ReNU Syndrome

Mendelian MONDO:0971172 Pathograph 22 Show in embeddings browser Neurodevelopmental Disorder

ReNU syndrome (also NEDHAFA; neurodevelopmental disorder with hypotonia, brain anomalies, distinctive facies, and absent language; OMIM:620851) is a syndromic neurodevelopmental disorder caused by de novo variants in RNU4-2, a non-coding gene encoding the U4 small nuclear RNA (snRNA), a critical component of the U4/U6.U5 tri-snRNP of the major spliceosome. Pathogenic variants cluster within an 18-base-pair critical region in the centre of RNU4-2 (mapping to the T-loop and stem III structural elements of the U4/U6 duplex), with a single highly recurrent single-base insertion (n.64_65insT) accounting for the majority of cases. The disorder is characterized by moderate-to-severe global developmental delay/intellectual disability, largely non-verbal speech, hypotonia, microcephaly (mostly congenital), short stature, seizures, and characteristic brain MRI findings (reduced white-matter volume, corpus callosum hypoplasia, ventriculomegaly, delayed myelination), together with a distinctive lip-and-philtrum facial gestalt. Because RNU4-2 is a short non-coding RNA gene, it is not captured by conventional exome sequencing, and affected individuals are typically exome-negative until genome sequencing is performed; variants in the critical region are estimated to explain ~0.4% of all neurodevelopmental disorders, making ReNU syndrome one of the most prevalent monogenic neurodevelopmental disorders. Inheritance is autosomal dominant, with variants arising de novo (observed on the maternal allele where parental origin could be resolved).

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1
Inheritance
5
Pathophys.
34
Phenotypes
4
Gaps
22
Pathograph
1
Genes
6
Medical Actions
2
Subtypes
3
Differentials
1
Models
1
References
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Classifications

Harrison's Part
NEUROLOGIC GENETICS ENVIRONMENT DISEASE
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Inheritance

1
Autosomal Dominant (de novo) HP:0000006
ReNU syndrome is inherited in an autosomal-dominant manner, with the causative heterozygous RNU4-2 variants arising de novo. Where parental origin could be determined, the de novo variants were consistently found on the maternal allele. The recurrent n.64_65insT insertion and other critical-region variants were confirmed de novo in trio (and, in a subset, long-read) sequencing.
Autosomal dominant, de novo
Show evidence (6 references)
PMID:38991538 SUPPORT Human Clinical
"In 54 individuals in whom it could be determined, the de novo variants were all on the maternal allele."
Chen et al. establish that the RNU4-2 variants arise de novo and, where resolvable, occur on the maternal allele, defining the de novo dominant mode of occurrence.
PMID:42419151 SUPPORT Human Clinical
"We identified a recurrent RNU4-2 variant (NR_003137.3:n.64_65insT) in five patients (5.3%), four of whom are described here. All variants occurred de novo."
Hiraide et al. independently confirm the recurrent n.64_65insT variant arising de novo in an exome-negative NDD cohort.
PMID:40011755 SUPPORT Human Clinical
"two were heterozygous for private/rare maternally inherited variants"
Qualifies the de novo rule rather than supporting it: two affected individuals inherited their variant from an apparently unaffected mother, so "de novo" describes the typical but not the invariant case.
+ 3 more references
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Subtypes

2
T-loop variant ReNU syndrome (including the recurrent n.64_65insT)
Variants in the T-loop element, which include the highly recurrent n.64_65insT insertion accounting for roughly 80% of all cases, define the severe end of the spectrum: developmental delay is severe and more than 70% of individuals remain non-verbal. This is the classical ReNU presentation on which the syndrome was originally delineated.
Show evidence (2 references)
PMID:40413032 SUPPORT Human Clinical
"T-loop variants manifested severe developmental delay with more than 70% of cases being non-verbal."
Defines the severity that distinguishes this subtype.
PMID:40413032 SUPPORT Human Clinical
"RNU4-2 variants are located in the T-loop or stem III region of U4 snRNA, of which approximately 80% are the n.64_65insT variant in the T-loop."
Establishes that the T-loop group, dominated by n.64_65insT, is the majority of cases.
Stem III variant ReNU syndrome
Variants in the stem III element produce a materially milder disorder: developmental delay is less severe, speech can be fluent, and gross motor milestones are close to normal. This subtype is the main reason the syndrome's severity is not uniform, and it matters diagnostically because a fluently speaking, ambulant individual may still have ReNU syndrome.
Show evidence (1 reference)
PMID:40413032 SUPPORT Human Clinical
"Stem III region variants resulted in milder developmental delay with fluent speech and nearly normal gross motor development milestones."
Defines the milder phenotype that distinguishes this subtype from the T-loop group.
?

Discussions and Knowledge Gaps

4
If ReNU syndrome is not caused by loss of RNU4-2 function, what does the dominant critical-region variant actually do to the spliceosome?
KNOWLEDGE GAP OPEN renu_mechanism_is_not_loss_of_function
Attached to
pathophysiology#RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function
The discovery of a recessive RNU4-2 disorder settles what ReNU syndrome is not. Biallelic variants outside the critical region reduce RNU4-2 transcript levels and cause a clinically distinct disease by loss of function; the authors state explicitly that this mechanism differs from the one underlying ReNU syndrome. The dominant critical-region variants must therefore act by some other route — a dominant-negative or altered-function effect on U4/U6 pairing and spliceosome activation — but which of these, and whether the mutant U4 is incorporated into tri-snRNPs and poisons them or acts before assembly, is not established. This matters for therapy: an antisense or allele-specific strategy is only coherent if the mutant transcript is doing something, rather than simply failing to.
Show evidence (1 reference)
PMID:41951959 SUPPORT Human Clinical
"we find reduced RNU4-2 transcript levels in individuals with the recessive disorder, suggesting a loss-of-function disease mechanism that is distinct from the mechanism underlying ReNU syndrome"
The source of the gap: it establishes that ReNU syndrome's mechanism is something other than loss of function, without saying what.
Why do variants in one 76-nucleotide non-coding gene produce either a severe neurodevelopmental syndrome or an isolated retinal degeneration, depending only on which structural element is affected?
OPEN QUESTION OPEN renu_rnu4_2_pleiotropy_ndd_versus_retinopathy
Attached to
genetic#RNU4-2 critical-region variants pathophysiology#Systematic Disruption of 5' Splice-Site Usage
RNU4-2 now has at least three distinct variant-position-to-disease mappings: the 18-bp T-loop/stem III critical region gives dominant ReNU syndrome; the three-way junction of the U4/U6 duplex gives dominant non-syndromic retinitis pigmentosa; and Stem II, the k-turn and the Sm site give a recessive neurodevelopmental disorder when biallelic. A single housekeeping snRNA used by essentially every transcript thus yields strikingly tissue-restricted and non-overlapping phenotypes. The retinal variants appear to act on snRNP biogenesis via tri-snRNP factor binding, echoing the PRPF-gene retinitis pigmentosas, which suggests the determinant is which spliceosome sub-process is perturbed rather than how much splicing is disturbed overall. Testing that would require comparing splicing outcomes across variant classes in the same cell system.
Show evidence (1 reference)
PMID:41513982 SUPPORT Human Clinical
"reveals pleiotropy in RNU4-2, where distinct variants underlie neurodevelopmental disorder and retinal degeneration"
States the pleiotropy that this question is about.
Is the skeletal fragility of ReNU syndrome caused by a splicing defect intrinsic to bone cells, or is it disuse osteoporosis secondary to hypotonia and limited ambulation?
KNOWLEDGE GAP OPEN renu_bone_disease_intrinsic_versus_disuse
Attached to
pathophysiology#Increased Bone Turnover and Reduced Bone Mineral Density
The distinction is not academic: it determines whether bone in ReNU syndrome should be managed as a primary skeletal disease with early surveillance and anti-resorptive therapy, or as a preventable consequence of immobility. One observation currently favours an intrinsic effect — a tibia biopsy showed increased numbers of both osteoclasts and osteoblasts with enlarged eroded surfaces, an activated high-turnover state, whereas disuse osteoporosis is typically low-turnover. But that is a single biopsy in a single patient who was also non-ambulatory, so disuse is not excluded, and the authors themselves call for the bone pathology to be defined. Resolving it needs histomorphometry in several patients stratified by ambulatory status.
Show evidence (1 reference)
PMID:40510867 SUPPORT Human Clinical
"Although skeletal abnormalities have been reported in individuals with ReNU syndrome,1,2,4–10 the underlying bone cell pathologies still need to be defined in order to prevent fractures by specific treatment strategies."
The authors state the gap directly and tie it to treatment selection; curated PARTIAL because it names the uncertainty rather than resolving it.
Twenty-one of this entry's 34 phenotypes are not attached to a mechanism node. Which of them have a real published mechanistic link, and which should stay unattached?
CURATION TODO OPEN renu_unwired_phenotypes
Attached to
phenotypes#Feeding difficulties phenotypes#Short stature phenotypes#Optic nerve hypoplasia phenotypes#Self-injurious behavior phenotypes#Joint hypermobility
The 2026 augmentation wired 13 of 34 phenotypes into the pathograph, in every case where a source supported the link. The 21 left unwired fall into groups: growth and dysmorphology (short stature, the lip-and-philtrum gestalt, everted lower lip); ophthalmological findings (optic nerve hypoplasia, strabismus, nystagmus); gastrointestinal and renal features (feeding difficulties, constipation, gastro-oesophageal reflux, proteinuria, kidney and urinary tract anomalies); skeletal features not covered by the bone-turnover node (scoliosis, hip dysplasia, rib morphology, talipes equinovarus, joint hypermobility); and the behavioural phenotype (autistic features, short attention span, midline stereotypies, sleep disturbance, self-injurious behaviour). The behavioural group is the most tempting to attach, since it is obviously neurodevelopmental, but the sources list these as features of the syndrome rather than as consequences of the brain-growth node, and association is not a mechanism. Likewise hypotonia to feeding difficulty, or to scoliosis and hip dysplasia, are clinically reasonable chains that no ReNU-specific source states. Inventing edges to raise a connectivity metric would make the pathograph assert more than the literature does. Each should be wired when a source supports it.
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Pathophysiology

5
RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function
RNU4-2 encodes the U4 small nuclear RNA, which base-pairs extensively with U6 snRNA within the U4/U6.U5 tri-snRNP of the major spliceosome. The 18-bp critical region harboring the recurrent n.64_65insT insertion maps to the T-loop and stem III structural elements that stabilize U4/U6 pairing and help position the U6 ACAGAGA sequence to receive the 5' splice site during initial spliceosome activation. Variants in this region perturb U4 structure and the U4/U6 duplex, compromising accurate spliceosome assembly/activation. RNU4-2 is highly expressed in the developing human brain (in contrast to the paralog RNU4-1), consistent with a developmental, brain-predominant impact. Saturation genome editing across the whole gene has since resolved this critical region to single-nucleotide resolution and shown that the severity of a variant's functional effect tracks with clinical severity. Note that this is not a loss-of-function mechanism: biallelic variants elsewhere in RNU4-2 reduce transcript levels and cause a separate recessive disorder, which is what distinguishes ReNU syndrome mechanistically from simple haploinsufficiency.
RNU4-2 hgnc:10193 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves RNU4-2 (hgnc:10193). hgnc:10193 is a gene from the HUGO Gene Nomenclature Committee.
U4/U6.U5 tri-snRNP spliceosome assembly GO:0000387 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal U4/U6.U5 tri-snRNP spliceosome assembly, annotated with spliceosomal snRNP assembly (GO:0000387). GO:0000387 is a biological process from the Gene Ontology. ⚠ ABNORMAL mRNA splicing via the major spliceosome GO:0000398 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal mRNA splicing via the major spliceosome, annotated with mRNA splicing, via spliceosome (GO:0000398). GO:0000398 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Experimental models
Saturation genome editing of RNU4-2 in HAP1 cells CELL LINE Quantifies the functional consequence of each RNU4-2 variant, resolving the critical region to single-nucleotide resolution and reclassifying variants of uncertain significance.
Downstream
Systematic Disruption of 5' Splice-Site Usage Impaired positioning of the U6 ACAGAGA region during spliceosome activation leads to systematically altered 5' splice-site recognition.
Show evidence (3 references)
PMID:38991538 SUPPORT Human Clinical
"RNU4-2 encodes the U4 small nuclear RNA (snRNA), which is a critical component of the U4/U6.U5 tri-snRNP complex of the major spliceosome"
Chen et al. establish the molecular identity and role of the U4 snRNA encoded by RNU4-2 within the major spliceosome.
PMID:38991538 SUPPORT Human Clinical
"We demonstrate that RNU4-2 is highly expressed in the developing human brain, in contrast to RNU4-1 and other U4 homologues."
Brain-predominant developmental expression of RNU4-2 supports the neurodevelopmental specificity of the disorder.
PMID:41951737 SUPPORT In Vitro
"we redefine the ReNU syndrome critical region at single-nucleotide resolution, resolve variant pathogenicity for variants of uncertain significance and show that SGE function scores delineate variants by phenotypic severity and the extent of observed splicing disruption"
Saturation genome editing refines the critical region and ties the magnitude of the functional defect to both splicing disruption and clinical severity.
Systematic Disruption of 5' Splice-Site Usage
RNA sequencing of individuals with RNU4-2 variants shows systematically disrupted 5' splice-site usage — notably increased use of unannotated 5' splice sites — consistent with the known role of the affected region during spliceosome activation. This global splicing dysregulation during neurodevelopment is the proposed convergence point linking the RNA-level defect to the neurodevelopmental phenotype, placing ReNU syndrome among the spliceosomopathies. Because the spliceosome is used by essentially every transcript, the downstream consequences are not confined to brain: skeletal and, in at least one report, glomerular involvement are part of the phenotype. Which downstream transcripts actually mediate each organ phenotype is not known, so the edges below are curated as indirect with unknown intermediates.
mRNA splicing via the major spliceosome GO:0000398 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal mRNA splicing via the major spliceosome, annotated with mRNA splicing, via spliceosome (GO:0000398). GO:0000398 is a biological process from the Gene Ontology. ⚠ ABNORMAL Nervous system development GO:0007399 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal Nervous system development (GO:0007399). GO:0007399 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Downstream
Impaired Brain Growth and White Matter Development Global splicing dysregulation during brain development is the proposed basis for the reduced brain growth and white-matter abnormalities that dominate the neuroimaging phenotype.
Cortical Network Hyperexcitability Epilepsy occurs in roughly 60% of individuals and, notably, without a structural epileptogenic lesion on MRI — pointing to a functional network abnormality rather than a visible malformation as the seizure substrate.
Increased Bone Turnover and Reduced Bone Mineral Density Bone involvement is common and its histology suggests a bone-cell-intrinsic effect rather than purely disuse osteoporosis, though this is inference from a single biopsy and is not established.
Show evidence (2 references)
PMID:38991538 SUPPORT Human Clinical
"we show how 5' splice-site use is systematically disrupted in individuals with RNU4-2 variants, consistent with the known role of this region during spliceosome activation"
Chen et al. demonstrate systematic 5' splice-site disruption by RNA-seq, the proximate functional consequence of the variants.
PMID:38821540 SUPPORT Human Clinical
"Our findings add to the growing evidence of spliceosome dysfunction in the etiologies of neurological disorders."
Greene et al. frame RNU4-2 disease within the broader class of spliceosome-dysfunction neurological disorders.
Impaired Brain Growth and White Matter Development
The convergent tissue-level consequence in the CNS is reduced brain growth with a white-matter-predominant imaging signature: decreased cerebral white matter volume, corpus callosum hypoplasia, ventriculomegaly and delayed myelination, together with mostly congenital microcephaly. Neuroimaging abnormality is close to universal in reported cohorts. This node is the point at which the molecular splicing defect becomes the clinical neurodevelopmental phenotype, and it is the parent of the cognitive, language and motor phenotypes below.
Oligodendrocyte CL:0000128 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Oligodendrocyte (CL:0000128). CL:0000128 is a cell type from the Cell Ontology.
Brain development GO:0007420 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal Brain development (GO:0007420). GO:0007420 is a biological process from the Gene Ontology. ⚠ ABNORMAL Myelination GO:0042552 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Myelination (GO:0042552). GO:0042552 is a biological process from the Gene Ontology. ↓ DECREASED
Cerebral white matter UBERON:0002316 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in Cerebral white matter, annotated with white matter (UBERON:0002316). UBERON:0002316 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Microcephaly Reduced brain growth presents clinically as mostly congenital microcephaly.
Reduced cerebral white matter volume Decreased white matter volume is a core component of the imaging signature.
Corpus callosum hypoplasia Callosal hypoplasia accompanies the white-matter deficit.
Ventriculomegaly Ventricular enlargement accompanies the reduced white-matter volume.
Delayed myelination Myelination is delayed, consistent with the oligodendrocyte/white-matter emphasis.
Global developmental delay / intellectual disability The cardinal clinical consequence of impaired brain development.
Severe intellectual disability Cognitive impairment is typically in the severe range.
Absent / non-verbal speech Expressive language is typically absent or minimal beyond the expected age.
Motor delay Gross motor milestones are delayed and often incompletely attained.
Hypotonia Central hypotonia is an early and near-universal manifestation.
Show evidence (2 references)
PMID:40546132 SUPPORT Human Clinical
"All patients had neuroradiological abnormalities."
Neuroradiological abnormality was present in every patient in a consecutive series, supporting this node as an obligate tissue-level feature.
PMID:40546132 SUPPORT Human Clinical
"Neuroradiological abnormalities, including ventriculomegaly, hypoplasia of the corpus callosum, and a decreased white matter volume, are observed in many individuals."
Specifies the white-matter-predominant imaging signature that defines this node.
Cortical Network Hyperexcitability
Epilepsy affects roughly 60% of individuals with ReNU syndrome. The seizure disorder is notable for what is absent as much as what is present: dedicated epilepsy-cohort imaging found no structural epileptogenic lesion, so the seizures are attributed to a functional network abnormality rather than to the malformations visible on MRI. Focal impaired-consciousness seizures predominate across all ages, onset is in early childhood, and the course is comparatively favourable, with seizure freedom achievable in about half of patients. The cellular substrate linking the splicing defect to network hyperexcitability is not known, which is why this node deliberately carries no biological_process or cell_type binding: no source examined identifies the channel, synapse or cell population involved, and a generic nervous-system-development term would assert nothing about excitability.
Downstream
Seizures Network hyperexcitability manifests as predominantly focal impaired-consciousness seizures with onset in early childhood.
Show evidence (2 references)
PMID:41570780 SUPPORT Human Clinical
"Epilepsy is a prominent feature in about 60% of patients with ReNU syndrome"
Establishes the frequency of epilepsy that this node represents.
PMID:41570780 SUPPORT Human Clinical
"The mean age at epilepsy onset was 2.8 ±2.1 years."
Dates the onset of this node's clinical expression to early childhood.
Increased Bone Turnover and Reduced Bone Mineral Density
Skeletal fragility is a common and clinically actionable part of the phenotype: bone abnormalities were present in 42% of individuals assessed. In the one published case with histomorphometry, an undecalcified tibia biopsy showed enlarged eroded surfaces with increased numbers of both osteoclasts and osteoblasts — an activated, high-turnover state rather than the low-turnover picture expected from immobility alone. That observation is the basis for suspecting a bone-cell-intrinsic splicing effect, but it rests on a single biopsy and disuse remains an unexcluded contributor in a population with hypotonia and limited ambulation. Vertebral fractures may be clinically silent until sought, which is why this node matters for management.
Osteoclast CL:0000092 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Osteoclast (CL:0000092). CL:0000092 is a cell type from the Cell Ontology. Osteoblast CL:0000062 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves Osteoblast (CL:0000062). CL:0000062 is a cell type from the Cell Ontology.
Bone resorption GO:0045453 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Bone resorption (GO:0045453). GO:0045453 is a biological process from the Gene Ontology. ↑ INCREASED Ossification GO:0001503 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal Ossification (GO:0001503). GO:0001503 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Bone UBERON:0001474 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in Bone, annotated with bone element (UBERON:0001474). UBERON:0001474 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Osteopenia Reduced bone mineral density is the direct densitometric expression of this node.
Recurrent fractures Fragility fractures, including clinically unrecognized vertebral fractures, follow from the reduced bone mass.
Show evidence (1 reference)
PMID:40510867 SUPPORT Human Clinical
"Laboratory tests indicated an activated bone turnover, which was confirmed by an increased number of osteoclasts and osteoblasts in an undecalcified tibia biopsy of the patient."
Direct histomorphometric evidence for the high-turnover state this node asserts, from bone biopsy rather than densitometry alone.
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Pathograph

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

34
Digestive 3
Feeding difficulties HP:0011968 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties (HP:0011968). HP:0011968 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report feeding issues requiring a gastrostomy tube among the gastrointestinal manifestations.
Constipation HP:0002019 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Constipation (HP:0002019). HP:0002019 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report constipation among the gastrointestinal manifestations.
Gastroesophageal reflux HP:0002020 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Gastroesophageal reflux (HP:0002020). HP:0002020 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report reflux among the gastrointestinal manifestations.
Eye 2
Strabismus HP:0000486 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Strabismus (HP:0000486). HP:0000486 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. list strabismus among the visual abnormalities reported in the multi-organ involvement.
Nystagmus HP:0000639 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Nystagmus (HP:0000639). HP:0000639 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. list nystagmus among the visual abnormalities reported in the multi-organ involvement.
Genitourinary 2
Proteinuria HP:0000093 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Proteinuria (HP:0000093). HP:0000093 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:41623289 SUPPORT Human Clinical
"A kidney biopsy showed minimal change disease with slight podocyte effacement."
Documents the renal histology underlying the proteinuria in the reported case.
PMID:41623289 SUPPORT Human Clinical
"This case is the first documented report of isolated, persistent proteinuria in ReNU syndrome."
Curated PARTIAL because it establishes the phenotype in a single individual and therefore does not support any claim about frequency.
Kidney and urinary tract anomalies Abnormality of the urinary system HP:0000079 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Kidney and urinary tract anomaly, annotated with Abnormality of the urinary system (HP:0000079). HP:0000079 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:42190036 SUPPORT Other
"kidney anomalies; urinary tract anomalies; bone health; and sleep issues"
GeneReviews names kidney and urinary tract anomalies as domains requiring dedicated surveillance, establishing them as recognised features.
PMID:41623289 SUPPORT Human Clinical
"Kidney involvement has been reported exclusively as anatomical abnormalities."
Independently confirms that anatomical anomaly was the previously reported form of renal involvement.
Head and Neck 2
Microcephaly FREQUENT HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
Chen et al. report microcephaly in ≥75% of individuals, supporting the FREQUENT band.
Distinctive lip-and-philtrum facial gestalt Abnormal facial shape HP:0001999 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Distinctive lip and philtrum facial gestalt, annotated with Abnormal facial shape (HP:0001999). HP:0001999 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42419151 SUPPORT Human Clinical
"Distinctive facial features involving the lips and philtrum were consistently observed, including a characteristic combination of a tented upper lip with an exaggerated Cupid's bow, an everted lower lip, and a horizontally oriented philtrum."
Hiraide et al. describe the characteristic lip-and-philtrum facial gestalt of ReNU syndrome.
Limbs 1
Talipes equinovarus HP:0001762 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Club foot, annotated with Talipes equinovarus (HP:0001762). HP:0001762 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42190036 SUPPORT Other
"bone/skeletal involvement (club feet, hip dysplasia, joint hyperlaxity, osteopenia/osteoporosis or history of low-impact fractures)"
GeneReviews lists club feet among the characteristic skeletal features.
Musculoskeletal 7
Hypotonia FREQUENT HP:0001252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypotonia (HP:0001252). HP:0001252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
Chen et al. report hypotonia in ≥75% of individuals, supporting the FREQUENT band.
Osteopenia HP:0000938 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Osteopenia (HP:0000938). HP:0000938 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report osteopenia among the bone/skeletal abnormalities.
Recurrent fractures HP:0002757 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent fractures (HP:0002757). HP:0002757 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report recurrent fractures among the bone/skeletal abnormalities.
Scoliosis HP:0002650 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Scoliosis (HP:0002650). HP:0002650 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report scoliosis among the skeletal abnormalities.
Hip dysplasia HP:0001385 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hip dysplasia (HP:0001385). HP:0001385 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report hip dysplasia among the skeletal abnormalities.
Abnormal rib morphology HP:0000772 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal rib morphology (HP:0000772). HP:0000772 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42419151 SUPPORT Human Clinical
"In addition, transient limb edema and rib dysplasia may expand the phenotypic spectrum."
Hiraide et al. identify rib dysplasia as an emerging phenotypic feature that expands the spectrum of skeletal abnormalities in ReNU syndrome.
Joint hypermobility HP:0001382 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Joint hyperlaxity, annotated with Joint hypermobility (HP:0001382). HP:0001382 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42190036 SUPPORT Other
"bone/skeletal involvement (club feet, hip dysplasia, joint hyperlaxity, osteopenia/osteoporosis or history of low-impact fractures)"
GeneReviews lists joint hyperlaxity among the characteristic skeletal features.
Nervous System 11
Global developmental delay / intellectual disability HP:0001263 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Global developmental delay (HP:0001263). HP:0001263 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38821540 SUPPORT Human Clinical
"We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
Greene et al. list intellectual disability as a defining feature of the RNU4-2 syndrome.
Severe intellectual disability HP:0010864 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Severe intellectual disability (HP:0010864). HP:0010864 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:42419151 SUPPORT Human Clinical
"Affected individuals exhibited severe intellectual disability, developmental delay, microcephaly, short stature, and consistent brain MRI findings, including ventricular enlargement and corpus callosum thinning."
Hiraide et al. document severe intellectual disability in the affected individuals.
PMID:42419151 SUPPORT Human Clinical
"The n.64_65insT variant, located within the functional T-loop of the U4 snRNA, appears to be associated with more severe cognitive impairment than other RNU4-2 variants."
Establishes the genotype-phenotype correlation of the recurrent variant with more severe cognitive impairment.
Absent / non-verbal speech Absent speech HP:0001344 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Absent speech (HP:0001344). HP:0001344 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures"
Chen et al. report speech abnormalities (mostly non-verbal) among the highly frequent phenotypes.
Seizures FREQUENT HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
Chen et al. report seizures in ≥75% of individuals, supporting the FREQUENT band.
Corpus callosum hypoplasia Hypoplasia of the corpus callosum HP:0002079 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoplasia of the corpus callosum (HP:0002079). HP:0002079 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
Chen et al. report corpus callosum hypoplasia as a frequent MRI finding.
Ventriculomegaly HP:0002119 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ventriculomegaly (HP:0002119). HP:0002119 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42419151 SUPPORT Human Clinical
"consistent brain MRI findings, including ventricular enlargement and corpus callosum thinning"
Hiraide et al. document ventricular enlargement (ventriculomegaly) as a consistent MRI finding.
Delayed myelination HP:0012448 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Delayed myelination (HP:0012448). HP:0012448 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
Chen et al. list delayed myelination among the frequent MRI findings.
Motor delay HP:0001270 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Motor delay (HP:0001270). HP:0001270 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38821540 SUPPORT Human Clinical
"We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
Greene et al. list motor delay among the defining features of the RNU4-2 syndrome.
Autistic features Autism HP:0000717 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Autism spectrum disorder, annotated with Autism (HP:0000717). HP:0000717 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41681065 SUPPORT Human Clinical
"Distinctive features included persistent attention deficits and Autistic Spectrum Disorder, which emerged as hallmarks of the Syndrome."
Identifies autism spectrum disorder as a hallmark behavioural feature.
Sleep disturbance HP:0002360 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sleep disturbance (HP:0002360). HP:0002360 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:42190036 SUPPORT Other
"neurobehavioral/psychiatric manifestations (autism spectrum disorder, midline stereotypies, sleep disturbances, aggressive or self-injurious behaviors)"
GeneReviews lists sleep disturbance among the defining neurobehavioral manifestations.
PMID:42190036 SUPPORT Other
"kidney anomalies; urinary tract anomalies; bone health; and sleep issues"
Sleep is a named domain of the recommended multidisciplinary surveillance, supporting it as a clinically tracked feature rather than an incidental one.
Self-injurious behavior HP:0100716 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Self-injurious behavior (HP:0100716). HP:0100716 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:42190036 SUPPORT Other
"neurobehavioral/psychiatric manifestations (autism spectrum disorder, midline stereotypies, sleep disturbances, aggressive or self-injurious behaviors)"
GeneReviews lists aggressive or self-injurious behaviour as a defining manifestation.
PMID:41681065 SUPPORT Human Clinical
"one patient developed self-injurious behavior and social anxiety during adolescence"
Documents the adolescent onset of self-injury in a longitudinally followed patient.
Growth 1
Short stature FREQUENT HP:0004322 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short stature (HP:0004322). HP:0004322 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
Chen et al. report short stature in ≥75% of individuals, supporting the FREQUENT band.
Other 5
Reduced cerebral white matter volume Aplasia/Hypoplasia of the cerebral white matter HP:0012429 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Reduced cerebral white matter volume, annotated with Aplasia/Hypoplasia of the cerebral white matter (HP:0012429). HP:0012429 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
Chen et al. list reduced white-matter volume as the most frequent MRI abnormality.
Everted lower lip Everted lower lip vermilion HP:0000232 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Everted lower lip vermilion (HP:0000232). HP:0000232 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42419151 SUPPORT Human Clinical
"a tented upper lip with an exaggerated Cupid's bow, an everted lower lip, and a horizontally oriented philtrum"
Hiraide et al. specify an everted lower lip within the facial gestalt.
Optic nerve hypoplasia HP:0000609 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Optic nerve hypoplasia (HP:0000609). HP:0000609 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38991538 SUPPORT Human Clinical
"often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
Chen et al. report optic nerve hypoplasia among the visual abnormalities of the multi-organ involvement described for affected individuals.
Short attention span HP:0000736 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Persistent attention deficit, annotated with Short attention span (HP:0000736). HP:0000736 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41681065 SUPPORT Human Clinical
"Distinctive features included persistent attention deficits and Autistic Spectrum Disorder, which emerged as hallmarks of the Syndrome."
Identifies persistent attention deficits as a hallmark behavioural feature.
Midline stereotypies Motor stereotypy HP:0000733 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Midline motor stereotypies, annotated with Motor stereotypy (HP:0000733). HP:0000733 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:42190036 SUPPORT Other
"neurobehavioral/psychiatric manifestations (autism spectrum disorder, midline stereotypies, sleep disturbances, aggressive or self-injurious behaviors)"
GeneReviews lists midline stereotypies among the defining neurobehavioral manifestations of the syndrome.
🧬

Genetic Associations

1
RNU4-2 critical-region variants (Causative)
Gene: RNU4-2 hgnc:10193 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is RNU4-2 (hgnc:10193). hgnc:10193 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (6 references)
PMID:38991538 SUPPORT Human Clinical
"We identify an 18 base pair region of RNU4-2 mapping to two structural elements in the U4/U6 snRNA duplex (the T-loop and stem III)"
Chen et al. localize the pathogenic variants to an 18-bp critical region mapping to the T-loop and stem III of the U4/U6 duplex.
PMID:38991538 SUPPORT Human Clinical
"Most individuals (77.4%) have the same highly recurrent single base insertion (n.64_65insT)."
Establishes n.64_65insT as the dominant recurrent variant across affected individuals.
PMID:42419151 SUPPORT Human Clinical
"ReNU syndrome is a neurodevelopmental disorder (NDD) caused by pathogenic variants in RNU4-2, a non-coding gene encoding the U4 small nuclear RNA (snRNA)."
Hiraide et al. define ReNU syndrome as an RNU4-2 / U4 snRNA disorder, the causal gene of this entry.
+ 3 more references
💊

Medical Actions

6
Multidisciplinary supportive care
Action: supportive careNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is supportive care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. Ontology label: Supportive Care NCIT:C15747
Management is supportive and symptomatic, addressing developmental, neurological, growth, feeding, and orthopedic needs through multidisciplinary care. There is no disease-modifying therapy. The saturation-editing work frames variant-function data as groundwork for future therapeutic development, which is the current state of play: no targeted treatment exists.
Show evidence (1 reference)
PMID:41951737 SUPPORT In Vitro
"providing critical insights for both diagnosis and therapeutic development"
Therapeutic development is framed as prospective, supporting the statement that management today is supportive rather than disease-modifying.
Anti-seizure pharmacotherapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: valproate CHEBI:39867 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses valproate, annotated with valproic acid (CHEBI:39867). CHEBI:39867 is a therapeutic agent from Chemical Entities of Biological Interest.
Seizures are managed with anti-seizure medications. In the only epilepsy-focused cohort, valproate was judged the most effective agent by the treating neurologists, followed by levetiracetam, clobazam, lamotrigine and phenytoin, and seizure freedom was achieved in half the cohort. Note that this is a retrospective clinician judgement in ten patients, not a controlled comparison, so it is weak grounds for preferring valproate over another agent in an individual patient.
Mechanism Target:
INHIBITS Cortical Network Hyperexcitability — Anti-seizure medication suppresses the network hyperexcitability that generates the seizures; it does not act on the upstream splicing defect.
Show evidence (1 reference)
PMID:41570780 SUPPORT Human Clinical
"Seizure freedom was achieved with antiseizure medications in 5 patients at a mean age of 7.2 ± 25.2."
Medication abolishes seizures in half the cohort, which is what this link asserts: the drug acts on the seizure-generating node, not on the cause.
Show evidence (2 references)
PMID:41570780 SUPPORT Human Clinical
"Valproate was judged the most effective medication by referring neurologists followed by levetiracetam, clobazam, lamotrigine and phenytoin."
Curated PARTIAL: this is retrospective clinician judgement in a ten-patient cohort, which supports valproate being used and considered effective but not a comparative efficacy claim.
PMID:41570780 SUPPORT Human Clinical
"Seizure freedom was achieved with antiseizure medications in 5 patients at a mean age of 7.2 ± 25.2."
Establishes that medically achieved seizure freedom is attainable in a substantial fraction.
Antiresorptive therapy for skeletal fragility
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: neridronate NCIT:C66230 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses neridronate, annotated with Neridronic Acid (NCIT:C66230). NCIT:C66230 is a therapeutic agent from the NCI Thesaurus.
Given the 42% frequency of bone abnormality and the occurrence of clinically silent vertebral fractures, osteological assessment is warranted. In the one published treated case, intravenous neridronate at 2 mg/kg every three months over three years was well tolerated, bone mineral density rose and then stabilised, and no further vertebral fractures occurred — though the patient did sustain a patella and a proximal humerus fracture after falls. This is a single treated patient, so it supports the approach being feasible and reasonable, not an established efficacy claim.
Mechanism Target:
INHIBITS Increased Bone Turnover and Reduced Bone Mineral Density — Bisphosphonate therapy suppresses the osteoclast-mediated resorption arm of the high-turnover state curated at this node.
Show evidence (1 reference)
PMID:40510867 SUPPORT Human Clinical
"we observed the expected reduction of bone turnover parameters"
Confirms the drug engaged the turnover process this node represents; PARTIAL because it is a pharmacodynamic effect in one patient, not an outcome.
Show evidence (2 references)
PMID:40510867 SUPPORT Human Clinical
"Anti-resorptive treatment with intravenous neridronate injections (2 mg per kg body weight, every 3 mo) was initiated, which was well tolerated by the patient without obvious side effects."
Documents the regimen and its tolerability in the reported patient.
PMID:40510867 SUPPORT Human Clinical
"Importantly, there were no additional vertebral fractures."
Curated PARTIAL: absence of further vertebral fractures in one uncontrolled patient who still sustained two appendicular fractures is suggestive, not demonstrative, of benefit.
Structured surveillance and avoidance of bone-toxic agents
GeneReviews recommends scheduled follow-up to monitor existing manifestations and detect new ones, across developmental, seizure, feeding, kidney, urinary tract, bone-health and sleep domains, and specifically advises weighing the bone consequences of any medication considered. That advice matters more here than in most neurodevelopmental disorders given the 42% frequency of bone abnormality and the demonstrated occurrence of vertebral fractures that were silent until imaged.
Show evidence (1 reference)
PMID:42190036 SUPPORT Other
"Consider avoiding or limiting any substance or medication that may affect bone health (e.g., steroids)."
The explicit agents-to-avoid recommendation, tied to this disorder's skeletal fragility.
Augmentative and alternative communication
Action: speech and language therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is speech and language therapy, annotated with Speech Language Therapy (NCIT:C159273). NCIT:C159273 is a clinical intervention from the NCI Thesaurus. Ontology label: Speech Language Therapy NCIT:C159273
Because most individuals never acquire meaningful speech while comprehension and social motivation are comparatively preserved, augmentative and alternative communication is emphasised as a priority intervention, together with cognitive-behavioural approaches aimed at the communicative frustration that appears to drive behavioural dysregulation and social anxiety.
Show evidence (1 reference)
PMID:41681065 SUPPORT Human Clinical
"with particular emphasis on augmentative and alternative communication strategies and cognitive-behavioral approaches to mitigate communicative frustration, behavioral dysregulation, and social anxiety"
States the recommended intervention and the behavioural rationale for it.
Physical and developmental therapy
Action: physical therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is physical therapy (NCIT:C15302). NCIT:C15302 is a clinical intervention from the NCI Thesaurus. Ontology label: Physical Therapy NCIT:C15302
Physical, occupational, and speech/communication therapies support motor development and function given hypotonia, motor delay, and non-verbal status. In the treated osteoporosis case a structured strength and coordination programme proved infeasible and supervised general mobility was substituted, which illustrates the practical ceiling on physical therapy in this population.
Show evidence (1 reference)
PMID:40510867 SUPPORT Human Clinical
"A structured training program to improve muscle strength and coordination was not feasible for the patient, but mobility in general was promoted in a protected environment under supervision."
Curated PARTIAL because it documents a limitation of this treatment rather than a benefit: structured training was not deliverable.
🔬

Diagnosis

2
Genome sequencing (exome-negative work-up)
The signature diagnostic feature of ReNU syndrome is that RNU4-2, as a short non-coding U4 snRNA gene, is not captured by conventional exome sequencing; affected individuals are therefore typically exome-negative and remain undiagnosed until clinical genome sequencing is performed and the RNU4-2 critical-region variant (most often the recurrent n.64_65insT insertion) is identified. Genome sequencing of exome-negative NDD cohorts is the actionable route to diagnosis and, given the recognizable lip-and-philtrum facial gestalt, RNU4-2 should be specifically interrogated in undiagnosed NDD.
clinical whole genome sequencing NCIT:C101294 NCI Thesaurus (NCIT)
Show evidence (3 references)
PMID:42419151 SUPPORT Human Clinical
"RNU4-2 is not captured by conventional exome sequencing (ES), often leaving affected individuals undiagnosed."
Hiraide et al. state that RNU4-2 is missed by exome sequencing, so affected individuals are exome-negative until genome sequencing is applied.
PMID:42419151 SUPPORT Human Clinical
"we performed genome sequencing in 95 patients with NDDs in whom prior ES had failed to identify a causative variant"
Hiraide et al. establish genome sequencing of exome-negative NDD patients as the diagnostic approach that identifies the RNU4-2 variant.
PMID:42190036 SUPPORT Other
"The diagnosis of ReNU syndrome is established in a proband with suggestive findings and a heterozygous pathogenic variant in RNU4-2 identified by molecular genetic testing."
The GeneReviews diagnostic criterion: suggestive clinical findings plus a heterozygous RNU4-2 variant on molecular genetic testing. The criterion is agnostic about method, which is why both the genome-sequencing and the targeted-Sanger routes curated here satisfy it.
Targeted Sanger sequencing of the RNU4-2 hotspot
Where genome sequencing is unavailable or slow, the recognisability of the syndrome makes a targeted approach viable: because the pathogenic variants cluster into a short region, direct Sanger sequencing of the 18-base-pair critical region is a reasonable first test in a clinically suspected case. This is how a nine-patient series was assembled from previously undiagnosed individuals, and how the diagnosis was reached in a patient whose trio exome had been uninformative. The facial gestalt — hooded upper eyelids, full cheeks, a tented philtrum, and a slightly open mouth with an everted lower lip vermilion — is the practical trigger for testing.
DNA sequence analysis NCIT:C153598 NCI Thesaurus (NCIT)
Show evidence (3 references)
PMID:40546132 SUPPORT Human Clinical
"If clinically suspected, it is reasonable to examine the 18-base pair region using the Sanger method."
States the targeted diagnostic recommendation directly.
PMID:40546132 SUPPORT Human Clinical
"All patients showed a distinctive pattern of dysmorphic features, including hooded upper eyelids, full cheeks, a tented philtrum, and a mouth constantly slightly open with an everted lower lip vermilion."
Specifies the recognisable facial pattern that makes targeted testing practical, present in every patient in the series.
PMID:40510867 SUPPORT Human Clinical
"As RNA encoding genes are not targeted by exome sequencing, we analyzed RNU4-2"
A worked instance of the targeted approach succeeding after uninformative trio exome sequencing.
📈

Progression

4
Infancy
Age: birth to 2 years
Presentation is with hypotonia, feeding difficulty and global developmental delay. Microcephaly is mostly congenital, and reduced head circumference may be noted prenatally. Seizures usually have not yet begun, though onset before 12 months occurs in a minority.
Show evidence (1 reference)
PMID:41570780 SUPPORT Human Clinical
"Focal impaired consciousness with observable manifestations (with onset before 12 months in 3 cases) were the predominant seizure type across all age ranges."
Establishes that seizure onset within the first year occurs but is the exception rather than the rule.
Early childhood
Age: 2 to 6 years
Epilepsy typically begins in this window, at a mean age of about 2.8 years. Expressive language largely fails to emerge: most individuals have not acquired meaningful words by age five. Independent walking is attained by roughly half.
Show evidence (2 references)
PMID:41570780 SUPPORT Human Clinical
"The mean age at epilepsy onset was 2.8 ±2.1 years."
Dates typical epilepsy onset to early childhood.
PMID:40546132 SUPPORT Human Clinical
"In six patients, meaningful words had not been acquired, even after the age of 5 years."
Marks failure of expressive language to emerge by school age.
Later childhood
Age: 6 to 12 years
Focal impaired-consciousness seizures peak in frequency between ages 6 and 11, and epileptiform EEG abnormality becomes more readily detected after age 3. Seizure freedom is achievable with medication in about half of patients.
Show evidence (2 references)
PMID:41570780 SUPPORT Human Clinical
"The frequency of this seizure type peaked between the ages of 6 and 11 years."
Locates the peak of the seizure burden in later childhood.
PMID:41570780 SUPPORT Human Clinical
"Seizure freedom was achieved with antiseizure medications in 5 patients at a mean age of 7.2 ± 25.2."
Records the comparatively favourable epilepsy outcome. The reported standard deviation (±25.2 years) is internally inconsistent with a mean of 7.2 years and is quoted here verbatim rather than corrected.
Adolescence and adulthood
Age: 12 years and older
Neuropsychiatric features come to the fore: persistent attention deficits and autistic features are described as hallmarks, and self-injurious behaviour and social anxiety may emerge in adolescence. Skeletal fragility becomes clinically important, with vertebral fractures that may be silent until specifically imaged. Individuals have been followed to at least age 29; the disorder is not known to be neurodegenerative, though longitudinal data remain sparse.
Show evidence (2 references)
PMID:41681065 SUPPORT Human Clinical
"one patient developed self-injurious behavior and social anxiety during adolescence"
Documents emergence of these behaviours specifically in adolescence.
PMID:40546132 SUPPORT Human Clinical
"Nine patients aged between 3 and 29 years all showed severe developmental delay and/or intellectual disability."
Establishes the upper age of reported follow-up and that severe impairment persists across it.
📊

Prevalence

1
Neurodevelopmental disorder (all-cause)
Period Prevalence Unknown
Not a population prevalence: variants in the 18-bp RNU4-2 critical region are estimated to explain ~0.4% of individuals with neurodevelopmental disorders, making ReNU syndrome one of the most prevalent monogenic NDDs. RNU4-2 is a more common etiological gene for neurodevelopmental abnormality than any previously reported autosomal gene in national diagnostic data.
Show evidence (2 references)
PMID:38991538 SUPPORT Human Clinical
"we estimate that variants in this 18 base pair region explain 0.4% of individuals with NDD"
Chen et al. estimate that critical-region RNU4-2 variants explain ~0.4% of all NDD, the basis for the disorder's high relative frequency.
PMID:38821540 SUPPORT Human Clinical
"Analysis of national genomic diagnostic data showed RNU4-2 to be a more common etiological gene for neurodevelopmental abnormality than any previously reported autosomal gene."
Greene et al. show RNU4-2 is a more common cause of neurodevelopmental abnormality than any previously reported autosomal gene.
⚖️

Clinical Burden

High
Burden is curated HIGH rather than VARIABLE because the core impairments are near-universal rather than distributed: developmental delay or intellectual disability was present in every patient across a 3-to-29-year age span, most never acquire meaningful speech, only about half walk independently, and neuroradiological abnormality was universal in a consecutive series. Epilepsy affects about 60%, and 42% of those assessed have bone abnormality with fractures that may go unrecognized. The milder Stem III genotype is the one real source of variability, and it is a minority of cases; it is captured as a subtype rather than by softening the overall burden level.
Show evidence (2 references)
PMID:40546132 SUPPORT Human Clinical
"Nine patients aged between 3 and 29 years all showed severe developmental delay and/or intellectual disability."
Universal severe impairment across the reported age range.
PMID:40510867 SUPPORT Human Clinical
"bone abnormalities have been described previously and were present in 72 out of 173 individuals (42%) with ReNU syndrome who underwent bone assessment"
Quantifies the added skeletal burden beyond the neurological phenotype.
🔀

Differential Diagnoses

3

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

🧫

Experimental Models

1
Saturation genome editing of RNU4-2 in HAP1 cells CELL_LINE
Because no established model existed for assaying RNU4-2 variants, the authors used saturation genome editing in a haploid human line, where the single copy of the gene makes each edited variant's effect directly visible in cell fitness. The resulting function scores separate ReNU syndrome variants from population variants, outperform in silico predictors, and scale with both splicing disruption and clinical severity. This is a variant-function assay rather than a disease model: it measures the molecular node, and does not reproduce any neurodevelopmental phenotype.
Organism
human NCBITaxon:9606 NCBI Taxonomy (NCBITaxon) Relation: this experimental model is built in this organism This experimental model is built in human, annotated with Homo sapiens (NCBITaxon:9606). NCBITaxon:9606 is an organism from the NCBI Taxonomy.
Cell source
HAP1 human near-haploid cell line
Culture
Haploid human HAP1 cells lacking LIG4 (HAP1-LIG4-KO), into which a library of 539 RNU4-2 variants was installed by Cas9-directed homology-directed repair; variant effects are read out as depletion or enrichment over time in culture.
Publication
PMID:41951737
Pathograph links
RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function measures fidelity: moderate Quantifies the functional consequence of each RNU4-2 variant, resolving the critical region to single-nucleotide resolution and reclassifying variants of uncertain significance.
Limitations: Fitness in a haploid cancer-derived cell line is a proxy for spliceosome impairment, not a measure of neurodevelopment; HAP1 is not a neural cell type, the assay is haploid whereas ReNU syndrome is heterozygous, and no clinical phenotype is recapitulated.
Readouts
SGE function score (cell fitness)
Direction: DECREASED
Interpretation: Pathogenic critical-region variants deplete from the edited cell pool, yielding low function scores that separate them from population variants.
Show evidence (1 reference)
PMID:41951737 SUPPORT In Vitro
"The resulting SGE function scores, derived from variants' effects on cell fitness, discriminate ReNU syndrome variants from those observed in the population and markedly outperform in silico variant effect prediction"
Defines the readout and establishes that it discriminates pathogenic from population variation better than computational prediction.
Show evidence (1 reference)
PMID:41951737 SUPPORT In Vitro
"Lacking established models for assaying RNU4-2 variants, we chose to perform SGE in HAP1 cells, a haploid human line in which growth effects have accurately distinguished pathogenic variants across several protein-coding genes"
States both the rationale for the model and, by naming the absence of established models, why it is informative for this node.
Show evidence (1 reference)
PMID:41951737 SUPPORT In Vitro
"Here we performed saturation genome editing (SGE) of RNU4-2 to identify the functional and clinical impact of variants across the entire gene."
Establishes the existence and purpose of the model system curated here.
{ }

Source YAML

click to show 
name: ReNU Syndrome
creation_date: "2026-07-10T00:00:00Z"
category: Mendelian
synonyms:
- NEDHAFA
- neurodevelopmental disorder with hypotonia, brain anomalies, distinctive facies, and absent language
- RNU4-2-related neurodevelopmental disorder
- RNU4-2 syndrome
parents:
- Neurodevelopmental Disorder
description: >-
  ReNU syndrome (also NEDHAFA; neurodevelopmental disorder with hypotonia, brain
  anomalies, distinctive facies, and absent language; OMIM:620851) is a syndromic
  neurodevelopmental disorder caused by de novo variants in RNU4-2, a non-coding
  gene encoding the U4 small nuclear RNA (snRNA), a critical component of the
  U4/U6.U5 tri-snRNP of the major spliceosome. Pathogenic variants cluster within
  an 18-base-pair critical region in the centre of RNU4-2 (mapping to the T-loop
  and stem III structural elements of the U4/U6 duplex), with a single highly
  recurrent single-base insertion (n.64_65insT) accounting for the majority of
  cases. The disorder is characterized by moderate-to-severe global developmental
  delay/intellectual disability, largely non-verbal speech, hypotonia, microcephaly
  (mostly congenital), short stature, seizures, and characteristic brain MRI
  findings (reduced white-matter volume, corpus callosum hypoplasia,
  ventriculomegaly, delayed myelination), together with a distinctive
  lip-and-philtrum facial gestalt. Because RNU4-2 is a short non-coding RNA gene, it is not
  captured by conventional exome sequencing, and affected individuals are typically
  exome-negative until genome sequencing is performed; variants in the critical
  region are estimated to explain ~0.4% of all neurodevelopmental disorders,
  making ReNU syndrome one of the most prevalent monogenic neurodevelopmental
  disorders. Inheritance is autosomal dominant, with variants arising de novo
  (observed on the maternal allele where parental origin could be resolved).
disease_term:
  preferred_term: ReNU syndrome
  term:
    id: MONDO:0971172
    label: neurodevelopmental disorder with hypotonia, brain anomalies, distinctive facies, and absent language
classifications:
  harrisons_chapter:
  - classification_value: NEUROLOGIC
    evidence:
    - reference: PMID:38821540
      reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
      explanation: >-
        The defining features are neurological, placing the disorder in the
        neurology chapter.
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    evidence:
    - reference: PMID:38991538
      reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "we estimate that variants in this 18 base pair region explain 0.4% of individuals with NDD"
      explanation: >-
        A monogenic non-coding-RNA aetiology explaining a measurable share of all
        NDD places the disorder in the genetics chapter.
inheritance:
- name: Autosomal Dominant (de novo)
  description: >-
    ReNU syndrome is inherited in an autosomal-dominant manner, with the causative
    heterozygous RNU4-2 variants arising de novo. Where parental origin could be
    determined, the de novo variants were consistently found on the maternal
    allele. The recurrent n.64_65insT insertion and other critical-region variants
    were confirmed de novo in trio (and, in a subset, long-read) sequencing.
  inheritance_term:
    preferred_term: Autosomal dominant, de novo
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In 54 individuals in whom it could be determined, the de novo variants were all on the maternal allele."
    explanation: >-
      Chen et al. establish that the RNU4-2 variants arise de novo and, where
      resolvable, occur on the maternal allele, defining the de novo dominant
      mode of occurrence.
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified a recurrent RNU4-2 variant (NR_003137.3:n.64_65insT) in five patients (5.3%), four of whom are described here. All variants occurred de novo."
    explanation: >-
      Hiraide et al. independently confirm the recurrent n.64_65insT variant
      arising de novo in an exome-negative NDD cohort.
  - reference: PMID:40011755
    reference_title: "Expanding the mutational spectrum of ReNU syndrome: insights into 5' Stem-loop variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "two were heterozygous for private/rare maternally inherited variants"
    explanation: >-
      Qualifies the de novo rule rather than supporting it: two affected
      individuals inherited their variant from an apparently unaffected mother, so
      "de novo" describes the typical but not the invariant case.
  - reference: PMID:40011755
    reference_title: "Expanding the mutational spectrum of ReNU syndrome: insights into 5' Stem-loop variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We propose that a more complex genetics likely underlies the inheritance of a subset of disease-causing RNU4-2 variants from an apparently unaffected parent."
    explanation: >-
      The authors flag transmission from an unaffected parent as unresolved,
      which is why this entry does not curate inheritance as strictly de novo.
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ReNU syndrome is an autosomal dominant disorder that is almost always caused by a de novo pathogenic variant."
    explanation: >-
      GeneReviews states the rule in its calibrated form - almost always de novo,
      rather than invariably - which is how this entry curates it.
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Very rarely, individuals diagnosed with ReNU syndrome have the disorder as the result of an RNU4-2 pathogenic variant inherited from a mildly affected parent."
    explanation: >-
      Independently corroborates inherited cases. Note GeneReviews describes the
      transmitting parent as mildly affected whereas the stem-loop series
      described theirs as apparently unaffected; both are curated rather than
      reconciled.
has_subtypes:
- name: T-loop
  display_name: T-loop variant ReNU syndrome (including the recurrent n.64_65insT)
  description: >-
    Variants in the T-loop element, which include the highly recurrent
    n.64_65insT insertion accounting for roughly 80% of all cases, define the
    severe end of the spectrum: developmental delay is severe and more than 70%
    of individuals remain non-verbal. This is the classical ReNU presentation on
    which the syndrome was originally delineated.
  evidence:
  - reference: PMID:40413032
    reference_title: "Genotype-phenotype correlations and phenotypic expansion in a case series of ReNU syndrome associated with RNU4-2 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "T-loop variants manifested severe developmental delay with more than 70% of cases being non-verbal."
    explanation: Defines the severity that distinguishes this subtype.
  - reference: PMID:40413032
    reference_title: "Genotype-phenotype correlations and phenotypic expansion in a case series of ReNU syndrome associated with RNU4-2 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "RNU4-2 variants are located in the T-loop or stem III region of U4 snRNA, of which approximately 80% are the n.64_65insT variant in the T-loop."
    explanation: Establishes that the T-loop group, dominated by n.64_65insT, is the majority of cases.
- name: Stem III
  display_name: Stem III variant ReNU syndrome
  description: >-
    Variants in the stem III element produce a materially milder disorder:
    developmental delay is less severe, speech can be fluent, and gross motor
    milestones are close to normal. This subtype is the main reason the syndrome's
    severity is not uniform, and it matters diagnostically because a fluently
    speaking, ambulant individual may still have ReNU syndrome.
  evidence:
  - reference: PMID:40413032
    reference_title: "Genotype-phenotype correlations and phenotypic expansion in a case series of ReNU syndrome associated with RNU4-2 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stem III region variants resulted in milder developmental delay with fluent speech and nearly normal gross motor development milestones."
    explanation: Defines the milder phenotype that distinguishes this subtype from the T-loop group.
prevalence:
- population: Neurodevelopmental disorder (all-cause)
  measure_type: PERIOD_PREVALENCE
  prevalence_class: UNKNOWN
  notes: >-
    Not a population prevalence: variants in the 18-bp RNU4-2 critical region are
    estimated to explain ~0.4% of individuals with neurodevelopmental disorders,
    making ReNU syndrome one of the most prevalent monogenic NDDs. RNU4-2 is a
    more common etiological gene for neurodevelopmental abnormality than any
    previously reported autosomal gene in national diagnostic data.
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we estimate that variants in this 18 base pair region explain 0.4% of individuals with NDD"
    explanation: >-
      Chen et al. estimate that critical-region RNU4-2 variants explain ~0.4% of
      all NDD, the basis for the disorder's high relative frequency.
  - reference: PMID:38821540
    reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Analysis of national genomic diagnostic data showed RNU4-2 to be a more common etiological gene for neurodevelopmental abnormality than any previously reported autosomal gene."
    explanation: >-
      Greene et al. show RNU4-2 is a more common cause of neurodevelopmental
      abnormality than any previously reported autosomal gene.
genetic:
- name: RNU4-2 critical-region variants
  association: Causative
  gene_term:
    preferred_term: RNU4-2
    term:
      id: hgnc:10193
      label: RNU4-2
  notes: >-
    RNU4-2 encodes the U4 small nuclear RNA, a critical component of the
    U4/U6.U5 tri-snRNP complex of the major spliceosome. Pathogenic variants
    cluster in an 18-bp critical region in the centre of the gene, mapping to the
    T-loop and stem III structural elements of the U4/U6 duplex; this region is
    severely depleted of variation in the general population. The highly recurrent
    single-base insertion n.64_65insT accounts for the majority of cases; other
    insertions (e.g., n.77_78insT) and single-nucleotide variants in the critical
    region cause the same phenotype. As a short non-coding RNA gene, RNU4-2 is not
    captured by conventional exome sequencing, so affected individuals are
    typically exome-negative until genome sequencing is performed.
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identify an 18 base pair region of RNU4-2 mapping to two structural elements in the U4/U6 snRNA duplex (the T-loop and stem III)"
    explanation: >-
      Chen et al. localize the pathogenic variants to an 18-bp critical region
      mapping to the T-loop and stem III of the U4/U6 duplex.
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Most individuals (77.4%) have the same highly recurrent single base insertion (n.64_65insT)."
    explanation: >-
      Establishes n.64_65insT as the dominant recurrent variant across affected
      individuals.
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ReNU syndrome is a neurodevelopmental disorder (NDD) caused by pathogenic variants in RNU4-2, a non-coding gene encoding the U4 small nuclear RNA (snRNA)."
    explanation: >-
      Hiraide et al. define ReNU syndrome as an RNU4-2 / U4 snRNA disorder, the
      causal gene of this entry.
  - reference: PMID:40011755
    reference_title: "Expanding the mutational spectrum of ReNU syndrome: insights into 5' Stem-loop variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings expand the mutational spectrum of ReNU syndrome, and confirm the 5' Stem-loop as a second mutational hotspot in RNU4-2."
    explanation: >-
      Establishes a second mutational hotspot outside the originally described
      18-bp critical region.
  - reference: PMID:40413032
    reference_title: "Genotype-phenotype correlations and phenotypic expansion in a case series of ReNU syndrome associated with RNU4-2 variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we report a patient demonstrating intractable epilepsy with neurological regression harbouring a novel de novo heterozygous RNU4-2 variant (n.66A>G)"
    explanation: >-
      Documents n.66A>G, a rare non-insertion critical-region variant, and its
      association with an unusually severe epilepsy course.
  - reference: PMID:41951737
    reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we identify variants affecting function in regions of RNU4-2 that are critical for interactions with other spliceosome components. We show that these variants cause a new recessive neurodevelopmental disorder that is distinct from ReNU syndrome."
    explanation: >-
      Bounds this entry's gene-disease claim: not every functionally damaging
      RNU4-2 variant causes ReNU syndrome.
pathophysiology:
- name: RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function
  biological_scale: MOLECULAR
  description: >-
    RNU4-2 encodes the U4 small nuclear RNA, which base-pairs extensively with U6
    snRNA within the U4/U6.U5 tri-snRNP of the major spliceosome. The 18-bp
    critical region harboring the recurrent n.64_65insT insertion maps to the
    T-loop and stem III structural elements that stabilize U4/U6 pairing and help
    position the U6 ACAGAGA sequence to receive the 5' splice site during initial
    spliceosome activation. Variants in this region perturb U4 structure and the
    U4/U6 duplex, compromising accurate spliceosome assembly/activation. RNU4-2 is
    highly expressed in the developing human brain (in contrast to the paralog
    RNU4-1), consistent with a developmental, brain-predominant impact. Saturation
    genome editing across the whole gene has since resolved this critical region to
    single-nucleotide resolution and shown that the severity of a variant's
    functional effect tracks with clinical severity. Note that this is not a
    loss-of-function mechanism: biallelic variants elsewhere in RNU4-2 reduce
    transcript levels and cause a separate recessive disorder, which is what
    distinguishes ReNU syndrome mechanistically from simple haploinsufficiency.
  genes:
  - preferred_term: RNU4-2
    term:
      id: hgnc:10193
      label: RNU4-2
  biological_processes:
  - preferred_term: U4/U6.U5 tri-snRNP spliceosome assembly
    term:
      id: GO:0000387
      label: spliceosomal snRNP assembly
    modifier: ABNORMAL
  - preferred_term: mRNA splicing via the major spliceosome
    term:
      id: GO:0000398
      label: mRNA splicing, via spliceosome
    modifier: ABNORMAL
  downstream:
  - target: Systematic Disruption of 5' Splice-Site Usage
    description: >-
      Impaired positioning of the U6 ACAGAGA region during spliceosome activation
      leads to systematically altered 5' splice-site recognition.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:41951737
      reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "ReNU syndrome variants disrupt spliceosome function and alter 5' splice site selection"
      explanation: >-
        States the direct link curated by this edge: the critical-region variants
        act on the spliceosome and thereby on 5' splice-site selection.
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "RNU4-2 encodes the U4 small nuclear RNA (snRNA), which is a critical component of the U4/U6.U5 tri-snRNP complex of the major spliceosome"
    explanation: >-
      Chen et al. establish the molecular identity and role of the U4 snRNA
      encoded by RNU4-2 within the major spliceosome.
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We demonstrate that RNU4-2 is highly expressed in the developing human brain, in contrast to RNU4-1 and other U4 homologues."
    explanation: >-
      Brain-predominant developmental expression of RNU4-2 supports the
      neurodevelopmental specificity of the disorder.
  - reference: PMID:41951737
    reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we redefine the ReNU syndrome critical region at single-nucleotide resolution, resolve variant pathogenicity for variants of uncertain significance and show that SGE function scores delineate variants by phenotypic severity and the extent of observed splicing disruption"
    explanation: >-
      Saturation genome editing refines the critical region and ties the magnitude
      of the functional defect to both splicing disruption and clinical severity.
- name: Systematic Disruption of 5' Splice-Site Usage
  biological_scale: MOLECULAR
  description: >-
    RNA sequencing of individuals with RNU4-2 variants shows systematically
    disrupted 5' splice-site usage — notably increased use of unannotated 5'
    splice sites — consistent with the known role of the affected region during
    spliceosome activation. This global splicing dysregulation during
    neurodevelopment is the proposed convergence point linking the RNA-level
    defect to the neurodevelopmental phenotype, placing ReNU syndrome among the
    spliceosomopathies. Because the spliceosome is used by essentially every
    transcript, the downstream consequences are not confined to brain: skeletal
    and, in at least one report, glomerular involvement are part of the phenotype.
    Which downstream transcripts actually mediate each organ phenotype is not
    known, so the edges below are curated as indirect with unknown intermediates.
  biological_processes:
  - preferred_term: mRNA splicing via the major spliceosome
    term:
      id: GO:0000398
      label: mRNA splicing, via spliceosome
    modifier: ABNORMAL
  - preferred_term: Nervous system development
    term:
      id: GO:0007399
      label: nervous system development
    modifier: ABNORMAL
  downstream:
  - target: Impaired Brain Growth and White Matter Development
    description: >-
      Global splicing dysregulation during brain development is the proposed
      basis for the reduced brain growth and white-matter abnormalities that
      dominate the neuroimaging phenotype.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38821540
      reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Our findings add to the growing evidence of spliceosome dysfunction in the etiologies of neurological disorders."
      explanation: >-
        Places the splicing defect as the etiological step upstream of the
        neurological phenotype; the intervening steps are not established.
  - target: Cortical Network Hyperexcitability
    description: >-
      Epilepsy occurs in roughly 60% of individuals and, notably, without a
      structural epileptogenic lesion on MRI — pointing to a functional network
      abnormality rather than a visible malformation as the seizure substrate.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:41570780
      reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "No structural epileptogenic lesions were detected on MRI."
      explanation: >-
        Absence of a structural lesion in an epilepsy-focused cohort supports a
        functional rather than lesional basis for the seizures.
  - target: Increased Bone Turnover and Reduced Bone Mineral Density
    description: >-
      Bone involvement is common and its histology suggests a bone-cell-intrinsic
      effect rather than purely disuse osteoporosis, though this is inference from
      a single biopsy and is not established.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:40510867
      reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The severe impairment of skeletal integrity in patients with ReNU syndrome suggests a specific impact of the RNU4-2 variant on bone cell differentiation and/or function."
      explanation: >-
        The authors propose, but do not demonstrate, a bone-cell-intrinsic
        splicing effect; curated as PARTIAL because the mechanism is hypothesized.
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we show how 5' splice-site use is systematically disrupted in individuals with RNU4-2 variants, consistent with the known role of this region during spliceosome activation"
    explanation: >-
      Chen et al. demonstrate systematic 5' splice-site disruption by RNA-seq,
      the proximate functional consequence of the variants.
  - reference: PMID:38821540
    reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our findings add to the growing evidence of spliceosome dysfunction in the etiologies of neurological disorders."
    explanation: >-
      Greene et al. frame RNU4-2 disease within the broader class of
      spliceosome-dysfunction neurological disorders.
- name: Impaired Brain Growth and White Matter Development
  biological_scale: TISSUE
  description: >-
    The convergent tissue-level consequence in the CNS is reduced brain growth
    with a white-matter-predominant imaging signature: decreased cerebral white
    matter volume, corpus callosum hypoplasia, ventriculomegaly and delayed
    myelination, together with mostly congenital microcephaly. Neuroimaging
    abnormality is close to universal in reported cohorts. This node is the point
    at which the molecular splicing defect becomes the clinical neurodevelopmental
    phenotype, and it is the parent of the cognitive, language and motor
    phenotypes below.
  biological_processes:
  - preferred_term: Brain development
    term:
      id: GO:0007420
      label: brain development
    modifier: ABNORMAL
  - preferred_term: Myelination
    term:
      id: GO:0042552
      label: myelination
    modifier: DECREASED
  cell_types:
  - preferred_term: Oligodendrocyte
    term:
      id: CL:0000128
      label: oligodendrocyte
  locations:
  - preferred_term: Cerebral white matter
    term:
      id: UBERON:0002316
      label: white matter
  downstream:
  - target: Microcephaly
    description: Reduced brain growth presents clinically as mostly congenital microcephaly.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38821540
      reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
      explanation: Establishes microcephaly as a defining feature of the syndrome.
  - target: Reduced cerebral white matter volume
    description: Decreased white matter volume is a core component of the imaging signature.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Neuroradiological abnormalities, including ventriculomegaly, hypoplasia of the corpus callosum, and a decreased white matter volume, are observed in many individuals."
      explanation: Names decreased white matter volume as part of the recurrent imaging pattern.
  - target: Corpus callosum hypoplasia
    description: Callosal hypoplasia accompanies the white-matter deficit.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Neuroradiological abnormalities, including ventriculomegaly, hypoplasia of the corpus callosum, and a decreased white matter volume, are observed in many individuals."
      explanation: Names corpus callosum hypoplasia as part of the recurrent imaging pattern.
  - target: Ventriculomegaly
    description: Ventricular enlargement accompanies the reduced white-matter volume.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "All patients had neuroradiological abnormalities."
      explanation: >-
        Establishes that neuroradiological abnormality was universal in this
        consecutive nine-patient series.
  - target: Delayed myelination
    description: Myelination is delayed, consistent with the oligodendrocyte/white-matter emphasis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38991538
      reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
      explanation: >-
        Names delayed myelination among the recurrent imaging findings in ReNU
        syndrome itself, which is what this edge asserts.
  - target: Global developmental delay / intellectual disability
    description: The cardinal clinical consequence of impaired brain development.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Nine patients aged between 3 and 29 years all showed severe developmental delay and/or intellectual disability."
      explanation: Developmental delay/ID was universal across a wide age range.
  - target: Severe intellectual disability
    description: Cognitive impairment is typically in the severe range.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Nine patients aged between 3 and 29 years all showed severe developmental delay and/or intellectual disability."
      explanation: Supports the severe end of the cognitive phenotype.
  - target: Absent / non-verbal speech
    description: Expressive language is typically absent or minimal beyond the expected age.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In six patients, meaningful words had not been acquired, even after the age of 5 years."
      explanation: Quantifies absent expressive speech persisting past age five.
  - target: Motor delay
    description: Gross motor milestones are delayed and often incompletely attained.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:40546132
      reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Independent walking was achieved by five patients."
      explanation: >-
        Only five of nine attained independent walking, quantifying the motor
        delay attached to this node.
  - target: Hypotonia
    description: Central hypotonia is an early and near-universal manifestation.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38821540
      reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
      explanation: Lists hypotonia among the defining features of the syndrome.
  evidence:
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had neuroradiological abnormalities."
    explanation: >-
      Neuroradiological abnormality was present in every patient in a consecutive
      series, supporting this node as an obligate tissue-level feature.
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Neuroradiological abnormalities, including ventriculomegaly, hypoplasia of the corpus callosum, and a decreased white matter volume, are observed in many individuals."
    explanation: >-
      Specifies the white-matter-predominant imaging signature that defines this
      node.
- name: Cortical Network Hyperexcitability
  biological_scale: TISSUE
  description: >-
    Epilepsy affects roughly 60% of individuals with ReNU syndrome. The seizure
    disorder is notable for what is absent as much as what is present: dedicated
    epilepsy-cohort imaging found no structural epileptogenic lesion, so the
    seizures are attributed to a functional network abnormality rather than to the
    malformations visible on MRI. Focal impaired-consciousness seizures predominate
    across all ages, onset is in early childhood, and the course is comparatively
    favourable, with seizure freedom achievable in about half of patients. The
    cellular substrate linking the splicing defect to network hyperexcitability is
    not known, which is why this node deliberately carries no biological_process or
    cell_type binding: no source examined identifies the channel, synapse or cell
    population involved, and a generic nervous-system-development term would assert
    nothing about excitability.
  downstream:
  - target: Seizures
    description: >-
      Network hyperexcitability manifests as predominantly focal
      impaired-consciousness seizures with onset in early childhood.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:41570780
      reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Focal impaired consciousness with observable manifestations (with onset before 12 months in 3 cases) were the predominant seizure type across all age ranges."
      explanation: Characterizes the predominant seizure semiology arising from this node.
  evidence:
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Epilepsy is a prominent feature in about 60% of patients with ReNU syndrome"
    explanation: Establishes the frequency of epilepsy that this node represents.
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mean age at epilepsy onset was 2.8 ±2.1 years."
    explanation: Dates the onset of this node's clinical expression to early childhood.
- name: Increased Bone Turnover and Reduced Bone Mineral Density
  biological_scale: TISSUE
  description: >-
    Skeletal fragility is a common and clinically actionable part of the phenotype:
    bone abnormalities were present in 42% of individuals assessed. In the one
    published case with histomorphometry, an undecalcified tibia biopsy showed
    enlarged eroded surfaces with increased numbers of both osteoclasts and
    osteoblasts — an activated, high-turnover state rather than the low-turnover
    picture expected from immobility alone. That observation is the basis for
    suspecting a bone-cell-intrinsic splicing effect, but it rests on a single
    biopsy and disuse remains an unexcluded contributor in a population with
    hypotonia and limited ambulation. Vertebral fractures may be clinically silent
    until sought, which is why this node matters for management.
  biological_processes:
  - preferred_term: Bone resorption
    term:
      id: GO:0045453
      label: bone resorption
    modifier: INCREASED
  - preferred_term: Ossification
    term:
      id: GO:0001503
      label: ossification
    modifier: ABNORMAL
  cell_types:
  - preferred_term: Osteoclast
    term:
      id: CL:0000092
      label: osteoclast
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  locations:
  - preferred_term: Bone
    term:
      id: UBERON:0001474
      label: bone element
  downstream:
  - target: Osteopenia
    description: Reduced bone mineral density is the direct densitometric expression of this node.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:40510867
      reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "bone abnormalities have been described previously and were present in 72 out of 173 individuals (42%) with ReNU syndrome who underwent bone assessment"
      explanation: >-
        Quantifies how common reduced bone mass and related abnormalities are
        among assessed individuals.
  - target: Recurrent fractures
    description: >-
      Fragility fractures, including clinically unrecognized vertebral fractures,
      follow from the reduced bone mass.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:40510867
      reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Lateral vertebral assessment identified multiple previously unrecognized vertebral fractures of the thoracic and lumbar spine."
      explanation: >-
        Documents fragility fractures that were silent until specifically imaged,
        the clinically important consequence of this node.
  evidence:
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Laboratory tests indicated an activated bone turnover, which was confirmed by an increased number of osteoclasts and osteoblasts in an undecalcified tibia biopsy of the patient."
    explanation: >-
      Direct histomorphometric evidence for the high-turnover state this node
      asserts, from bone biopsy rather than densitometry alone.
phenotypes:
- name: Global developmental delay / intellectual disability
  category: Neurologic
  description: >-
    Moderate-to-severe global developmental delay and intellectual disability are
    cardinal features; most affected individuals are non-verbal. The recurrent
    n.64_65insT variant is associated with more severe cognitive impairment than
    other RNU4-2 variants.
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:38821540
    reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
    explanation: >-
      Greene et al. list intellectual disability as a defining feature of the
      RNU4-2 syndrome.
- name: Severe intellectual disability
  category: Neurologic
  description: >-
    Affected individuals typically show severe intellectual disability; the
    functional T-loop n.64_65insT variant is associated with more severe
    cognitive impairment than other RNU4-2 variants.
  phenotype_term:
    preferred_term: Severe intellectual disability
    term:
      id: HP:0010864
      label: Severe intellectual disability
  evidence:
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Affected individuals exhibited severe intellectual disability, developmental delay, microcephaly, short stature, and consistent brain MRI findings, including ventricular enlargement and corpus callosum thinning."
    explanation: >-
      Hiraide et al. document severe intellectual disability in the affected
      individuals.
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The n.64_65insT variant, located within the functional T-loop of the U4 snRNA, appears to be associated with more severe cognitive impairment than other RNU4-2 variants."
    explanation: >-
      Establishes the genotype-phenotype correlation of the recurrent variant
      with more severe cognitive impairment.
- name: Absent / non-verbal speech
  category: Neurologic
  description: >-
    Speech is severely affected, with most individuals being non-verbal.
  phenotype_term:
    preferred_term: Absent speech
    term:
      id: HP:0001344
      label: Absent speech
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures"
    explanation: >-
      Chen et al. report speech abnormalities (mostly non-verbal) among the
      highly frequent phenotypes.
- name: Hypotonia
  category: Neurologic
  description: >-
    Hypotonia is a highly frequent feature (present in ≥75% of individuals).
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  frequency: FREQUENT
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
    explanation: >-
      Chen et al. report hypotonia in ≥75% of individuals, supporting the
      FREQUENT band.
- name: Microcephaly
  category: Neurologic
  description: >-
    Microcephaly (mostly congenital) is a highly frequent feature.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  frequency: FREQUENT
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
    explanation: >-
      Chen et al. report microcephaly in ≥75% of individuals, supporting the
      FREQUENT band.
- name: Short stature
  category: Growth
  description: >-
    Short stature is a highly frequent growth feature.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  frequency: FREQUENT
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
    explanation: >-
      Chen et al. report short stature in ≥75% of individuals, supporting the
      FREQUENT band.
- name: Seizures
  category: Neurologic
  description: >-
    Seizures are a highly frequent feature, with variable onset and multiple
    seizure types reported.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  frequency: FREQUENT
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Associated growth and neurodevelopmental phenotypes present in more than or equal to 75% of individuals include short stature, microcephaly (mostly congenital), speech abnormalities (mostly non-verbal), hypotonia and seizures."
    explanation: >-
      Chen et al. report seizures in ≥75% of individuals, supporting the
      FREQUENT band.
- name: Corpus callosum hypoplasia
  category: Neurologic
  description: >-
    Brain MRI frequently shows hypoplasia (thinning) of the corpus callosum.
  phenotype_term:
    preferred_term: Hypoplasia of the corpus callosum
    term:
      id: HP:0002079
      label: Hypoplasia of the corpus callosum
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
    explanation: >-
      Chen et al. report corpus callosum hypoplasia as a frequent MRI finding.
- name: Ventriculomegaly
  category: Neurologic
  description: >-
    Enlargement of the cerebral ventricles is a frequent brain MRI finding.
  phenotype_term:
    preferred_term: Ventriculomegaly
    term:
      id: HP:0002119
      label: Ventriculomegaly
  evidence:
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "consistent brain MRI findings, including ventricular enlargement and corpus callosum thinning"
    explanation: >-
      Hiraide et al. document ventricular enlargement (ventriculomegaly) as a
      consistent MRI finding.
- name: Reduced cerebral white matter volume
  category: Neurologic
  description: >-
    Reduced white-matter volume is the most frequent brain MRI abnormality.
  phenotype_term:
    preferred_term: Reduced cerebral white matter volume
    term:
      id: HP:0012429
      label: Aplasia/Hypoplasia of the cerebral white matter
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
    explanation: >-
      Chen et al. list reduced white-matter volume as the most frequent MRI
      abnormality.
- name: Delayed myelination
  category: Neurologic
  description: >-
    Delayed myelination is a recurrent brain MRI finding.
  phenotype_term:
    preferred_term: Delayed myelination
    term:
      id: HP:0012448
      label: Delayed myelination
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "most frequently reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, delayed myelination"
    explanation: >-
      Chen et al. list delayed myelination among the frequent MRI findings.
- name: Distinctive lip-and-philtrum facial gestalt
  category: Craniofacial
  description: >-
    A characteristic facial gestalt involving the lips and philtrum is
    consistently observed: a tented upper lip with an exaggerated Cupid's bow, an
    everted lower lip, and a horizontally oriented (short/flat) philtrum. This
    "lip and philtrum gestalt" is a recognizable clinical clue prompting targeted
    genetic evaluation.
  phenotype_term:
    preferred_term: Distinctive lip and philtrum facial gestalt
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distinctive facial features involving the lips and philtrum were consistently observed, including a characteristic combination of a tented upper lip with an exaggerated Cupid's bow, an everted lower lip, and a horizontally oriented philtrum."
    explanation: >-
      Hiraide et al. describe the characteristic lip-and-philtrum facial gestalt
      of ReNU syndrome.
- name: Everted lower lip
  category: Craniofacial
  description: >-
    An everted lower lip is part of the characteristic facial gestalt.
  phenotype_term:
    preferred_term: Everted lower lip vermilion
    term:
      id: HP:0000232
      label: Everted lower lip vermilion
  evidence:
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a tented upper lip with an exaggerated Cupid's bow, an everted lower lip, and a horizontally oriented philtrum"
    explanation: >-
      Hiraide et al. specify an everted lower lip within the facial gestalt.
- name: Motor delay
  category: Neurologic
  description: >-
    Delayed motor development (both gross and fine motor) is a core
    neurodevelopmental feature, accompanying the global developmental delay and
    hypotonia. In the Genomics England cohort, n.64_65insT carriers were
    significantly enriched for delayed gross and fine motor development relative
    to other NDD probands.
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: PMID:38821540
    reference_title: "Mutations in the U4 snRNA gene RNU4-2 cause one of the most prevalent monogenic neurodevelopmental disorders."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We implicated de novo variants among 47 cases in two regions of RNU4-2 in the etiology of a syndrome characterized by ID, microcephaly, short stature, hypotonia, seizures and motor delay."
    explanation: >-
      Greene et al. list motor delay among the defining features of the RNU4-2
      syndrome.
- name: Optic nerve hypoplasia
  category: Ophthalmologic
  description: >-
    Visual system involvement is common; optic nerve hypoplasia is among the
    reported ophthalmologic abnormalities (alongside cortical blindness).
  phenotype_term:
    preferred_term: Optic nerve hypoplasia
    term:
      id: HP:0000609
      label: Optic nerve hypoplasia
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report optic nerve hypoplasia among the visual abnormalities of
      the multi-organ involvement described for affected individuals.
- name: Strabismus
  category: Ophthalmologic
  description: >-
    Strabismus is a frequently reported ophthalmologic feature of the visual
    system involvement.
  phenotype_term:
    preferred_term: Strabismus
    term:
      id: HP:0000486
      label: Strabismus
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. list strabismus among the visual abnormalities reported in the
      multi-organ involvement.
- name: Nystagmus
  category: Ophthalmologic
  description: >-
    Nystagmus is among the reported visual/ophthalmologic abnormalities.
  phenotype_term:
    preferred_term: Nystagmus
    term:
      id: HP:0000639
      label: Nystagmus
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. list nystagmus among the visual abnormalities reported in the
      multi-organ involvement.
- name: Feeding difficulties
  category: Gastrointestinal
  description: >-
    Gastrointestinal involvement is common; feeding difficulties can be severe
    enough to require a gastrostomy tube and contribute to the poor growth of
    affected individuals.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report feeding issues requiring a gastrostomy tube among the
      gastrointestinal manifestations.
- name: Constipation
  category: Gastrointestinal
  description: >-
    Constipation is among the reported gastrointestinal manifestations.
  phenotype_term:
    preferred_term: Constipation
    term:
      id: HP:0002019
      label: Constipation
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report constipation among the gastrointestinal manifestations.
- name: Gastroesophageal reflux
  category: Gastrointestinal
  description: >-
    Gastroesophageal reflux is among the reported gastrointestinal
    manifestations.
  phenotype_term:
    preferred_term: Gastroesophageal reflux
    term:
      id: HP:0002020
      label: Gastroesophageal reflux
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report reflux among the gastrointestinal manifestations.
- name: Osteopenia
  category: Skeletal
  description: >-
    Bone and skeletal abnormalities are common; reduced bone mineral density
    (osteopenia) is reported and can predispose to fractures.
  phenotype_term:
    preferred_term: Osteopenia
    term:
      id: HP:0000938
      label: Osteopenia
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report osteopenia among the bone/skeletal abnormalities.
- name: Recurrent fractures
  category: Skeletal
  description: >-
    Recurrent fractures are reported among the bone/skeletal manifestations,
    consistent with the reduced bone mineral density.
  phenotype_term:
    preferred_term: Recurrent fractures
    term:
      id: HP:0002757
      label: Recurrent fractures
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report recurrent fractures among the bone/skeletal
      abnormalities.
- name: Scoliosis
  category: Skeletal
  description: >-
    Scoliosis is among the reported skeletal abnormalities.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report scoliosis among the skeletal abnormalities.
- name: Hip dysplasia
  category: Skeletal
  description: >-
    Hip dysplasia is among the reported skeletal abnormalities.
  phenotype_term:
    preferred_term: Hip dysplasia
    term:
      id: HP:0001385
      label: Hip dysplasia
  evidence:
  - reference: PMID:38991538
    reference_title: "De novo variants in the RNU4-2 snRNA cause a frequent neurodevelopmental syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "often including visual (optic nerve hypoplasia, cortical blindness, strabismus, nystagmus), gastrointestinal (constipation, reflux, feeding issues with need for a gastrostomy tube, poor growth) and bone and/or skeletal abnormalities (osteopenia, recurrent fractures, scoliosis, kyphosis, hip dysplasia)"
    explanation: >-
      Chen et al. report hip dysplasia among the skeletal abnormalities.
- name: Abnormal rib morphology
  category: Skeletal
  description: >-
    Rib dysplasia is reported as an additional phenotypic feature in the
    exome-negative cohort, expanding the previously documented skeletal
    manifestations. This finding may contribute to thoracic insufficiency or
    respiratory compromise in affected individuals.
  phenotype_term:
    preferred_term: Abnormal rib morphology
    term:
      id: HP:0000772
      label: Abnormal rib morphology
  evidence:
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, transient limb edema and rib dysplasia may expand the phenotypic spectrum."
    explanation: >-
      Hiraide et al. identify rib dysplasia as an emerging phenotypic feature
      that expands the spectrum of skeletal abnormalities in ReNU syndrome.
- name: Autistic features
  category: Neurologic
  description: >-
    Autism spectrum disorder emerged as a hallmark of the behavioural phenotype in
    the first longitudinal neuropsychiatric characterisation of the syndrome,
    alongside persistent attention deficits. Behavioural features are reported as
    developing and persisting across childhood into adolescence rather than as a
    transient early finding.
  phenotype_term:
    preferred_term: Autism spectrum disorder
    term:
      id: HP:0000717
      label: Autism
  evidence:
  - reference: PMID:41681065
    reference_title: "Longitudinal Behavior Phenotype Hallmarks in RNU4-2 Syndrome: Implications for Clinical Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distinctive features included persistent attention deficits and Autistic Spectrum Disorder, which emerged as hallmarks of the Syndrome."
    explanation: Identifies autism spectrum disorder as a hallmark behavioural feature.
- name: Short attention span
  category: Neurologic
  description: >-
    Persistent attention deficits are described as a hallmark of the syndrome's
    behavioural phenotype. The binding is deliberately to short attention span
    rather than to attention deficit hyperactivity disorder, because the source
    describes attention deficits rather than a formal ADHD diagnosis.
  phenotype_term:
    preferred_term: Persistent attention deficit
    term:
      id: HP:0000736
      label: Short attention span
  evidence:
  - reference: PMID:41681065
    reference_title: "Longitudinal Behavior Phenotype Hallmarks in RNU4-2 Syndrome: Implications for Clinical Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Distinctive features included persistent attention deficits and Autistic Spectrum Disorder, which emerged as hallmarks of the Syndrome."
    explanation: Identifies persistent attention deficits as a hallmark behavioural feature.
- name: Proteinuria
  category: Renal
  description: >-
    Kidney involvement in ReNU syndrome had been reported only as anatomical
    abnormality of the kidney and urinary tract until a single case of isolated,
    persistent, steroid-unresponsive nephrotic-range proteinuria was described,
    with minimal change disease and podocyte effacement on biopsy and preserved
    kidney function at age 16. This rests on one reported patient and its frequency
    is unknown; it is curated because the authors recommend monitoring for
    proteinuria in ReNU syndrome, which makes it clinically actionable even at n=1.
  phenotype_term:
    preferred_term: Proteinuria
    term:
      id: HP:0000093
      label: Proteinuria
  evidence:
  - reference: PMID:41623289
    reference_title: "ReNU Syndrome due to a de novo RNU4-2 Variant as a Novel Genetic Cause of Proteinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A kidney biopsy showed minimal change disease with slight podocyte effacement."
    explanation: Documents the renal histology underlying the proteinuria in the reported case.
  - reference: PMID:41623289
    reference_title: "ReNU Syndrome due to a de novo RNU4-2 Variant as a Novel Genetic Cause of Proteinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This case is the first documented report of isolated, persistent proteinuria in ReNU syndrome."
    explanation: >-
      Curated PARTIAL because it establishes the phenotype in a single individual
      and therefore does not support any claim about frequency.
- name: Midline stereotypies
  category: Neurologic
  description: >-
    Midline stereotypies are listed by GeneReviews among the neurobehavioral
    manifestations presenting in infancy or childhood. They are recorded here as a
    named feature of the behavioural phenotype alongside autism and attention
    deficits; no source examined quantifies their frequency.
  phenotype_term:
    preferred_term: Midline motor stereotypies
    term:
      id: HP:0000733
      label: Motor stereotypy
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "neurobehavioral/psychiatric manifestations (autism spectrum disorder, midline stereotypies, sleep disturbances, aggressive or self-injurious behaviors)"
    explanation: >-
      GeneReviews lists midline stereotypies among the defining neurobehavioral
      manifestations of the syndrome.
- name: Sleep disturbance
  category: Neurologic
  description: >-
    Sleep disturbance is one of the neurobehavioral manifestations GeneReviews uses
    to characterise the syndrome, and sleep issues are a named domain in its
    recommended surveillance schedule - so it is a management concern as well as a
    descriptive feature.
  phenotype_term:
    preferred_term: Sleep disturbance
    term:
      id: HP:0002360
      label: Sleep disturbance
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "neurobehavioral/psychiatric manifestations (autism spectrum disorder, midline stereotypies, sleep disturbances, aggressive or self-injurious behaviors)"
    explanation: GeneReviews lists sleep disturbance among the defining neurobehavioral manifestations.
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "kidney anomalies; urinary tract anomalies; bone health; and sleep issues"
    explanation: >-
      Sleep is a named domain of the recommended multidisciplinary surveillance,
      supporting it as a clinically tracked feature rather than an incidental one.
- name: Self-injurious behavior
  category: Neurologic
  description: >-
    Aggressive or self-injurious behaviours are listed by GeneReviews among the
    neurobehavioral manifestations, and a longitudinal case description records
    self-injury emerging specifically in adolescence, alongside social anxiety.
    This is the behavioural feature with the clearest developmental timing.
  phenotype_term:
    preferred_term: Self-injurious behavior
    term:
      id: HP:0100716
      label: Self-injurious behavior
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "neurobehavioral/psychiatric manifestations (autism spectrum disorder, midline stereotypies, sleep disturbances, aggressive or self-injurious behaviors)"
    explanation: GeneReviews lists aggressive or self-injurious behaviour as a defining manifestation.
  - reference: PMID:41681065
    reference_title: "Longitudinal Behavior Phenotype Hallmarks in RNU4-2 Syndrome: Implications for Clinical Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "one patient developed self-injurious behavior and social anxiety during adolescence"
    explanation: Documents the adolescent onset of self-injury in a longitudinally followed patient.
- name: Talipes equinovarus
  category: Musculoskeletal
  description: >-
    Club feet are listed by GeneReviews within the bone and skeletal involvement
    that characterises the syndrome. It sits in the same skeletal cluster as hip
    dysplasia, joint hyperlaxity and the osteopenia/fracture phenotype already
    curated here.
  phenotype_term:
    preferred_term: Club foot
    term:
      id: HP:0001762
      label: Talipes equinovarus
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "bone/skeletal involvement (club feet, hip dysplasia, joint hyperlaxity, osteopenia/osteoporosis or history of low-impact fractures)"
    explanation: GeneReviews lists club feet among the characteristic skeletal features.
- name: Joint hypermobility
  category: Musculoskeletal
  description: >-
    Joint hyperlaxity is listed by GeneReviews within the syndrome's bone and
    skeletal involvement. Together with hypotonia it is plausibly relevant to the
    hip dysplasia and scoliosis also seen, though no source examined asserts that
    chain, so it is not modelled as a causal edge.
  phenotype_term:
    preferred_term: Joint hyperlaxity
    term:
      id: HP:0001382
      label: Joint hypermobility
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "bone/skeletal involvement (club feet, hip dysplasia, joint hyperlaxity, osteopenia/osteoporosis or history of low-impact fractures)"
    explanation: GeneReviews lists joint hyperlaxity among the characteristic skeletal features.
- name: Kidney and urinary tract anomalies
  category: Renal
  description: >-
    Structural anomalies of the kidney and urinary tract are a named surveillance
    domain in GeneReviews and were the form in which renal involvement was
    originally reported, before the separate description of isolated proteinuria
    curated below. Both are kept: the anatomical anomalies and the glomerular
    lesion are different renal phenotypes, not one claim at two resolutions.
  phenotype_term:
    preferred_term: Kidney and urinary tract anomaly
    term:
      id: HP:0000079
      label: Abnormality of the urinary system
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "kidney anomalies; urinary tract anomalies; bone health; and sleep issues"
    explanation: >-
      GeneReviews names kidney and urinary tract anomalies as domains requiring
      dedicated surveillance, establishing them as recognised features.
  - reference: PMID:41623289
    reference_title: "ReNU Syndrome due to a de novo RNU4-2 Variant as a Novel Genetic Cause of Proteinuria."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Kidney involvement has been reported exclusively as anatomical abnormalities."
    explanation: >-
      Independently confirms that anatomical anomaly was the previously reported
      form of renal involvement.
treatments:
- name: Multidisciplinary supportive care
  therapeutic_modality: OTHER
  description: >-
    Management is supportive and symptomatic, addressing developmental,
    neurological, growth, feeding, and orthopedic needs through multidisciplinary
    care. There is no disease-modifying therapy. The saturation-editing work
    frames variant-function data as groundwork for future therapeutic development,
    which is the current state of play: no targeted treatment exists.
  treatment_term:
    preferred_term: supportive care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:41951737
    reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "providing critical insights for both diagnosis and therapeutic development"
    explanation: >-
      Therapeutic development is framed as prospective, supporting the statement
      that management today is supportive rather than disease-modifying.
- name: Anti-seizure pharmacotherapy
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Seizures are managed with anti-seizure medications. In the only epilepsy-focused
    cohort, valproate was judged the most effective agent by the treating
    neurologists, followed by levetiracetam, clobazam, lamotrigine and phenytoin,
    and seizure freedom was achieved in half the cohort. Note that this is a
    retrospective clinician judgement in ten patients, not a controlled comparison,
    so it is weak grounds for preferring valproate over another agent in an
    individual patient.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: valproate
      term:
        id: CHEBI:39867
        label: valproic acid
  target_mechanisms:
  - target: Cortical Network Hyperexcitability
    treatment_effect: INHIBITS
    description: >-
      Anti-seizure medication suppresses the network hyperexcitability that
      generates the seizures; it does not act on the upstream splicing defect.
    evidence:
    - reference: PMID:41570780
      reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Seizure freedom was achieved with antiseizure medications in 5 patients at a mean age of 7.2 ± 25.2."
      explanation: >-
        Medication abolishes seizures in half the cohort, which is what this link
        asserts: the drug acts on the seizure-generating node, not on the cause.
  evidence:
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Valproate was judged the most effective medication by referring neurologists followed by levetiracetam, clobazam, lamotrigine and phenytoin."
    explanation: >-
      Curated PARTIAL: this is retrospective clinician judgement in a ten-patient
      cohort, which supports valproate being used and considered effective but not
      a comparative efficacy claim.
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizure freedom was achieved with antiseizure medications in 5 patients at a mean age of 7.2 ± 25.2."
    explanation: Establishes that medically achieved seizure freedom is attainable in a substantial fraction.
- name: Antiresorptive therapy for skeletal fragility
  therapeutic_modality: SMALL_MOLECULE
  description: >-
    Given the 42% frequency of bone abnormality and the occurrence of clinically
    silent vertebral fractures, osteological assessment is warranted. In the one
    published treated case, intravenous neridronate at 2 mg/kg every three months
    over three years was well tolerated, bone mineral density rose and then
    stabilised, and no further vertebral fractures occurred — though the patient
    did sustain a patella and a proximal humerus fracture after falls. This is a
    single treated patient, so it supports the approach being feasible and
    reasonable, not an established efficacy claim.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: neridronate
      term:
        id: NCIT:C66230
        label: Neridronic Acid
  target_mechanisms:
  - target: Increased Bone Turnover and Reduced Bone Mineral Density
    treatment_effect: INHIBITS
    description: >-
      Bisphosphonate therapy suppresses the osteoclast-mediated resorption arm of
      the high-turnover state curated at this node.
    evidence:
    - reference: PMID:40510867
      reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "we observed the expected reduction of bone turnover parameters"
      explanation: >-
        Confirms the drug engaged the turnover process this node represents;
        PARTIAL because it is a pharmacodynamic effect in one patient, not an
        outcome.
  evidence:
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Anti-resorptive treatment with intravenous neridronate injections (2 mg per kg body weight, every 3 mo) was initiated, which was well tolerated by the patient without obvious side effects."
    explanation: Documents the regimen and its tolerability in the reported patient.
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Importantly, there were no additional vertebral fractures."
    explanation: >-
      Curated PARTIAL: absence of further vertebral fractures in one uncontrolled
      patient who still sustained two appendicular fractures is suggestive, not
      demonstrative, of benefit.
- name: Structured surveillance and avoidance of bone-toxic agents
  therapeutic_modality: OTHER
  description: >-
    GeneReviews recommends scheduled follow-up to monitor existing manifestations
    and detect new ones, across developmental, seizure, feeding, kidney, urinary
    tract, bone-health and sleep domains, and specifically advises weighing the
    bone consequences of any medication considered. That advice matters more here
    than in most neurodevelopmental disorders given the 42% frequency of bone
    abnormality and the demonstrated occurrence of vertebral fractures that were
    silent until imaged.
  treatment_term:
    preferred_term: scheduled multi-system clinical surveillance
  notes: >-
    treatment_term is deliberately left unbound. NCIT:C15719 (Surveillance) is not
    reachable from NCIT:C25218 (Clinical Intervention or Procedure) and so fails
    the TreatmentActionTerm enum, and no NCIT clinical-action term was found that
    means scheduled multi-system surveillance. Per the project rule that no term
    beats a bad one, a free-text preferred_term is used rather than forcing a
    generic Therapeutic Procedure or reusing Supportive Care, which already labels
    a different treatment in this entry.
  evidence:
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Consider avoiding or limiting any substance or medication that may affect bone health (e.g., steroids)."
    explanation: >-
      The explicit agents-to-avoid recommendation, tied to this disorder's
      skeletal fragility.
- name: Augmentative and alternative communication
  therapeutic_modality: BEHAVIORAL
  description: >-
    Because most individuals never acquire meaningful speech while comprehension
    and social motivation are comparatively preserved, augmentative and alternative
    communication is emphasised as a priority intervention, together with
    cognitive-behavioural approaches aimed at the communicative frustration that
    appears to drive behavioural dysregulation and social anxiety.
  treatment_term:
    preferred_term: speech and language therapy
    term:
      id: NCIT:C159273
      label: Speech Language Therapy
  evidence:
  - reference: PMID:41681065
    reference_title: "Longitudinal Behavior Phenotype Hallmarks in RNU4-2 Syndrome: Implications for Clinical Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "with particular emphasis on augmentative and alternative communication strategies and cognitive-behavioral approaches to mitigate communicative frustration, behavioral dysregulation, and social anxiety"
    explanation: States the recommended intervention and the behavioural rationale for it.
- name: Physical and developmental therapy
  therapeutic_modality: BEHAVIORAL
  description: >-
    Physical, occupational, and speech/communication therapies support motor
    development and function given hypotonia, motor delay, and non-verbal status.
    In the treated osteoporosis case a structured strength and coordination
    programme proved infeasible and supervised general mobility was substituted,
    which illustrates the practical ceiling on physical therapy in this population.
  treatment_term:
    preferred_term: physical therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A structured training program to improve muscle strength and coordination was not feasible for the patient, but mobility in general was promoted in a protected environment under supervision."
    explanation: >-
      Curated PARTIAL because it documents a limitation of this treatment rather
      than a benefit: structured training was not deliverable.
diagnosis:
- name: Genome sequencing (exome-negative work-up)
  description: >-
    The signature diagnostic feature of ReNU syndrome is that RNU4-2, as a short
    non-coding U4 snRNA gene, is not captured by conventional exome sequencing;
    affected individuals are therefore typically exome-negative and remain
    undiagnosed until clinical genome sequencing is performed and the RNU4-2
    critical-region variant (most often the recurrent n.64_65insT insertion) is
    identified. Genome sequencing of exome-negative NDD cohorts is the actionable
    route to diagnosis and, given the recognizable lip-and-philtrum facial
    gestalt, RNU4-2 should be specifically interrogated in undiagnosed NDD.
  diagnosis_term:
    preferred_term: clinical whole genome sequencing
    term:
      id: NCIT:C101294
      label: Whole Genome Sequencing
  evidence:
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "RNU4-2 is not captured by conventional exome sequencing (ES), often leaving affected individuals undiagnosed."
    explanation: >-
      Hiraide et al. state that RNU4-2 is missed by exome sequencing, so affected
      individuals are exome-negative until genome sequencing is applied.
  - reference: PMID:42419151
    reference_title: "Recurrent RNU4-2 n.64_65insT variant in ReNU syndrome identified in exome-negative cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we performed genome sequencing in 95 patients with NDDs in whom prior ES had failed to identify a causative variant"
    explanation: >-
      Hiraide et al. establish genome sequencing of exome-negative NDD patients as
      the diagnostic approach that identifies the RNU4-2 variant.
  - reference: PMID:42190036
    reference_title: "RNU4-2-Related Autosomal Dominant Neurodevelopmental Disorder."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The diagnosis of ReNU syndrome is established in a proband with suggestive findings and a heterozygous pathogenic variant in RNU4-2 identified by molecular genetic testing."
    explanation: >-
      The GeneReviews diagnostic criterion: suggestive clinical findings plus a
      heterozygous RNU4-2 variant on molecular genetic testing. The criterion is
      agnostic about method, which is why both the genome-sequencing and the
      targeted-Sanger routes curated here satisfy it.
- name: Targeted Sanger sequencing of the RNU4-2 hotspot
  description: >-
    Where genome sequencing is unavailable or slow, the recognisability of the
    syndrome makes a targeted approach viable: because the pathogenic variants
    cluster into a short region, direct Sanger sequencing of the 18-base-pair
    critical region is a reasonable first test in a clinically suspected case. This
    is how a nine-patient series was assembled from previously undiagnosed
    individuals, and how the diagnosis was reached in a patient whose trio exome
    had been uninformative. The facial gestalt — hooded upper eyelids, full cheeks,
    a tented philtrum, and a slightly open mouth with an everted lower lip
    vermilion — is the practical trigger for testing.
  diagnosis_term:
    preferred_term: DNA sequence analysis
    term:
      id: NCIT:C153598
      label: DNA Sequencing
  evidence:
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "If clinically suspected, it is reasonable to examine the 18-base pair region using the Sanger method."
    explanation: States the targeted diagnostic recommendation directly.
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients showed a distinctive pattern of dysmorphic features, including hooded upper eyelids, full cheeks, a tented philtrum, and a mouth constantly slightly open with an everted lower lip vermilion."
    explanation: >-
      Specifies the recognisable facial pattern that makes targeted testing
      practical, present in every patient in the series.
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "As RNA encoding genes are not targeted by exome sequencing, we analyzed RNU4-2"
    explanation: >-
      A worked instance of the targeted approach succeeding after uninformative
      trio exome sequencing.
progression:
- phase: Infancy
  age_range: birth to 2 years
  notes: >-
    Presentation is with hypotonia, feeding difficulty and global developmental
    delay. Microcephaly is mostly congenital, and reduced head circumference may
    be noted prenatally. Seizures usually have not yet begun, though onset before
    12 months occurs in a minority.
  evidence:
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Focal impaired consciousness with observable manifestations (with onset before 12 months in 3 cases) were the predominant seizure type across all age ranges."
    explanation: >-
      Establishes that seizure onset within the first year occurs but is the
      exception rather than the rule.
- phase: Early childhood
  age_range: 2 to 6 years
  notes: >-
    Epilepsy typically begins in this window, at a mean age of about 2.8 years.
    Expressive language largely fails to emerge: most individuals have not
    acquired meaningful words by age five. Independent walking is attained by
    roughly half.
  evidence:
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The mean age at epilepsy onset was 2.8 ±2.1 years."
    explanation: Dates typical epilepsy onset to early childhood.
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In six patients, meaningful words had not been acquired, even after the age of 5 years."
    explanation: Marks failure of expressive language to emerge by school age.
- phase: Later childhood
  age_range: 6 to 12 years
  notes: >-
    Focal impaired-consciousness seizures peak in frequency between ages 6 and 11,
    and epileptiform EEG abnormality becomes more readily detected after age 3.
    Seizure freedom is achievable with medication in about half of patients.
  evidence:
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The frequency of this seizure type peaked between the ages of 6 and 11 years."
    explanation: Locates the peak of the seizure burden in later childhood.
  - reference: PMID:41570780
    reference_title: "Epilepsy phenotypes of Renu syndrome: Novel insights from a European multicentre retrospective cohort study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Seizure freedom was achieved with antiseizure medications in 5 patients at a mean age of 7.2 ± 25.2."
    explanation: >-
      Records the comparatively favourable epilepsy outcome. The reported standard
      deviation (±25.2 years) is internally inconsistent with a mean of 7.2 years
      and is quoted here verbatim rather than corrected.
- phase: Adolescence and adulthood
  age_range: 12 years and older
  notes: >-
    Neuropsychiatric features come to the fore: persistent attention deficits and
    autistic features are described as hallmarks, and self-injurious behaviour and
    social anxiety may emerge in adolescence. Skeletal fragility becomes clinically
    important, with vertebral fractures that may be silent until specifically
    imaged. Individuals have been followed to at least age 29; the disorder is not
    known to be neurodegenerative, though longitudinal data remain sparse.
  evidence:
  - reference: PMID:41681065
    reference_title: "Longitudinal Behavior Phenotype Hallmarks in RNU4-2 Syndrome: Implications for Clinical Management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "one patient developed self-injurious behavior and social anxiety during adolescence"
    explanation: Documents emergence of these behaviours specifically in adolescence.
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nine patients aged between 3 and 29 years all showed severe developmental delay and/or intellectual disability."
    explanation: >-
      Establishes the upper age of reported follow-up and that severe impairment
      persists across it.
clinical_burden:
  burden_level: HIGH
  rationale: >-
    Burden is curated HIGH rather than VARIABLE because the core impairments are
    near-universal rather than distributed: developmental delay or intellectual
    disability was present in every patient across a 3-to-29-year age span, most
    never acquire meaningful speech, only about half walk independently, and
    neuroradiological abnormality was universal in a consecutive series. Epilepsy
    affects about 60%, and 42% of those assessed have bone abnormality with
    fractures that may go unrecognized. The milder Stem III genotype is the one
    real source of variability, and it is a minority of cases; it is captured as a
    subtype rather than by softening the overall burden level.
  evidence:
  - reference: PMID:40546132
    reference_title: "A Clinical Study of Nine Patients With ReNU Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Nine patients aged between 3 and 29 years all showed severe developmental delay and/or intellectual disability."
    explanation: Universal severe impairment across the reported age range.
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "bone abnormalities have been described previously and were present in 72 out of 173 individuals (42%) with ReNU syndrome who underwent bone assessment"
    explanation: Quantifies the added skeletal burden beyond the neurological phenotype.
experimental_models:
- name: Saturation genome editing of RNU4-2 in HAP1 cells
  experimental_model_type: CELL_LINE
  culture_system: >-
    Haploid human HAP1 cells lacking LIG4 (HAP1-LIG4-KO), into which a library of
    539 RNU4-2 variants was installed by Cas9-directed homology-directed repair;
    variant effects are read out as depletion or enrichment over time in culture.
  cell_source: HAP1 human near-haploid cell line
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  publication: PMID:41951737
  description: >-
    Because no established model existed for assaying RNU4-2 variants, the authors
    used saturation genome editing in a haploid human line, where the single copy
    of the gene makes each edited variant's effect directly visible in cell
    fitness. The resulting function scores separate ReNU syndrome variants from
    population variants, outperform in silico predictors, and scale with both
    splicing disruption and clinical severity. This is a variant-function assay
    rather than a disease model: it measures the molecular node, and does not
    reproduce any neurodevelopmental phenotype.
  evidence:
  - reference: PMID:41951737
    reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Here we performed saturation genome editing (SGE) of RNU4-2 to identify the functional and clinical impact of variants across the entire gene."
    explanation: >-
      Establishes the existence and purpose of the model system curated here.
  modeled_mechanisms:
  - target: RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function
    relationship: MEASURES
    fidelity: MODERATE
    description: >-
      Quantifies the functional consequence of each RNU4-2 variant, resolving the
      critical region to single-nucleotide resolution and reclassifying variants
      of uncertain significance.
    limitations: >-
      Fitness in a haploid cancer-derived cell line is a proxy for spliceosome
      impairment, not a measure of neurodevelopment; HAP1 is not a neural cell
      type, the assay is haploid whereas ReNU syndrome is heterozygous, and no
      clinical phenotype is recapitulated.
    readouts:
    - name: SGE function score (cell fitness)
      target: RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function
      direction: DECREASED
      interpretation: >-
        Pathogenic critical-region variants deplete from the edited cell pool,
        yielding low function scores that separate them from population variants.
      evidence:
      - reference: PMID:41951737
        reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: "The resulting SGE function scores, derived from variants' effects on cell fitness, discriminate ReNU syndrome variants from those observed in the population and markedly outperform in silico variant effect prediction"
        explanation: >-
          Defines the readout and establishes that it discriminates pathogenic
          from population variation better than computational prediction.
    evidence:
    - reference: PMID:41951737
      reference_title: "Saturation editing of RNU4-2 reveals distinct dominant and recessive disorders."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Lacking established models for assaying RNU4-2 variants, we chose to perform SGE in HAP1 cells, a haploid human line in which growth effects have accurately distinguished pathogenic variants across several protein-coding genes"
      explanation: >-
        States both the rationale for the model and, by naming the absence of
        established models, why it is informative for this node.
differential_diagnoses:
- name: Recessive RNU4-2-related neurodevelopmental disorder
  description: >-
    The same gene causes a second, separate disorder. Biallelic variants falling
    outside the 18-nucleotide ReNU critical region — in Stem II, the k-turn and the
    Sm protein binding site — produce a clinically distinct recessive
    neurodevelopmental syndrome. Distinguishing it matters mechanistically as well
    as diagnostically: the recessive disorder shows reduced RNU4-2 transcript and
    so acts by loss of function, which ReNU syndrome does not.
  distinguishing_features:
  - Biallelic (homozygous or compound heterozygous) rather than de novo heterozygous
  - Variants outside the 18-nucleotide critical region, in Stem II, the k-turn or the Sm site
  - Distinctive white matter abnormalities including enlarged perivascular spaces
  - Reduced RNU4-2 transcript levels, indicating a loss-of-function mechanism
  evidence:
  - reference: PMID:41951959
    reference_title: "Biallelic variants in the noncoding RNA gene RNU4-2 cause a recessive neurodevelopmental syndrome with distinct white matter changes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identify 38 individuals with biallelic variants outside the 18-nucleotide ReNU syndrome region that cluster within other functionally important elements of U4: Stem II, the k-turn and the Sm protein binding site."
    explanation: Defines the genotype that separates this disorder from ReNU syndrome.
  - reference: PMID:41951959
    reference_title: "Biallelic variants in the noncoding RNA gene RNU4-2 cause a recessive neurodevelopmental syndrome with distinct white matter changes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we find reduced RNU4-2 transcript levels in individuals with the recessive disorder, suggesting a loss-of-function disease mechanism that is distinct from the mechanism underlying ReNU syndrome"
    explanation: >-
      Establishes the mechanistic distinction, which is the reason this is a
      separate disease rather than a severity variant of ReNU syndrome.
- name: RNU4-2- and RNU6-related retinitis pigmentosa
  description: >-
    Heterozygous variants in RNU4-2 also cause non-syndromic retinitis pigmentosa,
    with no neurodevelopmental phenotype. These variants sit in the three-way
    junction of the U4/U6 duplex rather than the ReNU critical region, and appear
    to act by impairing snRNP biogenesis through altered binding of tri-snRNP
    factors. The same gene therefore produces either a neurodevelopmental disorder
    or an isolated retinal degeneration depending on which structural element is
    hit.
  disease_term:
    preferred_term: retinitis pigmentosa
    term:
      id: MONDO:0019200
      label: retinitis pigmentosa
  distinguishing_features:
  - Progressive retinal degeneration without intellectual disability or microcephaly
  - Variants cluster in the U4/U6 three-way junction, not the 18-bp ReNU critical region
  - Often inherited rather than de novo
  evidence:
  - reference: PMID:41513982
    reference_title: "De novo and inherited dominant variants in U4 and U6 snRNA genes cause retinitis pigmentosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "reveals pleiotropy in RNU4-2, where distinct variants underlie neurodevelopmental disorder and retinal degeneration"
    explanation: >-
      States the pleiotropy directly: which variant, not which gene, determines
      whether the phenotype is neurodevelopmental or retinal.
  - reference: PMID:41513982
    reference_title: "De novo and inherited dominant variants in U4 and U6 snRNA genes cause retinitis pigmentosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These variants cluster within the three-way junction of the U4/U6 duplex, a site that interacts with tri-snRNP splicing factors also known to cause RP (PRPF3, PRPF8, PRPF31), and seem to affect snRNP biogenesis."
    explanation: Localizes the RP variants to a different structural element than the ReNU critical region.
- name: Other snRNA-related neurodevelopmental disorders (RNU2-2, RNU5B-1)
  description: >-
    Variants in other major-spliceosome snRNA genes cause neurodevelopmental
    disorders that overlap ReNU syndrome clinically and, like it, are invisible to
    exome sequencing. They belong to the same emerging class of snRNA
    spliceosomopathies and are the main alternative diagnoses when genome
    sequencing of an exome-negative individual is being interpreted.
  distinguishing_features:
  - Causal variant in RNU2-2 or RNU5B-1 rather than RNU4-2
  - Both dominant and recessive forms have been described for RNU2-2
  evidence:
  - reference: PMID:41513982
    reference_title: "De novo and inherited dominant variants in U4 and U6 snRNA genes cause retinitis pigmentosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Likewise, RNU2-2 and RNU5B-1 have been recently associated with NDDs"
    explanation: Establishes these genes as the sibling snRNA causes of neurodevelopmental disorder.
discussions:
- discussion_id: renu_mechanism_is_not_loss_of_function
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#RNU4-2 Critical-Region Variant Disrupts U4 snRNA / Spliceosome Function
  prompt: >-
    If ReNU syndrome is not caused by loss of RNU4-2 function, what does the
    dominant critical-region variant actually do to the spliceosome?
  rationale: >-
    The discovery of a recessive RNU4-2 disorder settles what ReNU syndrome is not.
    Biallelic variants outside the critical region reduce RNU4-2 transcript levels
    and cause a clinically distinct disease by loss of function; the authors state
    explicitly that this mechanism differs from the one underlying ReNU syndrome.
    The dominant critical-region variants must therefore act by some other route —
    a dominant-negative or altered-function effect on U4/U6 pairing and spliceosome
    activation — but which of these, and whether the mutant U4 is incorporated into
    tri-snRNPs and poisons them or acts before assembly, is not established. This
    matters for therapy: an antisense or allele-specific strategy is only coherent
    if the mutant transcript is doing something, rather than simply failing to.
  evidence:
  - reference: PMID:41951959
    reference_title: "Biallelic variants in the noncoding RNA gene RNU4-2 cause a recessive neurodevelopmental syndrome with distinct white matter changes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we find reduced RNU4-2 transcript levels in individuals with the recessive disorder, suggesting a loss-of-function disease mechanism that is distinct from the mechanism underlying ReNU syndrome"
    explanation: >-
      The source of the gap: it establishes that ReNU syndrome's mechanism is
      something other than loss of function, without saying what.
- discussion_id: renu_rnu4_2_pleiotropy_ndd_versus_retinopathy
  kind: OPEN_QUESTION
  status: OPEN
  attaches_to:
  - genetic#RNU4-2 critical-region variants
  - pathophysiology#Systematic Disruption of 5' Splice-Site Usage
  prompt: >-
    Why do variants in one 76-nucleotide non-coding gene produce either a severe
    neurodevelopmental syndrome or an isolated retinal degeneration, depending only
    on which structural element is affected?
  rationale: >-
    RNU4-2 now has at least three distinct variant-position-to-disease mappings: the
    18-bp T-loop/stem III critical region gives dominant ReNU syndrome; the
    three-way junction of the U4/U6 duplex gives dominant non-syndromic retinitis
    pigmentosa; and Stem II, the k-turn and the Sm site give a recessive
    neurodevelopmental disorder when biallelic. A single housekeeping snRNA used by
    essentially every transcript thus yields strikingly tissue-restricted and
    non-overlapping phenotypes. The retinal variants appear to act on snRNP
    biogenesis via tri-snRNP factor binding, echoing the PRPF-gene retinitis
    pigmentosas, which suggests the determinant is which spliceosome sub-process is
    perturbed rather than how much splicing is disturbed overall. Testing that would
    require comparing splicing outcomes across variant classes in the same cell
    system.
  evidence:
  - reference: PMID:41513982
    reference_title: "De novo and inherited dominant variants in U4 and U6 snRNA genes cause retinitis pigmentosa."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "reveals pleiotropy in RNU4-2, where distinct variants underlie neurodevelopmental disorder and retinal degeneration"
    explanation: States the pleiotropy that this question is about.
- discussion_id: renu_bone_disease_intrinsic_versus_disuse
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Increased Bone Turnover and Reduced Bone Mineral Density
  prompt: >-
    Is the skeletal fragility of ReNU syndrome caused by a splicing defect intrinsic
    to bone cells, or is it disuse osteoporosis secondary to hypotonia and limited
    ambulation?
  rationale: >-
    The distinction is not academic: it determines whether bone in ReNU syndrome
    should be managed as a primary skeletal disease with early surveillance and
    anti-resorptive therapy, or as a preventable consequence of immobility. One
    observation currently favours an intrinsic effect — a tibia biopsy showed
    increased numbers of both osteoclasts and osteoblasts with enlarged eroded
    surfaces, an activated high-turnover state, whereas disuse osteoporosis is
    typically low-turnover. But that is a single biopsy in a single patient who was
    also non-ambulatory, so disuse is not excluded, and the authors themselves call
    for the bone pathology to be defined. Resolving it needs histomorphometry in
    several patients stratified by ambulatory status.
  evidence:
  - reference: PMID:40510867
    reference_title: "Assessment and treatment of osteoporosis in a patient with a neurodevelopmental disorder caused by a RNU4-2 pathogenic variant (ReNU syndrome)."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although skeletal abnormalities have been reported in individuals with ReNU syndrome,1,2,4–10 the underlying bone cell pathologies still need to be defined in order to prevent fractures by specific treatment strategies."
    explanation: >-
      The authors state the gap directly and tie it to treatment selection; curated
      PARTIAL because it names the uncertainty rather than resolving it.
- discussion_id: renu_unwired_phenotypes
  kind: CURATION_TODO
  status: OPEN
  attaches_to:
  - phenotypes#Feeding difficulties
  - phenotypes#Short stature
  - phenotypes#Optic nerve hypoplasia
  - phenotypes#Self-injurious behavior
  - phenotypes#Joint hypermobility
  prompt: >-
    Twenty-one of this entry's 34 phenotypes are not attached to a mechanism node.
    Which of them have a real published mechanistic link, and which should stay
    unattached?
  rationale: >-
    The 2026 augmentation wired 13 of 34 phenotypes into the pathograph, in every
    case where a source supported the link. The 21 left unwired fall into groups:
    growth and dysmorphology (short stature, the lip-and-philtrum gestalt, everted
    lower lip); ophthalmological findings (optic nerve hypoplasia, strabismus,
    nystagmus); gastrointestinal and renal features (feeding difficulties,
    constipation, gastro-oesophageal reflux, proteinuria, kidney and urinary tract
    anomalies); skeletal features not covered by the bone-turnover node (scoliosis,
    hip dysplasia, rib morphology, talipes equinovarus, joint hypermobility); and
    the behavioural phenotype (autistic features, short attention span, midline
    stereotypies, sleep disturbance, self-injurious behaviour). The behavioural
    group is the most tempting to attach, since it is obviously neurodevelopmental,
    but the sources list these as features of the syndrome rather than as
    consequences of the brain-growth node, and association is not a mechanism.
    Likewise hypotonia to feeding difficulty, or to scoliosis and hip dysplasia,
    are clinically reasonable chains that no ReNU-specific source states. Inventing
    edges to raise a connectivity metric would make the pathograph assert more than
    the literature does. Each should be wired when a source supports it.
references:
- reference: PMID:42190036
  title: RNU4-2–Related Autosomal Dominant Neurodevelopmental Disorder.
  tags:
  - GeneReviews
  findings: []
notes: >-
  ReNU syndrome was delineated in 2024 by two concurrent large genome-sequencing
  studies (Chen et al., Nature; Greene et al., Nat Med) identifying de novo
  variants in the non-coding U4 snRNA gene RNU4-2 as a frequent cause of
  neurodevelopmental disorder. Because RNU4-2 is a short non-coding RNA not
  covered by exome capture, cases are typically exome-negative and require genome
  sequencing; the recurrent T-loop insertion n.64_65insT accounts for most cases.
  MONDO:0971172 (NEDHAFA; OMIM:620851; Orphanet:686488) is the corresponding
  disease term.


  This entry was substantially augmented in 2026 against literature published
  after the original curation, which changed several claims rather than merely
  adding to them.


  What changed. (1) The pathograph was extended from two molecular nodes to five
  and the phenotypes were wired into it; previously all 25 phenotypes were
  causally unattached, and one causal edge pointed at "Neurodevelopmental
  impairment", a target that existed nowhere in the file and so resolved to
  nothing. (2) ReNU syndrome is now known not to be a loss-of-function disorder:
  biallelic variants elsewhere in RNU4-2 reduce transcript levels and cause a
  separate recessive disease, whose authors state that its mechanism is distinct
  from ReNU's. What the dominant variants actually do is recorded as an open
  knowledge gap rather than asserted. (3) Variant position, not gene identity,
  determines the disease: the same gene yields ReNU syndrome, a recessive
  neurodevelopmental disorder, or non-syndromic retinitis pigmentosa depending on
  which structural element is affected. (4) T-loop and Stem III variants are
  curated as subtypes because they differ materially in severity, Stem III being
  the milder. (5) Inheritance is no longer described as strictly de novo: two
  individuals with 5' Stem-loop variants inherited them from an apparently
  unaffected mother.


  Deliberately not done. Twenty-one of 34 phenotypes remain causally unwired. Chains
  such as hypotonia to feeding difficulty, or to scoliosis and hip dysplasia, are
  clinically plausible but no ReNU-specific source was found asserting them, and
  manufacturing edges to raise a connectivity score would make the pathograph
  claim more than the literature does; this is recorded as a CURATION_TODO
  discussion rather than papered over. No animal-model section was added because
  none was identified in the searched literature - that is an absence of evidence
  found, not a verified absence of models. PMID:41351592 (Genet Med, deep
  phenotyping of 11 individuals) is deliberately uncited: its cache entry is
  content_type "unavailable", so no quotable text exists and citing it would mean
  inventing a snippet.


  Ontology notes. Two NCIT identifiers were rejected during curation after being
  checked against the ontology rather than assumed: NCIT:C17003 resolves to
  Polymerase Chain Reaction, not DNA Sequencing (which is NCIT:C153598), and
  NCIT:C64381 resolves to Regional Anesthesia Procedure, not patient monitoring.
  The surveillance treatment is left with an unbound treatment_term because
  neither NCIT:C15719 (Surveillance) nor NCIT:C15722 (Patient Observation) is
  reachable from NCIT:C25218, and no other suitable clinical-action term was
  found. Attention deficits are bound to HP:0000736
  (Short attention span) rather than HP:0007018 (Attention deficit hyperactivity
  disorder) because the source describes attention deficits, not a formal ADHD
  diagnosis. Kidney and urinary tract anomalies are bound to HP:0000079
  (Abnormality of the urinary system) rather than the broader HP:0000119
  (Abnormality of the genitourinary system): kidney abnormality is a descendant of
  both, but HP:0000119 additionally covers genital anomalies that the GeneReviews
  sentence does not mention, so the narrower term is the most specific one that
  accurately represents the claim.


  Review response. Four blocking items were raised and fixed. The most
  substantive was a claim-evidence mismatch of my own making: the Delayed
  myelination edge had been evidenced by PMID:41951959, a paper about the
  recessive RNU4-2 disorder whose quoted sentence explicitly distinguishes that
  disorder from ReNU syndrome. It could not support the claim, and my own
  explanation had conceded as much - which was the signal it did not belong there.
  It is replaced by the ReNU-specific imaging quote from PMID:38991538, and the
  edge is now DIRECT rather than indirect. The GeneReviews chapter is now tagged
  in a top-level references block, and its CLINICAL CHARACTERISTICS and
  DIAGNOSIS/TESTING sections are mined: six phenotypes it names were absent and
  have been added (midline stereotypies, sleep disturbance, self-injurious
  behaviour, talipes equinovarus, joint hypermobility, kidney and urinary tract
  anomalies), and its diagnostic criterion now backs the diagnosis section.


  Snippet note. Several sources use U+2009 thin spaces between numbers and units
  ("5 years", "2 mg per kg"), so a few snippets match the cache under the
  validator's whitespace normalization rather than byte-for-byte. All 111 were
  independently re-checked under that normalization; nothing here is paraphrased.
📚

References & Deep Research

References

1
PMID:42190036
RNU4-2–Related Autosomal Dominant Neurodevelopmental Disorder.
No top-level findings curated for this source.