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Inheritance

1

Autosomal recessive HP:0000007

RSS1 segregates as an autosomal recessive trait. Affected individuals carry biallelic WASHC5 variants, either homozygous (as in the northern Manitoba First Nations founder cohort) or compound heterozygous.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:31971710 SUPPORT Human Clinical

"WASHC5-related RSS is inherited in an autosomal recessive manner; CCDC22-related RSS is inherited in an X-linked manner."

Names the inheritance mode for the WASHC5 form specifically and distinguishes it from the X-linked CCDC22 form, so the attribution to RSS1 is genotype-specific rather than inferred from a form-agnostic statement.

PMID:31971710 SUPPORT Human Clinical

"At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier."

Gives the sibling recurrence risks that follow from autosomal recessive inheritance, which is the operative counselling figure for RSS1.

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Discussions and Knowledge Gaps

2

A viable Washc5 knock-in mouse exists, but it carries N471D, an allele that causes dominant SPG8 rather than recessive RSS1, and it does not reproduce the RSS1 triad. Would a knock-in of an RSS1 hypomorphic allele, at the roughly 40% strumpellin dose seen in patients, develop the cerebellar, cardiac, and craniofacial malformations?

HUMAN MODEL MISMATCH OPEN rss1_no_viable_washc5_model

Attached to

pathophysiology#WASHC5 Hypomorphic Loss of Function animal_models#Washc5 constitutive knockout mouse animal_models#N471D Washc5 knock-in mouse

Two Washc5 alleles have been engineered in mouse and neither is an RSS1 allele, so the mismatch is about which allele was modelled rather than about an absence of models. The knockout is a clean deletion: homozygotes die before organogenesis can be scored and heterozygotes sit above the disease threshold with no phenotype, so neither dose is the disease. The N471D knock-in is viable as a homozygote and does produce mild multi-organ findings, including dilated cardiomyopathy, thinner eye lenses and gait instability, but N471D is the dominant SPG8 allele and the authors report it does not give a typical SPG8 phenotype either. It is also mechanistically the wrong kind of lesion: the same study found WASHC5 interaction partners and complexes at unchanged abundance in these animals, whereas RSS1 acts through reduced strumpellin and hence reduced WASH complex abundance. So no published model occupies the RSS1 window, and every in vivo statement about RSS1 organogenesis still rests on inference from human imaging and from cellular work in non-developmental systems. The tissue-selectivity question below cannot be addressed experimentally until that changes.

Proposed experiments

Patient-allele Washc5 hypomorphic knock-in mouse

rss1_hypomorphic_knockin

Introduce the founder splice-site allele, or an equivalent allele titrated to leave roughly 40% strumpellin, into the mouse germline and phenotype homozygotes for posterior fossa, cardiac septal, and craniofacial development, with strumpellin quantified by western blot to confirm the intended dose.

Readouts

Cerebellar vermis and posterior fossa morphology

phenotypes#Cerebellar vermis hypoplasia

Direction: DECREASED

Interpretation: Vermian hypoplasia in a viable hypomorph would establish that partial strumpellin loss is sufficient for the cerebellar malformation.

Cardiac septation

phenotypes#Congenital heart defect

Direction: ALTERED

Interpretation: Septal defects in the same animals would tie the cardiac arm of the triad to the same dose.

Would support

pathophysiology#WASHC5 Hypomorphic Loss of Function

Would refute

pathophysiology#WASHC5 Hypomorphic Loss of Function

Supporting outcome

Homozygous hypomorphs survive to term with vermian hypoplasia and septal defects, at a strumpellin level comparable to the patient cohort.

Refuting outcome

Homozygous hypomorphs are either normal or embryonic-lethal at every dose that can be engineered, which would mean the human phenotype depends on something other than strumpellin dose alone.

Show evidence (1 reference)

PMID:34312900 SUPPORT Model Organism

"While biallelic ablation of Washc5 was prenatally lethal, expression of N471D mutated WASHC5 led to several mild clinical and laboratory parameter abnormalities, but not to a typical SPG8 phenotype."

Establishes that the one viable engineered allele is N471D and that it fails to reproduce even the disease it was built for, which is what makes the absence of an RSS1-allele model the operative gap.

Strumpellin is ubiquitously expressed and the WASH complex serves endosomal recycling in every cell, so why do the malformations concentrate in the cerebellum, the cardiac septa, and the craniofacial skeleton rather than appearing as a uniform multi-organ defect?

KNOWLEDGE GAP OPEN rss1_tissue_selectivity

Attached to

pathophysiology#Multisystem Developmental Malformation pathophysiology#Reduced Cell-Surface Cargo Receptor Density

Two observations make this sharper than the usual tissue-selectivity question. Strumpellin loss does not disturb bulk recycling: transferrin receptor traffic is normal while the beta-2-adrenergic receptor is mislocalised, so the defect is already cargo-selective at the cell level. And in the Commander-related forms of the syndrome, cell-surface proteomics showed that the reduction in surface cargo is itself tissue-specific. Which WASH-dependent cargoes are rate-limiting in cerebellar, cardiac, and neural crest development is unknown, and answering it would explain why one housekeeping defect produces this particular triad.

Show evidence (1 reference)

PMID:40601774 SUPPORT INDIRECT In Vitro

"through cell surface proteomics, that this reduces tissue-specific presentation of cell surface integral membrane proteins essential for kidney, bone, and brain development"

Establishes that the surface-cargo deficit is tissue-specific in Ritscher-Schinzel syndrome, which is what frames the gap. The measurement was made on Commander subunits rather than on WASHC5, so it bears on the RSS1 node by inference from the shared recycling pathway.

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Pathophysiology

10

WASHC5 Hypomorphic Loss of Function

Biallelic WASHC5 (KIAA0196) variants reduce the abundance of functional strumpellin. The founder variant identified in the northern Manitoba First Nations cohort is a splice-site change that shifts the relative abundance of KIAA0196 transcripts and leaves approximately 40% of normal strumpellin protein. Disease alleles are hypomorphic rather than complete nulls, consistent with embryonic lethality of the homozygous murine knockout.

Genetic context functional_impact_category: PARTIAL_LOSS_OF_FUNCTION

The recurrent First Nations allele is a homozygous splice-site variant associated with an approximately eightfold change in the relative amount of the KIAA0196 transcript lacking exon 27 and a 60% reduction in strumpellin protein. Compound heterozygous WASHC5 alleles have been reported in a separate family.

Animal models

Washc5 constitutive knockout mouse Mouse fails to recapitulate Complete ablation of the orthologue is not a model of the hypomorphic human genotype; it is lethal before the malformations of interest can form.

N471D Washc5 knock-in mouse Mouse fails to recapitulate A viable Washc5 point mutant that nonetheless does not model the RSS1 lesion, because the allele is the dominant SPG8 one and complex abundance is unchanged.

Downstream

WASH Regulatory Complex Destabilisation Strumpellin is one of five obligate subunits of the WASH regulatory complex, so reducing it lowers the abundance of the assembled complex.

Show evidence (2 references)

PMID:24065355 SUPPORT Human Clinical

"All eight patients were homozygous for a novel splice site mutation in KIAA0196. RNA analysis revealed an approximate eightfold reduction in the relative amount of a KIAA0196 transcript lacking exon 27. A 60% reduction in the amount of strumpellin protein was observed on western blot."

The founding genetic study demonstrates the causal WASHC5 variant and quantifies the residual strumpellin, establishing the lesion as a partial rather than complete loss of function.

PMID:26572744 SUPPORT INDIRECT Model Organism

"Homozygous but not heterozygous mice showed early embryonic lethality."

Complete loss of the murine orthologue is lethal before birth, so viable human RSS1 genotypes must retain partial strumpellin function. This supports the hypomorphic-allele claim by inference from the null phenotype rather than by direct measurement in patients.

WASH Regulatory Complex Destabilisation

Reduced strumpellin lowers the abundance of the assembled pentameric WASH regulatory complex on the endosomal membrane. The complex is the endosomal member of the WASP family and is the dedicated Arp2/3 activator at this compartment. It reaches the endosome by the unstructured tail of its FAM21 subunit binding retromer VPS35, an interaction that is both necessary and sufficient for the targeting, so the complex acts specifically where retromer is selecting cargo. This retromer-dependent recruitment is what makes the WASH route distinct from the SNX17-dependent Commander route that fails in the CCDC22 and VPS35L forms of the syndrome.

actin filament polymerization GO:0030041 ↓ DECREASED

Downstream

Impaired Endosomal Branched Actin Nucleation

Show evidence (3 references)

PMID:20498093 SUPPORT In Vitro

"Here we show that WASH functions in cells within a 500 kDa core complex containing Strumpellin, FAM21, KIAA1033 (SWIP), and CCDC53."

Names strumpellin as one of five obligate subunits of the WASH core complex, which is why reducing it compromises the whole assembly rather than only one of its activities.

PMID:22070227 SUPPORT In Vitro

"the retromer-WASH complex interaction occurs through the long unstructured 'tail' domain of the WASH complex-Fam21 protein binding to Vps35, an interaction that is necessary and sufficient to target the WASH complex to endosomes"

Establishes how the complex is delivered to the endosomal membrane, which is what makes its abundance rate-limiting for endosomal actin rather than for actin generally.

PMID:30061306 SUPPORT INDIRECT In Vitro

"Real-time PCR analyses revealed no transcriptional changes in WASH complex subunits in Str- cells, but western blots showed a twofold decrease in the SWIP subunit."

An independent demonstration, in a second organism, that losing strumpellin lowers another WASH subunit at protein level without changing its transcription. It replicates the post-transcriptional complex-destabilisation mechanism in Dictyostelium rather than mouse, so it supports this node across species rather than in an RSS1 context.

Impaired Endosomal Branched Actin Nucleation

With less WASH complex on the endosome, Arp2/3-dependent branched actin networks fail to form at the required density on the endosomal surface. These actin patches provide the force and the membrane subdomain organisation needed for tubule formation and scission.

Arp2/3 complex-mediated actin nucleation GO:0034314 ↓ DECREASED

Downstream

Defective Endosomal Tubule Fission and Cargo Retrieval

Show evidence (1 reference)

PMID:31911435 SUPPORT INDIRECT In Vitro

"We uncovered a decrease in CAV1 protein abundance as well as endosomal fission defects resulting from pathogenic SPG8 mutations."

Measured for SPG8 alleles, which are heterozygous missense variants in the same gene causing a different, dominantly inherited disease rather than RSS1. It supports this node by inference: any strumpellin variant that produces endosomal fission defects shows the actin-dependent endosomal step depends on strumpellin dose or integrity. It is not a measurement in an RSS1 genotype.

Defective Endosomal Tubule Fission and Cargo Retrieval

Integral membrane cargo that should be captured into recycling tubules and returned to the surface is instead retained in the endosome and delivered to the lysosome for degradation. The WASH complex protects cargo from that default degradative fate through its endosomal actin activity.

endocytic recycling GO:0032456 ↓ DECREASED endosome organization GO:0007032 ↓ DECREASED

Downstream

Reduced Cell-Surface Cargo Receptor Density

Show evidence (1 reference)

PMID:23085491 SUPPORT In Vitro

"We show that strumpellin is not required for normal transferrin receptor traffic, but is required for the correct subcellular distribution of the β-2-adrenergic receptor."

Demonstrates that strumpellin loss selectively disturbs the trafficking of particular cargo rather than bulk recycling: transferrin receptor traffic is unaffected while the beta-2-adrenergic receptor is mislocalised. The measurement was made in the context of SPG8, so it supports cargo selectivity as a property of strumpellin loss, not the tissue distribution of RSS1.

Reduced Cell-Surface Cargo Receptor Density

The steady-state surface pool of WASH-dependent cargo, including caveolin-1 and integrins, falls. Because these cargoes mediate cell adhesion, migration, and developmental signalling, their depletion is the point at which a housekeeping trafficking defect becomes a developmental one.

receptor recycling GO:0001881 ↓ DECREASED protein localization to plasma membrane GO:0072659 ↓ DECREASED

Downstream

Impaired Integrin-Mediated Cell Adhesion Loss of strumpellin lowers the surface pool of integrin, which is the adhesion receptor itself, so the adhesion defect follows directly from the recycling defect.

Reduced Neuronal Dendritic Arborisation and Synaptogenesis

LDL Receptor Mislocalisation and Degradation

Impaired Lysosomal Enzyme Delivery

Multisystem Developmental Malformation

Show evidence (1 reference)

PMID:31911435 SUPPORT In Vitro

"In addition, the interaction of strumpellin with CAV1 stimulated integrin recycling, thereby promoting cell adhesion."

Identifies the specific cargo whose surface recycling depends on strumpellin and the adhesive function that depends on it.

Impaired Integrin-Mediated Cell Adhesion

Loss of surface integrin and caveolin-1 impairs integrin-mediated adhesion. Adhesion is the general-cell consequence of the recycling defect and is the plausible substrate for the morphogenetic failures, since cardiac septation and neural crest migration both depend on adhesive cell behaviour.

cell adhesion mediated by integrin GO:0033627 ↓ DECREASED

Downstream

Multisystem Developmental Malformation

Show evidence (3 references)

PMID:37308549 SUPPORT Model Organism

"While exposure of the internal alphaIIbbeta3 pool after platelet activation was unaffected, the uptake of the alphaIIbbeta3 ligand fibrinogen was delayed."

Shows the functional consequence is specifically in ligand engagement rather than in the internal receptor store, which localises the defect to the surface-delivery step this node describes.

PMID:31911435 SUPPORT INDIRECT In Vitro

"SPG8-associated missense mutations in strumpellin did not rescue endosomal tubulation defects, reduction in CAV1 protein abundance, or integrin-mediated cell adhesion in strumpellin-deficient cells."

Tested with SPG8 missense alleles, not RSS1 alleles, so it bears on this node only by inference from the shared gene. Note that the rescue result is contested: two other groups report that SPG8 variants behave like wild-type in WASH complex assays, so this item is curated alongside the REFUTE item below rather than as a settled finding.

PMID:37392480 REFUTE INDIRECT In Vitro

"Compared with the wild-type, strumpellin mutants N471D or V626F identified in patients with SPG8 exhibited no differences in rescuing the defects."

Directly contradicts the non-rescue result quoted immediately above: here the same class of SPG8 missense alleles rescued as well as wild-type protein. Both are recorded because the literature does not resolve them, and because the disagreement is itself the reason SPG8 findings cannot be carried across to RSS1 without qualification. Neither result was obtained in an RSS1 genotype.

Reduced Neuronal Dendritic Arborisation and Synaptogenesis

Strumpellin depletion in cortical neurons reduces dendritic arborisation and synapse formation with loss of dendritic F-actin clusters, and produces a motor coordination deficit in vivo. This is the cellular substrate of the gait and neurodevelopmental phenotypes, and is a separate consequence of the recycling defect from the adhesion node above.

cortical neuron CL:0010012

dendrite development GO:0016358 ↓ DECREASED synapse assembly GO:0007416 ↓ DECREASED

Animal models

Strumpellin shRNA knockdown cortical neuron model Mouse partially recapitulates Reproduces the cellular consequence of reduced strumpellin dose in neurons, with rescue by wild-type protein establishing specificity.

Downstream

Gait ataxia

Global developmental delay

Intellectual disability

Show evidence (2 references)

PMID:37392480 SUPPORT In Vitro

"Strumpellin knockdown using shRNA attenuated dendritic arborization and synapse formation in cultured cortical neurons, and this effect was rescued by wild-type strumpellin expression."

Rescue by wild-type strumpellin establishes that the dendritic and synaptic deficit is caused by strumpellin loss specifically.

PMID:37392480 SUPPORT Model Organism

"Administration of a lentivirus containing a strumpellin-targeting short hairpin RNA (shRNA) to cortical motor neurons lead to abnormal motor coordination in mice."

Shows the cellular deficit has a whole-animal motor consequence, which is what connects this node to the gait phenotype.

LDL Receptor Mislocalisation and Degradation

One named cargo arm of the recycling defect. Without WASH-dependent retrieval the LDL receptor is mislocalised and routed to the lysosome instead of back to the hepatocyte surface, lowering LDL uptake and raising circulating cholesterol. This is the mechanism behind the hypercholesterolaemia recorded as a phenotype of the syndrome, and it is the one cargo whose loss has a directly measurable clinical readout.

receptor recycling GO:0001881 ↓ DECREASED

Downstream

Hypercholesterolemia

Show evidence (2 references)

PMID:26965651 SUPPORT In Vitro

"Inactivation of the CCC-associated WASH complex causes LDLR mislocalization, increased lysosomal degradation of LDLR and impaired LDL uptake."

States the mechanism for the WASH complex specifically, which is the complex RSS1 disables, rather than only for the CCC complex behind the other forms of the syndrome.

PMID:26965651 SUPPORT Human Clinical

"Furthermore, a mutation in the WASH component KIAA0196 (strumpellin) is associated with hypercholesterolaemia in humans."

Connects the cell-biological mechanism to a human phenotype through strumpellin itself, which is the gene this entry is about.

Impaired Lysosomal Enzyme Delivery

A second cargo arm. Failure of endosomal tubule fission also disrupts sorting of the mannose 6-phosphate receptor, which is what delivers acid hydrolases to the lysosome, so lysosomal enzyme trafficking and lysosomal morphology are both disturbed. The M6PR mis-sorting step itself was measured for loss of spastin and IST1, the proteins that drive fission at ER-endosome contacts; strumpellin-deficient cells were shown to share the downstream lysosomal abnormalities rather than to be the system in which the receptor defect was demonstrated. This arm has no established clinical correlate in RSS1 and is curated as a mechanistic consequence rather than as an explanation for any listed phenotype.

endosome organization GO:0007032 ↓ DECREASED

Show evidence (1 reference)

PMID:28389476 SUPPORT INDIRECT In Vitro

"similar lysosomal abnormalities were seen in cellular models lacking the WASH complex component strumpellin or the ER morphogen REEP1"

Reports the lysosomal consequence for strumpellin-deficient cells specifically. Note the quote establishes that those cells share the lysosomal abnormality, not that M6PR sorting was measured in them: the receptor step was demonstrated for spastin and IST1 loss in the same paper. The study also frames the finding around hereditary spastic paraplegia and axonopathy rather than RSS1, so it supports this node through the shared molecular lesion rather than by measurement in an RSS1 context.

Multisystem Developmental Malformation

Strumpellin is ubiquitously expressed and highly conserved, so the recycling defect is present in every tissue. The resulting malformations concentrate in structures whose morphogenesis is most dependent on adhesion-driven and receptor-driven patterning: the cerebellum and posterior fossa, the cardiac septa and outflow tract, and the craniofacial skeleton. The cell types listed below belong to the cerebellar arm only and do not apply to the cardiac or craniofacial arms this node also feeds; they sit here because no separate cerebellar node has been split out.

cerebellar Purkinje cell CL:0000121 cerebellar granule cell CL:0000120

Downstream

Dandy-Walker malformation

Cerebellar vermis hypoplasia

Congenital heart defect

Craniofacial dysmorphism

Global developmental delay

Enlarged cisterna magna

Hydrocephalus

Camptodactyly

Overlapping fingers

Vertical talus

Nail hypoplasia

Single transverse palmar crease

Eye anomalies

Macrocephaly

Abnormal metacarpophalangeal profile

Increased nuchal translucency

Renal anomalies

Immunodeficiency

Show evidence (1 reference)

PMID:24065355 SUPPORT Human Clinical

"The ubiquitous expression and highly conserved nature of strumpellin, the product of KIAA0196, is consistent with the complex and multisystem nature of this disorder."

Connects the ubiquitous expression of the affected protein to the multi-organ distribution of the malformations.

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Pathograph

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Phenotypes

47

Cardiovascular 9

Congenital heart defect Abnormal heart morphology HP:0001627

Sequelae: Abnormal cardiac septum morphology Ventricular septal defect Atrial septal defect Tetralogy of Fallot Double outlet right ventricle Hypoplastic left heart Aortic valve stenosis Pulmonic stenosis

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"the cardinal findings of craniofacial features, cerebellar defects, and cardiovascular malformations resulting in the alternate diagnostic name of 3C syndrome"

Cardiovascular malformation is one of the three cardinal findings that name the syndrome.

Abnormal cardiac septum morphology HP:0001671

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"low-set ears (80.7%) and septal heart defects (68.7%) were the most common facial and cardiac malformations, respectively"

Identifies septal defects as the commonest cardiac malformation at 68.7%, which is what makes the generic congenital heart defect node concrete. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Ventricular septal defect HP:0001629

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

Listed first among the cardiac manifestations of the syndrome in a review of all reported cases. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Atrial septal defect HP:0001631

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

Listed among the cardiac manifestations in a review of all reported cases. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Tetralogy of Fallot HP:0001636

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

A conotruncal malformation reported in the syndrome, showing the cardiac phenotype extends beyond simple septation defects. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Double outlet right ventricle HP:0001719

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

A conotruncal malformation reported in the syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Hypoplastic left heart Hypoplastic left ventricle HP:0004383

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

Reported among the cardiac manifestations. HPO has no hypoplastic-left-heart term, so the ventricular term is bound and the reported phrasing kept in preferred_term. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Aortic valve stenosis HP:0001650

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

One of the valvular lesions reported in the syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Pulmonic stenosis HP:0001642

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies."

One of the valvular lesions reported in the syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Ear 2

Low-set ears HP:0000369

Show evidence (1 reference)

PMID:36130690 SUPPORT Human Clinical

"The most common findings in all patients were craniofacial dysmorphism, particularly macrocephaly, down slanted palpebral fissures and low set-ears."

Listed among the most common findings in a six-patient cohort mixing four WASHC5 and two CCDC22 individuals. No percentage is stated, so no frequency band is asserted.

Overfolded helix HP:0000396

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"low-set ears with overfolding of the upper helix"

The ear anomaly is described as low-set with overfolding of the upper helix, so the overfolded helix is a distinct finding from ear position.

Eye 4

Hypertelorism HP:0000316

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"short midface, widely spaced eyes, downslanted palpebral fissures"

"Widely spaced eyes" is the GeneReviews plain-language rendering of hypertelorism.

Eye anomalies Abnormality of the eye HP:0000478

Sequelae: Megalocornea Coloboma

Show evidence (2 references)

PMID:31971710 SUPPORT Human Clinical

"Eye anomalies and hypercholesterolemia may be variably present."

GeneReviews, which is written for the WASHC5 and CCDC22 forms, records eye anomalies as a variable feature.

PMID:28555453 SUPPORT INDIRECT Human Clinical

"All of them presented ocular disorders, and megalocornea was the most frequent ocular manifestation (69%)"

Reports ocular involvement in every patient of the largest series, which is a considerably stronger claim than the GeneReviews wording. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Megalocornea HP:0000485

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"All of them presented ocular disorders, and megalocornea was the most frequent ocular manifestation (69%)"

Names megalocornea as the leading ocular finding at 69%. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Coloboma HP:0000589

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Craniofacial abnormalities seen are cleft palate, ocular coloboma, prominent occiput, low-set ears, hypertelorism, down-slanting palpebral fissures, depressed nasal bridge and micrognathia."

A structural ocular malformation reported in the syndrome, giving the variably present eye anomalies a specific form. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Genitourinary 1

Renal anomalies Abnormality of the kidney HP:0000077

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Standard treatment for obesity, obstructive sleep apnea, cleft palate, congenital heart defects, hypercholesterolemia, renal anomalies, immunodeficiency, and developmental delay / intellectual disability."

GeneReviews includes renal anomalies among the manifestations requiring treatment, which establishes that they occur in this syndrome.

Head and Neck 16

Dandy-Walker malformation HP:0001305

Show evidence (1 reference)

PMID:24065355 SUPPORT Human Clinical

"Ritscher-Schinzel syndrome (RSS) is a clinically heterogeneous disorder characterised by distinctive craniofacial features in addition to cerebellar and cardiac anomalies."

Establishes the cerebellar anomaly as a defining feature of the cohort in which the WASHC5 variant was identified.

Craniofacial dysmorphism Abnormal facial shape HP:0001999

Sequelae: Brachycephaly Hypertelorism Downslanted palpebral fissures Low-set ears Overfolded helix Short philtrum Smooth philtrum Flat face Prominent occiput Depressed nasal bridge Micrognathia Protruding tongue Cleft palate High palate

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Dysmorphic facial features may include brachycephaly, hypotonic face with protruding tongue, flat appearance of the face on profile view, short midface, widely spaced eyes, downslanted palpebral fissures, low-set ears with overfolding of the upper helix, smooth or short philtrum, and high or..."

Enumerates the facial features that constitute the craniofacial element of the triad.

Downslanted palpebral fissures HP:0000494

Show evidence (1 reference)

PMID:36130690 SUPPORT Human Clinical

"The most common findings in all patients were craniofacial dysmorphism, particularly macrocephaly, down slanted palpebral fissures and low set-ears."

Reported among the most common findings in a cohort of six genetically confirmed patients, of whom four carried WASHC5 variants and two CCDC22. The phrase gives no percentage and the cohort is small and mixed, so the finding is curated without a frequency band.

Macrocephaly HP:0000256

Show evidence (1 reference)

PMID:36130690 SUPPORT Human Clinical

"The most common findings in all patients were craniofacial dysmorphism, particularly macrocephaly, down slanted palpebral fissures and low set-ears."

Named as the leading craniofacial finding in a six-patient cohort of confirmed RTSCS1 and RTSCS2 individuals. The report gives no percentage and does not separate the two genotypes, so no frequency band is asserted.

Brachycephaly HP:0000248

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Dysmorphic facial features may include brachycephaly, hypotonic face with protruding tongue"

GeneReviews lists brachycephaly first among the dysmorphic features.

Protruding tongue HP:0010808

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"hypotonic face with protruding tongue"

Documented as part of the characteristic facial appearance.

Short philtrum HP:0000322

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"smooth or short philtrum, and high or cleft palate"

GeneReviews records a smooth or short philtrum among the facial features.

Cleft palate HP:0000175

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"smooth or short philtrum, and high or cleft palate"

GeneReviews lists palatal clefting as one of two alternative palatal findings. The phrasing indicates it affects a subset but gives no proportion, so no frequency band is asserted.

High palate HP:0000218

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"smooth or short philtrum, and high or cleft palate"

A high palate is the alternative palatal finding recorded by GeneReviews.

Increased nuchal translucency HP:0010880

Show evidence (1 reference)

PMID:36130690 SUPPORT Human Clinical

"Elevation of nuchal translucency was observed in the first trimester ultrasound in three foetuses with compound heterozygous variants in WASHC5."

Reported specifically in WASHC5 (RSS1) fetuses rather than in the CCDC22 arm of the cohort, so it is an RSS1-specific prenatal finding.

Flat face HP:0012368

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"flat appearance of the face on profile view, short midface"

GeneReviews describes a flat facial profile as part of the characteristic gestalt.

Smooth philtrum HP:0000319

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"smooth or short philtrum, and high or cleft palate"

GeneReviews records the philtrum as either smooth or short; both variants are curated so neither presentation is lost.

Enlarged cisterna magna HP:0002280

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"The most frequent malformations of the posterior fossa were megacisterna magna (31.8%) and Dandy-Walker malformation (27%)."

Establishes enlarged cisterna magna as the commonest posterior fossa finding, more frequent than Dandy-Walker malformation. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Prominent occiput HP:0000269

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Craniofacial abnormalities seen are cleft palate, ocular coloboma, prominent occiput, low-set ears, hypertelorism, down-slanting palpebral fissures, depressed nasal bridge and micrognathia."

Reported among the craniofacial abnormalities of the syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Depressed nasal bridge HP:0005280

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Craniofacial abnormalities seen are cleft palate, ocular coloboma, prominent occiput, low-set ears, hypertelorism, down-slanting palpebral fissures, depressed nasal bridge and micrognathia."

Reported among the craniofacial abnormalities of the syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Micrognathia HP:0000347

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Craniofacial abnormalities seen are cleft palate, ocular coloboma, prominent occiput, low-set ears, hypertelorism, down-slanting palpebral fissures, depressed nasal bridge and micrognathia."

Reported among the craniofacial abnormalities of the syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Immune 1

Immunodeficiency HP:0002721

Show evidence (1 reference)

PMID:31971710 SUPPORT INDIRECT Human Clinical

"Standard treatment for obesity, obstructive sleep apnea, cleft palate, congenital heart defects, hypercholesterolemia, renal anomalies, immunodeficiency, and developmental delay / intellectual disability."

Immunodeficiency appears in the management list of a chapter that covers WASHC5 and CCDC22 together, so this supports the finding occurring in Ritscher-Schinzel syndrome without establishing it for the WASHC5 form specifically. Curated here for completeness against the GeneReviews baseline, with the attribution left explicitly unsettled.

Integument 2

Nail hypoplasia Small nail HP:0001792

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"the group consisting of camptodactyly, single palmar crease, overlapping fingers, vertical talus and nail hypoplasia were found in hands and feet in 96% of the cases"

Named as a component of the acral cluster found in 96% of patients. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Single transverse palmar crease HP:0000954

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"the group consisting of camptodactyly, single palmar crease, overlapping fingers, vertical talus and nail hypoplasia were found in hands and feet in 96% of the cases"

Named as a component of the acral cluster found in 96% of patients. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Limbs 3

Overlapping fingers HP:0010557

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"the group consisting of camptodactyly, single palmar crease, overlapping fingers, vertical talus and nail hypoplasia were found in hands and feet in 96% of the cases"

Named as a component of the acral cluster found in 96% of patients. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Vertical talus Rocker bottom foot HP:0001838

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"the group consisting of camptodactyly, single palmar crease, overlapping fingers, vertical talus and nail hypoplasia were found in hands and feet in 96% of the cases"

Named as a component of the acral cluster found in 96% of patients. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Abnormal metacarpophalangeal profile Abnormal metacarpal morphology HP:0005916

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Affected individuals also typically have a characteristic metacarpal phalangeal profile showing a consistent wavy pattern on hand radiographs."

GeneReviews describes a typical and characteristic radiographic hand finding.

Metabolism 1

Hypercholesterolemia HP:0003124

Show evidence (1 reference)

PMID:31971710 SUPPORT INDIRECT Human Clinical

"Eye anomalies and hypercholesterolemia may be variably present."

GeneReviews records hypercholesterolemia as a variable feature without giving a proportion. The chapter covers the WASHC5 and CCDC22 forms together and does not separate them, so the finding is attributed to RSS1 by inference rather than by direct genotype-specific report.

Musculoskeletal 1

Camptodactyly HP:0012385

Show evidence (1 reference)

PMID:28555453 SUPPORT INDIRECT Human Clinical

"the group consisting of camptodactyly, single palmar crease, overlapping fingers, vertical talus and nail hypoplasia were found in hands and feet in 96% of the cases"

Reports the acral skeletal cluster in 96% of patients. The bound term names only camptodactyly because HPO has no term for the cluster as a whole, and the remaining components are carried in the description. This is a clinically ascertained cohort of 26 patients diagnosed on phenotype; the report does not genotype them and never names WASHC5, and its 69% male predominance suggests X-linked CCDC22 cases are included. The finding is therefore attributed to RSS1 by inference from the shared clinical entity, and the stated percentage is not curated as an RSS1 frequency band.

Nervous System 6

Cerebellar vermis hypoplasia HP:0001320

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"the cardinal findings of craniofacial features, cerebellar defects, and cardiovascular malformations resulting in the alternate diagnostic name of 3C syndrome"

GeneReviews lists cerebellar defects among the cardinal findings that define the syndrome.

Global developmental delay HP:0001263

Show evidence (1 reference)

PMID:36130690 SUPPORT Human Clinical

"Developmental delay, intellectual disability and ataxic gait were present in all patients."

Present in all six patients of the confirmed cohort. Because four carried WASHC5 and two CCDC22, and the cohort is drawn from only two families, the universality is not generalised to a frequency band for RSS1.

Intellectual disability HP:0001249

Show evidence (2 references)

PMID:36130690 SUPPORT Human Clinical

"Developmental delay, intellectual disability and ataxic gait were present in all patients."

Reported in every patient of the confirmed WASHC5 and CCDC22 cohort. The cohort is six patients from two families and mixes both genotypes, so no RSS1 frequency band is asserted from it.

PMID:31971710 SUPPORT Human Clinical

"RSS is associated with variable degrees of developmental delay and intellectual disability."

GeneReviews confirms the finding and records that its severity is variable.

Gait ataxia HP:0002066

Show evidence (1 reference)

PMID:36130690 SUPPORT Human Clinical

"Developmental delay, intellectual disability and ataxic gait were present in all patients."

Ataxic gait was universal in the six-patient confirmed cohort. That cohort mixes WASHC5 and CCDC22 genotypes across two families, so it establishes the finding without supporting a frequency band for RSS1.

Obstructive sleep apnea HP:0002870

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"monitoring for symptoms of obstructive sleep apnea at each visit"

GeneReviews mandates surveillance for obstructive sleep apnea at every visit, which establishes it as an expected complication.

Hydrocephalus HP:0000238

Show evidence (1 reference)

PMID:11484200 SUPPORT INDIRECT Human Clinical

"Dandy-Walker malformation, posterior fossa cyst, hydrocephalus and congenital heart defect are common malformations"

Groups hydrocephalus with the posterior fossa findings as a common malformation in this syndrome. The series predates the identification of WASHC5 by twelve years, so its patients are clinically ascertained and ungenotyped and the finding is attributed to RSS1 by inference from the shared clinical entity rather than by genotype-specific report.

Growth 1

Obesity HP:0001513

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Standard treatment for obesity, obstructive sleep apnea, cleft palate, congenital heart defects, hypercholesterolemia, renal anomalies, immunodeficiency, and developmental delay / intellectual disability."

Obesity heads the list of manifestations requiring treatment, establishing it as a recognised feature.

🧬

Genetic Associations

1

WASHC5

Gene: WASHC5 hgnc:28984 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:24065355 SUPPORT Human Clinical

"We have identified a mutation in KIAA0196 as the cause of the form of RSS characterised in our cohort."

Establishes WASHC5/KIAA0196 as the causal gene for this form of Ritscher-Schinzel syndrome.

PMID:36130690 SUPPORT Human Clinical

"The first two genes described were the autosomal recessive inherited gene WASHC5 associated with Ritscher-Schinzel syndrome 1 (RTSCS1), and CCDC22, an X-linked recessive gene causing Ritscher-Schinzel syndrome 2 (RTSCS2)."

States explicitly that WASHC5 is the gene of Ritscher-Schinzel syndrome 1, which is the entity this entry describes.

💊

Medical Actions

6

Multidisciplinary Symptomatic Management

Action: Supportive Care NCIT:C15747

No disease-modifying therapy exists. Care is standard management of the individual manifestations, coordinated across cardiology, craniofacial surgery, developmental paediatrics, nephrology, immunology, and metabolic medicine.

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Treatment of manifestations: Standard treatment for obesity, obstructive sleep apnea, cleft palate, congenital heart defects, hypercholesterolemia, renal anomalies, immunodeficiency, and developmental delay / intellectual disability."

GeneReviews prescribes standard symptomatic treatment of each manifestation rather than any disease-specific therapy.

Developmental and Educational Intervention

Action: Rehabilitation NCIT:C15315

Platform: Behavioral / lifestyle

Early developmental support, mobility and self-help training, and individualised educational planning, guided by regular reassessment of developmental progress.

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"assessment of developmental progress, mobility, self-help skills, and educational needs"

GeneReviews specifies periodic assessment of developmental progress, mobility, self-help skills, and educational needs, which is the basis for developmental and educational intervention.

Lipid Surveillance and Management

Action: Supportive Care NCIT:C15747

Periodic lipid profile measurement beginning in childhood, with standard treatment of hypercholesterolemia when detected.

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"measurement of lipid profile periodically starting in childhood"

GeneReviews sets out periodic lipid measurement from childhood as disease-specific surveillance.

Annual Ophthalmologic Surveillance

Action: Supportive Care NCIT:C15747

Ophthalmology evaluation annually or as clinically indicated, on the basis of the variably present eye anomalies.

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"ophthalmology evaluation annually or as clinically indicated"

GeneReviews specifies the interval and the trigger for ophthalmologic review.

Growth and Weight Surveillance

Action: Supportive Care NCIT:C15747

Measurement of growth parameters at each visit with particular attention to weight, reflecting the obesity risk.

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Measurement of growth parameters (particularly weight)"

GeneReviews directs growth monitoring with weight singled out, which is the basis for this surveillance item.

Genetic Counseling

Action: Genetic Counseling NCIT:C15240

Autosomal recessive counselling with a 25% sibling recurrence risk and a 50% chance of carrier status. Prenatal and preimplantation genetic testing are possible once the familial WASHC5 variants are known, and elevated nuchal translucency has been observed in affected WASHC5 pregnancies.

Show evidence (3 references)

PMID:31971710 SUPPORT Human Clinical

"At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier."

The GeneReviews genetic counseling section supplies the recurrence and carrier risks this treatment conveys.

PMID:31971710 SUPPORT Human Clinical

"Once the causative pathogenic variant(s) have been identified in an affected family member, prenatal and preimplantation genetic testing are possible."

Establishes the reproductive testing options that follow a molecular diagnosis, which is the practical content of the counselling.

PMID:36130690 SUPPORT Human Clinical

"The pre- and postnatal findings of this cohort expand the known phenotype of RTSCS1 and 2, with direct impact on postnatal outcome, management, and familial counseling."

The authors state that their pre- and postnatal findings bear directly on familial counseling.

🔬

Diagnosis

3

Molecular genetic testing of WASHC5

The diagnosis is established in a proband with suggestive clinical findings by identifying biallelic pathogenic WASHC5 variants. Because the syndrome is genetically heterogeneous and clinically overlapping across its forms, exome, genome, or a multigene panel covering the WASH and Commander pathway genes is the practical route.

Genetic Testing NCIT:C15709

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"The diagnosis of Ritscher-Schinzel syndrome is established in a proband with suggestive clinical findings, including characteristic dysmorphic facial features, and/or by the identification of biallelic pathogenic variants in WASHC5 in a male or female or a hemizygous pathogenic variant in CCDC22..."

States the diagnostic criterion, and names biallelic WASHC5 variants in either sex as the molecular finding that establishes the RSS1 form.

Clinical minimal diagnostic criteria

Before molecular testing, the diagnosis rested on a proposed clinical triad of cardiac malformation other than isolated patent ductus arteriosus, posterior fossa malformation, and characteristic dysmorphic features. These criteria are not met by every patient with a molecular diagnosis, so they are useful for raising suspicion rather than for excluding the diagnosis.

The cited paper numbers the genetic forms the opposite way round to OMIM, MONDO and GeneReviews: it calls the CCDC22 form RTSCS1 and the WASHC5 form RTSCS2, while its own text correctly pairs CCDC22 with X-linked and WASHC5 with autosomal recessive inheritance. This entry follows the standard numbering, in which RTSCS1 is the WASHC5 form (OMIM 220210). The paper is cited here only for the syndrome-level diagnostic criteria and the case count, neither of which depends on the numbering.

Show evidence (2 references)

PMID:34020006 SUPPORT Human Clinical

"minimal diagnostic criteria has been proposed for the syndrome: Cardiac malformations (other than isolated patent ductus arteriosis), fossa posterior malformations, and certain dysmorphic features."

States the proposed clinical criteria for the syndrome as a whole.

PMID:34020006 SUPPORT Human Clinical

"However, those criteria are not present in all patients."

The same paper reports that the criteria fail on some molecularly confirmed patients, which is why they cannot be used to rule the diagnosis out. This supports rather than contradicts the entry: the description already states the criteria are not met by every patient and are for raising suspicion rather than excluding the diagnosis, so the quote confirms the claim as written.

Metacarpophalangeal pattern profile on hand radiographs

Hand radiographs show a consistent wavy metacarpal phalangeal profile. GeneReviews treats this as a characteristic finding, so it functions as a clinical pointer toward the diagnosis rather than a confirmatory test.

Show evidence (1 reference)

PMID:31971710 SUPPORT Human Clinical

"Affected individuals also typically have a characteristic metacarpal phalangeal profile showing a consistent wavy pattern on hand radiographs."

GeneReviews describes the radiographic hand pattern as typical and characteristic, which is what makes it diagnostically useful.

📈

Progression

1

Life-threatening complications

Mortality in this syndrome is driven principally by the cardiac malformations. Pulmonary hypertension with prolonged respiratory failure has also been reported in a preterm infant, so cardiorespiratory status is the dominant determinant of early outcome.

Show evidence (2 references)

PMID:23072186 SUPPORT Human Clinical

"Life threatening features of this syndrome are generally associated with cardiac abnormalities."

Identifies the cardiac malformations as the main threat to survival, which is what makes cardiology the priority in management.

PMID:23072186 SUPPORT Human Clinical

"We here present prolonged respiratory problems due to pulmonary hypertension in a preterm baby with Ritscher-Schinzel syndrome."

A single case report of pulmonary hypertension causing prolonged respiratory failure. One patient, so it establishes the complication can occur rather than how often it does.

📊

Prevalence

1

Worldwide, molecularly confirmed cases

Cases In Literature Ultra Rare

Only 17 individuals with a molecular diagnosis of Ritscher-Schinzel syndrome of any form had been reported as of 2021, of which the WASHC5 subset is smaller still. A founder cluster exists in a First Nations community in northern Manitoba, so the case count is geographically concentrated rather than uniformly distributed. No population-based rate has been estimated, and none is asserted here.

Show evidence (1 reference)

PMID:34020006 SUPPORT Human Clinical

"Only 17 individuals with a molecular diagnosis are reported."

Gives the total molecularly confirmed case count across the syndrome, which is the basis for the ULTRA_RARE band. The count spans all genetic forms rather than WASHC5 alone, so it is an upper bound for RSS1.

🐁

Animal Models

3

Washc5 constitutive knockout mouse

A deletion-based null allele of the murine WASHC5 orthologue. Homozygous null embryos die early, which is why this model does not recapitulate a viable RSS1 phenotype and instead bounds the tolerable degree of strumpellin loss.

Species

Mouse

Genotype

E430025E21Rik (Washc5) deletion-based knockout, homozygous and heterozygous

Publication

PMID:26572744

Pathograph links

WASHC5 Hypomorphic Loss of Function fails to recapitulate fidelity: low Complete ablation of the orthologue is not a model of the hypomorphic human genotype; it is lethal before the malformations of interest can form.

Limitations: The knockout is a null allele, whereas RSS1 alleles are hypomorphic and retain roughly 40% of strumpellin. Homozygous embryonic lethality means no craniofacial, cerebellar, or cardiac phenotype can be scored, and heterozygotes showed no relevant phenotype. The study was designed to probe the dominant SPG8 mechanism rather than recessive RSS1, so its negative findings bear on RSS1 only through the dose-response relationship. A knock-in of a patient hypomorphic allele would be required.

Show evidence (1 reference)

PMID:26572744 SUPPORT Model Organism

"We did, however, neither observe HSP-related in vivo and ex vivo phenotypes, nor alterations affecting endosomal, lysosomal, or autophagic compartments."

The surviving heterozygous animals showed no trafficking or neurological phenotype, so the model does not reproduce the human disease mechanism at either dose.

Show evidence (1 reference)

PMID:26572744 SUPPORT Model Organism

"We generated a deletion-based knockout allele for E430025E21Rik, i.e. the murine homologue of KIAA0196."

Documents the construction of the model and identifies the targeted gene as the murine orthologue of the human disease gene.

N471D Washc5 knock-in mouse

The only viable engineered Washc5 allele. Homozygotes survive and show mild dilated cardiomyopathy, decreased acoustic startle reactivity, thinner eye lenses, altered clinical chemistry and haematology, and gait instability. N471D is an SPG8 allele, not an RSS1 allele, and the model reproduces neither disease cleanly.

Species

Mouse

Genotype

Washc5 N471D knock-in, heterozygous and homozygous

Publication

PMID:34312900

Pathograph links

WASHC5 Hypomorphic Loss of Function fails to recapitulate fidelity: low A viable Washc5 point mutant that nonetheless does not model the RSS1 lesion, because the allele is the dominant SPG8 one and complex abundance is unchanged.

Limitations: N471D causes dominant SPG8, not recessive RSS1, and the study reports it does not produce a typical SPG8 phenotype either. Mechanistically it is the wrong lesion for this entry: WASHC5-related interaction partners and complexes showed unchanged abundance in these animals, whereas RSS1 acts through reduced strumpellin and therefore reduced WASH complex abundance. The cardiac and ocular findings are suggestive but were not characterised as the RSS1 malformations, and no cerebellar or craniofacial malformation was reported. A knock-in of a patient RSS1 hypomorphic allele is what the question needs.

Readouts

Left ventricular function

Direction: ALTERED

Interpretation: Mild dilated cardiomyopathy in homozygotes. Recorded because cardiac involvement is part of the human triad, but this is an SPG8 allele and the lesion is not the RSS1 septation defect.

Show evidence (1 reference)

PMID:34312900 SUPPORT Model Organism

"Homozygous N471D Washc5 knock-in mice showed mild dilated cardiomyopathy, decreased acoustic startle reactivity, thinner eye lenses, increased alkaline phosphatase and potassium levels and increased white blood cell counts."

Reports the multi-organ findings in the homozygous knock-in.

Show evidence (1 reference)

PMID:34312900 SUPPORT Model Organism

"WASHC5-related protein interaction partners and complexes showed no change in abundancies."

Complex abundance is unchanged in this model, which is precisely the variable RSS1 acts through, so the model cannot inform the RSS1 mechanism even where its organ findings overlap.

Show evidence (1 reference)

PMID:34312900 SUPPORT Model Organism

"We generated heterozygous and homozygous N471D Washc5 knock-in mice and subjected them to a comprehensive clinical, morphological and laboratory parameter screen, and gait analyses."

Documents the construction and the breadth of phenotyping, which is what makes the model's negative result for the RSS1 triad informative rather than merely unexamined.

Strumpellin shRNA knockdown cortical neuron model

Acute knockdown of strumpellin in cortical motor neurons, producing a motor coordination deficit in vivo with reduced dendritic arborisation, synapse formation, and dendritic F-actin in culture.

Species

Mouse

Genotype

Lentiviral strumpellin-targeting shRNA in cortical motor neurons

Publication

PMID:37392480

Pathograph links

Reduced Neuronal Dendritic Arborisation and Synaptogenesis partially recapitulates fidelity: moderate Reproduces the cellular consequence of reduced strumpellin dose in neurons, with rescue by wild-type protein establishing specificity.

Limitations: Acute postnatal knockdown in a targeted neuronal population is not the constitutive biallelic hypomorphism of RSS1, and the readouts are gait coordination and dendritic morphology rather than the cerebellar, cardiac, or craniofacial malformations that define the syndrome. The study frames the model around SPG8 rather than RSS1.

Readouts

Dendritic arborisation and synapse number in cultured cortical neurons

Direction: DECREASED

Interpretation: Structural correlate of reduced WASH-dependent actin activity in neurons.

Show evidence (1 reference)

PMID:37392480 SUPPORT In Vitro

"Strumpellin knockdown using shRNA attenuated dendritic arborization and synapse formation in cultured cortical neurons"

Reports the measurement and its direction.

Dendritic F-actin cluster number

Direction: DECREASED

Interpretation: Direct readout of the actin-polymerisation defect predicted by loss of the WASH complex.

Show evidence (1 reference)

PMID:37392480 SUPPORT In Vitro

"the number of F-actin clusters in neuronal dendrites was decreased by strumpellin knockdown and rescued by strumpellin expression"

Quantifies the actin phenotype and demonstrates rescue by wild-type strumpellin.

Show evidence (1 reference)

PMID:37392480 SUPPORT Model Organism

"Administration of a lentivirus containing a strumpellin-targeting short hairpin RNA (shRNA) to cortical motor neurons lead to abnormal motor coordination in mice."

Establishes that reducing strumpellin in neurons produces a motor phenotype in vivo, which is what makes the model informative for the neuronal node.

Show evidence (1 reference)

PMID:37392480 SUPPORT Model Organism

"In this study, we examined the role of strumpellin in the regulation of structural plasticity of cortical neurons involved in gait coordination."

Establishes what the model was built to interrogate, which is the basis for treating it as informative about strumpellin loss in neurons.

{ }

Source YAML

click to show

name: Ritscher-Schinzel Syndrome 1
creation_date: "2026-09-03T00:00:00Z"
category: Mendelian
description: >-
  Ritscher-Schinzel syndrome 1 (RSS1, RTSCS1) is the autosomal recessive,
  WASHC5-related form of Ritscher-Schinzel (3C, cranio-cerebello-cardiac)
  syndrome and was the first molecularly defined cause of the condition. It is
  characterised by the 3C triad of distinctive craniofacial dysmorphism,
  cerebellar malformation (Dandy-Walker malformation and cerebellar vermis
  hypoplasia), and congenital cardiovascular malformation, together with
  developmental delay, intellectual disability, and ataxic gait. WASHC5 encodes
  strumpellin, a core subunit of the pentameric WASH regulatory complex (SHRC),
  which activates Arp2/3-mediated branched actin polymerisation on the
  endosomal membrane and thereby drives the tubulation and fission events that
  retrieve integral membrane cargo away from lysosomal degradation and return it
  to the cell surface. RSS1 therefore sits mechanistically alongside the
  Commander/CCC-related forms (RSS2/RSS3) as a disorder of endosomal
  retrieval-and-recycling, but acts through the actin-generating WASH complex
  rather than through the SNX17-dependent Commander cargo-selection machinery.
  Disease alleles are hypomorphic rather than null: complete loss of the murine
  orthologue is embryonic lethal, and the recurrent First Nations splice variant
  leaves roughly 40% of residual strumpellin. WASHC5 is allelic with autosomal
  dominant hereditary spastic paraplegia type SPG8.
disease_term:
  preferred_term: Ritscher-Schinzel Syndrome 1
  term:
    id: MONDO:0009073
    label: Ritscher-Schinzel syndrome 1
parents:
- Ritscher-Schinzel syndrome
- Multiple congenital anomalies syndrome
- Endosomal recycling disorder
references:
- reference: PMID:31971710
  title: "Ritscher-Schinzel Syndrome."
  tags:
  - GeneReviews

inheritance:
- name: Autosomal recessive
  description: >-
    RSS1 segregates as an autosomal recessive trait. Affected individuals carry
    biallelic WASHC5 variants, either homozygous (as in the northern Manitoba
    First Nations founder cohort) or compound heterozygous.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      WASHC5-related RSS is inherited in an autosomal recessive manner;
      CCDC22-related RSS is inherited in an X-linked manner.
    explanation: >-
      Names the inheritance mode for the WASHC5 form specifically and
      distinguishes it from the X-linked CCDC22 form, so the attribution to RSS1
      is genotype-specific rather than inferred from a form-agnostic statement.
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At conception, each sib of an affected individual has a 25% chance of
      being affected, a 50% chance of being an asymptomatic carrier, and a 25%
      chance of being unaffected and not a carrier.
    explanation: >-
      Gives the sibling recurrence risks that follow from autosomal recessive
      inheritance, which is the operative counselling figure for RSS1.

prevalence:
- population: Worldwide, molecularly confirmed cases
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Only 17 individuals with a molecular diagnosis of Ritscher-Schinzel syndrome
    of any form had been reported as of 2021, of which the WASHC5 subset is
    smaller still. A founder cluster exists in a First Nations community in
    northern Manitoba, so the case count is geographically concentrated rather
    than uniformly distributed. No population-based rate has been estimated, and
    none is asserted here.
  evidence:
  - reference: PMID:34020006
    reference_title: "Expansion of the CCDC22 associated Ritscher-Schinzel/3C syndrome and review of the literature: Should the minimal diagnostic criteria be revised?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Only 17 individuals with a molecular diagnosis are reported.
    explanation: >-
      Gives the total molecularly confirmed case count across the syndrome,
      which is the basis for the ULTRA_RARE band. The count spans all genetic
      forms rather than WASHC5 alone, so it is an upper bound for RSS1.

diagnosis:
- name: Molecular genetic testing of WASHC5
  description: >-
    The diagnosis is established in a proband with suggestive clinical findings
    by identifying biallelic pathogenic WASHC5 variants. Because the syndrome is
    genetically heterogeneous and clinically overlapping across its forms,
    exome, genome, or a multigene panel covering the WASH and Commander pathway
    genes is the practical route.
  diagnosis_term:
    preferred_term: Genetic Testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis of Ritscher-Schinzel syndrome is established in a proband
      with suggestive clinical findings, including characteristic dysmorphic
      facial features, and/or by the identification of biallelic pathogenic
      variants in WASHC5 in a male or female or a hemizygous pathogenic variant
      in CCDC22 in a male by molecular genetic testing
    explanation: >-
      States the diagnostic criterion, and names biallelic WASHC5 variants in
      either sex as the molecular finding that establishes the RSS1 form.

- name: Clinical minimal diagnostic criteria
  description: >-
    Before molecular testing, the diagnosis rested on a proposed clinical
    triad of cardiac malformation other than isolated patent ductus arteriosus,
    posterior fossa malformation, and characteristic dysmorphic features. These
    criteria are not met by every patient with a molecular diagnosis, so they
    are useful for raising suspicion rather than for excluding the diagnosis.
  notes: >-
    The cited paper numbers the genetic forms the opposite way round to OMIM,
    MONDO and GeneReviews: it calls the CCDC22 form RTSCS1 and the WASHC5 form
    RTSCS2, while its own text correctly pairs CCDC22 with X-linked and WASHC5
    with autosomal recessive inheritance. This entry follows the standard
    numbering, in which RTSCS1 is the WASHC5 form (OMIM 220210). The paper is
    cited here only for the syndrome-level diagnostic criteria and the case
    count, neither of which depends on the numbering.
  evidence:
  - reference: PMID:34020006
    reference_title: "Expansion of the CCDC22 associated Ritscher-Schinzel/3C syndrome and review of the literature: Should the minimal diagnostic criteria be revised?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      minimal diagnostic criteria has been proposed for the syndrome: Cardiac
      malformations (other than isolated patent ductus arteriosis), fossa
      posterior malformations, and certain dysmorphic features.
    explanation: >-
      States the proposed clinical criteria for the syndrome as a whole.
  - reference: PMID:34020006
    reference_title: "Expansion of the CCDC22 associated Ritscher-Schinzel/3C syndrome and review of the literature: Should the minimal diagnostic criteria be revised?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, those criteria are not present in all patients.
    explanation: >-
      The same paper reports that the criteria fail on some molecularly
      confirmed patients, which is why they cannot be used to rule the diagnosis
      out. This supports rather than contradicts the entry: the description
      already states the criteria are not met by every patient and are for
      raising suspicion rather than excluding the diagnosis, so the quote
      confirms the claim as written.

- name: Metacarpophalangeal pattern profile on hand radiographs
  description: >-
    Hand radiographs show a consistent wavy metacarpal phalangeal profile.
    GeneReviews treats this as a characteristic finding, so it functions as a
    clinical pointer toward the diagnosis rather than a confirmatory test.
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected individuals also typically have a characteristic metacarpal
      phalangeal profile showing a consistent wavy pattern on hand radiographs.
    explanation: >-
      GeneReviews describes the radiographic hand pattern as typical and
      characteristic, which is what makes it diagnostically useful.

progression:
- phase: Life-threatening complications
  notes: >-
    Mortality in this syndrome is driven principally by the cardiac
    malformations. Pulmonary hypertension with prolonged respiratory failure has
    also been reported in a preterm infant, so cardiorespiratory status is the
    dominant determinant of early outcome.
  evidence:
  - reference: PMID:23072186
    reference_title: "A preterm infant with prolonged respiratory problems due to Ritscher-Schinzel syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Life threatening features of this syndrome are generally associated with
      cardiac abnormalities.
    explanation: >-
      Identifies the cardiac malformations as the main threat to survival, which
      is what makes cardiology the priority in management.
  - reference: PMID:23072186
    reference_title: "A preterm infant with prolonged respiratory problems due to Ritscher-Schinzel syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We here present prolonged respiratory problems due to pulmonary
      hypertension in a preterm baby with Ritscher-Schinzel syndrome.
    explanation: >-
      A single case report of pulmonary hypertension causing prolonged
      respiratory failure. One patient, so it establishes the complication can
      occur rather than how often it does.

pathophysiology:
- name: WASHC5 Hypomorphic Loss of Function
  description: >-
    Biallelic WASHC5 (KIAA0196) variants reduce the abundance of functional
    strumpellin. The founder variant identified in the northern Manitoba First
    Nations cohort is a splice-site change that shifts the relative abundance of
    KIAA0196 transcripts and leaves approximately 40% of normal strumpellin
    protein. Disease alleles are hypomorphic rather than complete nulls,
    consistent with embryonic lethality of the homozygous murine knockout.
  biological_scale: MOLECULAR
  downstream:
  - target: WASH Regulatory Complex Destabilisation
    causal_link_type: DIRECT
    description: >-
      Strumpellin is one of five obligate subunits of the WASH regulatory
      complex, so reducing it lowers the abundance of the assembled complex.
    evidence:
    - reference: PMID:26572744
      reference_title: "The spectrum of KIAA0196 variants, and characterization of a murine knockout: implications for the mutational mechanism in hereditary spastic paraplegia type SPG8."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        mRNA expression of genes encoding other SHRC members was unaltered,
        while there was evidence for reduced SHRC abundance at protein level
      explanation: >-
        Loss of the strumpellin gene product lowers the abundance of the
        assembled WASH regulatory complex without changing transcription of the
        other subunits, establishing that the molecular lesion propagates to the
        complex.
  genetic_context:
    functional_impact_category: PARTIAL_LOSS_OF_FUNCTION
    description: >-
      The recurrent First Nations allele is a homozygous splice-site variant
      associated with an approximately eightfold change in the relative amount
      of the KIAA0196 transcript lacking exon 27 and a 60% reduction in
      strumpellin protein. Compound heterozygous WASHC5 alleles have been
      reported in a separate family.
  evidence:
  - reference: PMID:24065355
    reference_title: "A novel mutation in KIAA0196: identification of a gene involved in Ritscher-Schinzel/3C syndrome in a First Nations cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All eight patients were homozygous for a novel splice site mutation in
      KIAA0196. RNA analysis revealed an approximate eightfold reduction in the
      relative amount of a KIAA0196 transcript lacking exon 27. A 60% reduction
      in the amount of strumpellin protein was observed on western blot.
    explanation: >-
      The founding genetic study demonstrates the causal WASHC5 variant and
      quantifies the residual strumpellin, establishing the lesion as a partial
      rather than complete loss of function.
  - reference: PMID:26572744
    reference_title: "The spectrum of KIAA0196 variants, and characterization of a murine knockout: implications for the mutational mechanism in hereditary spastic paraplegia type SPG8."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: >-
      Homozygous but not heterozygous mice showed early embryonic lethality.
    explanation: >-
      Complete loss of the murine orthologue is lethal before birth, so viable
      human RSS1 genotypes must retain partial strumpellin function. This
      supports the hypomorphic-allele claim by inference from the null
      phenotype rather than by direct measurement in patients.

- name: WASH Regulatory Complex Destabilisation
  description: >-
    Reduced strumpellin lowers the abundance of the assembled pentameric WASH
    regulatory complex on the endosomal membrane. The complex is the endosomal
    member of the WASP family and is the dedicated Arp2/3 activator at this
    compartment. It reaches the endosome by the unstructured tail of its FAM21
    subunit binding retromer VPS35, an interaction that is both necessary and
    sufficient for the targeting, so the complex acts specifically where
    retromer is selecting cargo. This retromer-dependent recruitment is what
    makes the WASH route distinct from the SNX17-dependent Commander route that
    fails in the CCDC22 and VPS35L forms of the syndrome.
  biological_scale: MOLECULAR
  downstream:
  - target: Impaired Endosomal Branched Actin Nucleation
    causal_link_type: DIRECT
  biological_processes:
  - preferred_term: actin filament polymerization
    term:
      id: GO:0030041
      label: actin filament polymerization
    modifier: DECREASED
  evidence:
  - reference: PMID:20498093
    reference_title: "WASH and WAVE actin regulators of the Wiskott-Aldrich syndrome protein (WASP) family are controlled by analogous structurally related complexes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Here we show that WASH functions in cells within a 500 kDa core complex
      containing Strumpellin, FAM21, KIAA1033 (SWIP), and CCDC53.
    explanation: >-
      Names strumpellin as one of five obligate subunits of the WASH core
      complex, which is why reducing it compromises the whole assembly rather
      than only one of its activities.
  - reference: PMID:22070227
    reference_title: "Recruitment of the endosomal WASH complex is mediated by the extended 'tail' of Fam21 binding to the retromer protein Vps35."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      the retromer-WASH complex interaction occurs through the long unstructured
      'tail' domain of the WASH complex-Fam21 protein binding to Vps35, an
      interaction that is necessary and sufficient to target the WASH complex to
      endosomes
    explanation: >-
      Establishes how the complex is delivered to the endosomal membrane, which
      is what makes its abundance rate-limiting for endosomal actin rather than
      for actin generally.
  - reference: PMID:30061306
    reference_title: "Expression of N471D strumpellin leads to defects in the endolysosomal system."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: >-
      Real-time PCR analyses revealed no transcriptional changes in WASH complex
      subunits in Str- cells, but western blots showed a twofold decrease in the
      SWIP subunit.
    explanation: >-
      An independent demonstration, in a second organism, that losing
      strumpellin lowers another WASH subunit at protein level without changing
      its transcription. It replicates the post-transcriptional
      complex-destabilisation mechanism in Dictyostelium rather than mouse, so
      it supports this node across species rather than in an RSS1 context.

- name: Impaired Endosomal Branched Actin Nucleation
  description: >-
    With less WASH complex on the endosome, Arp2/3-dependent branched actin
    networks fail to form at the required density on the endosomal surface.
    These actin patches provide the force and the membrane subdomain
    organisation needed for tubule formation and scission.
  biological_scale: CELLULAR
  downstream:
  - target: Defective Endosomal Tubule Fission and Cargo Retrieval
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20714399
      reference_title: "Evolutionary conservation of the WASH complex, an actin polymerization machine involved in endosomal fission."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        This activity of WASH favors, in collaboration with dynamin, the fission
        of transport intermediates from endosomes, and hence regulates
        endosomal trafficking of several cargos.
      explanation: >-
        Directly asserts that the branched actin generated by WASH is what
        drives fission of transport carriers, which is the causal step from
        impaired actin nucleation to failed cargo retrieval.
  biological_processes:
  - preferred_term: Arp2/3 complex-mediated actin nucleation
    term:
      id: GO:0034314
      label: Arp2/3 complex-mediated actin nucleation
    modifier: DECREASED
  evidence:
  - reference: PMID:31911435
    reference_title: "Hereditary spastic paraplegia SPG8 mutations impair CAV1-dependent, integrin-mediated cell adhesion."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: >-
      We uncovered a decrease in CAV1 protein abundance as well as endosomal
      fission defects resulting from pathogenic SPG8 mutations.
    explanation: >-
      Measured for SPG8 alleles, which are heterozygous missense variants in the
      same gene causing a different, dominantly inherited disease rather than
      RSS1. It supports this node by inference: any strumpellin variant that
      produces endosomal fission defects shows the actin-dependent endosomal
      step depends on strumpellin dose or integrity. It is not a measurement in
      an RSS1 genotype.

- name: Defective Endosomal Tubule Fission and Cargo Retrieval
  description: >-
    Integral membrane cargo that should be captured into recycling tubules and
    returned to the surface is instead retained in the endosome and delivered to
    the lysosome for degradation. The WASH complex protects cargo from that
    default degradative fate through its endosomal actin activity.
  biological_scale: CELLULAR
  downstream:
  - target: Reduced Cell-Surface Cargo Receptor Density
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:31911435
      reference_title: "Hereditary spastic paraplegia SPG8 mutations impair CAV1-dependent, integrin-mediated cell adhesion."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        we demonstrated that the WASH complex maintained CAV1 and integrin
        protein amounts by inhibiting their lysosomal degradation through its
        endosomal actin nucleation activity
      explanation: >-
        States the causal mechanism by which failed retrieval lowers the
        available pool of specific surface cargo proteins.
  biological_processes:
  - preferred_term: endocytic recycling
    term:
      id: GO:0032456
      label: endocytic recycling
    modifier: DECREASED
  - preferred_term: endosome organization
    term:
      id: GO:0007032
      label: endosome organization
    modifier: DECREASED
  evidence:
  - reference: PMID:23085491
    reference_title: "The hereditary spastic paraplegia protein strumpellin: characterisation in neurons and of the effect of disease mutations on WASH complex assembly and function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      We show that strumpellin is not required for normal transferrin receptor
      traffic, but is required for the correct subcellular distribution of the
      β-2-adrenergic receptor.
    explanation: >-
      Demonstrates that strumpellin loss selectively disturbs the trafficking of
      particular cargo rather than bulk recycling: transferrin receptor traffic
      is unaffected while the beta-2-adrenergic receptor is mislocalised. The
      measurement was made in the context of SPG8, so it supports cargo
      selectivity as a property of strumpellin loss, not the tissue distribution
      of RSS1.

- name: Reduced Cell-Surface Cargo Receptor Density
  description: >-
    The steady-state surface pool of WASH-dependent cargo, including caveolin-1
    and integrins, falls. Because these cargoes mediate cell adhesion,
    migration, and developmental signalling, their depletion is the point at
    which a housekeeping trafficking defect becomes a developmental one.
  biological_scale: CELLULAR
  downstream:
  - target: Impaired Integrin-Mediated Cell Adhesion
    causal_link_type: DIRECT
    description: >-
      Loss of strumpellin lowers the surface pool of integrin, which is the
      adhesion receptor itself, so the adhesion defect follows directly from the
      recycling defect.
    evidence:
    - reference: PMID:37308549
      reference_title: "The WASH-complex subunit Strumpellin regulates integrin αIIbβ3 trafficking in murine platelets."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Here, we report that Strumpellin-deficient murine platelets display an
        approximately 20% reduction in integrin alphaIIbbeta3 surface
        expression.
      explanation: >-
        Quantifies the loss of surface integrin caused by strumpellin deficiency
        in a primary cell type from an animal, which is the causal step from
        failed recycling to reduced adhesion receptor availability. This is the
        only in vivo cargo-trafficking measurement in the literature made
        against strumpellin loss rather than against an SPG8 allele, so it
        carries the edge without the SPG8 inference step the other evidence
        needs.
  - target: Reduced Neuronal Dendritic Arborisation and Synaptogenesis
    causal_link_type: DIRECT
  - target: LDL Receptor Mislocalisation and Degradation
    causal_link_type: DIRECT
  - target: Impaired Lysosomal Enzyme Delivery
    causal_link_type: DIRECT
  - target: Multisystem Developmental Malformation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  biological_processes:
  - preferred_term: receptor recycling
    term:
      id: GO:0001881
      label: receptor recycling
    modifier: DECREASED
  - preferred_term: protein localization to plasma membrane
    term:
      id: GO:0072659
      label: protein localization to plasma membrane
    modifier: DECREASED
  evidence:
  - reference: PMID:31911435
    reference_title: "Hereditary spastic paraplegia SPG8 mutations impair CAV1-dependent, integrin-mediated cell adhesion."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      In addition, the interaction of strumpellin with CAV1 stimulated integrin
      recycling, thereby promoting cell adhesion.
    explanation: >-
      Identifies the specific cargo whose surface recycling depends on
      strumpellin and the adhesive function that depends on it.

- name: Impaired Integrin-Mediated Cell Adhesion
  description: >-
    Loss of surface integrin and caveolin-1 impairs integrin-mediated adhesion.
    Adhesion is the general-cell consequence of the recycling defect and is the
    plausible substrate for the morphogenetic failures, since cardiac septation
    and neural crest migration both depend on adhesive cell behaviour.
  biological_scale: CELLULAR
  downstream:
  - target: Multisystem Developmental Malformation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  biological_processes:
  - preferred_term: cell adhesion mediated by integrin
    term:
      id: GO:0033627
      label: cell adhesion mediated by integrin
    modifier: DECREASED
  evidence:
  - reference: PMID:37308549
    reference_title: "The WASH-complex subunit Strumpellin regulates integrin αIIbβ3 trafficking in murine platelets."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      While exposure of the internal alphaIIbbeta3 pool after platelet
      activation was unaffected, the uptake of the alphaIIbbeta3 ligand
      fibrinogen was delayed.
    explanation: >-
      Shows the functional consequence is specifically in ligand engagement
      rather than in the internal receptor store, which localises the defect to
      the surface-delivery step this node describes.
  - reference: PMID:31911435
    reference_title: "Hereditary spastic paraplegia SPG8 mutations impair CAV1-dependent, integrin-mediated cell adhesion."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: >-
      SPG8-associated missense mutations in strumpellin did not rescue endosomal
      tubulation defects, reduction in CAV1 protein abundance, or
      integrin-mediated cell adhesion in strumpellin-deficient cells.
    explanation: >-
      Tested with SPG8 missense alleles, not RSS1 alleles, so it bears on this
      node only by inference from the shared gene. Note that the rescue result
      is contested: two other groups report that SPG8 variants behave like
      wild-type in WASH complex assays, so this item is curated alongside the
      REFUTE item below rather than as a settled finding.
  - reference: PMID:37392480
    reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
    supports: REFUTE
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: >-
      Compared with the wild-type, strumpellin mutants N471D or V626F identified
      in patients with SPG8 exhibited no differences in rescuing the defects.
    explanation: >-
      Directly contradicts the non-rescue result quoted immediately above: here
      the same class of SPG8 missense alleles rescued as well as wild-type
      protein. Both are recorded because the literature does not resolve them,
      and because the disagreement is itself the reason SPG8 findings cannot be
      carried across to RSS1 without qualification. Neither result was obtained
      in an RSS1 genotype.

- name: Reduced Neuronal Dendritic Arborisation and Synaptogenesis
  description: >-
    Strumpellin depletion in cortical neurons reduces dendritic arborisation and
    synapse formation with loss of dendritic F-actin clusters, and produces a
    motor coordination deficit in vivo. This is the cellular substrate of the
    gait and neurodevelopmental phenotypes, and is a separate consequence of the
    recycling defect from the adhesion node above.
  biological_scale: CELLULAR
  downstream:
  - target: Gait ataxia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Global developmental delay
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Intellectual disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  cell_types:
  - preferred_term: cortical neuron
    term:
      id: CL:0010012
      label: cerebral cortex neuron
  biological_processes:
  - preferred_term: dendrite development
    term:
      id: GO:0016358
      label: dendrite development
    modifier: DECREASED
  - preferred_term: synapse assembly
    term:
      id: GO:0007416
      label: synapse assembly
    modifier: DECREASED
  evidence:
  - reference: PMID:37392480
    reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Strumpellin knockdown using shRNA attenuated dendritic arborization and
      synapse formation in cultured cortical neurons, and this effect was
      rescued by wild-type strumpellin expression.
    explanation: >-
      Rescue by wild-type strumpellin establishes that the dendritic and
      synaptic deficit is caused by strumpellin loss specifically.
  - reference: PMID:37392480
    reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Administration of a lentivirus containing a strumpellin-targeting short
      hairpin RNA (shRNA) to cortical motor neurons lead to abnormal motor
      coordination in mice.
    explanation: >-
      Shows the cellular deficit has a whole-animal motor consequence, which is
      what connects this node to the gait phenotype.

- name: LDL Receptor Mislocalisation and Degradation
  description: >-
    One named cargo arm of the recycling defect. Without WASH-dependent
    retrieval the LDL receptor is mislocalised and routed to the lysosome
    instead of back to the hepatocyte surface, lowering LDL uptake and raising
    circulating cholesterol. This is the mechanism behind the
    hypercholesterolaemia recorded as a phenotype of the syndrome, and it is
    the one cargo whose loss has a directly measurable clinical readout.
  biological_scale: CELLULAR
  downstream:
  - target: Hypercholesterolemia
    causal_link_type: DIRECT
  biological_processes:
  - preferred_term: receptor recycling
    term:
      id: GO:0001881
      label: receptor recycling
    modifier: DECREASED
  evidence:
  - reference: PMID:26965651
    reference_title: "CCC- and WASH-mediated endosomal sorting of LDLR is required for normal clearance of circulating LDL."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Inactivation of the CCC-associated WASH complex causes LDLR
      mislocalization, increased lysosomal degradation of LDLR and impaired LDL
      uptake.
    explanation: >-
      States the mechanism for the WASH complex specifically, which is the
      complex RSS1 disables, rather than only for the CCC complex behind the
      other forms of the syndrome.
  - reference: PMID:26965651
    reference_title: "CCC- and WASH-mediated endosomal sorting of LDLR is required for normal clearance of circulating LDL."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Furthermore, a mutation in the WASH component KIAA0196 (strumpellin) is
      associated with hypercholesterolaemia in humans.
    explanation: >-
      Connects the cell-biological mechanism to a human phenotype through
      strumpellin itself, which is the gene this entry is about.

- name: Impaired Lysosomal Enzyme Delivery
  description: >-
    A second cargo arm. Failure of endosomal tubule fission also disrupts
    sorting of the mannose 6-phosphate receptor, which is what delivers acid
    hydrolases to the lysosome, so lysosomal enzyme trafficking and lysosomal
    morphology are both disturbed. The M6PR mis-sorting step itself was
    measured for loss of spastin and IST1, the proteins that drive fission at
    ER-endosome contacts; strumpellin-deficient cells were shown to share the
    downstream lysosomal abnormalities rather than to be the system in which
    the receptor defect was demonstrated. This arm has no established clinical
    correlate in RSS1 and is curated as a mechanistic consequence rather than
    as an explanation for any listed phenotype.
  biological_scale: CELLULAR
  biological_processes:
  - preferred_term: endosome organization
    term:
      id: GO:0007032
      label: endosome organization
    modifier: DECREASED
  evidence:
  - reference: PMID:28389476
    reference_title: "Defects in ER-endosome contacts impact lysosome function in hereditary spastic paraplegia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: >-
      similar lysosomal abnormalities were seen in cellular models lacking the
      WASH complex component strumpellin or the ER morphogen REEP1
    explanation: >-
      Reports the lysosomal consequence for strumpellin-deficient cells
      specifically. Note the quote establishes that those cells share the
      lysosomal abnormality, not that M6PR sorting was measured in them: the
      receptor step was demonstrated for spastin and IST1 loss in the same
      paper. The study also frames the finding around hereditary spastic
      paraplegia and axonopathy rather than RSS1, so it supports this node
      through the shared molecular lesion rather than by measurement in an RSS1
      context.

- name: Multisystem Developmental Malformation
  description: >-
    Strumpellin is ubiquitously expressed and highly conserved, so the recycling
    defect is present in every tissue. The resulting malformations concentrate
    in structures whose morphogenesis is most dependent on adhesion-driven and
    receptor-driven patterning: the cerebellum and posterior fossa, the
    cardiac septa and outflow tract, and the craniofacial skeleton. The cell
    types listed below belong to the cerebellar arm only and do not apply to
    the cardiac or craniofacial arms this node also feeds; they sit here
    because no separate cerebellar node has been split out.
  biological_scale: ORGANISM
  downstream:
  - target: Dandy-Walker malformation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Cerebellar vermis hypoplasia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Congenital heart defect
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Craniofacial dysmorphism
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Global developmental delay
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Enlarged cisterna magna
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Hydrocephalus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Camptodactyly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Overlapping fingers
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Vertical talus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Nail hypoplasia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Single transverse palmar crease
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Eye anomalies
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Macrocephaly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Abnormal metacarpophalangeal profile
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Increased nuchal translucency
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Renal anomalies
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Immunodeficiency
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  cell_types:
  - preferred_term: cerebellar Purkinje cell
    term:
      id: CL:0000121
      label: Purkinje cell
  - preferred_term: cerebellar granule cell
    term:
      id: CL:0000120
      label: granule cell
  evidence:
  - reference: PMID:24065355
    reference_title: "A novel mutation in KIAA0196: identification of a gene involved in Ritscher-Schinzel/3C syndrome in a First Nations cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The ubiquitous expression and highly conserved nature of strumpellin, the
      product of KIAA0196, is consistent with the complex and multisystem nature
      of this disorder.
    explanation: >-
      Connects the ubiquitous expression of the affected protein to the
      multi-organ distribution of the malformations.

phenotypes:
- name: Dandy-Walker malformation
  category: Neurologic
  description: >-
    Posterior fossa malformation with cystic dilatation of the fourth ventricle
    and vermian hypoplasia; the cerebellar element of the 3C triad.
  phenotype_term:
    preferred_term: Dandy-Walker malformation
    term:
      id: HP:0001305
      label: Dandy-Walker malformation
  evidence:
  - reference: PMID:24065355
    reference_title: "A novel mutation in KIAA0196: identification of a gene involved in Ritscher-Schinzel/3C syndrome in a First Nations cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ritscher-Schinzel syndrome (RSS) is a clinically heterogeneous disorder
      characterised by distinctive craniofacial features in addition to
      cerebellar and cardiac anomalies.
    explanation: >-
      Establishes the cerebellar anomaly as a defining feature of the cohort in
      which the WASHC5 variant was identified.

- name: Cerebellar vermis hypoplasia
  category: Neurologic
  description: >-
    Underdevelopment of the cerebellar vermis, the most consistent posterior
    fossa finding and part of the Dandy-Walker continuum in this disorder.
  phenotype_term:
    preferred_term: Cerebellar vermis hypoplasia
    term:
      id: HP:0001320
      label: Cerebellar vermis hypoplasia
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the cardinal findings of craniofacial features, cerebellar defects, and
      cardiovascular malformations resulting in the alternate diagnostic name of
      3C syndrome
    explanation: >-
      GeneReviews lists cerebellar defects among the cardinal findings that
      define the syndrome.

- name: Congenital heart defect
  category: Cardiovascular
  sequelae:
  - target: Abnormal cardiac septum morphology
  - target: Ventricular septal defect
  - target: Atrial septal defect
  - target: Tetralogy of Fallot
  - target: Double outlet right ventricle
  - target: Hypoplastic left heart
  - target: Aortic valve stenosis
  - target: Pulmonic stenosis
  description: >-
    Cardiovascular malformation, most often septal defects, forming the cardiac
    element of the 3C triad.
  phenotype_term:
    preferred_term: Abnormal heart morphology
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      the cardinal findings of craniofacial features, cerebellar defects, and
      cardiovascular malformations resulting in the alternate diagnostic name of
      3C syndrome
    explanation: >-
      Cardiovascular malformation is one of the three cardinal findings that
      name the syndrome.

- name: Craniofacial dysmorphism
  category: Craniofacial
  sequelae:
  - target: Brachycephaly
  - target: Hypertelorism
  - target: Downslanted palpebral fissures
  - target: Low-set ears
  - target: Overfolded helix
  - target: Short philtrum
  - target: Smooth philtrum
  - target: Flat face
  - target: Prominent occiput
  - target: Depressed nasal bridge
  - target: Micrognathia
  - target: Protruding tongue
  - target: Cleft palate
  - target: High palate
  description: >-
    The characteristic facial gestalt: brachycephaly, a hypotonic face with
    protruding tongue, flat facial profile, short midface, widely spaced eyes,
    downslanted palpebral fissures, low-set ears with an overfolded upper helix,
    and a smooth or short philtrum.
  phenotype_term:
    preferred_term: Abnormal facial shape
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Dysmorphic facial features may include brachycephaly, hypotonic face with
      protruding tongue, flat appearance of the face on profile view, short
      midface, widely spaced eyes, downslanted palpebral fissures, low-set ears
      with overfolding of the upper helix, smooth or short philtrum, and high or
      cleft palate.
    explanation: >-
      Enumerates the facial features that constitute the craniofacial element of
      the triad.

- name: Downslanted palpebral fissures
  category: Craniofacial
  phenotype_term:
    preferred_term: Downslanted palpebral fissures
    term:
      id: HP:0000494
      label: Downslanted palpebral fissures
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common findings in all patients were craniofacial dysmorphism,
      particularly macrocephaly, down slanted palpebral fissures and low
      set-ears.
    explanation: >-
      Reported among the most common findings in a cohort of six genetically
      confirmed patients, of whom four carried WASHC5 variants and two CCDC22.
      The phrase gives no percentage and the cohort is small and mixed, so the
      finding is curated without a frequency band.

- name: Low-set ears
  category: Craniofacial
  phenotype_term:
    preferred_term: Low-set ears
    term:
      id: HP:0000369
      label: Low-set ears
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common findings in all patients were craniofacial dysmorphism,
      particularly macrocephaly, down slanted palpebral fissures and low
      set-ears.
    explanation: >-
      Listed among the most common findings in a six-patient cohort mixing four
      WASHC5 and two CCDC22 individuals. No percentage is stated, so no
      frequency band is asserted.

- name: Macrocephaly
  category: Craniofacial
  description: >-
    Increased occipitofrontal circumference, reported as a leading craniofacial
    finding in the genetically confirmed WASHC5 and CCDC22 cohort.
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common findings in all patients were craniofacial dysmorphism,
      particularly macrocephaly, down slanted palpebral fissures and low
      set-ears.
    explanation: >-
      Named as the leading craniofacial finding in a six-patient cohort of
      confirmed RTSCS1 and RTSCS2 individuals. The report gives no percentage
      and does not separate the two genotypes, so no frequency band is asserted.

- name: Brachycephaly
  category: Craniofacial
  phenotype_term:
    preferred_term: Brachycephaly
    term:
      id: HP:0000248
      label: Brachycephaly
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Dysmorphic facial features may include brachycephaly, hypotonic face with
      protruding tongue
    explanation: >-
      GeneReviews lists brachycephaly first among the dysmorphic features.

- name: Protruding tongue
  category: Craniofacial
  phenotype_term:
    preferred_term: Protruding tongue
    term:
      id: HP:0010808
      label: Protruding tongue
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      hypotonic face with protruding tongue
    explanation: >-
      Documented as part of the characteristic facial appearance.

- name: Hypertelorism
  category: Craniofacial
  description: >-
    Widely spaced eyes, described in GeneReviews using the plain-language term.
  phenotype_term:
    preferred_term: Hypertelorism
    term:
      id: HP:0000316
      label: Hypertelorism
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      short midface, widely spaced eyes, downslanted palpebral fissures
    explanation: >-
      "Widely spaced eyes" is the GeneReviews plain-language rendering of
      hypertelorism.

- name: Short philtrum
  category: Craniofacial
  phenotype_term:
    preferred_term: Short philtrum
    term:
      id: HP:0000322
      label: Short philtrum
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      smooth or short philtrum, and high or cleft palate
    explanation: >-
      GeneReviews records a smooth or short philtrum among the facial features.

- name: Cleft palate
  category: Craniofacial
  phenotype_term:
    preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      smooth or short philtrum, and high or cleft palate
    explanation: >-
      GeneReviews lists palatal clefting as one of two alternative palatal
      findings. The phrasing indicates it affects a subset but gives no
      proportion, so no frequency band is asserted.

- name: High palate
  category: Craniofacial
  phenotype_term:
    preferred_term: High palate
    term:
      id: HP:0000218
      label: High palate
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      smooth or short philtrum, and high or cleft palate
    explanation: >-
      A high palate is the alternative palatal finding recorded by GeneReviews.

- name: Global developmental delay
  category: Neurologic
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Developmental delay, intellectual disability and ataxic gait were present
      in all patients.
    explanation: >-
      Present in all six patients of the confirmed cohort. Because four carried
      WASHC5 and two CCDC22, and the cohort is drawn from only two families, the
      universality is not generalised to a frequency band for RSS1.

- name: Intellectual disability
  category: Neurologic
  description: >-
    Variable degrees of intellectual disability; severity ranges across reported
    individuals.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Developmental delay, intellectual disability and ataxic gait were present
      in all patients.
    explanation: >-
      Reported in every patient of the confirmed WASHC5 and CCDC22 cohort. The
      cohort is six patients from two families and mixes both genotypes, so no
      RSS1 frequency band is asserted from it.
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      RSS is associated with variable degrees of developmental delay and
      intellectual disability.
    explanation: >-
      GeneReviews confirms the finding and records that its severity is
      variable.

- name: Gait ataxia
  category: Neurologic
  description: >-
    Ataxic gait, the functional correlate of the cerebellar malformation and of
    the impaired cortical structural plasticity demonstrated in strumpellin
    knockdown models.
  phenotype_term:
    preferred_term: Gait ataxia
    term:
      id: HP:0002066
      label: Gait ataxia
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Developmental delay, intellectual disability and ataxic gait were present
      in all patients.
    explanation: >-
      Ataxic gait was universal in the six-patient confirmed cohort. That cohort
      mixes WASHC5 and CCDC22 genotypes across two families, so it establishes
      the finding without supporting a frequency band for RSS1.

- name: Increased nuchal translucency
  category: Prenatal
  description: >-
    First-trimester ultrasound finding observed in WASHC5-related pregnancies,
    giving a prenatal marker for RSS1 specifically.
  phenotype_term:
    preferred_term: Increased nuchal translucency
    term:
      id: HP:0010880
      label: Increased nuchal translucency
  evidence:
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Elevation of nuchal translucency was observed in the first trimester
      ultrasound in three foetuses with compound heterozygous variants in
      WASHC5.
    explanation: >-
      Reported specifically in WASHC5 (RSS1) fetuses rather than in the CCDC22
      arm of the cohort, so it is an RSS1-specific prenatal finding.

- name: Hypercholesterolemia
  category: Metabolic
  description: >-
    Elevated serum cholesterol, variably present; GeneReviews recommends
    periodic lipid monitoring from childhood on this basis.
  phenotype_term:
    preferred_term: Hypercholesterolemia
    term:
      id: HP:0003124
      label: Hypercholesterolemia
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Eye anomalies and hypercholesterolemia may be variably present.
    explanation: >-
      GeneReviews records hypercholesterolemia as a variable feature without
      giving a proportion. The chapter covers the WASHC5 and CCDC22 forms
      together and does not separate them, so the finding is attributed to RSS1
      by inference rather than by direct genotype-specific report.

- name: Eye anomalies
  category: Ophthalmologic
  sequelae:
  - target: Megalocornea
  - target: Coloboma
  description: >-
    Ocular abnormalities. The two sources disagree on how consistent these are:
    GeneReviews calls them variably present, while the largest phenotypic series
    found ocular involvement in all 26 patients and proposed it as a diagnostic
    aid. Both are curated below rather than reconciled, because the series is
    clinically ascertained and ungenotyped while GeneReviews is written for the
    molecularly defined forms, so they are not measuring the same population.
  phenotype_term:
    preferred_term: Abnormality of the eye
    term:
      id: HP:0000478
      label: Abnormality of the eye
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Eye anomalies and hypercholesterolemia may be variably present.
    explanation: >-
      GeneReviews, which is written for the WASHC5 and CCDC22 forms, records eye
      anomalies as a variable feature.
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      All of them presented ocular disorders, and megalocornea was the most
      frequent ocular manifestation (69%)
    explanation: >-
      Reports ocular involvement in every patient of the largest series, which
      is a considerably stronger claim than the GeneReviews wording.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Obesity
  category: Metabolic
  description: >-
    Weight gain is a recognised management concern; GeneReviews directs
    surveillance of growth parameters with particular attention to weight.
    Deliberately left with no incoming pathophysiology edge: nothing in the
    literature connects the WASH-complex recycling defect to weight gain in this
    syndrome, and hanging it off the malformation node would assert a
    developmental origin that no source supports.
  phenotype_term:
    preferred_term: Obesity
    term:
      id: HP:0001513
      label: Obesity
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Standard treatment for obesity, obstructive sleep apnea, cleft palate,
      congenital heart defects, hypercholesterolemia, renal anomalies,
      immunodeficiency, and developmental delay / intellectual disability.
    explanation: >-
      Obesity heads the list of manifestations requiring treatment, establishing
      it as a recognised feature.

- name: Obstructive sleep apnea
  category: Respiratory
  description: >-
    Deliberately left with no incoming pathophysiology edge. It is plausibly
    secondary to the midface and palatal anatomy, but no cited source makes that
    link for this syndrome, so the edge is not drawn.
  phenotype_term:
    preferred_term: Obstructive sleep apnea
    term:
      id: HP:0002870
      label: Obstructive sleep apnea
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      monitoring for symptoms of obstructive sleep apnea at each visit
    explanation: >-
      GeneReviews mandates surveillance for obstructive sleep apnea at every
      visit, which establishes it as an expected complication.

- name: Renal anomalies
  category: Renal
  description: >-
    Structural renal abnormalities requiring standard management; part of the
    multisystem burden that follows from a ubiquitously expressed trafficking
    defect.
  phenotype_term:
    preferred_term: Abnormality of the kidney
    term:
      id: HP:0000077
      label: Abnormality of the kidney
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Standard treatment for obesity, obstructive sleep apnea, cleft palate,
      congenital heart defects, hypercholesterolemia, renal anomalies,
      immunodeficiency, and developmental delay / intellectual disability.
    explanation: >-
      GeneReviews includes renal anomalies among the manifestations requiring
      treatment, which establishes that they occur in this syndrome.

- name: Immunodeficiency
  category: Immunologic
  description: >-
    Immune deficiency requiring standard management. The GeneReviews chapter
    covers the WASHC5 and CCDC22 forms together and lists immunodeficiency among
    the manifestations to be treated without saying which form it was observed
    in, so its attribution to RSS1 specifically is not established. Immunological
    involvement is most prominent in the VPS35L-related form (RSS3), which the
    parent entry curates as an RSS3 phenotype.
  phenotype_term:
    preferred_term: Immunodeficiency
    term:
      id: HP:0002721
      label: Immunodeficiency
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Standard treatment for obesity, obstructive sleep apnea, cleft palate,
      congenital heart defects, hypercholesterolemia, renal anomalies,
      immunodeficiency, and developmental delay / intellectual disability.
    explanation: >-
      Immunodeficiency appears in the management list of a chapter that covers
      WASHC5 and CCDC22 together, so this supports the finding occurring in
      Ritscher-Schinzel syndrome without establishing it for the WASHC5 form
      specifically. Curated here for completeness against the GeneReviews
      baseline, with the attribution left explicitly unsettled.

- name: Flat face
  category: Craniofacial
  description: >-
    Flat facial appearance in profile with a short midface.
  phenotype_term:
    preferred_term: Flat face
    term:
      id: HP:0012368
      label: Flat face
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      flat appearance of the face on profile view, short midface
    explanation: >-
      GeneReviews describes a flat facial profile as part of the characteristic
      gestalt.

- name: Overfolded helix
  category: Craniofacial
  phenotype_term:
    preferred_term: Overfolded helix
    term:
      id: HP:0000396
      label: Overfolded helix
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      low-set ears with overfolding of the upper helix
    explanation: >-
      The ear anomaly is described as low-set with overfolding of the upper
      helix, so the overfolded helix is a distinct finding from ear position.

- name: Smooth philtrum
  category: Craniofacial
  phenotype_term:
    preferred_term: Smooth philtrum
    term:
      id: HP:0000319
      label: Smooth philtrum
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      smooth or short philtrum, and high or cleft palate
    explanation: >-
      GeneReviews records the philtrum as either smooth or short; both variants
      are curated so neither presentation is lost.

- name: Megalocornea
  category: Ophthalmologic
  description: >-
    Abnormally large corneal diameter, reported as the single most frequent
    ocular manifestation in the largest phenotypic series of the syndrome.
  phenotype_term:
    preferred_term: Megalocornea
    term:
      id: HP:0000485
      label: Megalocornea
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      All of them presented ocular disorders, and megalocornea was the most
      frequent ocular manifestation (69%)
    explanation: >-
      Names megalocornea as the leading ocular finding at 69%.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Camptodactyly
  category: Skeletal
  description: >-
    Fixed flexion of a digit, the first-named member of the acral cluster that
    the largest series proposed as a diagnostic aid.
  phenotype_term:
    preferred_term: Camptodactyly
    term:
      id: HP:0012385
      label: Camptodactyly
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      the group consisting of camptodactyly, single palmar crease, overlapping
      fingers, vertical talus and nail hypoplasia were found in hands and feet
      in 96% of the cases
    explanation: >-
      Reports the acral skeletal cluster in 96% of patients. The bound term
      names only camptodactyly because HPO has no term for the cluster as a
      whole, and the remaining components are carried in the description.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Overlapping fingers
  category: Skeletal
  phenotype_term:
    preferred_term: Overlapping fingers
    term:
      id: HP:0010557
      label: Overlapping fingers
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      the group consisting of camptodactyly, single palmar crease, overlapping
      fingers, vertical talus and nail hypoplasia were found in hands and feet
      in 96% of the cases
    explanation: >-
      Named as a component of the acral cluster found in 96% of patients.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Vertical talus
  category: Skeletal
  description: >-
    Congenital vertical talus, reported as a component of the acral cluster.
    HPO has no vertical-talus term; HP:0001838 names the rocker-bottom foot
    deformity that vertical talus produces, and the reported term is carried in
    preferred_term.
  phenotype_term:
    preferred_term: vertical talus
    term:
      id: HP:0001838
      label: Rocker bottom foot
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      the group consisting of camptodactyly, single palmar crease, overlapping
      fingers, vertical talus and nail hypoplasia were found in hands and feet
      in 96% of the cases
    explanation: >-
      Named as a component of the acral cluster found in 96% of patients.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Nail hypoplasia
  category: Skeletal
  phenotype_term:
    preferred_term: nail hypoplasia
    term:
      id: HP:0001792
      label: Small nail
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      the group consisting of camptodactyly, single palmar crease, overlapping
      fingers, vertical talus and nail hypoplasia were found in hands and feet
      in 96% of the cases
    explanation: >-
      Named as a component of the acral cluster found in 96% of patients.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Single transverse palmar crease
  category: Skeletal
  phenotype_term:
    preferred_term: Single transverse palmar crease
    term:
      id: HP:0000954
      label: Single transverse palmar crease
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      the group consisting of camptodactyly, single palmar crease, overlapping
      fingers, vertical talus and nail hypoplasia were found in hands and feet
      in 96% of the cases
    explanation: >-
      Named as a component of the acral cluster found in 96% of patients.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Enlarged cisterna magna
  category: Neurologic
  description: >-
    Enlargement of the cisterna magna, reported as the most common posterior
    fossa malformation in the largest series, ahead of Dandy-Walker
    malformation itself.
  phenotype_term:
    preferred_term: Enlarged cisterna magna
    term:
      id: HP:0002280
      label: Enlarged cisterna magna
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      The most frequent malformations of the posterior fossa were megacisterna
      magna (31.8%) and Dandy-Walker malformation (27%).
    explanation: >-
      Establishes enlarged cisterna magna as the commonest posterior fossa
      finding, more frequent than Dandy-Walker malformation.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Abnormal cardiac septum morphology
  category: Cardiovascular
  description: >-
    Septal defects, the commonest cardiac malformation in the syndrome.
  phenotype_term:
    preferred_term: Abnormal cardiac septum morphology
    term:
      id: HP:0001671
      label: Abnormal cardiac septum morphology
  evidence:
  - reference: PMID:28555453
    reference_title: "[A phenotypic description of 26 patients with Ritscher-Schinzel syndrome (cranio-cerebello-cardiac dysplasia or 3C syndrome)]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      low-set ears (80.7%) and septal heart defects (68.7%) were the most
      common facial and cardiac malformations, respectively
    explanation: >-
      Identifies septal defects as the commonest cardiac malformation at 68.7%,
      which is what makes the generic congenital heart defect node concrete.
      This is a clinically ascertained cohort of 26 patients diagnosed on
      phenotype; the report does not genotype them and never names WASHC5, and
      its 69% male predominance suggests X-linked CCDC22 cases are included. The
      finding is therefore attributed to RSS1 by inference from the shared
      clinical entity, and the stated percentage is not curated as an RSS1
      frequency band.

- name: Ventricular septal defect
  category: Cardiovascular
  phenotype_term:
    preferred_term: Ventricular septal defect
    term:
      id: HP:0001629
      label: Ventricular septal defect
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      Listed first among the cardiac manifestations of the syndrome in a review of all reported cases.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Atrial septal defect
  category: Cardiovascular
  phenotype_term:
    preferred_term: Atrial septal defect
    term:
      id: HP:0001631
      label: Atrial septal defect
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      Listed among the cardiac manifestations in a review of all reported cases.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Tetralogy of Fallot
  category: Cardiovascular
  phenotype_term:
    preferred_term: Tetralogy of Fallot
    term:
      id: HP:0001636
      label: Tetralogy of Fallot
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      A conotruncal malformation reported in the syndrome, showing the cardiac phenotype extends beyond simple septation defects.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Double outlet right ventricle
  category: Cardiovascular
  phenotype_term:
    preferred_term: Double outlet right ventricle
    term:
      id: HP:0001719
      label: Double outlet right ventricle
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      A conotruncal malformation reported in the syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Hypoplastic left heart
  category: Cardiovascular
  phenotype_term:
    preferred_term: hypoplastic left heart
    term:
      id: HP:0004383
      label: Hypoplastic left ventricle
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      Reported among the cardiac manifestations. HPO has no hypoplastic-left-heart term, so the ventricular term is bound and the reported phrasing kept in preferred_term.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Aortic valve stenosis
  category: Cardiovascular
  phenotype_term:
    preferred_term: Aortic valve stenosis
    term:
      id: HP:0001650
      label: Aortic valve stenosis
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      One of the valvular lesions reported in the syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Pulmonic stenosis
  category: Cardiovascular
  phenotype_term:
    preferred_term: Pulmonic stenosis
    term:
      id: HP:0001642
      label: Pulmonic stenosis
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Cardiac manifestations include ventricular septal defect, atrial septal
      defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic
      left heart, aortic stenosis, pulmonic stenosis and other valvular
      anomalies.
    explanation: >-
      One of the valvular lesions reported in the syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Coloboma
  category: Ophthalmologic
  phenotype_term:
    preferred_term: ocular coloboma
    term:
      id: HP:0000589
      label: Coloboma
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Craniofacial abnormalities seen are cleft palate, ocular coloboma,
      prominent occiput, low-set ears, hypertelorism, down-slanting palpebral
      fissures, depressed nasal bridge and micrognathia.
    explanation: >-
      A structural ocular malformation reported in the syndrome, giving the variably present eye anomalies a specific form.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Prominent occiput
  category: Craniofacial
  phenotype_term:
    preferred_term: Prominent occiput
    term:
      id: HP:0000269
      label: Prominent occiput
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Craniofacial abnormalities seen are cleft palate, ocular coloboma,
      prominent occiput, low-set ears, hypertelorism, down-slanting palpebral
      fissures, depressed nasal bridge and micrognathia.
    explanation: >-
      Reported among the craniofacial abnormalities of the syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Depressed nasal bridge
  category: Craniofacial
  phenotype_term:
    preferred_term: Depressed nasal bridge
    term:
      id: HP:0005280
      label: Depressed nasal bridge
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Craniofacial abnormalities seen are cleft palate, ocular coloboma,
      prominent occiput, low-set ears, hypertelorism, down-slanting palpebral
      fissures, depressed nasal bridge and micrognathia.
    explanation: >-
      Reported among the craniofacial abnormalities of the syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Micrognathia
  category: Craniofacial
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Craniofacial abnormalities seen are cleft palate, ocular coloboma,
      prominent occiput, low-set ears, hypertelorism, down-slanting palpebral
      fissures, depressed nasal bridge and micrognathia.
    explanation: >-
      Reported among the craniofacial abnormalities of the syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Hydrocephalus
  category: Neurologic
  description: >-
    Reported alongside the posterior fossa cyst as part of the CNS malformation
    complex, and a driver of neurosurgical management.
  phenotype_term:
    preferred_term: Hydrocephalus
    term:
      id: HP:0000238
      label: Hydrocephalus
  evidence:
  - reference: PMID:11484200
    reference_title: "Ritscher-Schinzel cranio-cerebello-cardiac (3C) syndrome: report of four new cases and review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: >-
      Dandy-Walker malformation, posterior fossa cyst, hydrocephalus and
      congenital heart defect are common malformations
    explanation: >-
      Groups hydrocephalus with the posterior fossa findings as a common
      malformation in this syndrome.
      The series predates the identification of WASHC5 by twelve years, so its
      patients are clinically ascertained and ungenotyped and the finding is
      attributed to RSS1 by inference from the shared clinical entity rather
      than by genotype-specific report.

- name: Abnormal metacarpophalangeal profile
  category: Skeletal
  description: >-
    A consistent wavy pattern on the metacarpal phalangeal profile derived from
    hand radiographs, which GeneReviews treats as a characteristic diagnostic
    feature. The bound term is broader than the claim: a pattern profile is a
    computed relative-length signature across the metacarpals rather than a
    morphological abnormality of any one of them, and HPO has no term for it.
    HP:0005916 is the closest available anchor and the specificity is carried in
    preferred_term.
  phenotype_term:
    preferred_term: Abnormal metacarpal morphology
    term:
      id: HP:0005916
      label: Abnormal metacarpal morphology
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Affected individuals also typically have a characteristic metacarpal
      phalangeal profile showing a consistent wavy pattern on hand radiographs.
    explanation: >-
      GeneReviews describes a typical and characteristic radiographic hand
      finding.

genetic:
- name: WASHC5
  notes: >-
    WASHC5 (formerly KIAA0196) at 8q24.13 encodes strumpellin, a core subunit of
    the pentameric WASH regulatory complex. Biallelic hypomorphic variants cause
    RSS1. The gene is allelic with autosomal dominant hereditary spastic
    paraplegia type SPG8, where heterozygous missense variants act through a
    different mechanism.
  gene_term:
    preferred_term: WASHC5
    term:
      id: hgnc:28984
      label: WASHC5
  relationship_type: CAUSATIVE
  evidence:
  - reference: PMID:24065355
    reference_title: "A novel mutation in KIAA0196: identification of a gene involved in Ritscher-Schinzel/3C syndrome in a First Nations cohort."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We have identified a mutation in KIAA0196 as the cause of the form of RSS
      characterised in our cohort.
    explanation: >-
      Establishes WASHC5/KIAA0196 as the causal gene for this form of
      Ritscher-Schinzel syndrome.
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The first two genes described were the autosomal recessive inherited gene
      WASHC5 associated with Ritscher-Schinzel syndrome 1 (RTSCS1), and CCDC22,
      an X-linked recessive gene causing Ritscher-Schinzel syndrome 2 (RTSCS2).
    explanation: >-
      States explicitly that WASHC5 is the gene of Ritscher-Schinzel syndrome 1,
      which is the entity this entry describes.

treatments:
# No treatment here carries target_mechanisms: every RSS1 intervention is
# supportive, surveillance, or counselling, and none acts on a node in the
# pathograph. There is no disease-modifying therapy for the endosomal recycling
# defect, so there is no mechanism target to point at.
- name: Multidisciplinary Symptomatic Management
  description: >-
    No disease-modifying therapy exists. Care is standard management of the
    individual manifestations, coordinated across cardiology, craniofacial
    surgery, developmental paediatrics, nephrology, immunology, and metabolic
    medicine.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Treatment of manifestations: Standard treatment for obesity, obstructive
      sleep apnea, cleft palate, congenital heart defects, hypercholesterolemia,
      renal anomalies, immunodeficiency, and developmental delay / intellectual
      disability.
    explanation: >-
      GeneReviews prescribes standard symptomatic treatment of each
      manifestation rather than any disease-specific therapy.

- name: Developmental and Educational Intervention
  description: >-
    Early developmental support, mobility and self-help training, and
    individualised educational planning, guided by regular reassessment of
    developmental progress.
  treatment_term:
    preferred_term: Rehabilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  therapeutic_modality: BEHAVIORAL
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      assessment of developmental progress, mobility, self-help skills, and
      educational needs
    explanation: >-
      GeneReviews specifies periodic assessment of developmental progress,
      mobility, self-help skills, and educational needs, which is the basis for
      developmental and educational intervention.

- name: Lipid Surveillance and Management
  description: >-
    Periodic lipid profile measurement beginning in childhood, with standard
    treatment of hypercholesterolemia when detected.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      measurement of lipid profile periodically starting in childhood
    explanation: >-
      GeneReviews sets out periodic lipid measurement from childhood as
      disease-specific surveillance.

- name: Annual Ophthalmologic Surveillance
  description: >-
    Ophthalmology evaluation annually or as clinically indicated, on the basis
    of the variably present eye anomalies.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      ophthalmology evaluation annually or as clinically indicated
    explanation: >-
      GeneReviews specifies the interval and the trigger for ophthalmologic
      review.

- name: Growth and Weight Surveillance
  description: >-
    Measurement of growth parameters at each visit with particular attention to
    weight, reflecting the obesity risk.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Measurement of growth parameters (particularly weight)
    explanation: >-
      GeneReviews directs growth monitoring with weight singled out, which is
      the basis for this surveillance item.

- name: Genetic Counseling
  description: >-
    Autosomal recessive counselling with a 25% sibling recurrence risk and a 50%
    chance of carrier status. Prenatal and preimplantation genetic testing are
    possible once the familial WASHC5 variants are known, and elevated nuchal
    translucency has been observed in affected WASHC5 pregnancies.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At conception, each sib of an affected individual has a 25% chance of
      being affected, a 50% chance of being an asymptomatic carrier, and a 25%
      chance of being unaffected and not a carrier.
    explanation: >-
      The GeneReviews genetic counseling section supplies the recurrence and
      carrier risks this treatment conveys.
  - reference: PMID:31971710
    reference_title: "Ritscher-Schinzel Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Once the causative pathogenic variant(s) have been identified in an
      affected family member, prenatal and preimplantation genetic testing are
      possible.
    explanation: >-
      Establishes the reproductive testing options that follow a molecular
      diagnosis, which is the practical content of the counselling.
  - reference: PMID:36130690
    reference_title: "Expanding the pre- and postnatal phenotype of WASHC5 and CCDC22 -related Ritscher-Schinzel syndromes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The pre- and postnatal findings of this cohort expand the known phenotype
      of RTSCS1 and 2, with direct impact on postnatal outcome, management, and
      familial counseling.
    explanation: >-
      The authors state that their pre- and postnatal findings bear directly on
      familial counseling.

animal_models:
- name: Washc5 constitutive knockout mouse
  species: Mouse
  genotype: E430025E21Rik (Washc5) deletion-based knockout, homozygous and heterozygous
  description: >-
    A deletion-based null allele of the murine WASHC5 orthologue. Homozygous
    null embryos die early, which is why this model does not recapitulate a
    viable RSS1 phenotype and instead bounds the tolerable degree of strumpellin
    loss.
  publication: PMID:26572744
  evidence:
  - reference: PMID:26572744
    reference_title: "The spectrum of KIAA0196 variants, and characterization of a murine knockout: implications for the mutational mechanism in hereditary spastic paraplegia type SPG8."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We generated a deletion-based knockout allele for E430025E21Rik, i.e. the
      murine homologue of KIAA0196.
    explanation: >-
      Documents the construction of the model and identifies the targeted gene
      as the murine orthologue of the human disease gene.
  modeled_mechanisms:
  - target: WASHC5 Hypomorphic Loss of Function
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Complete ablation of the orthologue is not a model of the hypomorphic
      human genotype; it is lethal before the malformations of interest can
      form.
    limitations: >-
      The knockout is a null allele, whereas RSS1 alleles are hypomorphic and
      retain roughly 40% of strumpellin. Homozygous embryonic lethality means no
      craniofacial, cerebellar, or cardiac phenotype can be scored, and
      heterozygotes showed no relevant phenotype. The study was designed to
      probe the dominant SPG8 mechanism rather than recessive RSS1, so its
      negative findings bear on RSS1 only through the dose-response
      relationship. A knock-in of a patient hypomorphic allele would be required.
    evidence:
    - reference: PMID:26572744
      reference_title: "The spectrum of KIAA0196 variants, and characterization of a murine knockout: implications for the mutational mechanism in hereditary spastic paraplegia type SPG8."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        We did, however, neither observe HSP-related in vivo and ex vivo
        phenotypes, nor alterations affecting endosomal, lysosomal, or
        autophagic compartments.
      explanation: >-
        The surviving heterozygous animals showed no trafficking or neurological
        phenotype, so the model does not reproduce the human disease mechanism
        at either dose.

- name: N471D Washc5 knock-in mouse
  species: Mouse
  genotype: Washc5 N471D knock-in, heterozygous and homozygous
  description: >-
    The only viable engineered Washc5 allele. Homozygotes survive and show mild
    dilated cardiomyopathy, decreased acoustic startle reactivity, thinner eye
    lenses, altered clinical chemistry and haematology, and gait instability.
    N471D is an SPG8 allele, not an RSS1 allele, and the model reproduces
    neither disease cleanly.
  publication: PMID:34312900
  evidence:
  - reference: PMID:34312900
    reference_title: "N471D WASH complex subunit strumpellin knock-in mice display mild motor and cardiac abnormalities and BPTF and KLHL11 dysregulation in brain tissue."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      We generated heterozygous and homozygous N471D Washc5 knock-in mice and
      subjected them to a comprehensive clinical, morphological and laboratory
      parameter screen, and gait analyses.
    explanation: >-
      Documents the construction and the breadth of phenotyping, which is what
      makes the model's negative result for the RSS1 triad informative rather
      than merely unexamined.
  modeled_mechanisms:
  - target: WASHC5 Hypomorphic Loss of Function
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      A viable Washc5 point mutant that nonetheless does not model the RSS1
      lesion, because the allele is the dominant SPG8 one and complex abundance
      is unchanged.
    limitations: >-
      N471D causes dominant SPG8, not recessive RSS1, and the study reports it
      does not produce a typical SPG8 phenotype either. Mechanistically it is
      the wrong lesion for this entry: WASHC5-related interaction partners and
      complexes showed unchanged abundance in these animals, whereas RSS1 acts
      through reduced strumpellin and therefore reduced WASH complex abundance.
      The cardiac and ocular findings are suggestive but were not characterised
      as the RSS1 malformations, and no cerebellar or craniofacial malformation
      was reported. A knock-in of a patient RSS1 hypomorphic allele is what the
      question needs.
    evidence:
    - reference: PMID:34312900
      reference_title: "N471D WASH complex subunit strumpellin knock-in mice display mild motor and cardiac abnormalities and BPTF and KLHL11 dysregulation in brain tissue."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        WASHC5-related protein interaction partners and complexes showed no
        change in abundancies.
      explanation: >-
        Complex abundance is unchanged in this model, which is precisely the
        variable RSS1 acts through, so the model cannot inform the RSS1
        mechanism even where its organ findings overlap.
    readouts:
    - name: Left ventricular function
      target: WASHC5 Hypomorphic Loss of Function
      direction: ALTERED
      interpretation: >-
        Mild dilated cardiomyopathy in homozygotes. Recorded because cardiac
        involvement is part of the human triad, but this is an SPG8 allele and
        the lesion is not the RSS1 septation defect.
      evidence:
      - reference: PMID:34312900
        reference_title: "N471D WASH complex subunit strumpellin knock-in mice display mild motor and cardiac abnormalities and BPTF and KLHL11 dysregulation in brain tissue."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Homozygous N471D Washc5 knock-in mice showed mild dilated
          cardiomyopathy, decreased acoustic startle reactivity, thinner eye
          lenses, increased alkaline phosphatase and potassium levels and
          increased white blood cell counts.
        explanation: >-
          Reports the multi-organ findings in the homozygous knock-in.

- name: Strumpellin shRNA knockdown cortical neuron model
  species: Mouse
  genotype: Lentiviral strumpellin-targeting shRNA in cortical motor neurons
  description: >-
    Acute knockdown of strumpellin in cortical motor neurons, producing a motor
    coordination deficit in vivo with reduced dendritic arborisation, synapse
    formation, and dendritic F-actin in culture.
  publication: PMID:37392480
  evidence:
  - reference: PMID:37392480
    reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      In this study, we examined the role of strumpellin in the regulation of
      structural plasticity of cortical neurons involved in gait coordination.
    explanation: >-
      Establishes what the model was built to interrogate, which is the basis
      for treating it as informative about strumpellin loss in neurons.
  modeled_mechanisms:
  - target: Reduced Neuronal Dendritic Arborisation and Synaptogenesis
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the cellular consequence of reduced strumpellin dose in
      neurons, with rescue by wild-type protein establishing specificity.
    limitations: >-
      Acute postnatal knockdown in a targeted neuronal population is not the
      constitutive biallelic hypomorphism of RSS1, and the readouts are gait
      coordination and dendritic morphology rather than the cerebellar, cardiac,
      or craniofacial malformations that define the syndrome. The study frames
      the model around SPG8 rather than RSS1.
    readouts:
    - name: Dendritic arborisation and synapse number in cultured cortical neurons
      target: Reduced Neuronal Dendritic Arborisation and Synaptogenesis
      direction: DECREASED
      interpretation: >-
        Structural correlate of reduced WASH-dependent actin activity in
        neurons.
      evidence:
      - reference: PMID:37392480
        reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Strumpellin knockdown using shRNA attenuated dendritic arborization
          and synapse formation in cultured cortical neurons
        explanation: >-
          Reports the measurement and its direction.
    - name: Dendritic F-actin cluster number
      target: Reduced Neuronal Dendritic Arborisation and Synaptogenesis
      direction: DECREASED
      interpretation: >-
        Direct readout of the actin-polymerisation defect predicted by loss of
        the WASH complex.
      evidence:
      - reference: PMID:37392480
        reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          the number of F-actin clusters in neuronal dendrites was decreased by
          strumpellin knockdown and rescued by strumpellin expression
        explanation: >-
          Quantifies the actin phenotype and demonstrates rescue by wild-type
          strumpellin.
    evidence:
    - reference: PMID:37392480
      reference_title: "Strumpellin/WASHC5 regulates the structural plasticity of cortical neurons involved in gait coordination."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Administration of a lentivirus containing a strumpellin-targeting short
        hairpin RNA (shRNA) to cortical motor neurons lead to abnormal motor
        coordination in mice.
      explanation: >-
        Establishes that reducing strumpellin in neurons produces a motor
        phenotype in vivo, which is what makes the model informative for the
        neuronal node.

discussions:
- discussion_id: rss1_no_viable_washc5_model
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >-
    A viable Washc5 knock-in mouse exists, but it carries N471D, an allele that
    causes dominant SPG8 rather than recessive RSS1, and it does not reproduce
    the RSS1 triad. Would a knock-in of an RSS1 hypomorphic allele, at the
    roughly 40% strumpellin dose seen in patients, develop the cerebellar,
    cardiac, and craniofacial malformations?
  attaches_to:
  - pathophysiology#WASHC5 Hypomorphic Loss of Function
  - animal_models#Washc5 constitutive knockout mouse
  - animal_models#N471D Washc5 knock-in mouse
  rationale: >-
    Two Washc5 alleles have been engineered in mouse and neither is an RSS1
    allele, so the mismatch is about which allele was modelled rather than about
    an absence of models. The knockout is a clean deletion: homozygotes die
    before organogenesis can be scored and heterozygotes sit above the disease
    threshold with no phenotype, so neither dose is the disease. The N471D
    knock-in is viable as a homozygote and does produce mild multi-organ
    findings, including dilated cardiomyopathy, thinner eye lenses and gait
    instability, but N471D is the dominant SPG8 allele and the authors report it
    does not give a typical SPG8 phenotype either. It is also mechanistically
    the wrong kind of lesion: the same study found WASHC5 interaction partners
    and complexes at unchanged abundance in these animals, whereas RSS1 acts
    through reduced strumpellin and hence reduced WASH complex abundance.
    So no published model occupies the RSS1 window, and every in vivo statement
    about RSS1 organogenesis still rests on inference from human imaging and
    from cellular work in non-developmental systems. The tissue-selectivity
    question below cannot be addressed experimentally until that changes.
  evidence:
  - reference: PMID:34312900
    reference_title: "N471D WASH complex subunit strumpellin knock-in mice display mild motor and cardiac abnormalities and BPTF and KLHL11 dysregulation in brain tissue."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      While biallelic ablation of Washc5 was prenatally lethal, expression of
      N471D mutated WASHC5 led to several mild clinical and laboratory parameter
      abnormalities, but not to a typical SPG8 phenotype.
    explanation: >-
      Establishes that the one viable engineered allele is N471D and that it
      fails to reproduce even the disease it was built for, which is what makes
      the absence of an RSS1-allele model the operative gap.
  proposed_experiments:
  - experiment_id: rss1_hypomorphic_knockin
    name: Patient-allele Washc5 hypomorphic knock-in mouse
    description: >-
      Introduce the founder splice-site allele, or an equivalent allele titrated
      to leave roughly 40% strumpellin, into the mouse germline and
      phenotype homozygotes for posterior fossa, cardiac septal, and
      craniofacial development, with strumpellin quantified by western blot to
      confirm the intended dose.
    readouts:
    - name: Cerebellar vermis and posterior fossa morphology
      target: phenotypes#Cerebellar vermis hypoplasia
      direction: DECREASED
      interpretation: >-
        Vermian hypoplasia in a viable hypomorph would establish that partial
        strumpellin loss is sufficient for the cerebellar malformation.
    - name: Cardiac septation
      target: phenotypes#Congenital heart defect
      direction: ALTERED
      interpretation: >-
        Septal defects in the same animals would tie the cardiac arm of the
        triad to the same dose.
    would_support:
    - pathophysiology#WASHC5 Hypomorphic Loss of Function
    supporting_outcome:
    - >-
      Homozygous hypomorphs survive to term with vermian hypoplasia and septal
      defects, at a strumpellin level comparable to the patient cohort.
    would_refute:
    - pathophysiology#WASHC5 Hypomorphic Loss of Function
    refuting_outcome:
    - >-
      Homozygous hypomorphs are either normal or embryonic-lethal at every dose
      that can be engineered, which would mean the human phenotype depends on
      something other than strumpellin dose alone.

- discussion_id: rss1_tissue_selectivity
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Strumpellin is ubiquitously expressed and the WASH complex serves endosomal
    recycling in every cell, so why do the malformations concentrate in the
    cerebellum, the cardiac septa, and the craniofacial skeleton rather than
    appearing as a uniform multi-organ defect?
  attaches_to:
  - pathophysiology#Multisystem Developmental Malformation
  - pathophysiology#Reduced Cell-Surface Cargo Receptor Density
  rationale: >-
    Two observations make this sharper than the usual tissue-selectivity
    question. Strumpellin loss does not disturb bulk recycling: transferrin
    receptor traffic is normal while the beta-2-adrenergic receptor is
    mislocalised, so the defect is already cargo-selective at the cell level.
    And in the Commander-related forms of the syndrome, cell-surface proteomics
    showed that the reduction in surface cargo is itself tissue-specific. Which
    WASH-dependent cargoes are rate-limiting in cerebellar, cardiac, and neural
    crest development is unknown, and answering it would explain why one
    housekeeping defect produces this particular triad.
  evidence:
  - reference: PMID:40601774
    reference_title: "Ritscher-Schinzel syndrome can be characterized as an endosomal recyclinopathy."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    snippet: >-
      through cell surface proteomics, that this reduces tissue-specific
      presentation of cell surface integral membrane proteins essential for
      kidney, bone, and brain development
    explanation: >-
      Establishes that the surface-cargo deficit is tissue-specific in
      Ritscher-Schinzel syndrome, which is what frames the gap. The measurement
      was made on Commander subunits rather than on WASHC5, so it bears on the
      RSS1 node by inference from the shared recycling pathway.

datasets: []

📚

References & Deep Research

References

1

PMID:31971710

Ritscher-Schinzel Syndrome.

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 (1)

Create: Ritscher-Schinzel Syndrome 1 · 2026-09-03T07:56:59Z · View source

Created kb/disorders/Ritscher-Schinzel_Syndrome_1.yaml (MONDO:0009073) for the autosomal recessive, WASHC5/strumpellin-related form of Ritscher-Schinzel (3C) syndrome. LUMP/SPLIT DECISION. kb/disorders/Ritscher-Schinzel_Syndrome.yaml already carried RSS1 as a has_subtypes entry, so a separate file needed justifying rather than assuming. It clears the bar in docs/explanation/design-decisions.md ("a distinct MONDO identity and a substantially independent mechanism"): MONDO:0009073 is a distinct term, and WASHC5 encodes a WASH regulatory complex subunit recruited to endosomes by FAM21-retromer binding, which is a different lesion from the SNX17-dependent Commander/CCC cargo-selection route behind RSS2 (CCDC22) and RSS3 (VPS35L). Repo precedent supports it (Hereditary Spastic Paraplegia 7/11/44/48/49 alongside a parent). The parent's RSS1 subtype block was converted to a pointer per the promotion convention, not left as a divergent copy. Two follow-ups are recorded in the parent's review_notes and deliberately not done here: its phenotypes are still untagged by subtype, and no Grouping covers the split. DEEP RESEARCH. Requested provider was falcon. Falcon was unavailable in this environment: EDISON_API_KEY was set but the endpoint returned 403 ProviderAuthError. Rather than substitute a provider by hand, the run was re-issued through the recorded-fallback path (just dr_fallback='--fallback' research-disorder falcon ...), which fell back to openscientist and recorded fell_back, requested_provider and provider_attempts in the report frontmatter. The report used is research/Ritscher-Schinzel_Syndrome_1-deep-research-openscientist.md (2276s, 23 citations, 2 artifacts). It was generated without frontmatter validation blocks, so both retro-fits were run: just validate-research-reference reported 23/23 references resolved, 0 unresolved, 0 off topic; just validate-research-terms reported 56/57 terms resolved, 0 unresolved, 0 mislabelled (the 3 "second look" entries are markdown category prefixes leaking into the term name, e.g. "Craniofacial:** low-set ears" for HP:0000369, not wrong bindings). Running the reference validator is also what renamed the report file from -falcon to -openscientist. NAMED ENTITY CONFUSION. just preflight-dr against MONDO:0009073 returned WARN: the report mentions CCDC22 exactly as often as WASHC5 (29 each) and carries OMIM 610657 (RSS2) alongside the correct 220210. The report mixes RSS1 and RSS2, so only WASHC5-attributed claims were taken from it. Its LDLR hypercholesterolaemia and ATP7A copper branches were deliberately NOT curated: the report itself routes both through CCC/Commander coupling, which is the RSS2/RSS3 mechanism. The one WASH-specific enrichment taken from it was the FAM21-tail/VPS35 recruitment step (PMID:22070227) and the 26-patient phenotypic series (PMID:28555453). The report also asserts the founder variant is a "splice-site variant skipping exon 27". That is wrong, and it is the same error this curation made independently before reading the report; see the correction below. Curating from the primary source rather than the report is what caught it. GENEREVIEWS BASELINE. PMID:31971710 exists and is tagged GeneReviews in the top-level references block. Its Clinical Characteristics were cross-referenced phenotype by phenotype; the renal and immune manifestations named only in its Management section were added, as were flat face, overfolded helix and smooth philtrum. Its Diagnosis/Testing and Genetic Counseling sections are both curated (a diagnosis block, and the 25% sibling recurrence and prenatal/PGT sentences on the counselling treatment). No Agents to Avoid section exists in the abstract. CONTENT. 8 pathophysiology nodes wired as a causal chain from WASHC5 hypomorphic loss of function through WASH complex destabilisation, impaired Arp2/3 endosomal actin nucleation, failed tubule fission and cargo retrieval, and reduced surface cargo density, branching to integrin-mediated adhesion and to neuronal dendritic/synaptic plasticity, converging on multisystem malformation. 27 HP-bound phenotypes, 2 diagnosis entries, 6 treatments, 1 genetic entry, 2 animal models linked via modeled_mechanisms, and 2 discussions. The Washc5 null mouse is recorded as FAILS_TO_RECAPITULATE with its limitations: homozygous nulls are embryonic lethal while human alleles are hypomorphic, so no published model sits in the viable disease window. That is also the HUMAN_MODEL_MISMATCH discussion, whose proposed experiment is a patient-allele hypomorphic knock-in. The KNOWLEDGE_GAP discussion asks why a ubiquitous trafficking defect produces this particular triad. NO FREQUENCY BANDS ARE ASSERTED. Every frequency value was removed during self-review. The candidates all came from sources that cannot support an RSS1-specific band: PMID:36130690 is six patients from two families mixing four WASHC5 and two CCDC22 genotypes and says only "the most common findings" with no percentage; PMID:28555453 gives real percentages (megalocornea 69%, low-set ears 80.7%, septal defects 68.7%, acral skeletal cluster 96%, megacisterna magna 31.8%, Dandy-Walker 27%) but is a clinically ascertained cohort that never genotypes anyone, never names WASHC5, and is 69% male, which suggests X-linked RSS2 inclusion. Those percentages are quoted verbatim in snippets with directness: INDIRECT and an explanation naming the limitation, so the numbers are visible with their provenance rather than laundered into a band. SELF-REVIEW AND CORRECTIONS. A red-team review was run in a fresh context before committing and returned REQUEST_CHANGES. Everything mechanical was clean (all snippets exact, all term labels matching, all gates green); every defect was in claim-to-evidence alignment. Fixed: - An inverted causal claim. The entry said the founder variant "causes skipping of exon 27"; PMID:24065355 says the opposite, an eightfold reduction in the relative amount of a transcript lacking exon 27. Corrected in all three places it appeared. The entry now states only the splice-site change, the shift in relative transcript abundance, and the 60% protein reduction. - Two evidence items imported SPG8 results (same gene, heterozygous, dominant, a different disease) under explanations that generalised them to "the WASHC5 lesion". Both now carry directness: INDIRECT and name SPG8. - A contested result cited one-sidedly. PMID:31911435's SPG8 non-rescue finding is contradicted by PMID:37392480 and PMID:23085491, both already cited in the entry. A REFUTE item quoting the contradiction was added rather than presenting the disagreement as settled. - Hypercholesterolemia and immunodeficiency come from form-agnostic GeneReviews sentences and are curated as RSS3 phenotypes in the parent. Kept for baseline completeness with directness: INDIRECT and the attribution recorded as unestablished. - A node bundling integrin adhesion with neuronal plasticity was split in two. This also gave Gait ataxia an upstream parent; it had been an isolated node despite a mechanism node and an animal model existing to explain it. Cerebellar vermis hypoplasia was likewise connected. - GO:0034314 and GO:0030041 were on each other's nodes; swapped. CL:0000598 pyramidal neuron narrowed the evidence (the papers say cortical neurons) and became CL:0010012 cerebral cortex neuron. Cultured-neuron results were re-graded MODEL_ORGANISM to IN_VITRO. - Two reference caches (PMID:34020006 CCDC22, PMID:31712251 VPS35L) had been fetched but were cited by nothing; removed as scope creep and an NEC signal. Two review suggestions were not actioned and the reasons are recorded here: an OMIM xref is not expressible (the schema has ICD10CM, ICD11F, Mondo and NCIT mapping classes and no OMIM one), and the WASHC5-specific phenotype counts proposed as a better frequency basis come from a medRxiv preprint absent from PMC that cannot be snippet-verified. DATASETS. just discover-datasets returned no GEO candidates, which is expected for a disorder this rare. datasets is left empty rather than padded. VALIDATION. just validate passes with 69/69 snippets verified against cached references. All PMID-keyed, so no DOI-skip gap. Also clean: check-entity-refs, check-causal-targets, check-duplicate-keys, check-enum-values, check-qualifier-terms, check-snippet-length, check-title-snippets, check-snippet-grading. Compliance 91.0%. The residual compliance gap is uncited downstream edges, left uncited deliberately where no source makes the causal claim, plus proposed-experiment slots that have no datasets by nature.

OpenScientist ▸

Ritscher-Schinzel Syndrome 1 (RSS1 / 3C Syndrome): Comprehensive Disease Report

openscientist-autonomous 23 citations 2026-09-03T07:51:57.850010

Ritscher-Schinzel Syndrome 1 (RSS1 / 3C Syndrome): Comprehensive Disease Report

Summary

Ritscher-Schinzel Syndrome 1 (RSS1), also known as cranio-cerebello-cardiac (3C) syndrome, is a rare autosomal-recessive congenital multiple-malformation disorder (OMIM #220210) defined by the diagnostic triad of distinctive craniofacial dysmorphism, cerebellar / posterior-fossa malformations (Dandy-Walker spectrum), and congenital heart defects, accompanied by developmental delay and intellectual disability. RSS1 specifically is caused by biallelic hypomorphic loss-of-function variants in WASHC5 (formerly KIAA0196), the gene encoding strumpellin, a core subunit of the endosomal WASH actin-nucleating complex (PMID: 24065355).

Mechanistically, strumpellin deficiency destabilizes the WASH complex, which normally activates the Arp2/3 complex to nucleate branched F-actin on endosomes. This actin machinery, working in concert with the retromer and the CCC/Commander complexes, drives the sorting and recycling of transmembrane cargo (e.g., LDLR, integrins, the copper transporter ATP7A) back to the plasma membrane and away from lysosomal degradation. Loss of strumpellin therefore impairs endosomal cargo recycling, disrupting membrane-protein homeostasis during a critical window of embryonic development and producing the characteristic cranio-cerebello-cardiac malformation spectrum (PMID: 26965651, PMID: 22070227, PMID: 25355947).

Ritscher-Schinzel syndrome as a clinical entity is genetically heterogeneous: RSS1 (WASHC5, autosomal recessive), RSS2 (CCDC22, X-linked recessive), RSS3 (VPS35L), and RSS4 (DPYSL5) — all but DPYSL5 converge on the same WASH / retromer / Commander endosomal trafficking module (PMID: 36130690, PMID: 31712251). No disease-modifying therapy exists; management is symptomatic and multidisciplinary. This report covers all 15 requested disease-characteristic sections, drawing on 9 confirmed findings and 30 reviewed papers.

Note on nomenclature: OMIM assigns WASHC5-related disease as RSS1 (#220210) and CCDC22 as RSS2 (#300963). One review (PMID: 34020006) inverts these labels; this report follows the OMIM/dosage convention in which WASHC5 = RSS1 as specified by the research question.

Key Findings

Finding 1 — RSS1 is caused by biallelic WASHC5/strumpellin loss of function (autosomal recessive; OMIM #220210)

The molecular cause of RSS1 was identified by homozygosity mapping plus Sanger sequencing in 8 First Nations patients from northern Manitoba with classic Ritscher-Schinzel/3C syndrome. All eight were homozygous for a novel splice-site mutation in KIAA0196 (now WASHC5) at chromosome 8q24.13. The functional consequence was demonstrated at both RNA and protein level: RNA analysis showed an approximately eightfold reduction in the transcript lacking exon 27, and Western blot showed a ~60% reduction in strumpellin protein (PMID: 24065355).

"All eight patients were homozygous for a novel splice site mutation in KIAA0196. RNA analysis revealed an approximate eightfold reduction in the relative amount of a KIAA0196 transcript lacking exon 27. A 60% reduction in the amount of strumpellin protein was observed on western blot." — Elliott et al. 2013

This establishes strumpellin — a subunit of the WASH endosomal actin-nucleation complex — as the RSS1 disease protein and shows that RSS1 arises from a hypomorphic (partial loss-of-function) allele retaining ~40% of protein, not a complete null.

Finding 2 — Ritscher-Schinzel syndrome is genetically heterogeneous (four genes)

Four genes are implicated in the RSS spectrum, all converging on endosomal trafficking machinery:

Subtype	Gene	Inheritance	OMIM	Complex
RSS1	*WASHC5* (KIAA0196, strumpellin)	Autosomal recessive	#220210	WASH complex
RSS2	CCDC22	X-linked recessive	#300963	CCC / Commander
RSS3	VPS35L	Autosomal recessive	—	Retriever / Commander
RSS4	DPYSL5	Autosomal dominant	—	(cytoskeletal / CRMP)

"The first two genes described were the autosomal recessive inherited gene WASHC5 associated with Ritscher-Schinzel syndrome 1 (RTSCS1), and CCDC22, an X-linked recessive gene causing Ritscher-Schinzel syndrome 2 (RTSCS2). In recent years, two other genes have been identified: VPS35L (RTSCS3) and DPYSL5 (RTSCS4)." — Neri et al. 2022 (PMID: 36130690)

RSS1 (WASHC5) and RSS2 (CCDC22) patients share a similar facial gestalt, reflecting the shared pathway (PMID: 34020006). Biallelic VPS35L variants cause a 3C/RSS-like syndrome through retriever-complex dysfunction (PMID: 31712251).

Finding 3 — Mechanism: WASH + CCC complexes mediate endosomal cargo recycling; strumpellin loss impairs receptor recycling and lysosomal function

The COMMD/CCDC22/CCDC93 (CCC) and WASH complexes are both required for endosomal sorting of transmembrane cargo. Using LDL receptor (LDLR) as a model cargo, inactivation of the WASH complex was shown to cause LDLR mislocalization, increased lysosomal degradation of LDLR, and impaired LDL uptake; strikingly, a mutation in KIAA0196 (strumpellin) is associated with human hypercholesterolaemia (PMID: 26965651).

"Inactivation of the CCC-associated WASH complex causes LDLR mislocalization, increased lysosomal degradation of LDLR and impaired LDL uptake. Furthermore, a mutation in the WASH component KIAA0196 (strumpellin) is associated with hypercholesterolaemia in humans." — Bartuzi et al. 2016

The upstream recruitment step is defined: the WASH complex is targeted to endosomes through the extended, unstructured "tail" domain of FAM21 binding the retromer subunit VPS35 (PMID: 22070227).

"the retromer-WASH complex interaction occurs through the long unstructured 'tail' domain of the WASH complex-Fam21 protein binding to Vps35, an interaction that is necessary and sufficient to target the WASH complex to endosomes" — Harbour et al. 2012

Downstream, strumpellin loss produces lysosomal abnormalities through failed endosomal tubule fission and disrupted mannose-6-phosphate-receptor sorting (PMID: 28389476).

Finding 4 — WASHC5 allelic series: dominant missense → SPG8; biallelic hypomorphic loss → RSS1; complete null → embryonic lethal

WASHC5 exhibits a striking allelic series governed by dosage:

Dominant missense mutations cause hereditary spastic paraplegia type 8 (SPG8), an adult-onset (3rd–4th decade) pure spastic paraparesis (PMID: 31814071, PMID: 26572744).
Biallelic hypomorphic loss (retaining ~40% protein) causes RSS1 (PMID: 24065355).
Complete loss (null) is embryonic lethal in mouse.

"Homozygous but not heterozygous mice showed early embryonic lethality. No transcripts from the knockout allele were detected, and the previously suggested compensation by the wild-type allele upon heterozygosity was disproven." — Jahic et al. 2015 (PMID: 26572744)

This dosage sensitivity explains why RSS1-causing alleles must be hypomorphic rather than complete nulls: complete loss of strumpellin is incompatible with life, and constrains gene-replacement strategies.

Finding 5 — RSS core clinical triad and phenotype frequencies (26-patient cohort)

In a cohort of 26 RSS patients (PMID: 28555453):

Phenotype	Frequency	HPO term (suggested)
Ocular disorders (any)	100%	HP:0000478 (Abnormality of the eye)
Megalocornea	69%	HP:0000485
Low-set ears	80.7%	HP:0000369
Septal heart defects	68.7%	HP:0001671
Delayed neurodevelopment / ID	84%	HP:0001263 / HP:0001249
Skeletal anomalies (camptodactyly, single palmar crease, overlapping fingers, vertical talus, nail hypoplasia)	96%	HP:0012385 / HP:0000954
Megacisterna magna	31.8%	HP:0002280
Dandy-Walker malformation	27%	HP:0001305
Male sex	69%	—

"All of them presented ocular disorders, and megalocornea was the most frequent ocular manifestation (69%), whereas low-set ears (80.7%) and septal heart defects (68.7%) were the most common facial and cardiac malformations, respectively. The most frequent malformations of the posterior fossa were megacisterna magna (31.8%) and Dandy-Walker malformation (27%). 84% of the cases had delayed neurodevelopment or intellectual disability." — Pira-Paredes et al. 2017

Neri et al. 2022 add that craniofacial dysmorphism (macrocephaly, down-slanted palpebral fissures, low-set ears), developmental delay/ID, and ataxic gait were present in essentially all WASHC5/CCDC22 patients, and that elevated first-trimester nuchal translucency was observed in 3 WASHC5 fetuses (PMID: 36130690). The 69% male predominance in mixed cohorts likely reflects inclusion of X-linked RSS2 (CCDC22) cases; autosomal RSS1 is expected ~1:1.

Finding 6 — WASH functionally couples to the Commander (CCC + retriever) assembly, linking RSS to NF-κB and copper homeostasis

The Commander complex is a 16-protein assembly (COMMD1–10, CCDC22, CCDC93, DENND10, VPS26C, VPS29, VPS35L) that governs endosomal cargo and cell homeostasis and is linked to Wilson's disease and atherosclerosis (PMID: 34943955).

"Commander complex is a 16-protein complex that plays multiple roles in various intracellular events in endosomal cargo and in the regulation of cell homeostasis, cell cycle and immune response. It consists of COMMD1-10, CCDC22, CCDC93, DENND10, VPS26C, VPS29, and VPS35L." — Laulumaa & Varjosalo 2021

CCDC22 binds all COMMD proteins and is required for NF-κB activation via IκB ubiquitination/degradation; CCDC22 deficiency blunts proinflammatory NF-κB signaling and can produce ectodermal-dysplasia features and X-linked intellectual disability (PMID: 23563313).

"we demonstrate that all COMMD proteins bind to CCDC22, a factor recently implicated in X-linked intellectual disability (XLID). We showed that an XLID-associated CCDC22 mutation decreased CCDC22 protein expression and impaired its binding to COMMD proteins." — Starokadomskyy et al. 2013

Because RSS-causal genes CCDC22 (RSS2) and VPS35L (RSS3) are Commander subunits while WASHC5 (RSS1) is in the WASH complex that cooperates with retromer/Commander, all RSS subtypes share a single endosomal trafficking module — explaining their overlapping phenotype.

Finding 7 — Full malformation spectrum and minimal diagnostic criteria

Leonardi et al. 2001 described RSS as a rare autosomal-recessive syndrome and catalogued the full malformation spectrum (PMID: 11484200):

"Cardiac manifestations include ventricular septal defect, atrial septal defect, tetralogy of Fallot, double outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis and other valvular anomalies. Central nervous system anomalies include Dandy-Walker malformation, cerebellar vermis hypoplasia and enlargement of the cisterna magna."

Cardiac: VSD, ASD, tetralogy of Fallot, double-outlet right ventricle, hypoplastic left heart, aortic stenosis, pulmonic stenosis, valvular anomalies (a broad conotruncal + left-heart spectrum).
CNS: Dandy-Walker malformation, cerebellar vermis hypoplasia, enlarged cisterna magna, posterior fossa cyst, hydrocephalus.
Craniofacial: cleft palate, ocular coloboma, prominent occiput, low-set ears, hypertelorism, down-slanting palpebral fissures, depressed nasal bridge, micrognathia.

Revised minimal diagnostic criteria (cardiac malformation other than isolated PDA + posterior-fossa malformation + certain dysmorphic features) are discussed by Gjerulfsen et al. 2021, who caution these are not present in all patients (PMID: 34020006).

Finding 8 — Strumpellin molecular function: WASH-mediated Arp2/3 actin polymerization drives cargo trafficking, endolysosomal integrity, and neuronal plasticity

The WASH complex activates Arp2/3-mediated actin polymerization and is pivotal for endosomal membrane trafficking. Strumpellin knockdown in cortical neurons reduced dendritic arborization, synapse formation, and dendritic F-actin clusters and caused abnormal motor coordination in mice — rescued by wild-type strumpellin (PMID: 37392480).

"WASH complex activates actin-related protein-2/3-mediated actin polymerization and plays a pivotal role in intracellular membrane trafficking in endosomes... Strumpellin knockdown using shRNA attenuated dendritic arborization and synapse formation in cultured cortical neurons, and this effect was rescued by wild-type strumpellin expression."

Additional concrete cargo readouts: strumpellin-deficient murine platelets show ~20% reduced integrin αIIbβ3 surface expression and delayed fibrinogen uptake (PMID: 37308549); SPG8 mutations impair CAV1-dependent integrin-mediated cell adhesion (PMID: 31911435); and N471D strumpellin produces endolysosomal defects (PMID: 30061306).

"Strumpellin-deficient murine platelets display an approximately 20% reduction in integrin αIIbβ3 surface expression. While exposure of the internal αIIbβ3 pool after platelet activation was unaffected, the uptake of the αIIbβ3 ligand fibrinogen was delayed." — Schurr et al. 2023

A N471D Washc5 knock-in mouse recapitulates RSS-relevant features: mild dilated cardiomyopathy, decreased acoustic startle, thinner eye lenses, gait instability, and brain BPTF up / KLHL11 down; biallelic Washc5 ablation is prenatally lethal (PMID: 34312900).

"Homozygous N471D Washc5 knock-in mice showed mild dilated cardiomyopathy, decreased acoustic startle reactivity, thinner eye lenses... While biallelic ablation of Washc5 was prenatally lethal, expression of N471D mutated WASHC5 led to several mild clinical and laboratory parameter[s]..."

Finding 9 — WASH complex regulates endosomal recycling of the copper transporter ATP7A via the CCC complex

COMMD1 is linked to early endosomes through the CCC complex (COMMD/CCDC22/CCDC93/C16orf62 = VPS35L), which interacts with the WASH complex required for endosomal F-actin deposition and cargo trafficking with retromer; FAM21 recruits the CCC complex to endosomes. Depletion of CCC components blocks copper-dependent movement of ATP7A from endosomes, causing intracellular copper accumulation, and humans with CCDC22 mutations show altered copper homeostasis (PMID: 25355947).

"This COMMD/CCDC22/CCDC93 (CCC) complex interacts with the multisubunit WASH complex... required for endosomal deposition of F-actin and cargo trafficking in conjunction with the retromer... depletion of CCC complex components leads to lack of copper-dependent movement of the copper transporter ATP7A from endosomes, resulting in intracellular copper accumulation" — Phillips-Krawczak et al. 2015

This adds a defined copper-metabolism branch (CHEBI:29036 copper(2+)) to the RSS trafficking pathophysiology.

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

Biallelic hypomorphic loss-of-function variant in WASHC5 (e.g., splice-site variant skipping exon 27) leads to ~40% residual strumpellin protein. (demonstrated — PMID: 24065355)
Reduced strumpellin results in destabilization of the pentameric WASH complex (WASHC1–5 + FAM21) and lowers its endosomal branched-actin nucleation activity. (demonstrated for actin function; inferred for RSS1 complex destabilization — PMID: 37392480)
Because WASH is recruited to endosomes via FAM21 binding retromer (VPS35), WASH deficiency impairs localized Arp2/3 activation and endosomal recycling-tubule formation. (demonstrated in vitro — PMID: 22070227)
Loss of endosomal F-actin leads to failed tubule fission, so transmembrane cargo is not returned to the surface. Parallel branches:
4a. LDLR mislocalized and degraded → impaired LDL uptake / hypercholesterolaemia (PMID: 26965651).
4b. Integrins (αIIbβ3, CAV1-dependent) show reduced surface expression / adhesion defects (PMID: 37308549, PMID: 31911435).
4c. Via CCC/Commander coupling, ATP7A copper-transporter recycling fails → intracellular copper dyshomeostasis (PMID: 25355947).
4d. Tubule-fission failure disrupts M6PR sorting → lysosomal dysfunction (PMID: 28389476).
Disrupted membrane-protein homeostasis during embryogenesis impairs morphogenetic signaling and cell adhesion/migration in developing brain, heart, eye, and neural-crest–derived craniofacial structures. (inferred — the specific developmental cargo(es) responsible for each malformation is not established)
This produces the clinical triad: posterior-fossa/cerebellar malformation, congenital heart defects, and craniofacial dysmorphism, plus developmental delay/intellectual disability (PMID: 28555453, PMID: 11484200).
In neurons, reduced WASH-dependent actin plasticity contributes to reduced dendritic arborization/synapse formation and ataxic gait (PMID: 37392480).

 WASHC5 biallelic hypomorph (~40% strumpellin)
      │
      ▼
   WASH complex destabilized on endosomes ◄── recruited by FAM21–VPS35 (retromer)
      │
      ▼
   ↓ Arp2/3 branched-actin nucleation on endosomes
      │
     ┌────────┼─────────────┬───────────────┬──────────────┐
     ▼        ▼             ▼               ▼              ▼
  LDLR      integrins   ATP7A/copper    M6PR/lysosome   neuronal
 recycling   surface     (via CCC/       function        actin
  fails      ↓            Commander)      impaired        plasticity ↓
     │        │             │               │              │
     └────────┴─────┬───────┴───────────────┴──────────────┘
            ▼
     Disrupted membrane-protein homeostasis in development (inferred)
            ▼
   Cranio-cerebello-cardiac malformations + ID  (RSS1 clinical triad)

Upstream vs downstream: The mutation and WASH-complex destabilization are the most upstream events; Arp2/3-actin failure is the central node; the specific cargo-recycling failures are parallel downstream branches; organ malformation is the terminal, integrated readout.

Suggested ontology terms. GO biological process: endosome to plasma membrane protein transport (GO:0099638), Arp2/3 complex-mediated actin nucleation (GO:0034314), retrograde transport endosome to Golgi (GO:0042147), endocytic recycling (GO:0032456). GO cellular component: WASH complex (GO:0071203), early endosome membrane (GO:0031901), lysosome (GO:0005764). Cell types (CL): cerebellar Purkinje (CL:0000121) and granule (CL:0000120) neurons, cardiomyocyte (CL:0000746), neural crest cell (CL:0000333), corneal epithelial cell (CL:0000575). Chemical entity (CHEBI): copper(2+) (CHEBI:29036), cholesterol (CHEBI:16113).

Section-by-Section Report

1. Disease Information

Overview: RSS1 is a rare autosomal-recessive congenital malformation syndrome (3C = cranio-cerebello-cardiac) characterized by the triad of craniofacial dysmorphism, cerebellar/posterior-fossa malformation, and congenital heart disease, with developmental delay/intellectual disability. First delineated by Ritscher & Schinzel (1987); reviewed with proposed diagnostic criteria by Leonardi et al. 2001 (PMID: 11484200).
Identifiers: OMIM #220210 (disease); WASHC5 gene OMIM 610657; Orphanet ORPHA:7 (3C syndrome); MONDO (suggested) MONDO:0009353 (Ritscher-Schinzel syndrome); ICD-10 Q87.8; ICD-11 LD2F (multiple developmental anomalies); no dedicated MeSH term (indexed under "Abnormalities, Multiple"/"Dandy-Walker Syndrome").
Synonyms: 3C syndrome; cranio-cerebello-cardiac dysplasia/syndrome; cranio-cerebro-cardiac syndrome; Ritscher-Schinzel syndrome (type 1).
Data source: Aggregated disease-level knowledge from case reports and small cohorts (largest ~26 patients, PMID: 28555453; 8-patient founder cohort, PMID: 24065355) plus molecular studies — not EHR-derived.

2. Etiology

Primary cause: purely genetic — biallelic hypomorphic loss-of-function variants in WASHC5 (autosomal recessive) (PMID: 24065355).
Genetic risk factors: causal WASHC5 variants; a founder splice allele in an isolated northern-Manitoba First Nations community produced a geographic cluster. Modifier genes not established; candidate modifiers are other WASH/CCC/retriever subunits.
Environmental risk / protective factors: none identified; not applicable to a monogenic disorder. Consanguinity increases recurrence risk for a recessive disorder (PMID: 15704124).
Gene–environment interactions: none documented; disease is essentially fully genotype-determined.

3. Phenotypes

See Finding 5 table. Additional detail and suggested HPO terms: - Ocular (100% affected): megalocornea (HP:0000485), coloboma (HP:0000589), posterior embryotoxon (HP:0000627), ptosis (HP:0000508). - Craniofacial: low-set ears (HP:0000369), prominent occiput (HP:0000269), macrocephaly (HP:0000256), hypertelorism (HP:0000316), down-slanting palpebral fissures (HP:0000494), depressed nasal bridge (HP:0005280), cleft palate (HP:0000175), micrognathia (HP:0000347), foramina parietalia (HP:0002697). - CNS: Dandy-Walker malformation (HP:0001305), cerebellar vermis hypoplasia (HP:0001320), megacisterna magna (HP:0002280), hydrocephalus (HP:0000238), intellectual disability (HP:0001249), ataxic gait (HP:0002066), hypotonia (HP:0001252). Epilepsy is generally absent in WASHC5 RSS1 (PMID: 36130690). - Cardiac: ASD/VSD (HP:0001631/HP:0001629), tetralogy of Fallot (HP:0001636), double-outlet right ventricle (HP:0011723), hypoplastic left heart (HP:0004383), pulmonary hypertension (HP:0002092). - Skeletal: camptodactyly (HP:0012385), single transverse palmar crease (HP:0000954), nail hypoplasia (HP:0001792). - Onset/severity/progression: congenital and structural (stable/non-progressive), but sequelae cause substantial lifelong disability; severity variable (from prenatal lethality to survival with moderate ID). QoL: intellectual disability, motor/gait impairment, and cardiac/surgical morbidity affect independence and daily functioning; formal EQ-5D/SF-36 data unavailable for this rare disease.

4. Genetic / Molecular Information

Causal gene (RSS1): WASHC5 (HGNC:28984; alias KIAA0196/SPG8; NCBI Gene 9897; Ensembl ENSG00000129680; UniProt Q12768), 8q24.13, encoding strumpellin (~134 kDa, spectrin-repeat-containing WASH-complex subunit). Gene OMIM 610657.
Variant types: splice-site (First Nations founder allele skipping exon 27, PMID: 24065355); compound-heterozygous missense/LoF combinations (PMID: 36130690). RSS1 alleles are hypomorphic. ACMG: pathogenic/likely pathogenic for reported recessive alleles; many novel variants remain VUS given rarity.
Allele frequency: individual pathogenic variants are ultra-rare/absent in gnomAD; the Manitoba splice allele is population-restricted.
Origin: germline (constitutional, biallelic).
Functional consequence: loss of function (reduced strumpellin → destabilized WASH complex). Distinct from dominant SPG8 alleles (Finding 4).
Modifier genes / epigenetics / chromosomal abnormalities: none established for RSS1. Phenotypically overlapping 6p25 subtelomeric deletions (FOX genes) cause a distinct 3C-like syndrome, not RSS1 (PMID: 15704124).

5. Environmental Information

Not applicable — RSS1 is monogenic. No environmental, lifestyle, or infectious factors are implicated in causation. Infectious/respiratory complications may occur secondarily (e.g., pulmonary hypertension/respiratory failure in a preterm infant, PMID: 23072186).

6. Mechanism / Pathophysiology

See the Mechanistic Model section above for the ordered causal chain, branch diagram, and GO/CL/CHEBI term suggestions. Core pathway: WASH complex → Arp2/3-mediated endosomal actin nucleation → retromer/CCC(Commander)-coupled cargo recycling, with downstream branches to cholesterol/LDLR, integrin adhesion, NF-κB (via CCC/COMMD), copper homeostasis (ATP7A), and lysosomal function. Disease-specific human omics signatures are unavailable; a mouse-brain proteomic signature (BPTF up, KLHL11 down) exists for the N471D knock-in (PMID: 34312900).

7. Anatomical Structures Affected

Organ (primary): cerebellum / posterior fossa (UBERON:0002037; vermis UBERON:0004720), heart (UBERON:0000948; septa, outflow tract), eyes/cornea (UBERON:0000970/UBERON:0000964), craniofacial skeleton (UBERON:0010323).
Secondary: ventricular system/CSF (hydrocephalus, UBERON:0002289), lungs/pulmonary vasculature, limbs/digits.
Body systems: nervous, cardiovascular, musculoskeletal, ocular/visual, craniofacial.
Tissue/cell: neuroectoderm-derived cerebellar neurons; neural crest derivatives (craniofacial mesenchyme, cardiac outflow). Strumpellin is ubiquitous → cell-autonomous defect across many cell types.
Subcellular: early/recycling endosome membrane (GO:0031901/GO:0055037), WASH complex (GO:0071203), lysosome (GO:0005764), trans-Golgi network, ER–endosome contact sites (PMID: 28389476).
Laterality: typically bilateral/midline (cerebellar vermis, septal defects), consistent with a developmental mechanism.

8. Temporal Development

Onset: congenital/prenatal; malformations form in utero; elevated first-trimester nuchal translucency is an early marker in some fetuses (PMID: 36130690). Diagnosis often neonatal/first year (42% <1 year in the Colombian cohort; PMID: 28555453).
Course: core malformations are static/non-progressive; neurodevelopmental disability is lifelong; prognosis dominated by cardiac/respiratory severity in infancy (PMID: 23072186).
Critical period: embryonic organogenesis (cardiac septation ~weeks 4–8, cerebellar/posterior-fossa, neural-crest craniofacial development); no post-developmental window reverses malformations.
Duration: chronic, lifelong.

9. Inheritance and Population

Inheritance: autosomal recessive (RSS1). Penetrance essentially complete for biallelic genotype; expressivity variable. No anticipation (not a repeat disorder).
Founder effect / consanguinity: founder splice allele in northern Manitoba First Nations; consanguinity enhances recessive recurrence (PMID: 24065355, PMID: 15704124).
Epidemiology: very rare; precise prevalence/incidence not established (<1/1,000,000 order of magnitude implied; <~50 molecularly confirmed cases worldwide). ~26-patient clinical cohort with 69% male (partly reflecting X-linked RSS2 inclusion) (PMID: 28555453); autosomal RSS1 expected ~1:1.
Geographic distribution: reported in Canada/First Nations, Austria, Colombia, China, and Europe; no endemic region beyond the founder cluster. Carrier frequency not formally estimated (elevated in the founder population).

10. Diagnostics

Genetic testing (definitive): WES/WGS or multigene malformation panels including WASHC5, CCDC22, VPS35L, DPYSL5; targeted founder-variant testing in the northern Manitoba First Nations population; Sanger segregation. CMA/karyotype to exclude phenocopies (e.g., 6p25 deletion). Research-grade confirmation: reduced strumpellin on Western blot / transcript analysis (PMID: 24065355, PMID: 24916641).
Imaging: brain MRI (Dandy-Walker spectrum, vermis hypoplasia, megacisterna magna), echocardiography (septal/conotruncal defects, PDA, coarctation, pulmonary hypertension), ophthalmologic exam (megalocornea, coloboma).
Clinical criteria: cardiac malformation (other than isolated PDA) + posterior-fossa malformation + characteristic dysmorphism, acknowledging incomplete criteria in some patients (PMID: 34020006).
Laboratory / biomarkers: consider lipid profile (LDLR trafficking defect → possible hypercholesterolaemia, PMID: 26965651); no validated RSS1-specific biomarker.
Differential diagnosis: 6p25 subtelomeric deletion syndrome (PMID: 15704124), Dandy-Walker malformation of other cause, RSS subtypes 2–4, Joubert/CHARGE (for coloboma/posterior fossa).
Screening: cascade/carrier testing in founder and consanguineous families; prenatal testing if familial variants known.

11. Outcome / Prognosis

Survival/mortality: variable, driven chiefly by cardiac and respiratory severity; life-threatening features are generally cardiac (PMID: 23072186). Severe cases include prenatal lethality/terminated pregnancies; milder cases survive into childhood/adulthood with disability (PMID: 36130690). No systematic survival statistics exist given rarity.
Morbidity/function: lifelong intellectual disability (84%), ataxia, motor and feeding difficulties, visual impairment; malformations non-progressive but disabling.
Complications: heart failure, pulmonary hypertension, hydrocephalus, feeding difficulty/failure to thrive, recurrent infections.
Prognostic factors: severity of congenital heart defect, degree of hydrocephalus/cerebellar malformation, and overall malformation burden. No validated molecular prognostic biomarker.

12. Treatment

No disease-modifying or curative therapy exists; management is symptomatic and multidisciplinary (NCIT: Supportive Care Intervention). - Surgical/interventional: congenital heart defect repair (ASD/VSD closure, PDA ligation, coarctation repair; NCIT cardiac surgical procedures); CSF diversion/ventriculoperitoneal shunt for hydrocephalus; ophthalmologic and craniofacial/orthopedic surgery as indicated. - Supportive/rehabilitative: feeding support (NG/gastrostomy for hypotonia/feeding difficulty, PMID: 33059814), physical/occupational/speech therapy, developmental and special-education services, respiratory support and pulmonary-hypertension management (PMID: 23072186). - Pharmacotherapy: symptom-directed only (heart-failure and pulmonary-hypertension agents); dyslipidaemia monitoring is biologically plausible but not a validated indication. No RSS1-specific pharmacogenomics. - Advanced/experimental: none approved or in trials; gene replacement is constrained by strumpellin dosage sensitivity (null is embryonic-lethal; overexpression potentially harmful, PMID: 26572744). - Genetic counseling is core (25% recurrence risk for AR RSS1; carrier testing).

13. Prevention

Primary: not possible for occurrence; genetic counseling, carrier screening in at-risk/founder/consanguineous families, and preimplantation or prenatal genetic testing where familial variants are known.
Secondary: prenatal ultrasound/MRI and molecular testing for early diagnosis; postnatal echocardiography/brain MRI for early complication detection.
Tertiary: proactive cardiac, neurosurgical, and developmental surveillance.
Immunization/public-health/environmental: not applicable (no infectious/environmental cause).

14. Other Species / Natural Disease

Orthologs: Washc5 (mouse, Mus musculus NCBITaxon:10090); strumpellin is highly conserved and ubiquitously expressed, with the WASH complex conserved to Dictyostelium and Drosophila (PMID: 24065355, PMID: 25355947).
Natural disease: no well-characterized naturally occurring RSS1 phenotype in other species (no established OMIA Washc5 entry). Related CCC-complex biology is disease-relevant in dogs: COMMD1 deficiency causes copper toxicosis in Bedlington Terriers, a comparative Commander-complex disorder (PMID: 34943955).
Comparative biology: the WASH–retromer–Commander module is evolutionarily conserved, validating cross-species mechanistic study. Transmission: not applicable (non-communicable genetic disorder).

15. Model Organisms

Mouse Washc5 knockout: homozygous null → early embryonic/prenatal lethality; heterozygotes viable with no wild-type compensation (PMID: 26572744, PMID: 34312900). Limitation: complete null cannot model the viable hypomorphic RSS1 state.
N471D Washc5 knock-in mouse (SPG8 allele, partially RSS-informative): homozygotes show mild dilated cardiomyopathy, thinner eye lenses, gait instability, decreased acoustic startle, brain BPTF/KLHL11 dysregulation (PMID: 34312900) — cardiac/ocular features are RSS-relevant, though the allele is missense rather than an RSS1 hypomorph.
VPS35L knockout mouse (RSS3 model): demonstrates biallelic VPS35L loss causes a 3C/RSS-like syndrome via retriever dysfunction (PMID: 31712251).
Cellular/in-vitro: strumpellin-knockdown cortical neurons (dendritic/synaptic deficits, PMID: 37392480); strumpellin-deficient platelets (integrin trafficking, PMID: 37308549); N471D cell models (endolysosomal defects, PMID: 30061306); WASH/CCC-knockdown lines (LDLR, ATP7A trafficking, PMID: 26965651, PMID: 25355947).
Gaps: conditional/hypomorphic mouse and iPSC/organoid models are lacking. No single model reproduces the complete human cranio-cerebello-cardiac triad.

Evidence Base

PMID	Paper (short)	Role in this report
24065355	Novel KIAA0196 mutation in First Nations 3C cohort	Establishes WASHC5/strumpellin as RSS1 cause (F001)
36130690	Pre/postnatal phenotype of WASHC5 & CCDC22 RSS	Four-gene heterogeneity; phenotype/NT data (F002, F005)
34020006	Expansion of CCDC22 RSS; diagnostic criteria	Shared facial gestalt; minimal criteria (F002, F007)
26965651	CCC/WASH sorting of LDLR	WASH cargo-recycling function; hypercholesterolaemia (F003)
22070227	FAM21–Vps35 recruits WASH	Upstream endosomal recruitment step (F003)
28389476	ER–endosome contacts / lysosome function in HSP	Lysosomal consequence of strumpellin loss (F003)
26572744	KIAA0196 spectrum + murine knockout	Allelic series; null embryonic lethal (F004)
28555453	26-patient RSS phenotype series	Quantitative phenotype frequencies (F005)
11484200	Leonardi RSS review, 4 new cases	Full malformation spectrum; AR inheritance (F007)
34943955	Commander Complex review	Commander composition; RSS gene network (F006)
23563313	CCDC22 & NF-κB	CCC/NF-κB; XLID link (F006)
25355947	COMMD1–WASH–ATP7A	Copper-homeostasis branch (F009)
37392480	Strumpellin & cortical neuron plasticity	Arp2/3 function; neurodevelopmental role (F008)
37308549	Strumpellin & platelet integrin trafficking	Concrete cargo readout (F008)
34312900	N471D Washc5 knock-in mice	Model recapitulating cardiac/ocular features (F008, §15)
31911435	SPG8 mutations & CAV1/integrin adhesion	Integrin/adhesion mechanism (F008)
30061306	N471D strumpellin endolysosomal defects	Endolysosomal phenotype (F008)
31712251	VPS35L → 3C/RSS-like via retriever	RSS3; retriever/Commander convergence (F002)
24916641	CCDC22 XLID with RSS features	RSS2; phenotypic overlap; WES diagnostics
15704124	6p25 subtelomeric deletion overlap	Differential diagnosis / phenocopy
31814071	SPG8 in Italian families	Dominant-missense SPG8 arm of allelic series (F004)
23072186	Preterm infant, RSS respiratory problems	Cardiac/pulmonary prognosis
33059814	CCDC22 RSS case, feeding difficulty/hypotonia	Supportive-care features

Evidence source types: human clinical (cohort/case series: 24065355, 28555453, 36130690, 34020006, 11484200, 24916641); model organism (mouse: 26572744, 34312900, 31712251); in-vitro/cell biology (26965651, 22070227, 25355947, 37392480, 37308549, 30061306, 28389476); review/computational (34943955).

Limitations and Knowledge Gaps

Ultra-rarity limits epidemiology. Fewer than ~50 molecularly confirmed RSS patients exist across all genes; precise prevalence, incidence, sex ratio, and survival for RSS1 specifically are not established. Mixed "3C cohorts" combine WASHC5 (AR) and CCDC22 (X-linked) patients, confounding sex-ratio and frequency estimates.
Nomenclature ambiguity. OMIM and some literature label WASHC5- vs CCDC22-related disease inconsistently; this report follows OMIM #220210 = WASHC5 = RSS1 per the research question.
Developmental causal link is inferred, not demonstrated. The specific WASH-dependent cargo(es) whose mis-trafficking produces cerebellar, cardiac, and craniofacial malformations are not identified; steps 4→6 of the causal chain are mechanistically plausible but not proven in developing human tissue.
No RSS1 patient-tissue omics. Transcriptomic, proteomic, metabolomic, or single-cell data from RSS1 patients are unavailable; mechanism is extrapolated from cell lines and heterologous models (platelets, cortical neurons, SPG8 knock-in mice).
No faithful animal model of RSS1. The null mouse is embryonic lethal; the available knock-in carries an SPG8 (dominant) allele, not a biallelic RSS1 hypomorph.
No treatment/trials. There is no targeted therapy, no clinical trial, and no validated biomarker; QoL and natural-history data are absent.

Proposed Follow-up Experiments / Actions

Generate a biallelic Washc5 hypomorphic mouse (e.g., the exon-27 splice allele or a graded-expression conditional allele) to model the viable ~40%-protein RSS1 state and test whether it reproduces the cranio-cerebello-cardiac triad.
Patient iPSC-derived cerebellar organoids and cardiomyocytes to define which endosomal cargoes are mis-recycled in disease-relevant cell types (single-cell RNA-seq + surface proteomics), linking specific cargo defects to specific malformations.
Systematic cargo screen (surface-proteome comparison of strumpellin-deficient vs rescued cells) to build the definitive list of WASH-dependent developmental cargoes beyond LDLR/integrins/ATP7A/M6PR.
Copper-homeostasis biomarker study in RSS1/CCDC22 patients (serum copper, ceruloplasmin, ATP7A trafficking assays) to test whether the copper branch is clinically measurable and potentially actionable (PMID: 25355947).
International RSS registry combining WASHC5/CCDC22/VPS35L/DPYSL5 cases with genotype–phenotype and natural-history data to establish penetrance, expressivity, survival, and refined diagnostic criteria.
Structural/biophysical characterization of RSS1 vs SPG8 strumpellin variants within the reconstituted WASH complex to explain the dominant-missense vs recessive-hypomorph allelic dichotomy at the molecular level.

Report compiled from 9 confirmed findings and 30 reviewed papers over 5 investigation iterations. All quoted text is verbatim from the cited PubMed abstracts. Evidence types: human clinical, model organism, in-vitro cell biology, and computational/review, as cited by PMID above.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	23
Resolved	23
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	23
On topic	13
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	57
Resolved	56
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	1
Terms whose name was checked	4
Terms named correctly	1
Terms named as a different term	0
Terms whose name is worth a second look	3

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:0000369 (2 mentions) - the report calls it "Craniofacial: low-set ears"; HP calls it Low-set ears**
HP:0012385 (2 mentions) - the report calls it "Skeletal: camptodactyly"; HP calls it Camptodactyly**
HP:0001305 (2 mentions) - the report calls it "CNS: Dandy-Walker malformation"; HP calls it Dandy-Walker malformation**

56 of 57 terms resolved to a current term; the rest could not be looked up either way.

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Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Progression

Prevalence

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Ritscher-Schinzel Syndrome 1 (RSS1 / 3C Syndrome): Comprehensive Disease Report

Summary

Key Findings

Finding 1 — RSS1 is caused by biallelic WASHC5/strumpellin loss of function (autosomal recessive; OMIM #220210)

Finding 2 — Ritscher-Schinzel syndrome is genetically heterogeneous (four genes)

Finding 3 — Mechanism: WASH + CCC complexes mediate endosomal cargo recycling; strumpellin loss impairs receptor recycling and lysosomal function

Finding 4 — WASHC5 allelic series: dominant missense → SPG8; biallelic hypomorphic loss → RSS1; complete null → embryonic lethal

Finding 5 — RSS core clinical triad and phenotype frequencies (26-patient cohort)

Finding 6 — WASH functionally couples to the Commander (CCC + retriever) assembly, linking RSS to NF-κB and copper homeostasis

Finding 7 — Full malformation spectrum and minimal diagnostic criteria

Finding 8 — Strumpellin molecular function: WASH-mediated Arp2/3 actin polymerization drives cargo trafficking, endolysosomal integrity, and neuronal plasticity

Finding 9 — WASH complex regulates endosomal recycling of the copper transporter ATP7A via the CCC complex

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

Section-by-Section Report

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic / Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Evidence Base

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Artifacts

Reference Validation

Term Validation

Terms whose name is worth a second look