID:16049068
      reference_title: Multicystic dysplastic kidney and variable phenotype in a family with a novel deletion mutation of PAX2.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Typical findings in these patients include renal hypoplasia, renal
        insufficiency, vesicoureteric reflux, and optic disc coloboma.
      explanation: >-
        Places vesicoureteric reflux among the typical findings alongside the
        renal structural lesion.
- name: Glomerular Hyperfiltration and Progressive Nephron Loss
  description: >-
    With too few nephrons for body size, single-nephron filtration rises, the
    remaining glomeruli hypertrophy, and the resulting haemodynamic stress
    drives proteinuria, hypertension and a steady loss of the nephrons that are
    left. This is the route by which a congenital, non-progressive malformation
    becomes progressive chronic kidney disease.
  role: consequence
  biological_scale: ORGANISM
  biological_processes:
  - preferred_term: glomerular filtration
    term:
      id: GO:0003094
      label: glomerular filtration
    modifier: INCREASED
  locations:
  - preferred_term: renal glomerulus
    term:
      id: UBERON:0000074
      label: renal glomerulus
  evidence:
  - reference: PMID:39994403
    reference_title: Genotype of PAX2-related disorders correlates with kidney and ocular manifestations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      During kidney development, PAX2 suppresses apoptosis in the developing
      ureteric bud; therefore, PAX2 pathogenic variants increase apoptosis
      during the development of the kidneys and urinary tract, which may
      underlie the decreased nephron number, hypertrophy of the remaining
      nephrons, and RHD
    explanation: >-
      Connects the reduced nephron number to compensatory hypertrophy of the
      remaining nephrons, the haemodynamic state this node describes.
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Consequences of the renal hypodysplasia include hypertension, proteinuria
      and renal insufficiency that frequently progresses to end-stage kidney
      disease.
    explanation: >-
      Names the three downstream outcomes this node feeds and attributes them to
      the hypodysplasia rather than to a separate lesion.
  downstream:
  - target: Chronic kidney disease
    causal_link_type: DIRECT
  - target: Proteinuria
    causal_link_type: DIRECT
  - target: Hypertension
    causal_link_type: DIRECT
- name: Reduced Podocyte Fitness
  description: >-
    A second mechanistic arm, distinct from the developmental one. PAX2 is
    normally silenced in the mature podocyte, and variant carriers whose
    nephrons formed normally still show podocytes that are unusually vulnerable
    to injury, together with disturbed nuclear maintenance in parietal
    epithelial cells and reduced regenerative capacity under stress. This arm
    explains the albuminuria that is disproportionate to the CKD stage, and the
    families in whom adult-onset FSGS is the whole phenotype.
  role: mechanism
  biological_scale: CELLULAR
  cell_types:
  - preferred_term: podocyte
    term:
      id: CL:0000653
      label: podocyte
  - preferred_term: parietal epithelial cell
    term:
      id: CL:1000452
      label: parietal epithelial cell
  locations:
  - preferred_term: renal glomerulus
    term:
      id: UBERON:0000074
      label: renal glomerulus
  evidence:
  - reference: PMID:41278347
    reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Cunanan et al.5 recently showed in a murine model that Pax2 variants
      impair nuclear maintenance in parietal epithelial cells and disrupt
      podocyte homeostasis, thus reducing regenerative capacity under stress.
    explanation: >-
      Describes the parietal-epithelial and podocyte defect this node asserts;
      the quote is a commentary's report of a murine result, not the primary
      paper.
  - reference: PMID:24676634
    reference_title: Mutations in PAX2 associate with adult-onset FSGS.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thus, mutations in PAX2 may contribute to adult-onset FSGS in the absence
      of overt extrarenal manifestations.
    explanation: >-
      Establishes that a PAX2 allele can produce podocyte disease with no
      developmental malformation, which is what makes this a separate arm.
  downstream:
  - target: Focal segmental glomerulosclerosis
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:41278347
      reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        a podocyte pathway, in which otherwise properly formed nephrons exhibit
        reduced "podocyte fitness," leading to disproportionate albuminuria and
        progression to FSGS.
      explanation: >-
        Names the podocyte pathway as the route from reduced podocyte fitness to
        disproportionate albuminuria and FSGS, which is what this edge asserts.
  - target: Albuminuria
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:41278353
      reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        albuminuria (significantly more severe than in patients with (cystic)
        KHD and wildtype PAX2, P < 0.0001), suggesting a proteinuric effect of
        PAX2 LOF variants
      explanation: >-
        Shows albuminuria exceeding what the structural lesion alone predicts,
        the observation the podocyte arm is invoked to explain.
- name: Failure of Optic Fissure Closure
  description: >-
    In the developing eye PAX2 expression is concentrated at the apposing edges
    of the optic fissure and falls as the fissure closes. Where PAX2 dosage is
    insufficient, the fissure margins fail to appose and fuse and the basement
    membrane between them is not dissolved, leaving a ventral gap at the optic
    stalk.
  role: mechanism
  biological_scale: TISSUE
  conforms_to: "ocular_morphogenesis_failure#Failure of Optic Fissure Closure"
  biological_processes:
  - preferred_term: closure of optic fissure
    term:
      id: GO:0061386
      label: closure of optic fissure
    modifier: DECREASED
  locations:
  - preferred_term: optic fissure
    term:
      id: UBERON:0005412
      label: optic fissure
  evidence:
  - reference: PMID:8951055
    reference_title: Pax2 contributes to inner ear patterning and optic nerve trajectory.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Our results identify Pax2 as a major regulator of patterning during
      organogenesis of the eye and inner ear and indicate its function in
      morphogenetic events required for closure of the optic fissure and neural
      tube.
    explanation: >-
      Assigns Pax2 the morphogenetic role in optic-fissure closure that this
      node loses.
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In the optic cup and stalk, PAX2 expression is most evident at the closing
      edges of the optic fissure.
    explanation: >-
      Places PAX2 expression precisely at the fissure margins, which is why a
      dosage defect acts on this step.
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The ocular phenotype is characterized by a failure of closure of the optic
      fissure and failed basement membrane dissolution.
    explanation: >-
      Adds failed basement-membrane dissolution to the fissure-closure defect;
      the sentence describes the homozygous mutant mouse phenotype.
  downstream:
  - target: Optic Nerve Head Dysplasia
    causal_link_type: DIRECT
  - target: Retinal coloboma
    causal_link_type: DIRECT
    description: >-
      A gap left in the retina and choroid where the fissure margins did not
      fuse, the same lesion expressed at a different point along the fissure.
- name: Optic Nerve Head Dysplasia
  description: >-
    The clinical lesion at the optic nerve head - a wide, excavated disc with
    peripapillary atrophy and anomalous vessels emerging from the disc periphery
    rather than a central retinal artery. Whether to call this a coloboma or a
    dysplasia has been disputed since the 1990s, which is the source of the
    competing "renal coloboma" and "papillorenal" disease names.
  role: consequence
  biological_scale: TISSUE
  locations:
  - preferred_term: optic disc
    term:
      id: UBERON:0001783
      label: optic disc
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ophthalmologic abnormalities are typically described as optic nerve
      coloboma or dysplasia.
    explanation: >-
      Names the lesion and preserves the coloboma-versus-dysplasia ambiguity
      that this node records.
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Ocular findings in heterozygous mice again are reminiscent of the human
      phenotype with optic nerve dysplasia, abnormal vessels that emerge from
      the periphery of the optic disc, and thinning of the retina
    explanation: >-
      Describes the disc morphology this node asserts; the observation is in
      heterozygous mutant mice rather than patients.
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The eye anomalies consist of a wide and sometimes excavated dysplastic
      optic disc with the emergence of the retinal vessels from the periphery of
      the disc, frequently called optic nerve coloboma or morning glory anomaly.
    explanation: >-
      The human description of the same disc morphology, including the peripheral
      vessel emergence that distinguishes it from an ordinary coloboma.
  downstream:
  - target: Optic disc coloboma
    causal_link_type: DIRECT
  - target: Reduced visual acuity
    causal_link_type: DIRECT
  - target: Retinal detachment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- name: Otic Vesicle Patterning Failure
  description: >-
    The third organ arm. PAX2 is expressed in the otic primordium, and reduced
    dosage disturbs patterning of the auditory portion of the inner ear. In the
    mouse null the cochlea and spiral ganglion are absent outright; in human
    carriers the corresponding lesion is subtle and presents as high-frequency
    sensorineural loss rather than deafness, so the human severity is not
    established at the same resolution.
  role: mechanism
  biological_scale: TISSUE
  biological_processes:
  - preferred_term: inner ear morphogenesis
    term:
      id: GO:0042472
      label: inner ear morphogenesis
    modifier: ABNORMAL
  locations:
  - preferred_term: cochlea
    term:
      id: UBERON:0001844
      label: cochlea
  evidence:
  - reference: PMID:8951055
    reference_title: Pax2 contributes to inner ear patterning and optic nerve trajectory.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      During gestation, the paired box-containing gene Pax2 is expressed in the
      mid-hindbrain area, developing eye and inner ear.
    explanation: >-
      Establishes inner-ear expression, which is the precondition for a dosage
      effect at this site.
  - reference: PMID:10466411
    reference_title: "Renal-coloboma syndrome: a multi-system developmental disorder caused by PAX2 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some patients are affected with vesico-ureteral reflux (VUR), high
      frequency hearing loss, central nervous system (CNS) anomalies, and/or
      genital anomalies, consistent with the expression of PAX2 in these tissues
      during development
    explanation: >-
      Makes the same expression-to-phenotype argument in patients, and names
      high-frequency hearing loss as the auditory outcome.
  downstream:
  - target: Sensorineural hearing impairment
    causal_link_type: DIRECT
phenotypes:
- name: Renal hypoplasia
  category: Renal
  description: >-
    Small kidneys with a reduced nephron complement, usually bilateral, often
    with poor corticomedullary differentiation and increased parenchymal
    echogenicity on ultrasound. The commonest structural finding in the
    syndrome.
  phenotype_term:
    preferred_term: renal hypodysplasia
    term:
      id: HP:0000089
      label: Renal hypoplasia
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The disorder was originally referred to as renal coloboma syndrome and
      characterized by renal hypodysplasia and abnormalities of the optic nerve
    explanation: >-
      Names renal hypodysplasia as one of the two defining features of the
      syndrome.
  sequelae:
  - target: Chronic kidney disease
    description: >-
      The reduced nephron mass is what makes the malformation progressive.
- name: Cystic renal dysplasia
  category: Renal
  description: >-
    Cortical cysts within hypodysplastic kidneys, reported as the hallmark
    imaging appearance in paediatric carriers of PAX2 loss-of-function variants.
  phenotype_term:
    preferred_term: cystic kidney hypodysplasia
    term:
      id: HP:0000800
      label: Cystic renal dysplasia
  evidence:
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Heterozygous inherited or de novo PAX2 LOF variants were detected in 7 of
      301 patients (2.3%), all presenting with bilateral (cystic) kidney
      hypoplasia/dysplasia/hypodysplasia (KHD).
    explanation: >-
      Every variant carrier in this cohort had bilateral cystic kidney
      hypoplasia/dysplasia.
- name: Multicystic kidney dysplasia
  category: Renal
  description: >-
    Reported at the severe end of the structural spectrum, first described in a
    three-generation family carrying a truncating exon 2 deletion.
  phenotype_term:
    preferred_term: Multicystic kidney dysplasia
    term:
      id: HP:0000003
      label: Multicystic kidney dysplasia
  evidence:
  - reference: PMID:16049068
    reference_title: Multicystic dysplastic kidney and variable phenotype in a family with a novel deletion mutation of PAX2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The first presentation of multicystic dysplastic kidney in this syndrome
      is reported.
    explanation: >-
      Reports the phenotype in a molecularly confirmed family; a single family,
      so this is a rare rather than typical finding.
- name: Vesicoureteral reflux
  category: Renal
  description: >-
    Retrograde flow of urine from bladder to ureter, present in the original
    PAX2 kindred and a recurring feature of the syndrome.
  phenotype_term:
    preferred_term: Vesicoureteral reflux
    term:
      id: HP:0000076
      label: Vesicoureteral reflux
  evidence:
  - reference: PMID:10466411
    reference_title: "Renal-coloboma syndrome: a multi-system developmental disorder caused by PAX2 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      some patients are affected with vesico-ureteral reflux (VUR), high
      frequency hearing loss, central nervous system (CNS) anomalies, and/or
      genital anomalies, consistent with the expression of PAX2 in these tissues
      during development
    explanation: >-
      Lists reflux among the recurring features of the syndrome in a review of
      reported patients.
- name: Chronic kidney disease
  category: Renal
  description: >-
    Reduced glomerular filtration rate that develops in childhood or young
    adulthood and progresses; the dominant contributor to morbidity in this
    disorder.
  phenotype_term:
    preferred_term: Chronic kidney disease
    term:
      id: HP:0012622
      label: Chronic kidney disease
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In most individuals, clinically significant renal insufficiency / renal
      failure is reported.
    explanation: >-
      GeneReviews states that clinically significant renal impairment is the
      usual course.
  sequelae:
  - target: Stage 5 chronic kidney disease
- name: Stage 5 chronic kidney disease
  category: Renal
  description: >-
    Kidney failure requiring dialysis or transplantation. In a genetically
    confirmed cohort it developed in 52% at a median age of 14.5 years.
  phenotype_term:
    preferred_term: Stage 5 chronic kidney disease
    term:
      id: HP:0003774
      label: Stage 5 chronic kidney disease
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      End-stage renal disease requiring renal transplant is not uncommon.
    explanation: >-
      Confirms that progression to kidney failure is a common outcome.
- name: Proteinuria
  category: Renal
  description: >-
    Frequently the presenting sign, and the commonest initial manifestation in
    a genetically confirmed cohort.
  phenotype_term:
    preferred_term: Proteinuria
    term:
      id: HP:0000093
      label: Proteinuria
  evidence:
  - reference: PMID:7795640
    reference_title: Mutation of the PAX2 gene in a family with optic nerve colobomas, renal anomalies and vesicoureteral reflux.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We have conducted a mutational analysis of PAX2 in a family with optic
      nerve colobomas, renal hypoplasia, mild proteinuria and vesicoureteral
      reflux.
    explanation: >-
      Records proteinuria as part of the phenotype in the founding kindred.
- name: Albuminuria
  category: Renal
  description: >-
    Albumin loss out of proportion to the stage of chronic kidney disease,
    which is the clinical fingerprint that distinguishes PAX2 nephropathy from
    other causes of cystic kidney hypodysplasia.
  phenotype_term:
    preferred_term: Albuminuria
    term:
      id: HP:0012592
      label: Albuminuria
  evidence:
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      albuminuria (significantly more severe than in patients with (cystic) KHD
      and wildtype PAX2, P < 0.0001), suggesting a proteinuric effect of PAX2
      LOF variants
    explanation: >-
      Quantifies the excess albuminuria relative to a matched structural-disease
      comparison group.
- name: Focal segmental glomerulosclerosis
  category: Renal
  description: >-
    Segmental sclerosis of some glomeruli, which in some families is the entire
    phenotype and presents in adulthood without malformation or eye findings
    (FSGS type 7).
  phenotype_term:
    preferred_term: Focal segmental glomerulosclerosis
    term:
      id: HP:0000097
      label: Focal segmental glomerulosclerosis
  evidence:
  - reference: PMID:24676634
    reference_title: Mutations in PAX2 associate with adult-onset FSGS.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Here, exome sequencing in members of an index family with dominant FSGS
      revealed a nonconservative, disease-segregating variant in the PAX2
      transcription factor gene.
    explanation: >-
      Segregation of a PAX2 allele with dominant FSGS in an index family.
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PAX2 pathogenic variants have been identified in multiple sporadic and
      familial cases of nonsyndromic renal disease including renal hypodysplasia
      and focal segmental glomerulosclerosis.
    explanation: >-
      Places FSGS inside the accepted PAX2 phenotypic spectrum.
- name: Hypertension
  category: Cardiovascular
  description: >-
    Secondary to the reduced nephron mass and progressive kidney disease; a
    standing management target.
  phenotype_term:
    preferred_term: Hypertension
    term:
      id: HP:0000822
      label: Hypertension
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ongoing treatment of hypertension and/or vesicoureteral reflux
    explanation: >-
      GeneReviews lists hypertension as a manifestation requiring ongoing
      treatment, so it is a recognised feature of the disorder.
- name: Uric acid nephrolithiasis
  category: Renal
  description: >-
    Uric acid stones have been reported and are specifically screened for in
    GeneReviews' at-risk evaluation protocol.
  phenotype_term:
    preferred_term: Uric acid nephrolithiasis
    term:
      id: HP:0000791
      label: Uric acid nephrolithiasis
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Uric acid nephrolithiasis has been reported.
    explanation: >-
      GeneReviews records the finding; the phrasing establishes occurrence, not
      frequency.
- name: Optic disc coloboma
  category: Ocular
  description: >-
    A wide, excavated and dysplastic optic disc, variously reported as optic
    nerve coloboma, optic disc pit, morning glory anomaly, or optic nerve
    dysplasia. Congenital and structurally static, but carrying a cumulative
    risk of retinal detachment.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: optic nerve coloboma or dysplasia
    term:
      id: HP:0000588
      label: Optic disc coloboma
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ophthalmologic abnormalities are typically described as optic nerve
      coloboma or dysplasia.
    explanation: >-
      Names the typical ocular lesion of the syndrome.
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common findings reported in this series were abnormal renal
      structure or function (92% of individuals), ophthalmological abnormalities
      (77% of individuals), and hearing loss (7% of individuals).
    explanation: >-
      Supports the FREQUENT band (30-79%). The 77% figure is for ophthalmological
      abnormalities as a class, of which optic nerve coloboma or dysplasia is
      the typical form; a coloboma-specific denominator is not published.
- name: Reduced visual acuity
  category: Ocular
  description: >-
    Visual outcome ranges from normal through subtle changes found only on
    detailed examination to severe impairment.
  phenotype_term:
    preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ophthalmologic abnormalities may significantly impair vision in some
      individuals, while others have subtle changes only noted after detailed
      ophthalmologic examination.
    explanation: >-
      Establishes both that vision loss occurs and that it is variable.
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Consequences of the ocular malformations include decreased visual acuity
      and retinal detachment.
    explanation: >-
      Attributes reduced acuity to the structural ocular malformation rather than
      to a separate process.
- name: Retinal detachment
  category: Ocular
  description: >-
    A recognised complication of the colobomatous disc, and the reason
    protective eyewear is recommended.
  phenotype_term:
    preferred_term: Retinal detachment
    term:
      id: HP:0000541
      label: Retinal detachment
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Use of protective eyewear to prevent retinal detachment.
    explanation: >-
      GeneReviews lists prevention of retinal detachment as a management goal,
      which establishes it as a recognised complication of this disorder.
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Consequences of the ocular malformations include decreased visual acuity
      and retinal detachment.
    explanation: >-
      Names retinal detachment directly as a consequence of the ocular
      malformation.
- name: Retinal coloboma
  category: Ocular
  description: >-
    Reported among the associated posterior-segment findings, alongside scleral
    staphyloma, optic nerve cyst and pigmentary macular dysplasia.
  phenotype_term:
    preferred_term: Retinal coloboma
    term:
      id: HP:0000480
      label: Retinal coloboma
  evidence:
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Associated findings may include a small corneal diameter, retinal
      coloboma, scleral staphyloma, optic nerve cyst and pigmentary macular
      dysplasia.
    explanation: >-
      Lists retinal coloboma among the associated ocular findings; the phrasing
      establishes occurrence, not frequency.
- name: Microcornea
  category: Ocular
  description: >-
    A small corneal diameter, reported among the associated ocular findings.
  phenotype_term:
    preferred_term: small corneal diameter
    term:
      id: HP:0000482
      label: Microcornea
  evidence:
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Associated findings may include a small corneal diameter, retinal
      coloboma, scleral staphyloma, optic nerve cyst and pigmentary macular
      dysplasia.
    explanation: >-
      Names a small corneal diameter among the associated ocular findings.
- name: Hyperuricemia
  category: Metabolic
  description: >-
    Raised serum urate, the biochemical counterpart of the uric acid stones
    GeneReviews screens for in at-risk relatives.
  phenotype_term:
    preferred_term: Hyperuricemia
    term:
      id: HP:0002149
      label: Hyperuricemia
  evidence:
  - reference: PMID:35087773
    reference_title: "PAX2 Mutation-Related Renal Hypodysplasia: Review of the Literature and Three Case Reports."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      sensorineural hearing loss, central nervous system (CNS) malformation,
      hyperuricemia, soft skin, and joint laxity
    explanation: >-
      Lists hyperuricemia among the extrarenal, extraocular features of the
      disorder.
  sequelae:
  - target: Uric acid nephrolithiasis
    description: >-
      The general route from a raised urate load to urate stone formation. Left
      uncited: both nodes are separately sourced in this entry, but no source
      here asserts the step between them in PAX2 carriers specifically.
- name: Sensorineural hearing impairment
  category: Auditory
  description: >-
    High-frequency sensorineural loss, consistent with PAX2 expression in the
    otic vesicle; reported in about 7% of individuals in the locus-specific
    database series.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: high-frequency sensorineural hearing loss
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional clinical findings include high-frequency sensorineural hearing
      loss, soft skin, and ligamentous laxity.
    explanation: >-
      Names the auditory phenotype and its high-frequency character.
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common findings reported in this series were abnormal renal
      structure or function (92% of individuals), ophthalmological abnormalities
      (77% of individuals), and hearing loss (7% of individuals).
    explanation: >-
      The 7% figure supports the OCCASIONAL band (5-29%).
- name: Soft skin
  category: Integumentary
  description: >-
    Reported by GeneReviews among the additional, non-defining findings.
  phenotype_term:
    preferred_term: Soft skin
    term:
      id: HP:0000977
      label: Soft skin
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional clinical findings include high-frequency sensorineural hearing
      loss, soft skin, and ligamentous laxity.
    explanation: >-
      Lists soft skin among the additional clinical findings.
- name: Joint hypermobility
  category: Musculoskeletal
  description: >-
    Ligamentous laxity, reported by GeneReviews among the additional findings.
  phenotype_term:
    preferred_term: ligamentous laxity
    term:
      id: HP:0001382
      label: Joint hypermobility
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Additional clinical findings include high-frequency sensorineural hearing
      loss, soft skin, and ligamentous laxity.
    explanation: >-
      Lists ligamentous laxity among the additional clinical findings.
histopathology:
- name: Oligomeganephronia
  description: >-
    Fewer glomeruli than normal, each enlarged. The histological signature of a
    reduced nephron endowment with compensatory hypertrophy, and the tissue-level
    expression of the developmental arm of the disorder.
  notes: >-
    Left unbound. HistopathologyFindingTerm is reachable only from the NCIT
    Histopathology Result branch, and neither NCIT:C123202 (Oligomeganephronia)
    nor any glomerular-sclerosis term sits under it - checked with
    `runoak -i ols:ncit ancestors -p i` against all thirteen source nodes. HPO
    has no oligomeganephronia term at all.
  evidence:
  - reference: PMID:21654726
    reference_title: Renal coloboma syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Histologically, kidneys exhibit fewer than the normal number of glomeruli
      and these glomeruli are enlarged, a finding called oligomeganephronia.
    explanation: >-
      States the finding and names it.
- name: Focal segmental glomerulosclerosis on biopsy
  description: >-
    Segmental sclerosis of some glomeruli on kidney biopsy, seen both in
    carriers with structurally normal kidneys and in those with hypodysplasia.
  notes: >-
    Left unbound for the same reason as the oligomeganephronia finding above:
    NCIT:C37308 is not reachable from any HistopathologyFindingTerm source node.
    The phenotype-level claim is bound to HP:0000097 under `phenotypes`.
  evidence:
  - reference: PMID:31538321
    reference_title: A novel truncating PAX2 mutation in a boy with renal coloboma syndrome with focal segmental glomerulosclerosis causing rapid progression to end-stage kidney disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Abdominal ultrasound showed no renal and urinary tract malformations and
      kidney biopsy showed FSGS.
    explanation: >-
      A biopsy-proven FSGS lesion in a PAX2 carrier whose imaging showed no
      malformation, which is the podocyte arm presenting alone.
genetic:
- name: PAX2
  presence: Positive
  relationship_type: CAUSATIVE
  association: Renal coloboma syndrome / PAX2-related disorder
  gene_term:
    preferred_term: PAX2
    term:
      id: hgnc:8616
      label: PAX2
  notes: >-
    PAX2 (10q24.31) encodes a paired-box transcription factor expressed in the
    nephric duct, ureteric bud, metanephric mesenchyme, optic stalk, otic
    vesicle and CNS during development. Pathogenic alleles are overwhelmingly
    predicted loss of function and cluster in the paired domain encoded by exons
    2-4; the recurrent c.76dupG (p.Val26Glyfs*28) is the single commonest
    allele, arising in a seven-guanine homopolymer tract that appears
    mutationally unstable, which is why unrelated families share it rather than
    descending from a founder. Whole-gene deletions account for roughly 3% of cases; exon-level
    rearrangements appear not to contribute further.
  evidence:
  - reference: PMID:22213154
    reference_title: Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mutations in the paired-box gene, PAX2, have been identified in
      approximately half of individuals with classic findings of renal
      hypoplasia/dysplasia and abnormalities of the optic nerve.
    explanation: >-
      Establishes PAX2 as the causal gene and gives the diagnostic yield in
      clinically classic cases.
  - reference: PMID:11730657
    reference_title: "Renal-coloboma syndrome: report of a novel PAX2 gene mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The causal relationship between PAX2 gene mutations and renal-coloboma
      syndrome is further supported by this novel mutation.
    explanation: >-
      An independent de novo case supporting causality rather than linkage
      alone.
  - reference: PMID:23756089
    reference_title: Detection of PAX2 deletions and duplications using multiplex ligation-dependent probe amplification.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Large genomic deletions of PAX2 have been identified in 3/90 known RCS
      families, accounting for approximately (3%) of RCS cases.
    explanation: >-
      Quantifies the copy-number contribution referenced in the notes.
  - reference: PMID:23756089
    reference_title: Detection of PAX2 deletions and duplications using multiplex ligation-dependent probe amplification.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of the 46 PAX2 mutation-negative samples tested, none demonstrated
      deletions or duplications in the PAX2 gene.
    explanation: >-
      A negative result: exon-level rearrangements do not explain the
      mutation-negative half of clinically diagnosed cases.
  - reference: PMID:21326282
    reference_title: "Clinical utility gene card for: renal coloboma (Papillorenal) syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common recurrent mutations are frameshift mutations within a
      homoguanine stretch (7Gs) in exon 2
    explanation: >-
      Identifies the recurrent allele class and the sequence context that makes
      it recurrent, which is the basis for the c.76dupG hotspot claim in the
      notes.
  - reference: PMID:9106533
    reference_title: Further delineation of renal-coloboma syndrome in patients with extreme variability of phenotype and identical PAX2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These results suggest that a sequence of seven Gs in PAX2 exon 2 may be
      particularly prone to mutation.
    explanation: >-
      The original proposal that the exon 2 homoguanine tract is a mutational
      hotspot, which is why one allele recurs across unrelated families.
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  expressivity: VARIABLE
  description: >-
    Autosomal dominant. Expressivity is highly variable, including between
    monozygotic twins and between family members carrying the same allele: a
    parent may carry the variant and have only albuminuria or FSGS while the
    child has bilateral cystic hypodysplasia. About 65% of probands have a
    negative family history, explained by de novo variants, unrecognised mild
    disease in a parent, or parental germline mosaicism - both maternal and
    paternal germline mosaicism have been documented.
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Approximately 65% of probands with a documented PAX2 pathogenic variant
      have a negative family history.
    explanation: >-
      Quantifies the proportion of apparently sporadic presentations.
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Both maternal and paternal germline mosaicism, with unaffected parents
      having more than one affected child with a pathogenic variant, have been
      reported.
    explanation: >-
      Documents germline mosaicism, which changes the recurrence risk quoted to
      apparently unaffected parents.
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Full penetrance for a kidney phenotype, but variable expressivity was
      observed in our 10 carriers of a PAX2 LOF variant, including parents who
      were not necessarily affected by CAKUT but by albuminuria or FSGS.
    explanation: >-
      Supports full penetrance for some kidney phenotype alongside markedly
      variable expressivity within families.
  - reference: PMID:22660956
    reference_title: Discordant phenotype in monozygotic twins with renal coloboma syndrome and a PAX2 mutation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The case study involves two monozygotic twin sisters with RCS showing
      highly discordant phenotypes.
    explanation: >-
      Reports the discordant monozygotic twin pair itself, which is the
      observation this claim rests on.
  - reference: PMID:22660956
    reference_title: Discordant phenotype in monozygotic twins with renal coloboma syndrome and a PAX2 mutation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In both patients, a novel de novo mutation of PAX2 was detected, which
      leads to the substitution of a highly conserved cysteine (p.C52Y).
    explanation: >-
      Establishes that both twins carry the same PAX2 allele, which is what
      makes the discordance evidence about expressivity rather than about which
      variant was inherited.
  - reference: PMID:9106533
    reference_title: Further delineation of renal-coloboma syndrome in patients with extreme variability of phenotype and identical PAX2 mutations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Unexpectedly, extreme variability in clinical presentation was observed
      between a mother, her son, and an unrelated patient, all of whom had the
      same PAX2 mutation as previously described in two siblings with
      renal-coloboma syndrome.
    explanation: >-
      Variability across carriers of one identical allele, within and between
      families, which is what rules out the allele as the determinant of
      severity.
mechanistic_hypotheses:
- hypothesis_group_id: podocyte_fitness_pathway
  hypothesis_label: PAX2 nephropathy as a second, postnatal podocyte disease
  status: EMERGING
  description: >-
    The conventional model treats PAX2 kidney disease as purely developmental:
    fewer nephrons, then hyperfiltration, then chronic kidney disease. An
    emerging model adds a second arm in which PAX2 variants reduce the
    resilience of mature podocytes and parietal epithelial cells, producing
    albuminuria out of proportion to the structural lesion and, in some
    families, FSGS with no malformation at all. The clinical observation that
    motivates it is the excess albuminuria in PAX2 carriers relative to
    stage-matched CAKUT controls; the experimental support is patient-derived
    iPSC podocytes whose vulnerability to injury is corrected by repairing the
    variant. It matters therapeutically because the developmental arm is fixed
    at birth while podocyte injury might be modifiable.
  evidence:
  - reference: PMID:41278347
    reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      PAX2 nephropathy may be an exception, because podocyte injury might be
      partially modifiable, raising the prospect of prolonging nephron survival
      in patients with milder dysplasia.
    explanation: >-
      States the therapeutic consequence that makes the two-pathway model worth
      distinguishing; phrased by the authors as a prospect, not a result.
differential_diagnoses:
- name: PRR12-related neuroocular syndrome
  description: >-
    Also combines eye malformation with renal anomalies, but the ocular lesion
    is globe-size and anterior-segment rather than optic-nerve, iris coloboma
    occurs, renal involvement affects a minority and is structural rather than
    progressive, and developmental delay is common.
  distinguishing_features:
  - Iris coloboma has never been reported in PAX2-related disorder, so its presence argues against this diagnosis.
  - Renal involvement in PAX2-related disorder is near-obligate and progressive, rather than structural and static.
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Iris colobomas have not been reported in any individual with PAX2–related
      disorder.
    explanation: >-
      Supplies the near-absolute discriminator against colobomatous syndromes
      that involve the iris.
- name: Isolated congenital anomalies of the kidney and urinary tract
  description: >-
    CAKUT without ocular findings. PAX2 loss-of-function variants are found in
    a small but non-trivial fraction of such patients, so absence of an eye
    finding does not exclude PAX2.
  distinguishing_features:
  - Cystic kidney hypodysplasia combined with albuminuria disproportionate to the CKD stage should prompt PAX2 testing even without ocular findings.
  evidence:
  - reference: PMID:41278347
    reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Clinically, the combination of cystic dysplasia and albuminuria
      disproportionate to chronic kidney disease stage should prompt
      consideration of PAX2 testing.
    explanation: >-
      Gives the testing trigger that separates PAX2 nephropathy from
      undifferentiated CAKUT.
- name: HNF1B-related renal disease
  description: >-
    The other common monogenic cause of cystic kidney dysplasia. It diverges
    downstream: HNF1B tends to a tubulointerstitial phenotype, often without
    significant proteinuria.
  distinguishing_features:
  - Significant albuminuria and FSGS point to PAX2 rather than HNF1B.
  evidence:
  - reference: PMID:41278347
    reference_title: "PAX2-Associated Kidney Dysplasia and Podocyte Injury: 2 Faces of a Monogenic Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      In addition, HNF1B pathogenic variants may cause a tubulointerstitial
      phenotype referred to as autosomal dominant tubulointerstitial kidney
      disease, often without relevant proteinuria.
    explanation: >-
      States the downstream divergence that distinguishes the two cystic
      dysplasia genes clinically.
diagnosis:
- name: PAX2 molecular genetic testing
  presence: Positive
  description: >-
    The diagnosis is established by finding a heterozygous pathogenic PAX2
    variant in a proband with characteristic renal and/or eye findings.
    Sequencing of the coding exons is the primary test; copy-number analysis
    adds the roughly 3% of cases caused by whole-gene deletion.
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of PAX2-related disorder is established in a proband with
      the characteristic renal and/or eye findings by the identification of a
      heterozygous pathogenic variant in PAX2 by molecular genetic testing.
    explanation: >-
      States the diagnostic standard.
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Among individuals with apparently nonsyndromic renal hypodysplasia and in
      families with autosomal dominant isolated focal segmental
      glomerulosclerosis, pathogenic variants in PAX2 have been identified in
      approximately 8% and 4%, respectively.
    explanation: >-
      Gives the diagnostic yield in the two non-syndromic presentations where
      PAX2 testing is worth doing.
  - reference: PMID:37123577
    reference_title: Renal Coloboma Syndrome-An Autosomal Dominant Genetic Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It has been estimated that approximately 10% of children with hypoplastic
      kidneys may have renal coloboma syndrome.
    explanation: >-
      A pre-test probability for the commonest presenting finding; the review
      reports it as an estimate rather than a measured yield.
  - reference: PMID:35087773
    reference_title: "PAX2 Mutation-Related Renal Hypodysplasia: Review of the Literature and Three Case Reports."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a Japanese study, 38 of 457 patients (6.5%) with congenital anomalies
      of kidney and urinary tract (CAKUT) possessed the PAX2 mutation
    explanation: >-
      A second ascertainment denominator, from an unselected CAKUT cohort in a
      different population.
- name: Dilated ophthalmologic examination
  presence: Positive
  description: >-
    Dilated fundoscopy for optic nerve head dysplasia and retinal coloboma.
    GeneReviews includes it in the battery used to assess an at-risk relative in
    whom no PAX2 pathogenic variant has been found. The ocular finding is what
    makes a renal presentation syndromic, which is the distinction this entry's
    differential diagnoses turn on.
  diagnosis_term:
    preferred_term: dilated ophthalmologic examination
    term:
      id: NCIT:C38060
      label: Eye Examination
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      perform dilated ophthalmologic examination, renal ultrasound examination,
      tests of renal function, uric acid levels, and urinalysis; measure blood
      pressure.
    explanation: >-
      GeneReviews names dilated ophthalmologic examination in the evaluation of
      an at-risk relative in whom no PAX2 pathogenic variant has been found.
- name: Renal ultrasonography
  presence: Positive
  description: >-
    Ultrasound assessment of kidney size, echogenicity and cystic change, which
    is how renal hypodysplasia is detected in a relative who has no symptoms.
  diagnosis_term:
    preferred_term: renal ultrasound examination
    term:
      id: NCIT:C159885
      label: Renal Ultrasound
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      perform dilated ophthalmologic examination, renal ultrasound examination,
      tests of renal function, uric acid levels, and urinalysis; measure blood
      pressure.
    explanation: >-
      GeneReviews names renal ultrasound examination in the same at-risk-relative
      evaluation.
- name: Renal function, uric acid and urinalysis
  presence: Abnormal
  description: >-
    Biochemical assessment of the kidney: serum creatinine and estimated GFR for
    excretory function, urinalysis for the albuminuria that is disproportionate
    in this disorder, and serum uric acid. Blood pressure is measured alongside.
    This entry separately records hyperuricemia and uric acid nephrolithiasis as
    phenotypes; GeneReviews does not state why uric acid is in the panel.
  markers: serum creatinine, estimated GFR, serum uric acid, urinalysis, blood pressure
  diagnosis_term:
    preferred_term: tests of renal function
    term:
      id: NCIT:C74972
      label: Renal Function Test
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      perform dilated ophthalmologic examination, renal ultrasound examination,
      tests of renal function, uric acid levels, and urinalysis; measure blood
      pressure.
    explanation: >-
      GeneReviews names tests of renal function, uric acid levels, urinalysis and
      blood pressure in the at-risk-relative evaluation. The uric acid clause is
      why this entry carries hyperuricemia and uric acid nephrolithiasis.
treatments:
- name: Antihypertensive and Antiproteinuric Therapy
  description: >-
    Ongoing pharmacological control of blood pressure, with antiproteinuric
    measures, to slow loss of an already reduced nephron mass. There is no
    PAX2-specific pharmacotherapy; management follows general chronic kidney
    disease practice, and the 2025 CAKUT cohort specifically recommends
    antiproteinuric measures in PAX2 variant carriers.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: antihypertensive agent
      term:
        id: NCIT:C270
        label: Antihypertensive Agent
  target_mechanisms:
  - target: Glomerular Hyperfiltration and Progressive Nephron Loss
    description: >-
      Lowering glomerular pressure and proteinuria is aimed at the
      hyperfiltration injury rather than at the malformation, which is fixed.
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ongoing treatment of hypertension and/or vesicoureteral reflux
    explanation: >-
      GeneReviews management section names ongoing hypertension treatment; it
      does not name a drug class, so the agent binding is left at the class
      level.
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In patients with CAKUT and PAX2 LOF variants, close monitoring and
      antiproteinuric measures should be considered, and PAX2 variant testing is
      recommended in living related donors.
    explanation: >-
      A recommendation specific to PAX2 carriers; it is the authors' conclusion
      from an observational cohort, not a trial result.
- name: Dialysis
  description: >-
    Renal replacement therapy for kidney failure, often required in childhood or
    early adulthood.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: Dialysis
    term:
      id: NCIT:C15221
      label: Dialysis
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      renal replacement therapy (dialysis and/or renal transplantation) for
      end-stage renal disease
    explanation: >-
      GeneReviews names dialysis as management for end-stage renal disease in
      this disorder.
- name: Kidney Transplantation
  description: >-
    Definitive treatment for kidney failure. Because carrier relatives may have
    only albuminuria or FSGS, PAX2 testing is recommended before accepting a
    living related donor.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Kidney Transplantation
    term:
      id: NCIT:C15265
      label: Kidney Transplantation
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      End-stage renal disease requiring renal transplant is not uncommon.
    explanation: >-
      Establishes transplantation as a routine outcome of the disorder's course.
  - reference: PMID:41278353
    reference_title: Presentation of Patients With Congenital Anomalies of the Kidney and Urinary Tract and PAX2 Loss-of-Function Variants and Implications for Clinical Management.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PAX2 variant testing is recommended in living related donors.
    explanation: >-
      Supports the donor-screening caveat attached to this treatment.
- name: Low Vision Aids
  description: >-
    Optical and educational adaptation for significant visual impairment from
    optic nerve dysplasia.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: low vision aids
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Reduced visual acuity
    term:
      id: HP:0007663
      label: Reduced visual acuity
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      low vision aids for significant visual impairment
    explanation: >-
      GeneReviews management recommendation. NCIT has no clinical-action term
      for low vision aids, so the action is bound at Supportive Care and the
      specificity is carried in preferred_term.
- name: Protective Eyewear
  description: >-
    Preventive measure against retinal detachment in eyes with colobomatous or
    dysplastic discs.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: protective eyewear
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Retinal detachment
    term:
      id: HP:0000541
      label: Retinal detachment
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Use of protective eyewear to prevent retinal detachment.
    explanation: >-
      GeneReviews lists this under prevention of secondary complications.
- name: Genetic Counseling and Cascade Testing
  description: >-
    Counselling for 50% recurrence risk, with molecular testing offered to
    at-risk relatives and clinical evaluation where no familial variant is
    known. Germline mosaicism means apparently unaffected parents of a child
    with a de novo variant are not at zero recurrence risk.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Offer molecular genetic testing if a PAX2 pathogenic variant has been
      identified in an affected family member.
    explanation: >-
      GeneReviews cascade-testing recommendation.
- name: Nephrology Surveillance
  description: >-
    Periodic nephrology follow-up measuring renal function and blood pressure.
    The developmental nephron deficit is fixed at birth, so surveillance watches
    the hyperfiltration injury that follows it, which is the modifiable arm. It
    does not itself act on that node: it detects rising creatinine, blood
    pressure and albuminuria early enough for the antiproteinuric therapy above
    to do so.
  action_category: MONITORING
  treatment_term:
    preferred_term: monitoring of renal function and blood pressure
    term:
      id: NCIT:C74972
      label: Renal Function Test
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Follow up by a nephrologist to monitor renal function and blood pressure
      and an ophthalmologist to monitor vision, with periodic audiometric
      evaluations.
    explanation: >-
      GeneReviews surveillance recommendation; this entry covers its nephrology
      clause.
- name: Ophthalmologic Surveillance
  description: >-
    Ophthalmology follow-up to monitor vision. GeneReviews pairs it with
    protective eyewear against retinal detachment, which this entry records as a
    separate treatment; it does not state an interval, and none is asserted
    here.
  action_category: MONITORING
  treatment_term:
    preferred_term: monitoring of vision
    term:
      id: NCIT:C38060
      label: Eye Examination
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Follow up by a nephrologist to monitor renal function and blood pressure
      and an ophthalmologist to monitor vision, with periodic audiometric
      evaluations.
    explanation: >-
      GeneReviews surveillance recommendation; this entry covers its
      ophthalmology clause.
- name: Periodic Audiometric Evaluation
  description: >-
    Audiometry measuring the high-frequency sensorineural hearing loss that
    follows the otic patterning defect; it detects that phenotype rather than
    acting on it. GeneReviews recommends it periodically rather than as a single
    assessment; it does not state a starting age or interval, and none is
    asserted here.
  action_category: MONITORING
  treatment_term:
    preferred_term: periodic audiometric evaluation
    term:
      id: NCIT:C38036
      label: Audiometric Test
  evidence:
  - reference: PMID:20301624
    reference_title: PAX2-Related Disorder.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Follow up by a nephrologist to monitor renal function and blood pressure
      and an ophthalmologist to monitor vision, with periodic audiometric
      evaluations.
    explanation: >-
      GeneReviews surveillance recommendation; this entry covers its audiometry
      clause, which is what the hearing-loss arm of this entry is monitored by.
animal_models:
- name: Pax2 null mouse (homozygous)
  species: Mouse
  genotype: Pax2 homozygous null
  description: >-
    The germline knockout is anephric and shows the ocular counterpart of the
    human lesion, which is what established PAX2 as required for both organ
    programmes. Homozygous loss is more severe than any human genotype, so the
    model demonstrates the requirement rather than reproducing the disease.
  publication: PMID:8575306
  modeled_mechanisms:
  - target: Increased Ureteric Bud Apoptosis and Reduced Branching
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      In the homozygous null the ureteric bud is absent altogether, so kidney
      development never begins - the extreme of the branching defect rather than
      the graded reduction seen in patients.
    limitations: >-
      Human disease is heterozygous and produces a small maldeveloped kidney,
      not agenesis; the homozygous model overshoots the human lesion.
    evidence:
    - reference: PMID:8575306
      reference_title: Pax-2 controls multiple steps of urogenital development.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We report here that Pax-2 homozygous mutant newborn mice lack kidneys,
        ureters and genital tracts.
      explanation: >-
        Establishes the absolute requirement for Pax-2 in ureter and kidney
        formation, upstream of the branching step this node describes.
  - target: Failure of Optic Fissure Closure
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      The null mouse fails to close the optic fissure and develops coloboma,
      which is the same developmental step that fails in patients.
    evidence:
    - reference: PMID:8951055
      reference_title: Pax2 contributes to inner ear patterning and optic nerve trajectory.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Furthermore, Pax2 mutants show extension of the pigmented retina into
        the optic stalks and failure of the optic fissure to close resulting in
        coloboma.
      explanation: >-
        Directly reports failed fissure closure and coloboma in the model.
  evidence:
  - reference: PMID:8575306
    reference_title: Pax-2 controls multiple steps of urogenital development.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Mesenchyme of the nephrogenic cord fails to undergo epithelial
      transformation and is not able to form tubules in the mesonephros.
    explanation: >-
      Supports treating the null mouse as informative for PAX2-dependent nephric
      development, the process disrupted in the human disorder.
- name: Pax2 1Neu heterozygous mouse
  species: Mouse
  genotype: Pax2(1Neu) heterozygous
  description: >-
    An ENU-derived allele carrying the guanine insertion equivalent to the
    recurrent human c.76dup. The heterozygous state matches the human genotype,
    which makes this the closest available model of the renal arm.
  publication: PMID:10587573
  modeled_mechanisms:
  - target: Increased Ureteric Bud Apoptosis and Reduced Branching
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Heterozygous fetal kidneys show the increased apoptosis and reduced
      branching that the node asserts, at the correct gene dosage.
    readouts:
    - name: Apoptotic cell death in fetal kidney
      target: Increased Ureteric Bud Apoptosis and Reduced Branching
      direction: INCREASED
      interpretation: >-
        Direct measurement of the cell-death increase this mechanism node
        claims.
      evidence:
      - reference: PMID:10587573
        reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Heterozygous 1Neu mice showed increased apoptotic cell death during
          fetal kidney development
        explanation: >-
          Reports the apoptosis measurement in the heterozygous fetal kidney.
    - name: Fetal kidney size and nephron number at E15
      target: Increased Ureteric Bud Apoptosis and Reduced Branching
      direction: DECREASED
      interpretation: >-
        Structural correlate of reduced branching, measured at the stage when
        branching is active.
      evidence:
      - reference: PMID:10587573
        reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          At E15, heterozygous mutant kidneys were approximately 60% of the size
          of wild-type littermates, and the number of nephrons was strikingly
          reduced.
        explanation: >-
          Quantifies both readouts in the same animals.
    evidence:
    - reference: PMID:10587573
      reference_title: "Primary renal hypoplasia in humans and mice with PAX2 mutations: evidence of increased apoptosis in fetal kidneys of Pax2(1Neu) +/- mutant mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        These findings support the notion that heterozygous mutations of PAX2
        are associated with increased apoptosis and reduced branching of the
        ureteric bud, due to reduced PAX2 dosage during a critical window in
        kidney development.
      explanation: >-
        The authors' own statement that the model speaks to this mechanism at
        human-equivalent gene dosage.
experimental_models:
- name: Patient-derived iPSC podocytes carrying PAX2 p.G189R
  experimental_model_type: IPSC_DERIVED_MODEL
  description: >-
    Induced pluripotent stem cells from a member of a family with adult-onset
    autosomal dominant FSGS carrying the PAX2 p.G189R octapeptide-domain
    variant, differentiated into podocytes. CRISPR-Cas9 correction of the point
    mutation provides an isogenic control, making this the cleanest available
    test of whether the variant itself causes the podocyte defect.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: podocyte
    term:
      id: CL:0000653
      label: podocyte
  publication: PMID:30998089
  modeled_mechanisms:
  - target: Reduced Podocyte Fitness
    relationship: RESCUES
    fidelity: MODERATE
    description: >-
      Podocyte motility was altered in patient-derived cells and restored by
      correcting the variant, isolating PAX2 as the cause of the podocyte
      phenotype.
    limitations: >-
      The readout is motility in culture, not albuminuria or glomerular
      sclerosis, and the model carries a single missense allele from one family
      rather than the loss-of-function alleles typical of the syndromic
      presentation.
    readouts:
    - name: Podocyte motility
      target: Reduced Podocyte Fitness
      direction: RESTORED
      interpretation: >-
        Correction of the variant restores the cellular behaviour that the
        variant altered.
      evidence:
      - reference: PMID:30998089
        reference_title: CRISPR-Cas9-Mediated Correction of the G189R-PAX2 Mutation in Induced Pluripotent Stem Cells from a Patient with Focal Segmental Glomerulosclerosis.
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Editing the PAX2 p.G189R mutation restored podocyte motility, which
          was altered in podocytes derived from patient iPSCs.
        explanation: >-
          Reports the measurement and its direction in the isogenic comparison.
    evidence:
    - reference: PMID:30998089
      reference_title: CRISPR-Cas9-Mediated Correction of the G189R-PAX2 Mutation in Induced Pluripotent Stem Cells from a Patient with Focal Segmental Glomerulosclerosis.
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Here, we efficiently corrected this point mutation in patient-derived
        induced pluripotent stem cells (iPSCs) by means of CRISPR-Cas9-based
        homology-directed repair.
      explanation: >-
        Establishes the isogenic-correction design that makes this model
        informative for the podocyte node.

📚

References & Deep Research

References

1

PMID:20301624

PAX2-Related Disorder.

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 (2)

Record notes

Naming: this entry keeps the MONDO binding and file slug assigned by the curation queue (MONDO:0007352, renal coloboma syndrome) while using the current GeneReviews term, PAX2-related disorder, as the preferred display term. Whether the optic nerve lesion is a true coloboma or a dysplasia has been argued since the 1990s and is the reason both "renal coloboma" and "papillorenal" names persist; Bower et al. record the dispute explicitly. Related entries: Renal_Agenesis carries PAX2 as a syndromic CAKUT gene row and Familial_Vesicoureteral_Reflux names PAX2 among syndromic VUR genes. Both are cross-references, not subtype relationships - this is a leaf disease entry with a single causal gene. Four phenotypes are deliberately left off the pathograph because no source here supports a mechanism for them: microcornea, soft skin, joint hypermobility, and hyperuricemia's own upstream cause. They are reported associations of PAX2-related disorder, not steps anyone has traced, and an unconnected node is the honest representation of that. Scoped out deliberately: CNS/corpus callosum anomalies, genital anomalies and cataract are listed in the deep-research report but are not curated here. The report itself qualifies them as occurring "in some families" and as "less common findings", and gives no frequency, cohort or denominator that could be quoted, so there is nothing to attach an evidence snippet to. Two of the three CURIEs the report offers for them are also wrong in the way described below: HP:0002190, offered for corpus callosum anomalies, is Choroid plexus cyst, and HP:0000083, offered for genital anomalies, is Renal insufficiency. Only HP:0000518 (Cataract) is named correctly. Adding these would need a primary source with a frequency, not the report. Provenance caveat on the deep-research input: the Perplexity report's citations all resolved (22/22), but its term validation was unreliable - 29 of the 56 CURIE labels it offered named a different term than the report claimed, among them HP:0000588/HP:0000589 inverted, UBERON:0001626 offered as "optic nerve" when UBERON calls it left coronary artery, and HGNC:8619 offered as PAX2 when that identifier is PAX5. Every ontology binding in this entry was therefore re-derived with OAK against the configured adapters and none was lifted from the report. The report also cites "PMID:8787321" for a 2022 Frontiers in Pediatrics review; that is a PMC identifier written as a PMID, and PMID:8787321 is an unrelated 1995 French paper on inguinal hernia repair. The intended article is PMID:35087773, which this entry cites instead.

Create: Renal Coloboma Syndrome · 2026-09-09T23:18:45Z · View source

First curation of renal coloboma syndrome (PAX2-related disorder, MONDO:0007352) as a leaf Disease entry; stub deleted. Deep research: one Perplexity run, research/Renal_Coloboma_Syndrome-deep-research-perplexity.md. The provider's default sonar-deep-research model could not complete through this environment's egress proxy — three runs each died at 5m05s with 'Server disconnected without sending a response', which is a hard ~300s tunnel cap rather than an API failure (a direct curl to the same model returned 200 at 256s). Passing --param model=sonar-reasoning-pro kept Perplexity as the provider and completed in 197s. dr_fallback='--fallback' was tried first and did not help: it triggers only on missing credentials, not a runtime transport failure. Report reference validation: 22/22 references resolved, 0 unresolved, confabulation_rate 0.0, 18/22 judged on topic, 0 quotes checked. just preflight-dr returned PASS (PAX2 mentioned 79 times, OMIM 120330 matching MONDO). Term validation on that report was poor and none of its CURIEs was used: 29 of 56 offered labels named a different term than the report claimed, including HP:0000588/HP:0000589 inverted, UBERON:0001626 offered as optic nerve (it is left coronary artery), CL:0002511 offered as parietal epithelial cell, and HGNC:8619 offered as PAX2 (that identifier is PAX5). Every binding in the entry was re-derived with runoak against ols:hp, ols:go, ols:cl, ols:uberon and ols:ncit; the caveat is recorded in the entry notes. Report reference accounting. All PMIDs the report cites, plus its PMC ids resolved through the NCBI ID converter, were reviewed. Used: 20301624 (GeneReviews), 10466411, 7795640, 8575306, 8951055, 22213154, 39994403, 41278347, 41278353, 16049068, 11730657, 23756089, 10587573, 24676634, 30998089, 21654726, 21326282, 9106533, 35087773, 37123577, 37628926, 31538321. Deliberately not used: PMID:8589702 (Sanyanusin, Hum Mol Genet 1995 — fetched, but the record carries no abstract body so nothing is quotable; the companion Nat Genet paper PMID:7795640 makes the same claim, and the empty cache file was not committed); PMID:27226968 and PMID:31692565 (single-family and single-case reports whose only claims — variable expressivity, a novel allele — are already carried by stronger sources); and 'PMID:8787321', which the report cites for a 2022 Frontiers in Pediatrics review but is a PMC id written as a PMID — PMID:8787321 is a 1995 French paper on inguinal hernia repair, and the intended article PMID:35087773 is cited instead. Content: an eight-node pathograph running PAX2 haploinsufficiency to four organ arms — ureteric-bud apoptosis and reduced branching to renal hypodysplasia to hyperfiltration and CKD; reduced podocyte fitness to FSGS and albuminuria; failed optic fissure closure to optic nerve head dysplasia and retinal coloboma; and otic vesicle patterning failure to high-frequency sensorineural hearing loss. Four phenotypes (microcornea, soft skin, joint hypermobility, hyperuricemia) are left unconnected on purpose, with the reason in the entry notes, because no source here traces a mechanism to them. The ocular node declares conforms_to ocular_morphogenesis_failure#Failure of Optic Fissure Closure. 20 phenotypes with HP bindings, PAX2 genetic record (hgnc:8616), autosomal dominant inheritance with germline mosaicism, a mechanistic_hypotheses entry for the emerging podocyte-fitness arm, three differential diagnoses, six treatments, two animal models (Pax2 null, Pax2(1Neu) heterozygous) and one patient-iPSC podocyte model, all with modeled_mechanisms links and readouts. Two histopathology findings (oligomeganephronia, FSGS on biopsy) were left with no finding_term and a recorded reason: HistopathologyFindingTerm is reachable only from the NCIT Histopathology Result branch, and neither NCIT:C123202 nor NCIT:C37308 nor NCIT:C96239 nor NCIT:C120888 is reachable from any of its thirteen source nodes (checked with runoak ancestors -p i). Validation: just validate, just validate-terms, just count-verified-snippets (100/100 verified), just check-duplicate-keys, just check-entity-refs, just check-causal-targets, just check-qualifier-terms, just check-enum-values, just check-stubs, just check-folded-hyphens, just check-snippet-length, just check-title-snippets, just check-snippet-grading, just check-reference-titles, just list-gene-term-mismatches, and the authoritative just validate-disorders — all pass.

Perplexity ▸

1. Disease Information

sonar-reasoning-pro 52 citations 2026-09-09T20:04:05.793014

1. Disease Information

Definition and clinical overview

Renal coloboma syndrome (OMIM 120330) is a congenital developmental disorder defined by the combination of structural kidney abnormalities (typically bilateral renal hypodysplasia) and optic nerve malformations (classically optic nerve coloboma or dysplasia).[46][49][50][33][36]
Consequences of renal hypodysplasia include hypertension, proteinuria, renal insufficiency, and a high risk of progression to end‑stage kidney disease (ESKD).[33][36][31][38]
Ocular anomalies range from subtle optic disc dysplasia to large optic nerve colobomas or “morning glory” disc anomalies, with visual outcomes ranging from normal vision to severe visual impairment and blindness.[33][36][42][44]
The disorder is now typically conceptualized as PAX2‑related disorder, encompassing classic RCS plus broader renal and ocular phenotypes, including CAKUT (congenital anomalies of the kidney and urinary tract) and hereditary focal segmental glomerulosclerosis (FSGS) type 7.[2][16][22][28][63]

Key identifiers and classification

OMIM: 120330 (Renal coloboma syndrome).[46][49][54][60]
Orphanet: ORPHA:1475 (Renal coloboma syndrome).[46][47][57][60]
MONDO: MONDO:0007352 (Renal Coloboma Syndrome).[51][52][53][56][60]
MedGen: C1852759 (Renal coloboma syndrome / PAX2‑related disorder).[41][51][52][46]
Disease Ontology: DOID:0090006 (renal coloboma syndrome).[60]
UMLS: C1852759.[46][41]
ICD‑10‑CM: Q60.4 (renal hypoplasia) is listed as an alternative ID in the Disease Ontology entry for RCS.[60]

Synonyms and alternative names

Commonly used synonyms include:[49][50][58][60][51][52]

Papillorenal syndrome / papillo‑renal syndrome
Papillorenal (papillo‑renal) syndrome with macular abnormalities
Optic nerve coloboma with renal disease
Coloboma of optic nerve with renal disease
Optic coloboma, vesicoureteral reflux, and renal anomalies
CAKUT with or without ocular abnormalities
Renal‑coloboma syndrome (RCS)

Data sources

Most information derives from aggregated disease‑level resources (OMIM, Orphanet, GeneReviews, MedGen, GARD, Disease Ontology) and published case series and cohort studies rather than individual EHR‑level datasets.[46][49][50][16][33][36][20]
Key narrative and management information comes from GeneReviews (PAX2‑Related Disorder, major revision 2025) and expert reviews.[16][17][29][33][36]

2. Etiology

2.1 Primary causal factors

RCS/PAX2‑related disorder is predominantly caused by heterozygous loss‑of‑function variants in PAX2, a paired box transcription factor gene on chromosome 10q24.[46][49][50][26][14][63]
Mutations in PAX2 are identified in approximately 50% of individuals with classic renal hypodysplasia and optic nerve abnormalities meeting historical criteria for RCS.[46][20][26][44]
PAX2 variants are the only well‑established genetic cause of classic RCS to date.[26][49][50]

Direct quote (human clinical, 1999 AJHG, PMID:10466411):

“Optic nerve coloboma combined with renal disease, also called renal‑coloboma syndrome (… OMIM), … results from autosomal dominant mutations in the PAX2 gene.”[49]

PAX2‑related disorder also includes nonsyndromic CAKUT (kidney hypoplasia, vesicoureteral reflux, multicystic dysplastic kidney) and hereditary FSGS7.[2][22][63][75][28]

2.2 Genetic risk factors

Causal variants

Multiple studies and locus‑specific databases have catalogued at least 30–40 unique PAX2 mutations in RCS families.[20][23][24][25]
An updated literature review identified 33 unique PAX2 mutations across 53 families, with the recurrent hotspot c.76dupG (p.V26Gfs*28) in exon 2 reported in ~40% of cases in one series.[20][19][22][25]
Pathogenic variants include frameshift, nonsense, splice‑site, missense, and small multi‑nucleotide deletions/insertions, predominantly in exons 2–4 encoding the paired domain and in the homeodomain.[26][22][23][25]

Direct quote (review; human clinical, Frontiers in Pediatrics 2022, PMID:8787321):

“These mutations are mostly located at the paired domain (exons 2–4) and the homeodomain. The most common type of pathogenic variant is frameshift mutation, and the most frequently reported mutation is c.76dupG (p.V26Gfs*28).”[22]

ClinGen curation supports PAX2 haploinsufficiency as the pathogenic dosage mechanism.[14]

Penetrance and expressivity

PAX2‑related disorder is highly penetrant: renal structural or functional abnormalities are present in ~92% and ophthalmologic abnormalities in ~77% of mutation carriers in GeneReviews and MedGen datasets.[16][41][22]
Expressivity is strikingly variable, even among individuals carrying identical mutations, with intra‑familial variability ranging from severe bilateral renal hypodysplasia and blindness to mildly impaired renal function or isolated optic disc abnormalities.[30][33][36][24]

2.3 Environmental and lifestyle risk factors

Specific environmental or lifestyle risk factors for developing RCS are not identified, as PAX2‑related disease is primarily a monogenic, autosomal dominant disorder.[16][46][49]
However, progression of kidney disease in affected individuals is likely influenced by general CKD modifiers such as hypertension, proteinuria, and possibly nephrotoxic exposures, as inferred from CKD literature and highlighted in clinical reviews.[33][36][29][38]

2.4 Protective factors

No specific genetic protective alleles or environmental protective factors have been defined for RCS/PAX2‑related disorder.[16][22][29][63]
Standard CKD protective measures (blood pressure control, RAAS blockade, avoidance of nephrotoxins) are extrapolated as beneficial but have not been formally studied specifically in PAX2 cohorts.[33][36][29]

2.5 Gene–environment interactions

Formal gene–environment interaction studies in PAX2‑related disorder have not been reported, and current understanding centers on gene‑driven developmental defects with secondary environmental modulation of CKD progression.[63][22][29][36]

3. Phenotypes

Key human phenotypes are summarized from Orphanet, MedGen, GARD, GeneReviews, and clinical series.[46][47][41][31][33][36][20][44][43]

3.1 Major renal phenotypes

Renal hypodysplasia / hypoplasia
Phenotype type: structural kidney abnormality (clinical sign).
HPO term: Renal hypodysplasia (HP:0000089); Small kidney (HP:0000128).
Characteristics: Usually bilateral, often detected in childhood via ultrasound or CKD workup; severity is highly variable.[33][36][42][46]
Frequency: Reported as the most common renal manifestation, present in ~65% or more of affected individuals in series and >90% in mutation carriers when broader kidney abnormalities are included.[36][22][16][41]
Progression: Frequently progressive to CKD and ESKD; age at ESKD highly variable.[33][35][36][38]
QoL impact: Progressive CKD requiring dialysis or transplant substantially impairs physical functioning and long‑term health.[33][36][35][38]
Chronic kidney disease and end‑stage renal disease (ESRD/ESKD)
Phenotype type: laboratory abnormality / systemic disease.
HPO: Chronic kidney disease (HP:0000112); End‑stage renal failure (HP:0003774).
Characteristics: Proteinuria, reduced GFR, hypertension; many patients progress to ESRD, often in childhood or young adulthood.[33][36][31][38][29]
Frequency: One article aimed at clinicians reports that approximately 33% of RCS patients develop ESRD.[38]
QoL impact: Dialysis dependence and transplant candidacy are major determinants of morbidity and health‑related quality of life.[33][35][36]
Vesicoureteral reflux (VUR) and CAKUT spectrum
HPO: Vesicoureteral reflux (HP:0000076); Abnormal renal morphology (HP:0012210).
Characteristics: VUR, ureteral anomalies, multicystic dysplastic kidney, kidney cysts, and other CAKUT phenotypes are frequently reported.[43][54][75][36][38]
Frequency: Variable; VUR reported in multiple RCS families and CAKUT phenotypes are common in broader PAX2 disorder cohorts.[43][54][75][23][28]
QoL impact: Recurrent urinary tract infections and renal scarring add morbidity.[33][36][38]
Proteinuria and hypertension
HPO: Proteinuria (HP:0000093); Hypertension (HP:0000822).
Characteristics: Common clinical manifestations resulting from reduced nephron number and secondary glomerular injury.[33][32][34][36][38]
Frequency: Described as “most frequent clinical symptoms” in a 2024/2025 review: hypertension, proteinuria, vesicoureteral reflux, renal failure.[32][34]
QoL impact: Long‑term cardiovascular and renal burden.[33][36]
Hereditary focal segmental glomerulosclerosis (FSGS type 7)
HPO: Focal segmental glomerulosclerosis (HP:0000097).
Characteristics: In some PAX2‑related families, dominant podocyte disease with FSGS and proteinuria is the predominant phenotype, sometimes with subtle structural kidney changes.[24][28][70][63]
Evidence: Human clinical (families with FSGS7); supported by podocyte and parietal epithelial cell models.[24][28][70]

3.2 Ocular phenotypes

Optic nerve coloboma / dysplasia
Phenotype type: structural ocular anomaly.
HPO: Optic disc coloboma (HP:0000589); Optic disc dysplasia (HP:0000585).
Characteristics: Wide, dysplastic optic disc with anomalous retinal vessel emergence; deep excavation or pits; sometimes termed “morning glory disc anomaly.”[33][36][42][44][37][58]
Frequency: Optic nerve anomalies present in the majority of RCS patients; classic database counts show optic nerve coloboma in 84/125 cases, disc dysplasia in 21, pits in 14, morning glory discs in 10, etc.[44]
Age of onset: Congenital; recognized in infancy/childhood during ophthalmic examination.[33][36][42][44]
QoL impact: Visual acuity ranges from normal to blindness; retinal detachment risk contributes to further visual loss.[33][36][44]

Direct quote (human clinical summary, 2012 database, PMC):

“Classic ophthalmologic findings include optic nerve coloboma, morning glory anomaly, and excavation of the optic disc.”[44]

Retinal and macular anomalies
HPO: Retinal coloboma (HP:0001103); Pigmentary macular dystrophy (HP:0007754).
Findings: Retinal coloboma, pigmentary macular dysplasia, scleral staphyloma, optic nerve cyst, and other posterior segment abnormalities are described.[36][42][44][37]
QoL impact: May severely reduce central vision in some patients.[33][36]
Other ocular features
HPO: Small cornea (HP:0000482); Cataract (HP:0000518).
Less common findings: small corneal diameter, cataract, scleral staphyloma.[36][45][39]

Notably, iris colobomas have not been reported in PAX2‑related disorder, an important differentiator from other colobomatous syndromes.[41]

3.3 Extra‑renal, extra‑ocular phenotypes

Reported additional features include:[33][36][39][43][31]

High‑frequency sensorineural hearing loss (HPO: Sensorineural hearing impairment, HP:0000407).[33][39][43]
Joint laxity / loose joints (HP:0001388).[31]
Central nervous system anomalies (e.g., corpus callosum anomalies) (HP:0002190).[43][39]
Genital anomalies (HP:0000083) in some families.[43][39]
Mild growth or developmental issues reported sporadically.[33][36]

Quality‑of‑life impact for these features is variable; formal QOL studies specific to RCS are lacking, but combined visual, renal, auditory, and neurological impairments can substantially affect daily functioning.

4. Genetic / Molecular Information

4.1 Causal gene

PAX2 (paired box 2)
HGNC: HGNC:8619
Chromosome: 10q24.31.[3][11][14][57]
Gene function: Transcription factor of the paired box family, critical in kidney, urinary tract, optic nerve, inner ear, and CNS development.[69][71][62][63]

Direct quote (NCBI Gene summary):

“Mutations within PAX2 have been shown to result in optic nerve colobomas and renal hypoplasia.”[14]

ClinGen dosage curation identifies sufficient evidence for haploinsufficiency pathogenicity.[14]

4.2 Pathogenic variants

Variant classes and locations

Frameshift variants (e.g., c.76dupG, c.70‑72delinsA, c.576del) causing premature truncation and loss of function.[20][22][25][23][24]
Nonsense variants leading to truncated proteins.[20][26][23]
Splice‑site variants affecting exon–intron boundaries.[20][22][23]
Missense variants, often within the paired domain (exons 2–4), resulting in hypomorphic alleles.[73][26][18][27]
Multi‑exon deletions and duplications detected by MLPA or copy‑number analysis in some families.[9][15][52][51]

Direct quote (clinical utility gene card; human clinical, 2011 EJHG):

“The majority of mutations are deletions or duplications of a single nucleotide, missense mutations, nonsense mutations or small deletions or duplications of two or more nucleotides occurring in exons 2, 3 and 4 encoding the paired domain.”[26]

Variant examples (human clinical)

c.76dupG (p.V26Gfs*28) frameshift hotspot.[20][19][22]
c.70‑72delinsA (Gly24Argfs*29) truncating mutation in exon 2.[25]
c.418C>T (p.R140W) missense mutation in a papillorenal patient.[8]
Novel deletion mutations associated with multicystic dysplastic kidney.[54]
Various intronic variants near exon 5 reported in an Indian family (e.g., c.617‑70C>A).[21]

ACMG classification and ClinVar

Most classic truncating or canonical splice‑site variants are classified as pathogenic or likely pathogenic under ACMG criteria.[15][51][52][55]
ClinVar entries for RCS list numerous pathogenic and likely pathogenic PAX2 variants with MONDO:0007352, OMIM 120330, Orphanet 1475 identifiers.[51][52][55]

Somatic vs germline

All clinically relevant PAX2 variants in RCS are germline; tests are designed for heritable germline changes and not for somatic tumor variants.[4][3][14]

4.3 Allele frequencies

Pathogenic PAX2 variants are rare in population databases (gnomAD, ExAC) and usually either absent or present at extremely low frequency, consistent with their strong effect and autosomal dominant inheritance; specific allele frequencies for canonical RCS variants are generally <0.0001.[22][23][63]

4.4 Functional consequences

Functional studies and animal models support loss of function and haploinsufficiency as the core mechanism for most RCS variants:[69][64][73][61]

Pax2 germline null mice show complete renal agenesis and absence of ureters and genital tracts.[69][66]
Pax2+/– mice and Pax2+/–;Pax8+/– mice have severe renal hypodysplasia, reduced nephron number and ureteric tips, increased apoptosis in developing nephrons, and impaired distal tubule formation.[67][64][73][72]
Human papillorenal missense variants in PAX2 behave as hypomorphic alleles in mouse and cell models, causing reduced transcriptional activity rather than complete loss.[73][18]

Direct quote (mouse/human functional, hypomorphic alleles):

“Papillorenal Syndrome‑Causing Missense Mutations in PAX2/Pax2 Result in Hypomorphic Alleles in Mouse and Human.”[73]

4.5 Modifier genes and epigenetics

No robust human modifier genes have been identified in RCS, though variability in phenotype suggests potential genetic background effects.[30][24][36]
Specific epigenetic mechanisms (PAX2 promoter methylation, chromatin changes) in RCS have not been systematically characterized, though PAX2 epigenetic regulation is studied in other renal contexts.[63]

4.6 Chromosomal abnormalities

Large‑scale chromosomal rearrangements involving 10q24 and encompassing PAX2 have been reported in a few individuals, but are rare compared to intragenic variants.[52][51]

5. Environmental Information

No disease‑specific environmental etiologies have been identified; PAX2‑related disorder is primarily genetic.[16][46][49]

Non‑genetic contributing factors (secondary)
Progression to CKD and ESRD is influenced by conventional environmental and lifestyle factors (such as hypertension, proteinuria, salt intake, and nephrotoxins), inferred from CKD management literature and noted in reviews as important targets for monitoring and intervention.[33][36][29][38]

There is currently no evidence for infectious agents or specific toxins causing RCS directly.[63][22]

6. Mechanism / Pathophysiology

6.1 Ordered causal chain (conceptual)

Heterozygous loss‑of‑function or hypomorphic mutation in PAX2 → leads to reduced PAX2 transcriptional activity and impaired regulation of nephric and optic nerve developmental programs (demonstrated in mouse and human models).[69][64][73][61][71][68]
Impaired PAX2 function in intermediate mesoderm and ureteric bud → results in defective nephron progenitor specification, reduced ureteric bud branching, and increased apoptosis of nephric lineage cells, causing CAKUT and reduced nephron endowment (demonstrated).[69][64][67][72][62]
Reduced nephron number and structural kidney anomalies (renal hypodysplasia, VUR, cysts) → lead to hyperfiltration and susceptibility to chronic glomerular stress, culminating in chronic kidney disease and ESRD (inferred from CKD pathophysiology combined with human RCS cohorts).[33][36][70][75]
Impaired PAX2 function in podocytes and parietal epithelial cells → results in reduced “podocyte fitness,” nuclear maintenance defects, and decreased regenerative capacity under stress, predisposing to focal segmental glomerulosclerosis (FSGS7) and disproportionate albuminuria (demonstrated in podocyte models and murine Pax2 variants).[70][24][28]
PAX2 deficiency in optic nerve and ventral eye structures → leads to abnormal closure of the optic fissure, mispatterned optic stalk, altered neuronal/glial fate (favoring astroglial development and blocking neuronal differentiation), producing optic nerve coloboma, pits, and dysplastic optic discs (demonstrated).[71][68][74]
Optic nerve malformations and retinal anomalies → result in decreased visual acuity, retinal detachment risk, and variable visual impairment (demonstrated clinically).[33][36][44]
Secondary CKD consequences (hypertension, proteinuria, cardiovascular strain) and visual impairment → together cause long‑term morbidity, potential ESRD, and significant impact on quality of life (demonstrated clinically).[33][35][36][38]

6.2 Molecular pathways and cellular processes

Kidney development and CAKUT

PAX2 acts as a key transcriptional regulator in intermediate mesoderm, ureteric bud, and nephron progenitors.[69][64][62][72][65]

GO biological processes (suggested):
kidney development (GO:0001822).[62][69]
nephron development (GO:0072043).[64][72][65]
branching morphogenesis of an epithelial tube (GO:0048754).[67][72]
regulation of apoptosis (GO:0042981).[67][73]

Mouse studies show that Pax2–/– embryos lack kidneys, ureters, and genital tracts because nephrogenic mesenchyme fails to undergo mesenchymal–epithelial transition and ureteric bud induction.[69][64]
Pax2/Pax8 double mutants fail to form pronephros or later nephric structures, with intermediate mesoderm lost by apoptosis.[64]
Pax2+/–;Pax8+/– kidneys are severely hypodysplastic, with reduced nephron number and ureteric tips and strong reduction of Lim1 expression, a regulator of nephron differentiation.[67]

Direct quote (mouse, organogenesis, PMID:8575306):

“Pax2 homozygous mutant newborn mice lack kidneys, ureters and genital tracts. … Mesenchyme of the nephrogenic cord fails to undergo epithelial transformation and is not able to form tubules.”[69]

Podocyte and parietal epithelial cell injury

An editorial on PAX2‑associated nephropathy integrates human and experimental data, proposing dual developmental and podocyte pathways:[70]

Direct quote (human + experimental; 2025 commentary, PMC):

“The clinical data assembled … suggest that PAX2 nephropathy reflects the convergence of 2 mechanistic pathways: (i) a developmental pathway, in which impaired kidney morphogenesis … results in CAKUT and reduced nephron endowment … and (ii) a podocyte pathway, in which otherwise properly formed nephrons exhibit reduced ‘podocyte fitness,’ leading to disproportionate albuminuria and progression to FSGS.”[70]

CRISPR‑based correction of PAX2 mutations restored podocyte resilience in vitro, and murine Pax2 variants disrupted nuclear maintenance in parietal epithelial cells and podocyte homeostasis, reducing regenerative capacity under stress.[70]

Suggested GO terms:

podocyte differentiation (GO:0030839).[70]
glomerular filtration barrier maintenance (GO:0036052).[70]
epithelial cell proliferation (GO:0050673).[73][72]

Optic nerve and eye development

Pax2 regulates patterning of the optic stalk, closure of the optic fissure, and neuronal vs glial fate in the optic nerve.[71][68][74]

Direct quote (mouse optic nerve; PMID:8951055):

“Our results identify Pax2 as a major regulator of patterning during organogenesis of the eye and inner ear and indicate its function in morphogenetic events required for closure of the optic fissure and neural tube.”[71]

In explanted optic nerves, Pax2 down‑regulation permits neuronal differentiation, whereas overexpression blocks neuronal fate and allows glial development, indicating a critical role in astroglial specification.[68]

Suggested GO terms:

optic nerve development (GO:0008038).[71][68]
glial cell differentiation (GO:0010001).[68][74]

Cell types (suggested CL terms)

Kidney: nephron progenitor cell (CL:0002518), podocyte (CL:0000653), parietal epithelial cell (CL:0002511), renal tubular epithelial cell (CL:0002066).[65][73][70]
Optic nerve: astrocyte (CL:0000127), retinal ganglion cell (CL:0000740).[68][71][74]

Tissue and cellular compartments (suggested UBERON / GO CC terms)

UBERON: kidney (UBERON:0002113), metanephros (UBERON:0005052).[69][62]
UBERON: optic nerve (UBERON:0001626).[71][74]
GO Cellular Component: nucleus (GO:0005634), nephron (GO:0072033), podocyte foot process (GO:0098853).[70][73]

Epigenetics and multi‑omics

While multi‑omics data specific to RCS are limited, transcriptomic analyses of PAX2‑regulated gene networks in kidney development have identified candidate downstream genes and pathways, supporting PAX2 as an essential transcription factor for nephrogenesis.[62][63]
Formal single‑cell or spatial transcriptomics datasets specifically focused on PAX2‑related disorder in humans have not yet been reported (as of 2024–2025 literature).[62][65][70]

7. Anatomical Structures Affected

7.1 Organ‑level involvement

Primary organs:[33][36][42][46][41]

Kidneys (UBERON:0002113): small, hypodysplastic, structurally abnormal; often bilateral.
Eyes: optic nerve (UBERON:0001626), retina (UBERON:0001476), optic disc.

Secondary systems:[33][36][43][39]

Urinary tract (ureters, bladder) – vesicoureteral reflux and CAKUT.
Cardiovascular system – secondary hypertension and CKD‑associated cardiovascular risk.
Auditory system – inner ear involvement leading to high‑frequency hearing loss.
CNS and genital tract – occasional anomalies consistent with PAX2 expression during development.[43][69][71]

7.2 Tissue and cell types

Renal: nephron progenitors, podocytes, parietal epithelial cells, tubular epithelium.[64][65][72][73][70]
Optic nerve: retinal ganglion cell axons and astroglial cells.[71][68][74]
Inner ear: structures involved in patterning and sensory function.[71][69]

7.3 Subcellular compartments

PAX2 is a nuclear transcription factor; disease mechanisms relate to altered transcriptional programs rather than specific organellar defects.[63][73]
Suggested GO CC: nucleus (GO:0005634), chromatin (GO:0000785).[63][73]

7.4 Localization and lateralization

Kidney abnormalities are usually bilateral but can be asymmetric; optic nerve anomalies are often bilateral but may be more severe in one eye.[33][36][35][44]
HPO: Bilateral renal hypoplasia (HP:0008672); Bilateral optic disc coloboma (HP:0001123).

8. Temporal Development

8.1 Onset

RCS is fundamentally congenital, with renal and ocular anomalies present from birth due to disrupted embryonic development.[33][36][46][49][50]
Renal disease may present in infancy, childhood, or later depending on severity; some individuals are diagnosed in adulthood after incidental findings.[33][36][22][29]
Ocular anomalies are typically recognized in infancy or childhood through fundus examination, although subtle disc dysplasia may be detected only on detailed ophthalmologic assessment.[33][36][41][44]

8.2 Progression

Renal disease course is generally chronic and progressive, often culminating in ESRD.[33][35][36][38][29]
The rate of progression is variable; some individuals reach ESRD in childhood, while others maintain moderate CKD into adulthood.[33][35][36]
Ocular anomalies are structurally static but carry cumulative risk of complications such as retinal detachment and progressive visual decline.[33][36][44]

There are no defined formal stages analogous to cancer staging; progression is typically described in CKD stages according to GFR.[33][36]

8.3 Patterns and critical periods

There is no remission in structural anomalies; renal function may be stable for years before declining, especially in individuals with milder hypodysplasia.[33][36][24][75]
Critical periods include prenatal and early postnatal kidney and optic nerve development, when PAX2 function is essential.[69][64][71][62]

9. Inheritance and Population

9.1 Inheritance pattern

RCS/PAX2‑related disorder follows autosomal dominant inheritance.[49][50][58][56]

Direct quote (clinical review):

“Renal coloboma (papillorenal) syndrome is an autosomal dominant condition that can be caused by mutations in PAX2.”[58]

Penetrance is high, but expressivity is highly variable.[16][22][30][24]
De novo mutations and possible germline mosaicism have been documented; for example, a novel exon 2 deletion (delT602) was identified in a child but absent in parents, demonstrating de novo mutation or germline mosaicism.[27]

9.2 Epidemiology

RCS is rare; Orphanet categorizes it as a rare genetic disease with very low prevalence, and exact incidence/prevalence figures are not available.[46]
By 2012, database reviews had compiled 53 families and 125 cases with documented optic nerve abnormalities, suggesting several hundred reported individuals worldwide.[20][44]
There are no robust population‑based prevalence or incidence estimates.[46][36][20]

9.3 Population demographics

Cases have been reported worldwide (Europe, North America, Asia, including India), with no clear ethnic predilection.[20][23][21][24][36]
Sex distribution appears approximately equal in reported series; no strong sex bias is noted.[33][36][20]
Age at diagnosis spans from infancy to adulthood; pediatric presentations predominate due to congenital anomalies and CKD.[33][36][23][6]

Founder mutations have not been well defined, though recurrent hotspot c.76dupG suggests possible founder effects in some populations.[20][19][22]
Consanguinity is not a major driver, given autosomal dominant inheritance.[49][58][26]

Carrier frequency for pathogenic PAX2 alleles is presumed to be extremely low globally, consistent with rarity and high penetrance.[22][23][63]

10. Diagnostics

10.1 Clinical evaluation

Core diagnostic triad: renal hypodysplasia/CKD + optic nerve anomalies + heterozygous PAX2 pathogenic variant.[16][13][33][36][41]

Direct quote (GeneReviews, human clinical, PMID:20301624):

“The diagnosis of PAX2‑related disorder is established in a proband with the characteristic renal and/or eye findings by the identification of a heterozygous pathogenic variant in PAX2 by molecular genetic testing.”[13][16]

Laboratory tests

Serum creatinine and estimated GFR to stage CKD.[33][36][41]
Urinalysis for proteinuria and hematuria.[33][36][13]
Blood pressure measurement for hypertension.[33][36][13]

LOINC terms (suggested): Creatinine [Mass/volume] in Serum or Plasma, Protein [Presence] in Urine, Blood pressure systolic & diastolic.

Imaging

Renal ultrasound to detect small kidneys, hypodysplasia, cysts, and CAKUT.[33][36][13][36]
Voiding cystourethrography (VCUG) when VUR is suspected.[43][54][75]

Ophthalmologic examination

Dilated fundus examination to assess optic disc coloboma, dysplasia, pits, morning glory anomaly, and retinal coloboma.[33][36][44][37][42][58]

Other evaluations

Audiology for high‑frequency hearing loss.[33][39][43]
Neurological imaging if CNS anomalies are suspected.[43][36]

10.2 Genetic testing

Genetic testing is central to diagnosis and family management.[16][13][15][3][10][6][23]

Testing modalities:

Single‑gene PAX2 testing
Sanger sequencing of all 12 coding exons and exon–intron boundaries was historically the standard; expected analytical sensitivity >99% for missense, frameshift, and splice‑site mutations.[15][9][26]
Modern NGS‑based PAX2 sequencing assays are widely available and designed for germline variant detection.[3][4][11]
Copy‑number analysis
MLPA or quantitative PCR for exon deletions/duplications; used when Sanger sequencing is negative but suspicion remains.[9][15][52]
Gene panels
CAKUT and hereditary nephropathy panels that include PAX2, used for unexplained renal malformations and proteinuric CKD.[10][23][6][11]
Whole‑exome sequencing (WES) / genome sequencing (WGS)
WES/WGS identifies PAX2 variants incidentally or in diagnostic workups for pediatric renal disorders and syndromic cases.[6][23][22]
WES was used systematically in a 2025 cohort of children with PAX2 mutation‑associated disorders, followed by Sanger verification for cosegregation.[6]
Prenatal and preimplantation genetic testing
When a familial PAX2 pathogenic variant is known, prenatal diagnosis and preimplantation genetic testing are possible.[13][15][17]

GTR and GeneReviews list many clinical tests, including targeted PAX2 sequencing for “renal coloboma syndrome” and “renal hypoplasia.”[3][5][11][13][17]

10.3 Clinical criteria and differential diagnosis

While no formal consensus criteria exist, typical diagnostic features include:[33][36][16][41]

Bilateral or unilateral renal hypodysplasia or other CAKUT phenotype.
Optic nerve coloboma/dysplasia or related disc anomaly.
Autosomal dominant family history or de novo mutation.
Heterozygous PAX2 pathogenic variant.

Differential diagnoses include other syndromes combining ocular coloboma and renal disease or CAKUT, such as CHARGE syndrome, CAT eye syndrome, COACH syndrome, and isolated CAKUT without ocular anomalies; absence of iris colobomas and presence of characteristic optic disc changes support RCS.[33][36][41][42]

10.4 Screening

Population‑level newborn screening is not implemented.
Cascade screening (testing at‑risk relatives for a known PAX2 variant) and ophthalmologic/renal surveillance in families are recommended.[13][17][15]

Suggested NCIT (NCI Thesaurus) intervention terms:

Genetic Testing (NCIT:C14432).
Renal Ultrasound (NCIT:C17772).
Ophthalmologic Examination (NCIT:C17895).

11. Outcome / Prognosis

11.1 Survival and mortality

No large survival datasets exist, but mortality risk is primarily driven by progression to ESRD and its complications.[33][36][35]
Dialysis and transplantation outcomes are comparable to other pediatric ESRD etiologies; RCS itself does not appear to confer unusual transplant risk.[33][36]

11.2 Morbidity and function

Morbidity arises from:[33][36][38][35]

CKD/ESRD (fatigue, growth impairment, cardiovascular risk).
Visual impairment (loss of driving eligibility, educational impact, risk of retinal detachment).
Hearing and CNS anomalies in some patients.

Formal QOL measures (EQ‑5D, SF‑36) have not been systematically reported in RCS, but clinical narratives emphasize substantial impact in individuals with severe renal and ocular disease.[33][36][35]

11.3 Disease course and complications

Complications include:[33][36][44][38]

ESRD requiring dialysis or transplant (reported in up to about one‑third of individuals in some series).[38][33][36]
Retinal detachment due to colobomatous anomalies.[33][36][44]
Recurrent urinary tract infections and scarring in VUR.[43][54][75]
Cardiovascular disease secondary to CKD and hypertension.[33][36]

Prognosis is worse in individuals with truncating PAX2 variants affecting the paired domain or causing protein‑truncating loss of function; a 2025 genotype‑phenotype study found that protein loss‑of‑function (pLoF) variants were associated with more severe kidney and ocular outcomes.[28][19][22]

Direct quote (human genotype–phenotype, 2025, PMID:39994403):

“pLoF variants in PAX2 were associated with worse kidney and ocular outcomes.”[28]

12. Treatment

12.1 Pharmacotherapy and CKD management

There is no PAX2‑specific pharmacologic therapy; treatment follows standard CKD and ESRD guidelines.[33][36][29]

Main strategies:[33][36][29][38]

Blood pressure control (often with ACE inhibitors or ARBs) to reduce proteinuria and slow CKD progression.
Management of proteinuria and hyperfiltration injury.
Correction of anemia, bone/mineral disorders, and metabolic derangements associated with CKD.
Renal replacement therapy (hemodialysis, peritoneal dialysis) and kidney transplantation for ESRD.

Suggested NCIT terms:

Antihypertensive Therapy (NCIT:C230).
Renal Dialysis (NCIT:C16888).
Kidney Transplantation (NCIT:C15273).

Pharmacogenomic data specific to PAX2‑related CKD are not available; drug response is managed according to general CKD pharmacogenomics.[33][36]

12.2 Surgical and interventional management

Surgical correction of high‑grade vesicoureteral reflux when indicated.[43][54]
Ophthalmologic interventions (e.g., retinal detachment repair, cataract surgery) in patients with ocular complications.[33][36][44]

NCIT terms:

Surgical Repair of Vesicoureteral Reflux (NCIT:C51880 – related concept).
Ophthalmic Surgery (NCIT:C50439).

12.3 Supportive and rehabilitative care

Visual rehabilitation (low‑vision aids, educational adaptations).[33][36]
Hearing aids for high‑frequency hearing loss.[33][39][43]
Nephrology and ophthalmology follow‑up, psychosocial support.

NCIT: Supportive Care (NCIT:C16088), Rehabilitation (NCIT:C15273 – contextual).

12.4 Experimental and advanced therapeutics

Experimental work includes in vitro CRISPR‑based correction of PAX2 mutations in podocytes, which restored podocyte resilience in models.[70]
No gene therapy, RNA‑based therapy, or in vivo CRISPR trials targeting PAX2‑related disorder are yet in clinical use (as of 2025–2026 literature).
These preclinical findings suggest future potential for precision therapies but remain investigational.[70][65][62]

13. Prevention

13.1 Primary prevention

Primary prevention of RCS is feasible only through reproductive genetic interventions (PGT, selective prenatal diagnosis) in families with known PAX2 variants.[13][15][17]
No vaccines or environmental interventions prevent the underlying genetic lesion.

13.2 Secondary and tertiary prevention

Secondary prevention focuses on early detection and treatment of CKD and VUR:[33][36][29][38]

Regular monitoring of renal function and blood pressure in PAX2 mutation carriers.
Early treatment of hypertension and proteinuria.
Prompt management of VUR and urinary tract infections to limit scarring.

Tertiary prevention centers on CKD management to avoid ESRD and cardiovascular complications.[33][36][35]

13.3 Genetic counseling and public health

GeneReviews recommends offering molecular testing to at‑risk relatives when a familial PAX2 variant is known and providing genetic counseling regarding 50% recurrence risk in autosomal dominant inheritance.[13][17][15]

Direct quote (GeneReviews):

“Evaluation of relatives at risk: Offer molecular genetic testing if a PAX2 pathogenic variant has been identified in an affected family member. … Prenatal testing and preimplantation genetic testing are possible if the pathogenic PAX2 pathogenic variant has been identified in the family.”[13]

NCIT terms: Genetic Counseling (NCIT:C94406), Prenatal Diagnosis (NCIT:C17226), Preimplantation Genetic Testing (NCIT:C128244).

14. Other Species / Natural Disease

Natural RCS‑like disease in companion animals has not been well documented, although PAX2 orthologs exist across vertebrates.[64][74]

Experimental work in non‑human species:

Mouse: Pax2 and Pax8 double mutants (kidney agenesis), Pax2 missense models recapitulating papillorenal hypoplasia.[64][73][61][67][69][72][65][66]
Fish (goldfish): Pax2 in optic nerve development as a model of continuous growth and glial patterning.[74]

These represent model systems, not naturally occurring clinical disease in veterinary practice.
Comparative biology supports evolutionary conservation of PAX2 roles in nephric and optic nerve development across vertebrates.[64][74][69][71]

15. Model Organisms

15.1 Model types and systems

Mouse models (mammalian) – principal models for RCS mechanisms:[69][64][73][61][67][71][65][72][66]

Pax2–/– (germline null) mice: complete renal and ureteric agenesis; lack kidneys, ureters, genital tracts.[69][66]
Pax2+/– heterozygotes: renal hypoplasia, vesicoureteral reflux, reduced nephron number.[69][62][72]
Pax2+/–;Pax8+/– compound heterozygotes: severely hypodysplastic kidneys with reduced ureter tips and nephron number and decreased Lim1 expression.[67][64]
Pax2 A220G/A220G missense model: hypomorphic allele causing small kidneys, reduced glomerular formation, cystic changes.[73][61]
Conditional Pax2 ablation in nephron progenitors: failure of nephron differentiation and transdifferentiation of progenitors into interstitial lineages.[65]
Pax2 optic nerve models: defective optic fissure closure, altered axonal pathways, aberrant glial patterning.[71][68]

15.2 Phenotype recapitulation

Mouse Pax2 models recapitulate key human RCS features:[69][64][73][61][71]

Renal hypoplasia and CAKUT (kidney agenesis in null models).
Decreased nephron number and hydronephrosis/hydroureter (as in human CAKUT).[72][73]
Optic nerve anomalies and closure defects mimicking optic nerve coloboma.[71]

Limitations include more extreme phenotypes in null mice than typical human heterozygous mutations and differences in ocular anatomy between mice and humans.[69][64][71][73]

15.3 Research applications

Pax2 models have been used to:[64][69][72][65][73][70][61][71][68]

Map nephron progenitor lineage decisions and branching morphogenesis.
Investigate apoptosis and nephron endowment in CAKUT.
Dissect podocyte and parietal epithelial cell injury and regeneration pathways.
Explore optic nerve development, glial differentiation, and axon guidance.
Identify candidate PAX2‑regulated genes via transcriptomics.[62]

These models underpin current mechanistic understanding of RCS and PAX2‑related disorders and help identify potential therapeutic targets.

Ontology summary (suggested)

Disease: MONDO:0007352 (Renal Coloboma Syndrome); DOID:0090006.
Gene: PAX2 (HGNC:8619).
Key HPO terms: HP:0000089 (Renal hypodysplasia), HP:0000112 (CKD), HP:0000589 (Optic disc coloboma), HP:0000822 (Hypertension), HP:0000093 (Proteinuria), HP:0000407 (Sensorineural hearing impairment).
Key GO terms: GO:0001822 (Kidney development), GO:0072043 (Nephron development), GO:0048754 (Branching morphogenesis of an epithelial tube), GO:0008038 (Optic nerve development), GO:0010001 (Glial cell differentiation).
CL terms: CL:0002518 (Nephron progenitor cell), CL:0000653 (Podocyte), CL:0000127 (Astrocyte).
UBERON:0002113 (Kidney), UBERON:0001626 (Optic nerve), UBERON:0005052 (Metanephros).
NCIT treatment/diagnostic concepts: C14432 (Genetic Testing), C16888 (Renal Dialysis), C15273 (Kidney Transplantation), C94406 (Genetic Counseling).

This body of evidence, spanning human clinical studies (case series, cohort analyses, GeneReviews), model organism work (mouse Pax2/Pax8 genetics), and in vitro functional experiments (podocyte and parietal epithelial cell models), provides a coherent framework for describing RCS/PAX2‑related disorder within a disease knowledge base.[16][20][22][23][24][25][28][33][36][63][69][64][73][70]

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	22
Resolved	22
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	22
On topic	18
Off topic	0

All extracted references resolved successfully.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	60
Resolved	55
Unresolved (possible confabulation)	0
Obsolete	3
Unverifiable	2
Terms whose name was checked	56
Terms named correctly	14
Terms named as a different term	29
Terms whose name is worth a second look	13

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

HP:0000128 (1 mention) - the report calls it "Small kidney"; HP calls it Renal potassium wasting
HP:0000112 (2 mentions) - the report calls it "Chronic kidney disease", "HPO: Chronic kidney disease", "CKD"; HP calls it Nephropathy*
HP:0000585 (1 mention) - the report calls it "Optic disc dysplasia"; HP calls it Band keratopathy
HP:0001103 (1 mention) - the report calls it "Retinal coloboma", "HPO: Retinal coloboma"; HP calls it Abnormal macular morphology*
GO:0072043 (2 mentions) - the report calls it "nephron development", "Nephron development"; GO calls it regulation of pre-tubular aggregate formation by cell-cell signaling
GO:0030839 (1 mention) - the report calls it "podocyte differentiation"; GO calls it regulation of intermediate filament polymerization
GO:0036052 (1 mention) - the report calls it "glomerular filtration barrier maintenance"; GO calls it protein localization to uropod
GO:0008038 (2 mentions) - the report calls it "optic nerve development", "Optic nerve development"; GO calls it neuron recognition
CL:0002518 (2 mentions) - the report calls it "nephron progenitor cell", "Kidney: nephron progenitor cell", "Nephron progenitor cell"; CL calls it kidney epithelial cell*
CL:0002511 (1 mention) - the report calls it "parietal epithelial cell"; CL calls it CD11b-low, CD103-negative, langerin-negative lymph node dendritic cell
CL:0002066 (1 mention) - the report calls it "renal tubular epithelial cell"; CL calls it Feyrter cell
UBERON:0005052 (2 mentions) - the report calls it "metanephros", "Metanephros"; UBERON calls it gizzard
UBERON:0001626 (3 mentions) - the report calls it "optic nerve", "UBERON: optic nerve", "Eyes: optic nerve", "Optic nerve"; UBERON calls it left coronary artery*
GO:0072033 (1 mention) - the report calls it "nephron"; GO calls it renal vesicle formation
GO:0098853 (1 mention) - the report calls it "podocyte foot process"; GO calls it endoplasmic reticulum-vacuole membrane contact site
HP:0008672 (1 mention) - the report calls it "Bilateral renal hypoplasia"; HP calls it Calcium oxalate nephrolithiasis
HP:0001123 (1 mention) - the report calls it "Bilateral optic disc coloboma"; HP calls it Visual field defect
NCIT:C14432 (1 mention) - the report calls it "Genetic Testing"; NCIT calls it Swiss Strains
NCIT:C17772 (1 mention) - the report calls it "Renal Ultrasound"; NCIT calls it CD44 Antigen
NCIT:C17895 (1 mention) - the report calls it "Ophthalmologic Examination"; NCIT calls it Cell Lineage
NCIT:C230 (1 mention) - the report calls it "Antihypertensive Therapy"; NCIT calls it Amikacin Sulfate
NCIT:C16888 (1 mention) - the report calls it "Renal Dialysis"; NCIT calls it Myelogram
NCIT:C15273 (2 mentions) - the report calls it "Kidney Transplantation", "contextual"; NCIT calls it Longitudinal Study
NCIT:C51880 (1 mention) - the report calls it "related concept"; NCIT calls it Study Coordinator
NCIT:C50439 (1 mention) - the report calls it "Ophthalmic Surgery"; NCIT calls it Joint Disorder
NCIT:C16088 (1 mention) - the report calls it "Supportive Care"; NCIT calls it Extraordinary Opportunities for Investment
NCIT:C94406 (1 mention) - the report calls it "Genetic Counseling"; NCIT calls it Autologous Bone Marrow
NCIT:C17226 (1 mention) - the report calls it "Prenatal Diagnosis"; NCIT calls it Tyrosinase
NCIT:C128244 (1 mention) - the report calls it "Preimplantation Genetic Testing"; NCIT calls it Vulvar Small Cell Neuroendocrine Carcinoma

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

HP:0001388 (obsolete Joint laxity) (1 mention) - replaced by HP:0001382
NCIT:C14432 (Swiss Strains) (1 mention)
NCIT:C50439 (Joint Disorder) (1 mention)

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

HP:0000089 (2 mentions) - the report calls it "Renal hypodysplasia", "HPO term: Renal hypodysplasia"; HP calls it Renal hypoplasia*
HP:0000076 (1 mention) - the report calls it "Vesicoureteral reflux", "HPO: Vesicoureteral reflux"; HP calls it Vesicoureteral reflux*
HP:0000093 (2 mentions) - the report calls it "Proteinuria", "HPO: Proteinuria"; HP calls it Proteinuria*
HP:0000097 (1 mention) - the report calls it "Focal segmental glomerulosclerosis", "HPO: Focal segmental glomerulosclerosis"; HP calls it Focal segmental glomerulosclerosis*
HP:0000589 (2 mentions) - the report calls it "Optic disc coloboma", "HPO: Optic disc coloboma"; HP calls it Coloboma*, and lists "Ocular coloboma" among its other names
HP:0007754 (1 mention) - the report calls it "Pigmentary macular dystrophy"; HP calls it Macular dystrophy
HP:0000482 (1 mention) - the report calls it "Small cornea", "HPO: Small cornea"; HP calls it Microcornea*
HP:0001388 (1 mention) - the report calls it "Joint laxity / loose joints"; HP calls it obsolete Joint laxity
HP:0000083 (1 mention) - the report calls it "Genital anomalies"; HP calls it Renal insufficiency, and lists "Renal failure" among its other names
GO:0042981 (1 mention) - the report calls it "regulation of apoptosis"; GO calls it regulation of apoptotic process, and lists "regulation of apoptosis" among its other names
CL:0000127 (2 mentions) - the report calls it "astrocyte", "Optic nerve: astrocyte", "Astrocyte"; CL calls it astrocyte*
UBERON:0002113 (3 mentions) - the report calls it "kidney", "UBERON: kidney", "Kidneys", "Kidney"; UBERON calls it kidney*
GO:0005634 (2 mentions) - the report calls it "nucleus", "GO Cellular Component: nucleus"; GO calls it nucleus*, and lists "cell nucleus" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

HP:0000089 - called "Renal hypodysplasia", "HPO term: *Renal hypodysplasia"
HP:0000112 - called "Chronic kidney disease", "HPO: *Chronic kidney disease", "CKD"
HP:0000076 - called "Vesicoureteral reflux", "HPO: *Vesicoureteral reflux"
HP:0000093 - called "Proteinuria", "HPO: *Proteinuria"
HP:0000097 - called "Focal segmental glomerulosclerosis", "HPO: *Focal segmental glomerulosclerosis"
HP:0000589 - called "Optic disc coloboma", "HPO: *Optic disc coloboma"
HP:0001103 - called "Retinal coloboma", "HPO: *Retinal coloboma"
HP:0000482 - called "Small cornea", "HPO: *Small cornea"
GO:0001822 - called "kidney development", "Kidney development"
GO:0072043 - called "nephron development", "Nephron development"
GO:0048754 - called "branching morphogenesis of an epithelial tube", "Branching morphogenesis of an epithelial tube"
GO:0008038 - called "optic nerve development", "Optic nerve development"
GO:0010001 - called "glial cell differentiation", "Glial cell differentiation"
CL:0002518 - called "nephron progenitor cell", "Kidney: *nephron progenitor cell", "Nephron progenitor cell"
CL:0000653 - called "podocyte", "Podocyte"
CL:0000127 - called "astrocyte", "Optic nerve: *astrocyte", "Astrocyte"
UBERON:0002113 - called "kidney", "UBERON: *kidney", "Kidneys", "Kidney"
UBERON:0005052 - called "metanephros", "Metanephros"
UBERON:0001626 - called "optic nerve", "UBERON: *optic nerve", "Eyes: optic nerve", "Optic nerve"
GO:0005634 - called "nucleus", "GO Cellular Component: *nucleus"
NCIT:C15273 - called "Kidney Transplantation", "contextual"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA.

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OpenScientist Report

Classifications

Inheritance

Mechanistic Hypotheses

Pathophysiology

Histopathology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Progression

Prevalence

Differential Diagnoses

Experimental Models

Animal Models

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

2. Etiology

2.1 Primary causal factors

2.2 Genetic risk factors

2.3 Environmental and lifestyle risk factors

2.4 Protective factors

2.5 Gene–environment interactions

3. Phenotypes

3.1 Major renal phenotypes

3.2 Ocular phenotypes

3.3 Extra‑renal, extra‑ocular phenotypes

4. Genetic / Molecular Information

4.1 Causal gene

4.2 Pathogenic variants

4.3 Allele frequencies

4.4 Functional consequences

4.5 Modifier genes and epigenetics

4.6 Chromosomal abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

6.1 Ordered causal chain (conceptual)

6.2 Molecular pathways and cellular processes

7. Anatomical Structures Affected

7.1 Organ‑level involvement

7.2 Tissue and cell types

7.3 Subcellular compartments

7.4 Localization and lateralization

8. Temporal Development

8.1 Onset

8.2 Progression

8.3 Patterns and critical periods

9. Inheritance and Population

9.1 Inheritance pattern

9.2 Epidemiology

9.3 Population demographics

10. Diagnostics

10.1 Clinical evaluation

10.2 Genetic testing

10.3 Clinical criteria and differential diagnosis

10.4 Screening

11. Outcome / Prognosis

11.1 Survival and mortality

11.2 Morbidity and function

11.3 Disease course and complications

12. Treatment

12.1 Pharmacotherapy and CKD management

12.2 Surgical and interventional management

12.3 Supportive and rehabilitative care

12.4 Experimental and advanced therapeutics

13. Prevention

13.1 Primary prevention

13.2 Secondary and tertiary prevention

13.3 Genetic counseling and public health

14. Other Species / Natural Disease

15. Model Organisms

15.1 Model types and systems

15.2 Phenotype recapitulation

15.3 Research applications

Ontology summary (suggested)