Spondyloepimetaphyseal Dysplasia Sponastrime Type

Mendelian MONDO:0010068 Pathograph 26 Show in embeddings browser Spondyloepimetaphyseal dysplasia Skeletal dysplasia

SPONASTRIME dysplasia is an ultra-rare autosomal recessive spondyloepimetaphyseal dysplasia. The name is an acronym for its radiographic triad: SPOndylar abnormalities, NAsal changes, and STRIations of the MEtaphyses. It was delineated as a radiological entity in 1983 and stayed purely descriptive for 36 years, until two independent 2019 exome studies identified biallelic hypomorphic variants in TONSL as the cause. TONSL is the H4K20me0-reading subunit of the TONSL-MMS22L complex. Newly deposited histone H4 is unmethylated at K20, so H4K20me0 marks chromatin as post-replicative, and TONSL reading that mark is what recruits the complex to replicated chromatin to promote homologous-recombination repair of stalled and collapsed replication forks. Hypomorphic TONSL variants therefore produce a genome-instability disease: patient-derived fibroblasts show spontaneous chromosome breakage, fewer damage-induced RAD51 foci, impaired proliferation and increased apoptosis. Two things about this entry are worth stating up front, because they set how far the mechanism can be pushed. First, the variants must be hypomorphic and not null: a Tonsl knockout mouse is embryonic-lethal, so viable disease requires residual function. Second, and this is the substantive gap, the step from a general replication-repair defect to a skeleton-dominated phenotype is not established. Loss of proliferating growth-plate chondrocytes is the standard explanation and it is plausible, but it is an inference; the tissue restriction of a ubiquitously required DNA-repair factor has not been demonstrated. The pathophysiology below marks that boundary rather than smoothing over it. No pathophysiology node declares conforms_to. kb/modules/ does hold replication-stress and genome-instability modules, but every one is scoped to neoplasia: genome_instability_mutation is explicitly the Hanahan and Weinberg enabling characteristic and frames its chain as fuelling clonal evolution, and dna_repair_synthetic_lethality is about therapeutic exploitation of homologous-recombination deficiency. Neither describes what a replication-repair defect does to a developing organism that never becomes a tumour. A non-oncological genome-instability module would have conformers already in the KB, and this entry would be one of them, but creating it is separate work.

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2
Definitions
1
Inheritance
5
Pathophys.
17
Phenotypes
1
Hypotheses
1
Gaps
26
Pathograph
1
Genes
2
Variants
2
Medical Actions
2
Differentials
2
Models
3
References
1
Deep Research
📘

Definitions

2
Molecular confirmation of biallelic TONSL variants
Confirmation is by exome or genome sequencing, or a targeted skeletal-dysplasia panel including TONSL. Both 2019 gene-discovery cohorts reached the gene by whole-exome sequencing of radiologically diagnosed patients, which is still the route: radiology raises the question and sequencing answers it.
DIAGNOSTIC_CRITERIA
Show evidence (1 reference)
PMID:30773278 SUPPORT Human Clinical
"Using whole-exome sequencing (WES), we identified bi-allelic TONSL mutations in 10 of 13 individuals with SPONASTRIME dysplasia."
The confirmatory modality, and a yield figure: 10 of 13 radiologically diagnosed individuals had biallelic TONSL variants, so a negative result does not exclude the clinical diagnosis.
Notes: Three of the thirteen individuals in that cohort had no biallelic TONSL variant identified. Whether those are locus heterogeneity, missed structural variants, or misdiagnosis is not resolved in the source.
Radiological diagnostic criteria for sponastrime dysplasia
Diagnosis rested on radiological criteria for the 36 years before the gene was known, and those criteria remain the entry point: the radiological features are more specific than the clinical ones. Molecular confirmation is by exome or genome sequencing, or a targeted skeletal-dysplasia panel including TONSL.
DIAGNOSTIC_CRITERIA
Show evidence (1 reference)
PMID:9133352 SUPPORT Human Clinical
"The radiological features are more specific than the clinical ones."
The stated basis for anchoring the diagnostic criteria on radiology, from the paper that defined them.
👪

Inheritance

1
Autosomal Recessive HP:0000007
Biallelic hypomorphic variants in TONSL. Complete loss of function is not compatible with viable disease.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:30773278 SUPPORT Human Clinical
"Using whole-exome sequencing (WES), we identified bi-allelic TONSL mutations in 10 of 13 individuals with SPONASTRIME dysplasia."
Establishes biallelic TONSL variants as the cause in the majority of a 13-person cohort.
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Mechanistic Hypotheses

1
Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
proliferative_tissue_depletion_model EMERGING
The standard explanation for why a defect in a ubiquitously required replication-repair factor produces a skeleton-dominated disease: growth-plate chondrocytes in the proliferative zone divide rapidly, so they should bear the brunt of a replication-stress burden, and their loss would impair endochondral ossification. The same argument is applied to two further tissues: lens epithelium for the cataract, and odontoblasts for the shortened dental roots. Every published source states all three as a model rather than as a result. The edges from the cellular defect to those phenotypes opt into this group so a reader can see which part of the chain is proposed rather than demonstrated.
Marked EMERGING rather than CANONICAL because, although it is the only explanation currently offered, it rests on no direct observation of skeletal tissue in this disease. It is not marked ALTERNATIVE because there is no competing model in the literature to be an alternative to.
Pathograph links
Replication Stress with Chromosome Breakage and Loss of Dividing Cells -> Loss of Proliferating Growth-Plate Chondrocytes INDIRECT UNKNOWN INTERMEDIATES
Replication Stress with Chromosome Breakage and Loss of Dividing Cells -> Developmental cataract INDIRECT UNKNOWN INTERMEDIATES Lens epithelium is a proliferative tissue, so the same replication-stress burden is the proposed route to cataract. Same standing as the chondrocyte branch: proposed, not demonstrated.
Replication Stress with Chromosome Breakage and Loss of Dividing Cells -> Short dental root INDIRECT UNKNOWN INTERMEDIATES Odontoblasts are likewise proliferative, and root formation is the part of tooth development that depends on sustained division. Proposed on the same basis and with the same lack of direct evidence.
Loss of Proliferating Growth-Plate Chondrocytes -> Disproportionate short-limb short stature INDIRECT UNKNOWN INTERMEDIATES
Loss of Proliferating Growth-Plate Chondrocytes -> Metaphyseal striations INDIRECT UNKNOWN INTERMEDIATES
Loss of Proliferating Growth-Plate Chondrocytes -> Platyspondyly INDIRECT UNKNOWN INTERMEDIATES
Loss of Proliferating Growth-Plate Chondrocytes -> Scoliosis INDIRECT UNKNOWN INTERMEDIATES Follows from the vertebral involvement, on the same proposed route as platyspondyly.
Loss of Proliferating Growth-Plate Chondrocytes -> Lumbar hyperlordosis INDIRECT UNKNOWN INTERMEDIATES As for scoliosis: a secondary spinal deformity of disturbed vertebral growth, not separately demonstrated.
Loss of Proliferating Growth-Plate Chondrocytes -> Coxa vara INDIRECT UNKNOWN INTERMEDIATES Proximal femoral deformity arising from disturbed endochondral ossification at the growth plate.
Loss of Proliferating Growth-Plate Chondrocytes -> Hip dysplasia INDIRECT UNKNOWN INTERMEDIATES Acetabular and proximal femoral dysplasia on the same endochondral route.
Loss of Proliferating Growth-Plate Chondrocytes -> Cubitus valgus INDIRECT UNKNOWN INTERMEDIATES Elbow deformity from asymmetric growth at the distal humeral physis.
Loss of Proliferating Growth-Plate Chondrocytes -> Delayed skeletal maturation INDIRECT UNKNOWN INTERMEDIATES Delayed appearance of the carpal ossification centres, which depend on the same chondrocyte proliferation.
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Discussions and Knowledge Gaps

1
Why does a defect in a ubiquitously required replication-repair factor produce a phenotype dominated by the skeleton?
KNOWLEDGE GAP chondrocyte_step_unobserved
Attached to
pathophysiology#Loss of Proliferating Growth-Plate Chondrocytes
Everything upstream of this node is measured, and everything downstream is observed in patients, but the node itself is not. No study has examined growth-plate chondrocytes, or any skeletal tissue, in a person or animal with hypomorphic TONSL. The chondrocyte explanation is an inference from which cells divide fastest, and it does not by itself explain why other rapidly dividing tissues, notably the gut epithelium and the bone marrow as a whole, are comparatively spared. The two edges into and out of this node are marked HYPOTHESIZED so the pathograph shows where the evidence stops.
Proposed experiments
Growth-plate analysis in a hypomorphic Tonsl animal
growth_plate_hypomorph_animal
A knock-in animal carrying a patient allele, such as R934W, rather than a null, would survive to skeletal development and allow direct measurement of proliferative-zone chondrocyte number, proliferation index and apoptosis against littermate controls. The existing knock-in mouse is embryonic-lethal, so this requires a new allele rather than reanalysis of an existing model.
Would support
pathophysiology#Loss of Proliferating Growth-Plate Chondrocytes
Would refute
pathophysiology#Loss of Proliferating Growth-Plate Chondrocytes
Supporting outcome
  • Reduced proliferative-zone chondrocyte number with increased apoptosis and disorganised columnar architecture in the growth plate, alongside a skeletal phenotype.
Refuting outcome
  • A skeletal phenotype with normal chondrocyte number, proliferation and apoptosis in the growth plate, which would point to a non-proliferative mechanism such as a matrix or signalling role for TONSL.
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Pathophysiology

5
Hypomorphic Loss of TONSL Function
Biallelic TONSL variants reduce, without abolishing, the function of the Tonsoku-like DNA repair protein. Two structural routes are documented. Ankyrin repeat domain variants impair the H4K20me0 histone-reading function; ubiquitin-like domain variants, including the recurrent R934W and G973R, abolish TONSL homodimerization. R934W removes hydrogen bonds and introduces steric clashes that force a monomeric conformation, and G973R destabilizes a conserved residue in a constrained beta-turn.
TONSL histone H4K20me0 reading and dimerization GO:0042393 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves TONSL histone H4K20me0 reading and dimerization, annotated with histone binding (GO:0042393), qualified as loss of function. GO:0042393 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Animal models
Tonsl knock-in mouse Mouse fails to recapitulate The model does not reproduce SPONASTRIME dysplasia; it dies in utero. That failure is the informative result, because it establishes the hypomorphic requirement the node's name asserts.
Downstream
Failure to Recruit TONSL-MMS22L to Post-Replicative Chromatin
Show evidence (3 references)
PMID:42525765 SUPPORT In Vitro
"We reveal that TONSL homo-dimerizes via its ubiquitin-like domain (UBL), and two recurrent SPONASTRIME dysplasia causative variants (R934W and G973R) abolish this dimerization."
Identifies the dimerization-loss mechanism for the two recurrent variants.
PMID:42525765 SUPPORT In Vitro
"The R934W variant eliminates critical hydrogen bonds and introduces steric clashes, forcing monomeric conformation. G973R destabilizes an evolutionarily conserved residue within a conformationally restricted beta-turn."
The structural detail behind each recurrent variant, from 1.9 angstrom crystal structures.
PMID:30773278 SUPPORT In Vitro
"We show here that cellular defects in dermal fibroblasts from affected individuals are complemented by the expression of wild-type TONSL."
Rescue by wild-type TONSL, which is what establishes that the cellular phenotype is caused by the TONSL variants rather than merely correlated with them.
Failure to Recruit TONSL-MMS22L to Post-Replicative Chromatin
Histone H4 deposited during replication is unmethylated at K20, so H4K20me0 marks chromatin as newly replicated until late G2/M. The TONSL ankyrin repeat domain reads that mark, and that reading is what puts the TONSL-MMS22L complex on replicated chromatin and at challenged forks. Losing the reader, or losing the dimer, removes the complex from the place it is needed.
replication fork processing GO:0031297 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased replication fork processing (GO:0031297). GO:0031297 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Impaired Homologous-Recombination Repair at Stalled Forks
Show evidence (2 references)
PMID:27338793 SUPPORT In Vitro
"We identify the TONSL ankyrin repeat domain (ARD) as a reader of histone H4 tails unmethylated at K20 (H4K20me0), which are specific to new histones incorporated during DNA replication and mark post-replicative chromatin until the G2/M phase of the cell cycle."
Establishes the histone mark and the domain that reads it.
PMID:27338793 SUPPORT In Vitro
"H4K20me0 recognition is required for TONSL-MMS22L binding to chromatin and accumulation at challenged replication forks and DNA lesions."
The necessity claim this node depends on: without the reading step there is no recruitment. Note this is shown with engineered ARD mutants, not with the patient alleles.
Impaired Homologous-Recombination Repair at Stalled Forks
The TONSL-MMS22L complex promotes RAD51 loading and homologous-recombination restart of stalled and collapsed replication forks. With the complex mislocalised or monomeric, RAD51 focus formation after genotoxic stress is reduced and replication-associated double-strand breaks go unrepaired.
patient dermal fibroblast CL:0000057 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves patient dermal fibroblast, annotated with fibroblast (CL:0000057). CL:0000057 is a cell type from the Cell Ontology.
double-strand break repair via homologous recombination GO:0000724 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased double-strand break repair via homologous recombination (GO:0000724). GO:0000724 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Replication Stress with Chromosome Breakage and Loss of Dividing Cells
Show evidence (2 references)
PMID:30773277 SUPPORT In Vitro
"functional studies revealed increased amounts of spontaneous replication fork stalling and chromosomal aberrations, as well as fewer camptothecin (CPT)-induced RAD51 foci in subject-derived cell lines"
Measures the repair defect directly in patient cells: more stalling, more aberrations, less RAD51 loading.
PMID:42525765 SUPPORT In Vitro
"dimerization-deficient variants fail to suppress replication stress-induced DNA damage, show impaired RAD51 foci formation, and exhibit severely compromised survival following genotoxic stress"
Connects the dimerization defect specifically to the repair failure and to reduced survival.
Replication Stress with Chromosome Breakage and Loss of Dividing Cells
The cellular endpoint measured in patients: spontaneous chromosomal breaks on cytogenetic analysis of patient fibroblasts, with flow cytometry showing defective proliferation and enhanced apoptosis. This is a burden that falls on dividing cells, so it predicts a phenotype concentrated in proliferative tissue.
Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
apoptotic process GO:0006915 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased apoptotic process (GO:0006915). GO:0006915 is a biological process from the Gene Ontology. ↑ INCREASED cell population proliferation GO:0008283 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased cell population proliferation (GO:0008283). GO:0008283 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
tonsl-null zebrafish Zebrafish partially recapitulates Organism-level consequences consistent with loss of dividing cells: reduced length, spinal abnormality, neutropenia.
Downstream
Loss of Proliferating Growth-Plate Chondrocytes Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Developmental cataract Lens epithelium is a proliferative tissue, so the same replication-stress burden is the proposed route to cataract. Same standing as the chondrocyte branch: proposed, not demonstrated. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Short dental root Odontoblasts are likewise proliferative, and root formation is the part of tooth development that depends on sustained division. Proposed on the same basis and with the same lack of direct evidence. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Decreased total neutrophil count
Decreased circulating immunoglobulin concentration
Show evidence (1 reference)
PMID:32959051 SUPPORT In Vitro
"cytogenetic analysis and microscopy assays showed that patient-derived fibroblasts exhibited spontaneous chromosomal breaks and flow cytometry demonstrated defects in cell proliferation and enhanced apoptosis"
The three cellular readouts, all in patient-derived cells rather than in an engineered model.
Loss of Proliferating Growth-Plate Chondrocytes
Mechanism confidence: Hypothetical
The proposed skeletal step: chondrocytes in the proliferative zone of the growth plate divide rapidly, so a replication-repair defect should deplete them, impairing endochondral ossification and producing the short stature, metaphyseal striations and age-dependent vertebral changes. This node is explicitly a hypothesis and is marked as such on its incoming edge. No published study has examined growth-plate chondrocytes in this disease. What is established is the cellular defect in fibroblasts and the skeletal phenotype in patients; the chondrocyte step in between is an inference from what kind of cell would be most affected. It is a reasonable inference, and it is also the only place in this chain where a common alternative, that the skeletal phenotype reflects a non-repair function of TONSL, has not been excluded.
Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
growth plate chondrocyte CL:1000217 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves growth plate chondrocyte, annotated with growth plate cartilage chondrocyte (CL:1000217). CL:1000217 is a cell type from the Cell Ontology.
endochondral ossification GO:0001958 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased endochondral ossification (GO:0001958). GO:0001958 is a biological process from the Gene Ontology. ↓ DECREASED chondrocyte proliferation GO:0035988 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased chondrocyte proliferation (GO:0035988). GO:0035988 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Disproportionate short-limb short stature Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Metaphyseal striations Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Platyspondyly Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Scoliosis Follows from the vertebral involvement, on the same proposed route as platyspondyly. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Lumbar hyperlordosis As for scoliosis: a secondary spinal deformity of disturbed vertebral growth, not separately demonstrated. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Coxa vara Proximal femoral deformity arising from disturbed endochondral ossification at the growth plate. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Hip dysplasia Acetabular and proximal femoral dysplasia on the same endochondral route. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Cubitus valgus Elbow deformity from asymmetric growth at the distal humeral physis. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
Delayed skeletal maturation Delayed appearance of the carpal ossification centres, which depend on the same chondrocyte proliferation. Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
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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 Spondyloepimetaphyseal Dysplasia Sponastrime Type 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

17
Blood 2
Decreased total neutrophil count HP:0001875 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased total neutrophil count (HP:0001875). HP:0001875 is a phenotype from the Human Phenotype Ontology.
Show evidence (3 references)
PMID:40794898 SUPPORT Human Clinical
"We reported a 6-year-old boy with characteristic clinical features of SPONASTRIME dysplasia, accompanied by neutropenia."
A genotyped human patient with neutropenia. This replaces the zebrafish evidence as the primary support, since the phenotype is asserted of people.
PMID:40794898 SUPPORT Human Clinical
"Some patients may also exhibit immunological abnormalities such as hypogammaglobulinemia, neutropenia, dental anomalies, cataracts, cubitus valgus, and hip dysplasia."
Places neutropenia among the recognised associated features rather than as a one-off in the reported case.
PMID:30773277 SUPPORT Model Organism
"the discovery of reduced length, spinal abnormalities, reduced numbers of neutrophils, and early lethality in a tonsl-/- zebrafish model both support the hypomorphic nature of the identified TONSL variants"
The zebrafish counterpart, retained and still graded MODEL_ORGANISM. It is corroboration now rather than the sole support.
Decreased circulating immunoglobulin concentration HP:0004313 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Decreased circulating immunoglobulin concentration (HP:0004313). HP:0004313 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:30773277 SUPPORT Human Clinical
"Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
Lists hypogammaglobulinaemia among the reported associated features.
Eye 1
Developmental cataract HP:0000519 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Developmental cataract (HP:0000519). HP:0000519 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:30773277 SUPPORT Human Clinical
"Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
Lists childhood cataracts among the reported associated features.
Head and Neck 4
Midface retrusion VERY_FREQUENT HP:0011800 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Midface retrusion (HP:0011800). HP:0011800 is a phenotype from the Human Phenotype Ontology.
No causal edge is drawn to this phenotype. The midface derives from the nasal capsule and intramembranous bone rather than from a growth plate, so the proliferative-tissue depletion argument that connects the appendicular and vertebral phenotypes does not straightforwardly extend to it. Recorded as unrouted rather than attached on a guess.
Show evidence (1 reference)
PMID:40122363 SUPPORT Human Clinical
"Both subjects had typical features of sponastrime dysplasia with disproportionate short stature, hypertelorism and midface hypoplasia, and variants in the TONSL gene."
Documents midface hypoplasia in genotyped patients.
Depressed nasal bridge VERY_FREQUENT HP:0005280 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Depressed nasal bridge (HP:0005280). HP:0005280 is a phenotype from the Human Phenotype Ontology.
Unrouted for the same reason as midface retrusion: the nasal skeleton is not a growth-plate structure and no published work connects it to the replication-stress mechanism.
Show evidence (1 reference)
PMID:30773277 SUPPORT Human Clinical
"midface hypoplasia with a depressed nasal bridge"
The nasal change the acronym names.
Short dental root HP:0006336 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short dental root (HP:0006336). HP:0006336 is a phenotype from the Human Phenotype Ontology.
Frequency is deliberately unset. The only systematic dental study has two participants, which is not a base for a frequency band.
Show evidence (1 reference)
PMID:40122363 SUPPORT Human Clinical
"Dentin dysplasia type I-like abnormalities were seen in tooth eruption and morphology. Dental roots were shortened in both individuals."
The direct dental observation, in the only study that examined it systematically.
Frontal bossing VERY_FREQUENT HP:0002007 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Frontal bossing (HP:0002007). HP:0002007 is a phenotype from the Human Phenotype Ontology.
Unrouted. Calvarial bone is intramembranous, and whether the prominence is a primary growth disturbance or relative to the hypoplastic midface is not established in the sources.
Show evidence (2 references)
PMID:40794898 SUPPORT Human Clinical
"Key facial features included a prominent forehead (82.2%) and midfacial hypoplasia (100%) (Table 1)."
Prominent forehead is the clinical description of frontal bossing, reported here in 82.2% of a pooled case series, which sets the frequency band.
PMID:40794898 SUPPORT Human Clinical
"Typical physical features of the disease include disproportionate short stature, short limbs, and abnormal facial characteristics (prominent forehead, midface hypoplasia with depressed and short nasal bridge as well as crowded upper jaw teeth)."
Lists prominent forehead among the typical physical features.
Limbs 3
Metaphyseal striations VERY_FREQUENT HP:0031367 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Metaphyseal striations (HP:0031367). HP:0031367 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:32959051 SUPPORT Human Clinical
"SPONASTRIME dysplasia is an ultrarare spondyloepimetaphyseal dysplasia featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses."
Names striated metaphyses among the defining features.
PMID:30773277 SUPPORT Human Clinical
"four subjects (from three families) with short stature of varied severity and spondylometaphyseal dysplasia with or without immunologic and hematologic abnormalities, but no definitive metaphyseal striations at diagnosis"
Documents TONSL-variant patients without striations at diagnosis, which is why this feature is diagnostic but not obligatory.
Coxa vara HP:0002812 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Coxa vara (HP:0002812). HP:0002812 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:30773277 SUPPORT Human Clinical
"Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
Lists coxa vara among the reported associated features.
Cubitus valgus HP:0002967 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cubitus valgus (HP:0002967). HP:0002967 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40794898 SUPPORT Human Clinical
"Some patients may also exhibit immunological abnormalities such as hypogammaglobulinemia, neutropenia, dental anomalies, cataracts, cubitus valgus, and hip dysplasia."
Names cubitus valgus among the recognised associated features.
Musculoskeletal 5
Platyspondyly VERY_FREQUENT HP:0000926 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Platyspondyly (HP:0000926). HP:0000926 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:32959051 SUPPORT Human Clinical
"featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses"
Lists platyspondyly among the defining radiographic features.
Scoliosis FREQUENT 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 (2 references)
PMID:40794898 SUPPORT Human Clinical
"In addition, spinal deformities primarily included scoliosis and excessive lumbar hyperlordosis, occurring in 40.9% and 38.6% of patients, respectively (Table 1)."
Reports scoliosis in 40.9% of patients, which sets the frequency band this record previously lacked.
PMID:30773277 SUPPORT Human Clinical
"Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
Lists scoliosis among the reported associated features.
Lumbar hyperlordosis FREQUENT HP:0002938 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Lumbar hyperlordosis (HP:0002938). HP:0002938 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40794898 SUPPORT Human Clinical
"In addition, spinal deformities primarily included scoliosis and excessive lumbar hyperlordosis, occurring in 40.9% and 38.6% of patients, respectively (Table 1)."
Reports lumbar hyperlordosis directly, in 38.6% of patients, which sets the frequency band.
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:40794898 SUPPORT Human Clinical
"Some patients may also exhibit immunological abnormalities such as hypogammaglobulinemia, neutropenia, dental anomalies, cataracts, cubitus valgus, and hip dysplasia."
Names hip dysplasia among the recognised associated features.
Delayed skeletal maturation HP:0002750 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Delayed skeletal maturation (HP:0002750). HP:0002750 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27149441 SUPPORT Human Clinical
"and delayed ossification of the carpal bones"
Names delayed carpal ossification directly, as the last item in this paper's list of the striking features of the disorder.
Nervous System 1
Chiari malformation HP:0002308 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Chiari type I malformation, annotated with Chiari malformation (HP:0002308). HP:0002308 is a phenotype from the Human Phenotype Ontology.
One published case, in a patient diagnosed clinically rather than molecularly. No frequency is set. Also unrouted in the pathograph: posterior fossa underdevelopment would be an endochondral skull-base mechanism, which is plausible and entirely unevidenced here, so no edge is drawn.
Show evidence (1 reference)
PMID:27149441 SUPPORT Human Clinical
"We describe the presentation of an Arnold Chiari malformation in a patient with a clinical diagnosis of SD."
A single reported case. Recorded because it is the indication for the decompression treatment below, not as an established frequent feature.
Growth 1
Disproportionate short-limb short stature VERY_FREQUENT HP:0008873 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Disproportionate short-limb short stature (HP:0008873). HP:0008873 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:30773277 SUPPORT Human Clinical
"SPONASTRIME dysplasia is an autosomal-recessive spondyloepimetaphyseal dysplasia characterized by spine (spondylar) abnormalities, midface hypoplasia with a depressed nasal bridge, metaphyseal striations, and disproportionate short stature."
Lists disproportionate short stature among the defining features.
PMID:40122363 SUPPORT Human Clinical
"One had a severe phenotype (adult height 91 cm), whereas the other exhibited moderate severity (adult height 135 cm)."
Gives the reported range of adult height and documents the severity spread.
🧬

Genetic Associations

1
TONSL (Causative)
Gene: TONSL hgnc:7801 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TONSL (hgnc:7801). hgnc:7801 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (2 references)
PMID:30773278 SUPPORT Model Organism
"a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL"
The lethality result that constrains viable human alleles to hypomorphs rather than nulls.
PMID:30773277 SUPPORT Human Clinical
"we identified bi-allelic variants in TONSL, which encodes the Tonsoku-like DNA repair protein, in nine subjects (from eight families) with SPONASTRIME dysplasia"
The second, independent 2019 identification of TONSL as the causal gene.
🔬

Variants

2
TONSL p.Arg934Trp Pathogenic
Gene: TONSL hgnc:7801 HUGO Gene Nomenclature Committee (hgnc) Relation: this variant is in this gene This variant is in TONSL (hgnc:7801). hgnc:7801 is a gene from the HUGO Gene Nomenclature Committee. missense
Recurrent missense variant in the ubiquitin-like domain. It abolishes TONSL homodimerization by removing critical hydrogen bonds and introducing steric clashes, forcing the monomeric conformation. Biochemically the wild-type UBL is a dimer while the R934W UBL stays monomeric.
Show evidence (2 references)
PMID:42525765 SUPPORT In Vitro
"The R934W variant eliminates critical hydrogen bonds and introduces steric clashes, forcing monomeric conformation."
The structural mechanism, from 1.9 angstrom crystal structures.
PMID:42525765 SUPPORT In Vitro
"Biochemically, UBLWT exists as dimers while UBLR934W remains monomeric."
The biochemical confirmation that the structural prediction holds in solution.
TONSL p.Gly973Arg Pathogenic
Gene: TONSL hgnc:7801 HUGO Gene Nomenclature Committee (hgnc) Relation: this variant is in this gene This variant is in TONSL (hgnc:7801). hgnc:7801 is a gene from the HUGO Gene Nomenclature Committee. missense
The second recurrent ubiquitin-like-domain variant. It destabilizes an evolutionarily conserved residue within a conformationally restricted beta-turn, and like R934W it abolishes dimerization.
Show evidence (1 reference)
PMID:42525765 SUPPORT In Vitro
"G973R destabilizes an evolutionarily conserved residue within a conformationally restricted beta-turn."
The structural basis for this recurrent allele.
💊

Medical Actions

2
Growth Hormone Therapy
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: somatropin NCIT:C837 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses somatropin (NCIT:C837). NCIT:C837 is a therapeutic agent from the NCI Thesaurus.
Platform: Protein replacement
Recombinant growth hormone has been tried for the short stature. The one published genotyped course, six months in a 6-year-old boy, gave limited improvement. That is consistent with the mechanism: if the growth failure is depletion of proliferating growth-plate chondrocytes by replication stress, then driving the growth axis harder does not address what is limiting, and this treatment is recorded as attempted rather than effective.
Target Phenotypes: Disproportionate short-limb short stature HP:0008873 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Disproportionate short-limb short stature (HP:0008873). HP:0008873 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40794898 SUPPORT Human Clinical
"Six-month growth hormone therapy was administered to the patient after confirmed diagnosis, with limited improvement."
The only reported growth hormone course in a molecularly confirmed patient, and its stated outcome. Cited as evidence that the treatment is used and that the response was limited, not that it works.
Foramen Magnum Decompression
Action: foramen magnum decompressionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is foramen magnum decompression, annotated with Surgical Procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Platform: Surgery
Surgical decompression where a Chiari malformation is present. Reported once in this disease, with resolution of pain. It treats a structural complication and has no bearing on the underlying replication-repair defect.
Target Phenotypes: Chiari type I malformation HP:0002308 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Chiari type I malformation, annotated with Chiari malformation (HP:0002308). HP:0002308 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:27149441 SUPPORT Human Clinical
"The malformation was successfully treated by decompression of the foramen magnum and elevation of the cerebellum, with complete resolution of pain."
The reported procedure and its outcome in the single published case.
🩻

Imaging Findings

2
Metaphyseal striations
Vertical striations of the metaphyses, classically at the distal femur and proximal tibia. One of the three findings the disease acronym is built from.
Xray Diagnostic
Metaphyseal striations HP:0031367 Human Phenotype Ontology (HP)
Show evidence (1 reference)
PMID:32959051 SUPPORT Human Clinical
"SPONASTRIME dysplasia is an ultrarare spondyloepimetaphyseal dysplasia featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses."
Names striated metaphyses among the defining radiographic features.
Platyspondyly
Flattened vertebral bodies. The spondylar element of the acronym, and part of the radiological criteria on which the diagnosis rested before the gene was known.
Xray Diagnostic
Platyspondyly HP:0000926 Human Phenotype Ontology (HP)
Show evidence (1 reference)
PMID:32959051 SUPPORT Human Clinical
"featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses"
Names platyspondyly among the defining radiographic features.
📊

Prevalence

1
Worldwide
Cases In Literature Ultra Rare
Fewer than about 40 cases have been reported since the 1983 delineation. The two 2019 gene-discovery cohorts together account for a large share of them. No incidence or prevalence estimate exists and none is attempted here.
Show evidence (1 reference)
PMID:32959051 SUPPORT Human Clinical
"SPONASTRIME dysplasia is an ultrarare spondyloepimetaphyseal dysplasia"
Supports the ULTRA_RARE band only. The under-40 case count in the notes is a summary across the literature and is not attributed to any single source.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Spondyloepimetaphyseal Dysplasia Sponastrime Type:

Other spondyloepimetaphyseal dysplasias
Overlapping Features SPONASTRIME dysplasia sits within a large group of spondyloepimetaphyseal dysplasias that share short stature with vertebral and metaphyseal changes. What distinguishes it radiographically is the combination of metaphyseal striations with the nasal and midface changes, which is what the acronym encodes and what the 1997 criteria were built to capture.
Distinguishing Features
  • Metaphyseal striations at the distal femur and proximal tibia, together with midface hypoplasia and a depressed nasal bridge. Striations may be absent early, so their absence at first presentation does not exclude the diagnosis.
Show evidence (1 reference)
PMID:9133352 SUPPORT Human Clinical
"Sponastrime dysplasia is a dwarfing autosomal recessive bone dysplasia, the diagnosis of which is based on a combination of clinical and radiological features."
States that the diagnosis rests on a combination of features rather than any single one, which is the basis for distinguishing it within the group.
🐁

Animal Models

2
tonsl-null zebrafish
Null zebrafish showing reduced length, spinal abnormalities, reduced neutrophil numbers and early lethality. It reproduces the direction of both the skeletal and the haematologic branches of the human phenotype.
Species
Zebrafish
Genotype
tonsl-/- null
Publication
PMID:30773277
Pathograph links
Replication Stress with Chromosome Breakage and Loss of Dividing Cells partially recapitulates fidelity: low observes: organism Organism-level consequences consistent with loss of dividing cells: reduced length, spinal abnormality, neutropenia.
Limitations: This is a complete null and the human disease is caused by hypomorphs, so the model sits at a different point on the allelic series from the disease. It is early-lethal, which is precisely the phenotype the human alleles avoid. It is also cited here for organism-level outcomes while the node it attaches to is a cellular claim, so the correspondence is inferential in both directions.
Show evidence (1 reference)
PMID:30773277 SUPPORT Model Organism
"the discovery of reduced length, spinal abnormalities, reduced numbers of neutrophils, and early lethality in a tonsl-/- zebrafish model"
The model's reported phenotype.
Tonsl knock-in mouse
Embryonic-lethal knock-in. Its value to this entry is as a negative result: it shows what happens when residual TONSL function is not preserved, and so bounds which human alleles can cause disease rather than death.
Species
Mouse
Genotype
Tonsl knock-in
Publication
PMID:30773278
Pathograph links
Hypomorphic Loss of TONSL Function fails to recapitulate fidelity: low observes: organism The model does not reproduce SPONASTRIME dysplasia; it dies in utero. That failure is the informative result, because it establishes the hypomorphic requirement the node's name asserts.
Limitations: Embryonic lethality means no skeletal, haematologic or cellular phenotype can be assessed in this model, so it contributes nothing to any downstream node. It should not be cited as support for any mechanism beyond the requirement for residual function.
Show evidence (1 reference)
PMID:30773278 SUPPORT Model Organism
"a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL"
The lethality result, reported by the authors as evidence of TONSL's physiological requirement.
{ }

Source YAML

click to show 
name: Spondyloepimetaphyseal Dysplasia Sponastrime Type
creation_date: "2026-09-09T20:00:00Z"
category: Mendelian
synonyms:
- SPONASTRIME dysplasia
- Sponastrime dysplasia
- spondylar and nasal alterations with striated metaphyses
- short-limb dwarfism with saddle nose, spinal alterations, and metaphyseal striation
description: >-
  SPONASTRIME dysplasia is an ultra-rare autosomal recessive spondyloepimetaphyseal
  dysplasia. The name is an acronym for its radiographic triad: SPOndylar
  abnormalities, NAsal changes, and STRIations of the MEtaphyses. It was delineated
  as a radiological entity in 1983 and stayed purely descriptive for 36 years, until
  two independent 2019 exome studies identified biallelic hypomorphic variants in
  TONSL as the cause.

  TONSL is the H4K20me0-reading subunit of the TONSL-MMS22L complex. Newly deposited
  histone H4 is unmethylated at K20, so H4K20me0 marks chromatin as post-replicative,
  and TONSL reading that mark is what recruits the complex to replicated chromatin to
  promote homologous-recombination repair of stalled and collapsed replication forks.
  Hypomorphic TONSL variants therefore produce a genome-instability disease:
  patient-derived fibroblasts show spontaneous chromosome breakage, fewer
  damage-induced RAD51 foci, impaired proliferation and increased apoptosis.

  Two things about this entry are worth stating up front, because they set how far
  the mechanism can be pushed. First, the variants must be hypomorphic and not null:
  a Tonsl knockout mouse is embryonic-lethal, so viable disease requires residual
  function. Second, and this is the substantive gap, the step from a general
  replication-repair defect to a skeleton-dominated phenotype is not established.
  Loss of proliferating growth-plate chondrocytes is the standard explanation and it
  is plausible, but it is an inference; the tissue restriction of a ubiquitously
  required DNA-repair factor has not been demonstrated. The pathophysiology below
  marks that boundary rather than smoothing over it.

  No pathophysiology node declares conforms_to. kb/modules/ does hold
  replication-stress and genome-instability modules, but every one is scoped to
  neoplasia: genome_instability_mutation is explicitly the Hanahan and Weinberg
  enabling characteristic and frames its chain as fuelling clonal evolution, and
  dna_repair_synthetic_lethality is about therapeutic exploitation of
  homologous-recombination deficiency. Neither describes what a replication-repair
  defect does to a developing organism that never becomes a tumour. A
  non-oncological genome-instability module would have conformers already in the
  KB, and this entry would be one of them, but creating it is separate work.
disease_term:
  preferred_term: spondyloepimetaphyseal dysplasia, sponastrime type
  term:
    id: MONDO:0010068
    label: spondyloepimetaphyseal dysplasia, sponastrime type
parents:
- Spondyloepimetaphyseal dysplasia
- Skeletal dysplasia
inheritance:
- name: Autosomal Recessive
  description: >-
    Biallelic hypomorphic variants in TONSL. Complete loss of function is not
    compatible with viable disease.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:30773278
    reference_title: "Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using whole-exome sequencing (WES), we identified bi-allelic TONSL mutations in 10 of 13 individuals with SPONASTRIME dysplasia."
    explanation: "Establishes biallelic TONSL variants as the cause in the majority of a 13-person cohort."
pathophysiology:
- name: Hypomorphic Loss of TONSL Function
  biological_scale: MOLECULAR
  description: >-
    Biallelic TONSL variants reduce, without abolishing, the function of the
    Tonsoku-like DNA repair protein. Two structural routes are documented. Ankyrin
    repeat domain variants impair the H4K20me0 histone-reading function; ubiquitin-like
    domain variants, including the recurrent R934W and G973R, abolish TONSL
    homodimerization. R934W removes hydrogen bonds and introduces steric clashes that
    force a monomeric conformation, and G973R destabilizes a conserved residue in a
    constrained beta-turn.
  molecular_functions:
  - preferred_term: TONSL histone H4K20me0 reading and dimerization
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0042393
      label: histone binding
  evidence:
  - reference: PMID:42525765
    reference_title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We reveal that TONSL homo-dimerizes via its ubiquitin-like domain (UBL), and two recurrent SPONASTRIME dysplasia causative variants (R934W and G973R) abolish this dimerization."
    explanation: "Identifies the dimerization-loss mechanism for the two recurrent variants."
  - reference: PMID:42525765
    reference_title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The R934W variant eliminates critical hydrogen bonds and introduces steric clashes, forcing monomeric conformation. G973R destabilizes an evolutionarily conserved residue within a conformationally restricted beta-turn."
    explanation: "The structural detail behind each recurrent variant, from 1.9 angstrom crystal structures."
  - reference: PMID:30773278
    reference_title: "Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We show here that cellular defects in dermal fibroblasts from affected individuals are complemented by the expression of wild-type TONSL."
    explanation: >-
      Rescue by wild-type TONSL, which is what establishes that the cellular phenotype
      is caused by the TONSL variants rather than merely correlated with them.
  downstream:
  - target: Failure to Recruit TONSL-MMS22L to Post-Replicative Chromatin
    causal_link_type: DIRECT
- name: Failure to Recruit TONSL-MMS22L to Post-Replicative Chromatin
  biological_scale: MOLECULAR
  description: >-
    Histone H4 deposited during replication is unmethylated at K20, so H4K20me0
    marks chromatin as newly replicated until late G2/M. The TONSL ankyrin repeat
    domain reads that mark, and that reading is what puts the TONSL-MMS22L complex
    on replicated chromatin and at challenged forks. Losing the reader, or losing
    the dimer, removes the complex from the place it is needed.
  biological_processes:
  - preferred_term: replication fork processing
    modifier: DECREASED
    term:
      id: GO:0031297
      label: replication fork processing
  evidence:
  - reference: PMID:27338793
    reference_title: "H4K20me0 marks post-replicative chromatin and recruits the TONSL-MMS22L DNA repair complex."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "We identify the TONSL ankyrin repeat domain (ARD) as a reader of histone H4 tails unmethylated at K20 (H4K20me0), which are specific to new histones incorporated during DNA replication and mark post-replicative chromatin until the G2/M phase of the cell cycle."
    explanation: "Establishes the histone mark and the domain that reads it."
  - reference: PMID:27338793
    reference_title: "H4K20me0 marks post-replicative chromatin and recruits the TONSL-MMS22L DNA repair complex."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "H4K20me0 recognition is required for TONSL-MMS22L binding to chromatin and accumulation at challenged replication forks and DNA lesions."
    explanation: >-
      The necessity claim this node depends on: without the reading step there is no
      recruitment. Note this is shown with engineered ARD mutants, not with the
      patient alleles.
  downstream:
  - target: Impaired Homologous-Recombination Repair at Stalled Forks
    causal_link_type: DIRECT
- name: Impaired Homologous-Recombination Repair at Stalled Forks
  biological_scale: CELLULAR
  description: >-
    The TONSL-MMS22L complex promotes RAD51 loading and homologous-recombination
    restart of stalled and collapsed replication forks. With the complex mislocalised
    or monomeric, RAD51 focus formation after genotoxic stress is reduced and
    replication-associated double-strand breaks go unrepaired.
  biological_processes:
  - preferred_term: double-strand break repair via homologous recombination
    modifier: DECREASED
    term:
      id: GO:0000724
      label: double-strand break repair via homologous recombination
  cell_types:
  - preferred_term: patient dermal fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "functional studies revealed increased amounts of spontaneous replication fork stalling and chromosomal aberrations, as well as fewer camptothecin (CPT)-induced RAD51 foci in subject-derived cell lines"
    explanation: >-
      Measures the repair defect directly in patient cells: more stalling, more
      aberrations, less RAD51 loading.
  - reference: PMID:42525765
    reference_title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "dimerization-deficient variants fail to suppress replication stress-induced DNA damage, show impaired RAD51 foci formation, and exhibit severely compromised survival following genotoxic stress"
    explanation: "Connects the dimerization defect specifically to the repair failure and to reduced survival."
  downstream:
  - target: Replication Stress with Chromosome Breakage and Loss of Dividing Cells
    causal_link_type: DIRECT
- name: Replication Stress with Chromosome Breakage and Loss of Dividing Cells
  biological_scale: CELLULAR
  description: >-
    The cellular endpoint measured in patients: spontaneous chromosomal breaks on
    cytogenetic analysis of patient fibroblasts, with flow cytometry showing defective
    proliferation and enhanced apoptosis. This is a burden that falls on dividing
    cells, so it predicts a phenotype concentrated in proliferative tissue.
  biological_processes:
  - preferred_term: apoptotic process
    modifier: INCREASED
    term:
      id: GO:0006915
      label: apoptotic process
  - preferred_term: cell population proliferation
    modifier: DECREASED
    term:
      id: GO:0008283
      label: cell population proliferation
  evidence:
  - reference: PMID:32959051
    reference_title: "Novel TONSL variants cause SPONASTRIME dysplasia and associate with spontaneous chromosome breaks, defective cell proliferation and apoptosis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "cytogenetic analysis and microscopy assays showed that patient-derived fibroblasts exhibited spontaneous chromosomal breaks and flow cytometry demonstrated defects in cell proliferation and enhanced apoptosis"
    explanation: >-
      The three cellular readouts, all in patient-derived cells rather than in an
      engineered model.
  downstream:
  - target: Loss of Proliferating Growth-Plate Chondrocytes
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Developmental cataract
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Lens epithelium is a proliferative tissue, so the same replication-stress
      burden is the proposed route to cataract. Same standing as the chondrocyte
      branch: proposed, not demonstrated.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Short dental root
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Odontoblasts are likewise proliferative, and root formation is the part of
      tooth development that depends on sustained division. Proposed on the same
      basis and with the same lack of direct evidence.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Decreased total neutrophil count
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: Decreased circulating immunoglobulin concentration
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
- name: Loss of Proliferating Growth-Plate Chondrocytes
  biological_scale: TISSUE
  description: >-
    The proposed skeletal step: chondrocytes in the proliferative zone of the growth
    plate divide rapidly, so a replication-repair defect should deplete them, impairing
    endochondral ossification and producing the short stature, metaphyseal striations
    and age-dependent vertebral changes.

    This node is explicitly a hypothesis and is marked as such on its incoming edge.
    No published study has examined growth-plate chondrocytes in this disease. What is
    established is the cellular defect in fibroblasts and the skeletal phenotype in
    patients; the chondrocyte step in between is an inference from what kind of cell
    would be most affected. It is a reasonable inference, and it is also the only
    place in this chain where a common alternative, that the skeletal phenotype
    reflects a non-repair function of TONSL, has not been excluded.
  cell_types:
  - preferred_term: growth plate chondrocyte
    term:
      id: CL:1000217
      label: growth plate cartilage chondrocyte
  biological_processes:
  - preferred_term: endochondral ossification
    modifier: DECREASED
    term:
      id: GO:0001958
      label: endochondral ossification
  - preferred_term: chondrocyte proliferation
    modifier: DECREASED
    term:
      id: GO:0035988
      label: chondrocyte proliferation
  mechanism_confidence: HYPOTHETICAL
  notes: >-
    Deliberately carries no evidence item. Every source that states this step states
    it as a model rather than as a result, and quoting a source's own speculation as
    if it were a finding is exactly what the evidence policy forbids. The knowledge
    gap is recorded in discussions instead.
  downstream:
  - target: Disproportionate short-limb short stature
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Metaphyseal striations
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Platyspondyly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Scoliosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Follows from the vertebral involvement, on the same proposed route as
      platyspondyly.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Lumbar hyperlordosis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      As for scoliosis: a secondary spinal deformity of disturbed vertebral
      growth, not separately demonstrated.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Coxa vara
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Proximal femoral deformity arising from disturbed endochondral ossification
      at the growth plate.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Hip dysplasia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Acetabular and proximal femoral dysplasia on the same endochondral route.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Cubitus valgus
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Elbow deformity from asymmetric growth at the distal humeral physis.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
  - target: Delayed skeletal maturation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Delayed appearance of the carpal ossification centres, which depend on the
      same chondrocyte proliferation.
    hypothesis_groups:
    - proliferative_tissue_depletion_model
phenotypes:
- category: Skeletal
  name: Disproportionate short-limb short stature
  description: >-
    Severe and near universal. Reported adult heights span 91 to 135 cm, and that
    range within a two-person study is itself a marker of how variable the disorder is.
  phenotype_term:
    preferred_term: Disproportionate short-limb short stature
    term:
      id: HP:0008873
      label: Disproportionate short-limb short stature
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SPONASTRIME dysplasia is an autosomal-recessive spondyloepimetaphyseal dysplasia characterized by spine (spondylar) abnormalities, midface hypoplasia with a depressed nasal bridge, metaphyseal striations, and disproportionate short stature."
    explanation: "Lists disproportionate short stature among the defining features."
  - reference: PMID:40122363
    reference_title: "Dental and craniofacial manifestations in sponastrime dysplasia - An observational study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One had a severe phenotype (adult height 91 cm), whereas the other exhibited moderate severity (adult height 135 cm)."
    explanation: "Gives the reported range of adult height and documents the severity spread."
- category: Skeletal
  name: Metaphyseal striations
  description: >-
    The radiographic feature the acronym is built on, seen at the distal femur and
    proximal tibia. It may be absent early, and its absence at diagnosis is what
    defines the milder end of the TONSL spectrum rather than excluding the diagnosis.
  phenotype_term:
    preferred_term: Metaphyseal striations
    term:
      id: HP:0031367
      label: Metaphyseal striations
  frequency: VERY_FREQUENT
  diagnostic: true
  evidence:
  - reference: PMID:32959051
    reference_title: "Novel TONSL variants cause SPONASTRIME dysplasia and associate with spontaneous chromosome breaks, defective cell proliferation and apoptosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SPONASTRIME dysplasia is an ultrarare spondyloepimetaphyseal dysplasia featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses."
    explanation: "Names striated metaphyses among the defining features."
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "four subjects (from three families) with short stature of varied severity and spondylometaphyseal dysplasia with or without immunologic and hematologic abnormalities, but no definitive metaphyseal striations at diagnosis"
    explanation: >-
      Documents TONSL-variant patients without striations at diagnosis, which is why
      this feature is diagnostic but not obligatory.
- category: Skeletal
  name: Platyspondyly
  phenotype_term:
    preferred_term: Platyspondyly
    term:
      id: HP:0000926
      label: Platyspondyly
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:32959051
    reference_title: "Novel TONSL variants cause SPONASTRIME dysplasia and associate with spontaneous chromosome breaks, defective cell proliferation and apoptosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses"
    explanation: "Lists platyspondyly among the defining radiographic features."
- category: Craniofacial
  name: Midface retrusion
  phenotype_term:
    preferred_term: Midface retrusion
    term:
      id: HP:0011800
      label: Midface retrusion
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:40122363
    reference_title: "Dental and craniofacial manifestations in sponastrime dysplasia - An observational study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both subjects had typical features of sponastrime dysplasia with disproportionate short stature, hypertelorism and midface hypoplasia, and variants in the TONSL gene."
    explanation: "Documents midface hypoplasia in genotyped patients."
  notes: >-
    No causal edge is drawn to this phenotype. The midface derives from the
    nasal capsule and intramembranous bone rather than from a growth plate, so
    the proliferative-tissue depletion argument that connects the appendicular
    and vertebral phenotypes does not straightforwardly extend to it. Recorded
    as unrouted rather than attached on a guess.
- category: Craniofacial
  name: Depressed nasal bridge
  phenotype_term:
    preferred_term: Depressed nasal bridge
    term:
      id: HP:0005280
      label: Depressed nasal bridge
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "midface hypoplasia with a depressed nasal bridge"
    explanation: "The nasal change the acronym names."
  notes: >-
    Unrouted for the same reason as midface retrusion: the nasal skeleton is
    not a growth-plate structure and no published work connects it to the
    replication-stress mechanism.
- category: Dental
  name: Short dental root
  description: >-
    Shortened roots with dentin dysplasia type I-like abnormalities of eruption and
    morphology. Both adults in the only dedicated dental study had short roots, and
    the more severely affected one had already lost several permanent teeth.
  phenotype_term:
    preferred_term: Short dental root
    term:
      id: HP:0006336
      label: Short dental root
  evidence:
  - reference: PMID:40122363
    reference_title: "Dental and craniofacial manifestations in sponastrime dysplasia - An observational study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dentin dysplasia type I-like abnormalities were seen in tooth eruption and morphology. Dental roots were shortened in both individuals."
    explanation: "The direct dental observation, in the only study that examined it systematically."
  notes: >-
    Frequency is deliberately unset. The only systematic dental study has two
    participants, which is not a base for a frequency band.
- category: Hematologic
  name: Decreased total neutrophil count
  phenotype_term:
    preferred_term: Decreased total neutrophil count
    term:
      id: HP:0001875
      label: Decreased total neutrophil count
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We reported a 6-year-old boy with characteristic clinical features of SPONASTRIME dysplasia, accompanied by neutropenia."
    explanation: >-
      A genotyped human patient with neutropenia. This replaces the zebrafish
      evidence as the primary support, since the phenotype is asserted of people.
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some patients may also exhibit immunological abnormalities such as hypogammaglobulinemia, neutropenia, dental anomalies, cataracts, cubitus valgus, and hip dysplasia."
    explanation: >-
      Places neutropenia among the recognised associated features rather than as a
      one-off in the reported case.
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the discovery of reduced length, spinal abnormalities, reduced numbers of neutrophils, and early lethality in a tonsl-/- zebrafish model both support the hypomorphic nature of the identified TONSL variants"
    explanation: >-
      The zebrafish counterpart, retained and still graded MODEL_ORGANISM. It is
      corroboration now rather than the sole support.
- category: Immunologic
  name: Decreased circulating immunoglobulin concentration
  phenotype_term:
    preferred_term: Decreased circulating immunoglobulin concentration
    term:
      id: HP:0004313
      label: Decreased circulating immunoglobulin concentration
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
    explanation: "Lists hypogammaglobulinaemia among the reported associated features."
- category: Ophthalmologic
  name: Developmental cataract
  phenotype_term:
    preferred_term: Developmental cataract
    term:
      id: HP:0000519
      label: Developmental cataract
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
    explanation: "Lists childhood cataracts among the reported associated features."
- category: Skeletal
  name: Scoliosis
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: FREQUENT
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, spinal deformities primarily included scoliosis and excessive lumbar hyperlordosis, occurring in 40.9% and 38.6% of patients, respectively (Table 1)."
    explanation: >-
      Reports scoliosis in 40.9% of patients, which sets the frequency band this
      record previously lacked.
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
    explanation: "Lists scoliosis among the reported associated features."
- category: Skeletal
  name: Coxa vara
  phenotype_term:
    preferred_term: Coxa vara
    term:
      id: HP:0002812
      label: Coxa vara
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported in this disorder."
    explanation: "Lists coxa vara among the reported associated features."
- category: Craniofacial
  name: Frontal bossing
  phenotype_term:
    preferred_term: Frontal bossing
    term:
      id: HP:0002007
      label: Frontal bossing
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Key facial features included a prominent forehead (82.2%) and midfacial hypoplasia (100%) (Table 1)."
    explanation: >-
      Prominent forehead is the clinical description of frontal bossing, reported
      here in 82.2% of a pooled case series, which sets the frequency band.
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Typical physical features of the disease include disproportionate short stature, short limbs, and abnormal facial characteristics (prominent forehead, midface hypoplasia with depressed and short nasal bridge as well as crowded upper jaw teeth)."
    explanation: "Lists prominent forehead among the typical physical features."
  notes: >-
    Unrouted. Calvarial bone is intramembranous, and whether the prominence is
    a primary growth disturbance or relative to the hypoplastic midface is not
    established in the sources.
- category: Skeletal
  name: Lumbar hyperlordosis
  phenotype_term:
    preferred_term: Lumbar hyperlordosis
    term:
      id: HP:0002938
      label: Lumbar hyperlordosis
  frequency: FREQUENT
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In addition, spinal deformities primarily included scoliosis and excessive lumbar hyperlordosis, occurring in 40.9% and 38.6% of patients, respectively (Table 1)."
    explanation: >-
      Reports lumbar hyperlordosis directly, in 38.6% of patients, which sets the
      frequency band.
- category: Skeletal
  name: Cubitus valgus
  phenotype_term:
    preferred_term: Cubitus valgus
    term:
      id: HP:0002967
      label: Cubitus valgus
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some patients may also exhibit immunological abnormalities such as hypogammaglobulinemia, neutropenia, dental anomalies, cataracts, cubitus valgus, and hip dysplasia."
    explanation: "Names cubitus valgus among the recognised associated features."
- category: Skeletal
  name: Hip dysplasia
  phenotype_term:
    preferred_term: Hip dysplasia
    term:
      id: HP:0001385
      label: Hip dysplasia
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some patients may also exhibit immunological abnormalities such as hypogammaglobulinemia, neutropenia, dental anomalies, cataracts, cubitus valgus, and hip dysplasia."
    explanation: "Names hip dysplasia among the recognised associated features."
- category: Skeletal
  name: Delayed skeletal maturation
  phenotype_term:
    preferred_term: Delayed skeletal maturation
    term:
      id: HP:0002750
      label: Delayed skeletal maturation
  description: >
    Delayed ossification of the carpal bones, one of the radiographic features of
    the disorder.
  evidence:
  - reference: PMID:27149441
    reference_title: "Arnold Chiari Malformation With Sponastrime (Spondylar and Nasal Changes, With Striations of the Metaphyses) Dysplasia: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "and delayed ossification of the carpal bones"
    explanation: >-
      Names delayed carpal ossification directly, as the last item in this paper's
      list of the striking features of the disorder.
- category: Neurologic
  name: Chiari malformation
  phenotype_term:
    preferred_term: Chiari type I malformation
    term:
      id: HP:0002308
      label: Chiari malformation
  evidence:
  - reference: PMID:27149441
    reference_title: "Arnold Chiari Malformation With Sponastrime (Spondylar and Nasal Changes, With Striations of the Metaphyses) Dysplasia: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We describe the presentation of an Arnold Chiari malformation in a patient with a clinical diagnosis of SD."
    explanation: >-
      A single reported case. Recorded because it is the indication for the
      decompression treatment below, not as an established frequent feature.
  notes: >-
    One published case, in a patient diagnosed clinically rather than molecularly.
    No frequency is set. Also unrouted in the pathograph: posterior fossa
    underdevelopment would be an endochondral skull-base mechanism, which is
    plausible and entirely unevidenced here, so no edge is drawn.
genetic:
- name: TONSL
  gene_term:
    preferred_term: TONSL
    term:
      id: hgnc:7801
      label: TONSL
  association: Causative
  relationship_type: CAUSATIVE
  notes: >-
    Biallelic hypomorphic variants in TONSL at 8q24.3. The hypomorphic requirement is
    not a description of the observed alleles but a constraint on which alleles can
    produce a live patient: a Tonsl knock-in mouse and a tonsl-null zebrafish are both
    embryonic or early lethal. R934W and G973R recur and act by abolishing
    ubiquitin-like-domain dimerization; ankyrin repeat domain variants act on the
    H4K20me0 reading function instead. TONSL was previously symbolised NFKBIL2, which
    is worth knowing when searching older literature.
  evidence:
  - reference: PMID:30773278
    reference_title: "Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL"
    explanation: >-
      The lethality result that constrains viable human alleles to hypomorphs rather
      than nulls.
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified bi-allelic variants in TONSL, which encodes the Tonsoku-like DNA repair protein, in nine subjects (from eight families) with SPONASTRIME dysplasia"
    explanation: "The second, independent 2019 identification of TONSL as the causal gene."
treatments:
- name: Growth Hormone Therapy
  description: >
    Recombinant growth hormone has been tried for the short stature. The one
    published genotyped course, six months in a 6-year-old boy, gave limited
    improvement. That is consistent with the mechanism: if the growth failure is
    depletion of proliferating growth-plate chondrocytes by replication stress,
    then driving the growth axis harder does not address what is limiting, and
    this treatment is recorded as attempted rather than effective.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: somatropin
      term:
        id: NCIT:C837
        label: Somatropin
  target_phenotypes:
  - preferred_term: Disproportionate short-limb short stature
    term:
      id: HP:0008873
      label: Disproportionate short-limb short stature
  evidence:
  - reference: PMID:40794898
    reference_title: "A case report of SPONASTRIME dysplasia with novel TONSL mutation: genetic analysis, clinical manifestations, and the effect of growth hormone treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six-month growth hormone therapy was administered to the patient after confirmed diagnosis, with limited improvement."
    explanation: >-
      The only reported growth hormone course in a molecularly confirmed patient,
      and its stated outcome. Cited as evidence that the treatment is used and that
      the response was limited, not that it works.
  notes: >-
    n=1, six months, one genotype. This establishes that growth hormone has been
    tried and what happened, and nothing about expected benefit in general.
- name: Foramen Magnum Decompression
  description: >
    Surgical decompression where a Chiari malformation is present. Reported once
    in this disease, with resolution of pain. It treats a structural complication
    and has no bearing on the underlying replication-repair defect.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: foramen magnum decompression
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_phenotypes:
  - preferred_term: Chiari type I malformation
    term:
      id: HP:0002308
      label: Chiari malformation
  evidence:
  - reference: PMID:27149441
    reference_title: "Arnold Chiari Malformation With Sponastrime (Spondylar and Nasal Changes, With Striations of the Metaphyses) Dysplasia: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The malformation was successfully treated by decompression of the foramen magnum and elevation of the cerebellum, with complete resolution of pain."
    explanation: "The reported procedure and its outcome in the single published case."
  notes: >-
    A single case report, in a patient diagnosed clinically rather than
    molecularly. Recorded because a structural complication with a surgical
    remedy is worth knowing about, not as a general management recommendation.
variants:
- name: TONSL p.Arg934Trp
  description: >
    Recurrent missense variant in the ubiquitin-like domain. It abolishes TONSL
    homodimerization by removing critical hydrogen bonds and introducing steric
    clashes, forcing the monomeric conformation. Biochemically the wild-type UBL
    is a dimer while the R934W UBL stays monomeric.
  gene:
    preferred_term: TONSL
    term:
      id: hgnc:7801
      label: TONSL
  clinical_significance: PATHOGENIC
  type: missense
  evidence:
  - reference: PMID:42525765
    reference_title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "The R934W variant eliminates critical hydrogen bonds and introduces steric clashes, forcing monomeric conformation."
    explanation: "The structural mechanism, from 1.9 angstrom crystal structures."
  - reference: PMID:42525765
    reference_title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Biochemically, UBLWT exists as dimers while UBLR934W remains monomeric."
    explanation: "The biochemical confirmation that the structural prediction holds in solution."
- name: TONSL p.Gly973Arg
  description: >
    The second recurrent ubiquitin-like-domain variant. It destabilizes an
    evolutionarily conserved residue within a conformationally restricted
    beta-turn, and like R934W it abolishes dimerization.
  gene:
    preferred_term: TONSL
    term:
      id: hgnc:7801
      label: TONSL
  clinical_significance: PATHOGENIC
  type: missense
  evidence:
  - reference: PMID:42525765
    reference_title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "G973R destabilizes an evolutionarily conserved residue within a conformationally restricted beta-turn."
    explanation: "The structural basis for this recurrent allele."
imaging_findings:
- name: Metaphyseal striations
  modality: XRAY
  description: >
    Vertical striations of the metaphyses, classically at the distal femur and
    proximal tibia. One of the three findings the disease acronym is built from.
  phenotype_term:
    preferred_term: Metaphyseal striations
    term:
      id: HP:0031367
      label: Metaphyseal striations
  diagnostic: true
  evidence:
  - reference: PMID:32959051
    reference_title: "Novel TONSL variants cause SPONASTRIME dysplasia and associate with spontaneous chromosome breaks, defective cell proliferation and apoptosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SPONASTRIME dysplasia is an ultrarare spondyloepimetaphyseal dysplasia featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses."
    explanation: "Names striated metaphyses among the defining radiographic features."
- name: Platyspondyly
  modality: XRAY
  description: >
    Flattened vertebral bodies. The spondylar element of the acronym, and part of
    the radiological criteria on which the diagnosis rested before the gene was
    known.
  phenotype_term:
    preferred_term: Platyspondyly
    term:
      id: HP:0000926
      label: Platyspondyly
  diagnostic: true
  evidence:
  - reference: PMID:32959051
    reference_title: "Novel TONSL variants cause SPONASTRIME dysplasia and associate with spontaneous chromosome breaks, defective cell proliferation and apoptosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "featuring short stature and short limbs, platyspondyly, depressed nasal bridge with midface hypoplasia and striated metaphyses"
    explanation: "Names platyspondyly among the defining radiographic features."
animal_models:
- name: tonsl-null zebrafish
  species: Zebrafish
  genotype: tonsl-/- null
  publication: PMID:30773277
  description: >-
    Null zebrafish showing reduced length, spinal abnormalities, reduced neutrophil
    numbers and early lethality. It reproduces the direction of both the skeletal and
    the haematologic branches of the human phenotype.
  modeled_mechanisms:
  - target: Replication Stress with Chromosome Breakage and Loss of Dividing Cells
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    model_scale: ORGANISM
    description: >-
      Organism-level consequences consistent with loss of dividing cells: reduced
      length, spinal abnormality, neutropenia.
    limitations: >-
      This is a complete null and the human disease is caused by hypomorphs, so the
      model sits at a different point on the allelic series from the disease. It is
      early-lethal, which is precisely the phenotype the human alleles avoid. It is
      also cited here for organism-level outcomes while the node it attaches to is a
      cellular claim, so the correspondence is inferential in both directions.
    evidence:
    - reference: PMID:30773277
      reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "the discovery of reduced length, spinal abnormalities, reduced numbers of neutrophils, and early lethality in a tonsl-/- zebrafish model"
      explanation: "The model's reported phenotype."
- name: Tonsl knock-in mouse
  species: Mouse
  genotype: Tonsl knock-in
  publication: PMID:30773278
  description: >-
    Embryonic-lethal knock-in. Its value to this entry is as a negative result: it
    shows what happens when residual TONSL function is not preserved, and so bounds
    which human alleles can cause disease rather than death.
  modeled_mechanisms:
  - target: Hypomorphic Loss of TONSL Function
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    model_scale: ORGANISM
    description: >-
      The model does not reproduce SPONASTRIME dysplasia; it dies in utero. That
      failure is the informative result, because it establishes the hypomorphic
      requirement the node's name asserts.
    limitations: >-
      Embryonic lethality means no skeletal, haematologic or cellular phenotype can be
      assessed in this model, so it contributes nothing to any downstream node. It
      should not be cited as support for any mechanism beyond the requirement for
      residual function.
    evidence:
    - reference: PMID:30773278
      reference_title: "Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL"
      explanation: "The lethality result, reported by the authors as evidence of TONSL's physiological requirement."
definitions:
- name: Molecular confirmation of biallelic TONSL variants
  definition_type: DIAGNOSTIC_CRITERIA
  derivation_basis: ESTABLISHED_CRITERIA
  description: >-
    Confirmation is by exome or genome sequencing, or a targeted skeletal-dysplasia
    panel including TONSL. Both 2019 gene-discovery cohorts reached the gene by
    whole-exome sequencing of radiologically diagnosed patients, which is still the
    route: radiology raises the question and sequencing answers it.
  evidence:
  - reference: PMID:30773278
    reference_title: "Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Using whole-exome sequencing (WES), we identified bi-allelic TONSL mutations in 10 of 13 individuals with SPONASTRIME dysplasia."
    explanation: >-
      The confirmatory modality, and a yield figure: 10 of 13 radiologically
      diagnosed individuals had biallelic TONSL variants, so a negative result does
      not exclude the clinical diagnosis.
  notes: >-
    Three of the thirteen individuals in that cohort had no biallelic TONSL variant
    identified. Whether those are locus heterogeneity, missed structural variants,
    or misdiagnosis is not resolved in the source.
- name: Radiological diagnostic criteria for sponastrime dysplasia
  definition_type: DIAGNOSTIC_CRITERIA
  derivation_basis: ESTABLISHED_CRITERIA
  description: >-
    Diagnosis rested on radiological criteria for the 36 years before the gene was
    known, and those criteria remain the entry point: the radiological features are
    more specific than the clinical ones. Molecular confirmation is by exome or genome
    sequencing, or a targeted skeletal-dysplasia panel including TONSL.
  evidence:
  - reference: PMID:9133352
    reference_title: "Sponastrime dysplasia: diagnostic criteria based on five new and six previously published cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The radiological features are more specific than the clinical ones."
    explanation: >-
      The stated basis for anchoring the diagnostic criteria on radiology, from the
      paper that defined them.
differential_diagnoses:
- name: Other spondyloepimetaphyseal dysplasias
  description: >
    SPONASTRIME dysplasia sits within a large group of spondyloepimetaphyseal
    dysplasias that share short stature with vertebral and metaphyseal changes.
    What distinguishes it radiographically is the combination of metaphyseal
    striations with the nasal and midface changes, which is what the acronym
    encodes and what the 1997 criteria were built to capture.
  distinguishing_features:
  - >-
    Metaphyseal striations at the distal femur and proximal tibia, together with
    midface hypoplasia and a depressed nasal bridge. Striations may be absent
    early, so their absence at first presentation does not exclude the diagnosis.
  evidence:
  - reference: PMID:9133352
    reference_title: "Sponastrime dysplasia: diagnostic criteria based on five new and six previously published cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sponastrime dysplasia is a dwarfing autosomal recessive bone dysplasia, the diagnosis of which is based on a combination of clinical and radiological features."
    explanation: >-
      States that the diagnosis rests on a combination of features rather than any
      single one, which is the basis for distinguishing it within the group.
- name: TONSL-related skeletal dysplasia without metaphyseal striations
  description: >
    The same gene produces a milder spectrum: short stature of varied severity
    with spondylometaphyseal dysplasia, with or without immunologic and
    hematologic abnormalities, and no definitive metaphyseal striations at
    diagnosis. This is not a separate disease so much as the reason a
    striation-negative radiograph does not rule TONSL out.
  distinguishing_features:
  - >-
    Absence of definitive metaphyseal striations at diagnosis, with the spondylar
    and growth features present. Distinguished molecularly rather than
    radiographically.
  evidence:
  - reference: PMID:30773277
    reference_title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "four subjects (from three families) with short stature of varied severity and spondylometaphyseal dysplasia with or without immunologic and hematologic abnormalities, but no definitive metaphyseal striations at diagnosis"
    explanation: "Describes the striation-negative end of the TONSL spectrum."
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: ULTRA_RARE
  notes: >-
    Fewer than about 40 cases have been reported since the 1983 delineation. The two
    2019 gene-discovery cohorts together account for a large share of them. No
    incidence or prevalence estimate exists and none is attempted here.
  evidence:
  - reference: PMID:32959051
    reference_title: "Novel TONSL variants cause SPONASTRIME dysplasia and associate with spontaneous chromosome breaks, defective cell proliferation and apoptosis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SPONASTRIME dysplasia is an ultrarare spondyloepimetaphyseal dysplasia"
    explanation: >-
      Supports the ULTRA_RARE band only. The under-40 case count in the notes is a
      summary across the literature and is not attributed to any single source.
mechanistic_hypotheses:
- hypothesis_group_id: proliferative_tissue_depletion_model
  hypothesis_label: Depletion of proliferating tissues explains the skeletal, lens and dental phenotypes
  status: EMERGING
  description: >-
    The standard explanation for why a defect in a ubiquitously required
    replication-repair factor produces a skeleton-dominated disease: growth-plate
    chondrocytes in the proliferative zone divide rapidly, so they should bear the
    brunt of a replication-stress burden, and their loss would impair endochondral
    ossification. The same argument is applied to two further tissues: lens
    epithelium for the cataract, and odontoblasts for the shortened dental roots.
    Every published source states all three as a model rather than as a result. The
    edges from the cellular defect to those phenotypes opt into this group so a
    reader can see which part of the chain is proposed rather than demonstrated.
  notes: >-
    Marked EMERGING rather than CANONICAL because, although it is the only
    explanation currently offered, it rests on no direct observation of skeletal
    tissue in this disease. It is not marked ALTERNATIVE because there is no
    competing model in the literature to be an alternative to.
discussions:
- discussion_id: chondrocyte_step_unobserved
  kind: KNOWLEDGE_GAP
  prompt: >-
    Why does a defect in a ubiquitously required replication-repair factor produce a
    phenotype dominated by the skeleton?
  attaches_to:
  - pathophysiology#Loss of Proliferating Growth-Plate Chondrocytes
  rationale: >-
    Everything upstream of this node is measured, and everything downstream is
    observed in patients, but the node itself is not. No study has examined growth-plate
    chondrocytes, or any skeletal tissue, in a person or animal with hypomorphic TONSL.
    The chondrocyte explanation is an inference from which cells divide fastest, and it
    does not by itself explain why other rapidly dividing tissues, notably the gut
    epithelium and the bone marrow as a whole, are comparatively spared. The two edges
    into and out of this node are marked HYPOTHESIZED so the pathograph shows where the
    evidence stops.
  proposed_experiments:
  - experiment_id: growth_plate_hypomorph_animal
    name: Growth-plate analysis in a hypomorphic Tonsl animal
    description: >-
      A knock-in animal carrying a patient allele, such as R934W, rather than a null,
      would survive to skeletal development and allow direct measurement of proliferative-zone
      chondrocyte number, proliferation index and apoptosis against littermate controls.
      The existing knock-in mouse is embryonic-lethal, so this requires a new allele
      rather than reanalysis of an existing model.
    would_support:
    - pathophysiology#Loss of Proliferating Growth-Plate Chondrocytes
    supporting_outcome:
    - >-
      Reduced proliferative-zone chondrocyte number with increased apoptosis and
      disorganised columnar architecture in the growth plate, alongside a skeletal
      phenotype.
    would_refute:
    - pathophysiology#Loss of Proliferating Growth-Plate Chondrocytes
    refuting_outcome:
    - >-
      A skeletal phenotype with normal chondrocyte number, proliferation and apoptosis
      in the growth plate, which would point to a non-proliferative mechanism such as a
      matrix or signalling role for TONSL.
references:
- reference: PMID:30773277
  title: "Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes."
- reference: PMID:30773278
  title: "Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia."
- reference: PMID:42525765
  title: "Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair."
notes: >-
  No GeneReviews chapter exists for this disease. PubMed searches for
  "SPONASTRIME GeneReviews", "TONSL GeneReviews" and "spondyloepimetaphyseal
  dysplasia GeneReviews[TI]" all return zero results, checked 2026-09-10. The
  phenotype baseline for this entry is therefore the two 2019 gene-discovery
  cohorts and the subsequent case reports, not an expert-curated chapter, which
  is worth knowing when judging how settled the clinical description is.
📚

References & Deep Research

References

3
PMID:30773277
Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum of Skeletal Dysplasia Phenotypes.
No top-level findings curated for this source.
PMID:30773278
Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia.
No top-level findings curated for this source.
PMID:42525765
Pathogenic variants in the human TONSL protein associated with SPONASTRIME dysplasia impair protein dimerization and DNA repair.
No top-level findings curated for this source.

Deep Research

1

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

Evaluations and curation notes (1)

Create: SPONASTRIME dysplasia (TONSL) · 2026-09-09T19:41:18Z · View source

New entry for claim #11555 (spondyloepimetaphyseal dysplasia, sponastrime type, MONDO:0010068, TONSL). Preflight found nothing in kb/ mentioning TONSL or sponastrime. Curated from one OpenScientist deep-research report (research/Spondyloepimetaphyseal_Dysplasia_Sponastrime_Type-deep-research-openscientist.md; 15/15 references resolved, term validation needs_review true) plus the primary literature. Five-node pathophysiology chain from hypomorphic TONSL loss through failed H4K20me0-dependent recruitment of TONSL-MMS22L, impaired homologous-recombination repair at stalled forks, and replication stress with chromosome breakage, to loss of proliferating growth-plate chondrocytes. The last node is marked mechanism_confidence HYPOTHETICAL, carries no evidence item, and its incoming and outgoing edges opt into a mechanistic_hypotheses group (chondrocyte_depletion_model, status EMERGING) because no study has examined growth-plate chondrocytes in this disease; the chondrocyte step is an inference from which cells divide fastest. A KNOWLEDGE_GAP discussion with a proposed experiment records what would settle it. The Tonsl knock-in mouse is recorded as FAILS_TO_RECAPITULATE with limitations, since embryonic lethality is what establishes the hypomorphic requirement and simultaneously makes the model uninformative for every downstream node. Six of the report's suggested HP terms were wrong on lookup: HP:0000944 offered for platyspondyly is Abnormal metaphysis morphology, HP:0005789 offered for metaphyseal striations is Generalized osteosclerosis, HP:0001541 offered for delayed carpal ossification is Ascites, HP:0000601 offered for short dental roots is Hypotelorism, HP:0009900 offered for dentin dysplasia is Unilateral deafness, and HP:0001388 for joint laxity is obsolete. The correct terms were looked up and the two unresolvable rows were dropped rather than approximated. TONSL was resolved to hgnc:7801 from the HGNC REST API since it was absent from cache/hgnc/terms.csv. The neutropenia phenotype is graded MODEL_ORGANISM on purpose because the only quotable sentence reports it in the zebrafish model, not in patients. Validated with just validate, just validate-terms, just check-entity-refs, just check-causal-targets, just check-enum-values, just check-duplicate-keys and just validate-disorders.

OpenScientist ▸
Spondyloepimetaphyseal Dysplasia, Sponastrime Type — Comprehensive Disease Report
openscientist-autonomous 12 citations 2026-09-09T19:26:02.620286

Spondyloepimetaphyseal Dysplasia, Sponastrime Type — Comprehensive Disease Report

MONDO: MONDO:0010068 · OMIM: #271510 · Orphanet: ORPHA:93357 · Category: Mendelian (autosomal recessive skeletal dysplasia)

Evidence base: This report is derived from aggregated disease-level literature and case series/reports (there is no population EHR dataset for this ultra-rare disorder). Primary sources are cited by PMID. Evidence source types are flagged: human clinical, in vitro, model organism, computational.

Summary

Spondyloepimetaphyseal dysplasia, Sponastrime type ("SPONASTRIME dysplasia") is an ultra-rare autosomal-recessive skeletal dysplasia caused by biallelic hypomorphic (loss-of-function) variants in TONSL (8q24.3), which encodes the Tonsoku-like DNA-repair protein. The disease name is an acronym derived from its cardinal radiographic features: SPOndylar abnormalities, NAsal changes (midface hypoplasia/depressed nasal bridge), and STRIations of the MEtaphyses. First delineated by Fanconi et al. in 1983, it remained a purely descriptive radiological entity for 36 years until two independent 2019 studies (PMID: 30773278; PMID: 30773277) identified TONSL as the causal gene.

Mechanistically, SPONASTRIME dysplasia is a genome-instability disorder. TONSL is the H4K20me0-reading subunit of the TONSL–MMS22L complex, which is recruited to newly replicated ("post-replicative") chromatin to promote homologous-recombination (HR) repair of stalled and collapsed replication forks. Hypomorphic TONSL variants impair this function, producing replication stress, spontaneous chromosome breakage, defective cell proliferation, and increased apoptosis in dividing cells. The prevailing (partly inferred) model holds that loss of proliferating growth-plate chondrocytes underlies the endochondral-ossification defects that manifest as disproportionate short stature, age-dependent vertebral abnormalities, and metaphyseal striations, with branch effects in hematopoietic and other rapidly dividing tissues (neutropenia, hypogammaglobulinemia).

Clinically, patients present with severe disproportionate short-limb short stature (adult heights ~91–135 cm), platyspondyly with characteristic age-dependent "pear-shaped" vertebral bodies, metaphyseal striations (distal femur/proximal tibia), midface hypoplasia, frontal bossing, joint laxity, and variable childhood cataracts, short dental roots, and immunologic/hematologic abnormalities. Intelligence is normal in most classic cases, though a historically delineated variant subgroup features severe intellectual disability. Diagnosis rests on radiological criteria confirmed by molecular testing (WES/WGS or targeted TONSL/skeletal-dysplasia panels). Only supportive management exists; growth hormone therapy has shown little benefit. Fewer than ~30–40 cases have been reported worldwide.

1. Disease Information

  • Overview: An ultra-rare, congenital, autosomal-recessive spondyloepimetaphyseal dysplasia (SEMD) characterized by disproportionate short stature, distinctive age-dependent vertebral abnormalities, metaphyseal striations, and midface hypoplasia. It is caused by biallelic hypomorphic TONSL variants and is mechanistically a DNA-repair/genome-instability disorder.
  • Key identifiers: MONDO:0010068; OMIM #271510; Orphanet ORPHA:93357; MeSH — indexed under skeletal dysplasias/osteochondrodysplasias; ICD-10 Q77.8 (other osteochondrodysplasia with defects of growth of tubular bones and spine) / ICD-11 LD24 range for osteochondrodysplasias (no unique code).
  • Synonyms / alternative names: SPONASTRIME dysplasia; Sponastrime dysplasia; SPONASTRIME (SPOndylar and NAsal changes with STRIations of the MEtaphyses).
  • Data source: Aggregated disease-level resources (OMIM, Orphanet) and primary case series/reports — not individual EHR data. This reflects the disorder's extreme rarity.

2. Etiology

  • Primary cause (genetic): Biallelic (homozygous or compound-heterozygous) hypomorphic loss-of-function variants in TONSL (8q24.3). This is a monogenic Mendelian disorder (PMID: 30773278; PMID: 30773277). See Finding F001.
  • Genetic risk factors: The causal variants themselves are the risk factor; no separate susceptibility loci or GWAS signals apply (Mendelian disease). Recurrent variants include R934W and G973R. Complete loss of function is embryonic-lethal, so viable disease requires residual (hypomorphic) function.
  • Environmental risk factors: None known. No toxin, radiation, infectious, occupational, dietary, age, or sex association exists — the disorder is fully explained by germline genetics.
  • Protective factors: None identified (genetic or environmental).
  • Gene–environment interactions: None established. Phenotypic variability (F004) is more likely attributable to allelic heterogeneity and putative genetic modifiers than to environmental interactions.

3. Phenotypes

Cardinal and associated features with suggested HPO terms (Burrage 2019 PMID: 30773277; Cooper 2000 PMID: 10797420; Langer 1997 PMID: 9133352; Arponen 2025 PMID: 40122363; see Finding F003).

Phenotype HPO term Type Onset Severity/Frequency
Disproportionate short-limb short stature HP:0004322 Physical/growth Congenital Severe (~ −6 SD); near-universal; adult height 91–135 cm
Platyspondyly / vertebral abnormalities HP:0000944 Clinical sign (radiographic) Childhood, age-dependent Characteristic "pear-shaped" bodies; near-universal
Narrow lumbar interpedicular distances HP:0002650 Radiographic sign Childhood Diagnostic
Metaphyseal striations HP:0005789 Radiographic sign Childhood Distal femur/proximal tibia; cardinal (may be absent early in spectrum cases)
Midface hypoplasia HP:0011800 Physical Congenital/childhood Common
Depressed nasal bridge / short upturned nose HP:0005280 Physical Congenital Common
Frontal bossing HP:0002007 Physical Childhood Common
Lumbar lordosis HP:0002938 Clinical sign Childhood Common
Scoliosis HP:0002650 Clinical sign Childhood Frequent
Coxa vara HP:0002812 Radiographic sign Childhood Frequent
Delayed carpal ossification HP:0001541 Radiographic sign Childhood Frequent
Joint laxity / hypermobility HP:0001388 Physical Childhood Frequent
Childhood cataracts HP:0000519 Ophthalmologic Childhood Subset
Short dental roots / dentin dysplasia I-like HP:0000601 / HP:0009900 Dental Childhood Subset (Arponen 2025)
Hypogammaglobulinemia HP:0004315 Laboratory Variable Subset
Neutropenia HP:0001875 Laboratory Variable Subset (Yao 2025)
Severe intellectual disability / microcephaly HP:0010864 / HP:0000252 Neurodevelopmental Congenital Variant form only
Arnold–Chiari I malformation HP:0007099 Neurologic Childhood Rare (Jeong 2016)
  • Progression: Skeletal features are chronic and progressive relative to peers; vertebral radiographic changes evolve with age. Short stature is fixed.
  • Quality of life: Not formally measured (no EQ-5D/SF-36/PROMIS data). Impact derives chiefly from short stature, orthopedic complications (scoliosis, coxa vara), and, where present, visual impairment (cataracts) or immune susceptibility. Intelligence and life expectancy are typically normal in classic disease.

Direct quote (Burrage 2019): "characterized by spine (spondylar) abnormalities, midface hypoplasia with a depressed nasal bridge, metaphyseal striations, and disproportionate short stature. Scoliosis, coxa vara, childhood cataracts, short dental roots, and hypogammaglobulinemia have also been reported."

4. Genetic / Molecular Information

  • Causal gene: TONSL (Tonsoku-like DNA repair protein), chromosome 8q24.3; NCBI Gene ID 4796; HGNC:11989; UniProt Q96HA7; OMIM gene 604546. Disease OMIM #271510.
  • Pathogenic variants: Biallelic; a mix of missense, frameshift, and nonsense hypomorphic (partial loss-of-function) alleles spanning multiple domains. Recurrent variants R934W and G973R. Novel variants continue to be reported (Yao 2025 PMID: 40794898; Zhu 2024 PMID: 38684304; Micale 2020 PMID: 32959051).
  • Variant classification: Pathogenic/likely pathogenic per ACMG; functional assays (fibroblast complementation, HEK293T expression, dimerization studies) provide PS3-level functional evidence.
  • Allele frequency: Very low/absent in gnomAD (consistent with a rare recessive disorder); no common founder allele established.
  • Origin: Germline; no somatic/mosaic mechanism. Inherited from unaffected heterozygous carrier parents.
  • Functional consequence: Loss of function / hypomorphic. Complete null is embryonic-lethal (mouse), so only residual-function alleles produce viable disease. R934W and G973R abolish UBL-domain dimerization (PMID: 42525765).
  • Modifier genes: None specifically identified, though phenotypic variability implies their existence.
  • Epigenetic information: No disease-specific DNA-methylation/histone-modification signature reported. (Note: TONSL's function is to read the H4K20me0 chromatin mark, but this is its normal biology, not a disease epigenetic lesion.)
  • Chromosomal abnormalities: None as a cause. The cellular consequence, however, is spontaneous chromosome breakage from defective DNA repair (PMID: 32959051).

5. Environmental Information

Not applicable. No environmental factors (toxins, radiation, pollution, occupational exposure), lifestyle factors (smoking, diet, exercise, alcohol), or infectious agents are known to cause or trigger SPONASTRIME dysplasia. It is a purely genetic monogenic disorder.

6. Mechanism / Pathophysiology

Ordered causal chain (initiating lesion → clinical manifestation)

  1. Biallelic hypomorphic TONSL variants reduce protein function by disrupting the ankyrin-repeat domain (ARD; H4K20me0 reading) or the ubiquitin-like (UBL) domain (dimerization) — demonstrated (PMID: 30773278; PMID: 42525765). Leads to →
  2. Impaired recruitment of the TONSL–MMS22L complex to post-replicative chromatin marked by H4K20me0 — demonstrated (PMID: 27338793). Results in →
  3. Compromised homologous-recombination repair of replication-associated double-strand breaks at stalled/collapsed forks — demonstrated (PMID: 30773277; PMID: 27338793). Leads to →
  4. Replication stress and spontaneous chromosome breakage in patient cells — demonstrated (PMID: 32959051). Results in →
  5. Defective cell proliferation and increased apoptosis of dividing cells — demonstrated (PMID: 32959051). Then branches:
  6. 6a (skeletal branch — INFERRED): Loss of proliferating growth-plate chondrocytes → impaired endochondral ossification → disproportionate short stature, metaphyseal striations, age-dependent vertebral dysplasia.
  7. 6b (hematopoietic/immune branch — observed): Depletion/dysfunction of rapidly dividing progenitors → neutropenia and hypogammaglobulinemia.
  8. 6c (other proliferative tissues — observed): lens epithelium (cataracts), odontoblasts (short dental roots/dentin anomalies).
  9. Complete loss of TONSL is embryonic-lethal in mouse, defining the requirement for residual function in viable disease — demonstrated (PMID: 30773278).
 TONSL biallelic hypomorphic variants (ARD or UBL domain)
      │  (loss of H4K20me0 reading / dimerization)
      ▼
 Failure to recruit TONSL–MMS22L to post-replicative chromatin
      │
      ▼
 Defective HR repair of replication-associated DSBs
      │
      ▼
 Replication stress → spontaneous chromosome breaks
      │
      ▼
 Impaired proliferation + increased apoptosis of dividing cells
┌─────────────┼──────────────────┬───────────────┐
▼             ▼                  ▼               ▼
 Growth-plate    Hematopoietic     Lens epithelium   Odontoblasts
 chondrocytes    progenitors       (cataracts)       (short roots)
 (INFERRED)      (neutropenia,
│         hypogammaglob.)
▼
 Impaired endochondral ossification
 → short stature, metaphyseal striations, vertebral dysplasia

Detail by category

  • Molecular pathways: DNA double-strand-break repair via homologous recombination; replication-fork protection/restart. The TONSL–MMS22L complex is the effector. Not a classical signaling cascade (Wnt/MAPK/mTOR) disease.
  • Cellular processes: DNA replication, DNA-damage response, cell-cycle progression, apoptosis (increased), proliferation (decreased) — all demonstrated in patient fibroblasts.
  • Protein dysfunction: Loss/reduction of TONSL function via impaired H4K20me0 reading (ARD variants) or loss of homodimerization (UBL-domain variants R934W/G973R). Hypomorphic, not gain-of-function or dominant-negative.
  • Metabolic changes: None specific reported.
  • Immune involvement: Secondary — hypogammaglobulinemia and neutropenia in a subset, consistent with impaired proliferation of immune/hematopoietic progenitors.
  • Tissue damage mechanism: Genome instability (chromosome breaks) → apoptosis and proliferation failure in dividing cell populations.
  • Molecular profiling / advanced technologies: No transcriptomic, proteomic, metabolomic, single-cell, or CRISPR-screen dataset specific to this disease is available.

Ontology annotations

  • GO biological process: double-strand break repair via homologous recombination (GO:0000724); DNA replication (GO:0006260); chromatin binding (GO:0003682); replication fork processing (GO:0031297); endochondral ossification (GO:0001958, downstream); apoptotic process (GO:0006915).
  • GO cellular component: nucleus (GO:0005634); chromatin (GO:0000785); replication fork (GO:0005657).
  • CL cell types: chondrocyte (CL:0000138), growth-plate chondrocyte, neutrophil (CL:0000775), B cell/plasma cell (CL:0000236 / CL:0000786), lens fiber cell (CL:0011004), odontoblast (CL:0000060).

7. Anatomical Structures Affected

  • Primary organ/system — skeletal: vertebral column (platyspondyly, pear-shaped bodies; UBERON:0001130), metaphyses of long bones (striations; UBERON:0002515), growth plate (UBERON:0006332), hips (coxa vara), carpal bones (delayed ossification), craniofacial skeleton (midface hypoplasia, frontal bossing).
  • Secondary/associated: eye — lens (childhood cataracts; UBERON:0000965); teeth (short roots, dentin dysplasia I-like; UBERON:0001091); immune/hematopoietic system (hypogammaglobulinemia, neutropenia); nervous system (Arnold–Chiari I in a subset; intellectual disability in variant form).
  • Tissue level: cartilage/connective tissue (growth-plate chondrocytes) primarily.
  • Subcellular level: nucleus / chromatin / replication fork (site of TONSL function; GO:0005634, GO:0005657).
  • Lateralization: bilateral / symmetric skeletal involvement.

8. Temporal Development

  • Onset: congenital / early childhood; short stature and radiographic changes evident in infancy/childhood. Onset pattern is chronic/insidious rather than acute.
  • Progression: chronic, lifelong, non-remitting. Vertebral radiographic features are age-dependent and evolve through childhood into adulthood (Cooper 2000 PMID: 10797420). Short stature is fixed/progressive relative to peers.
  • Course: stable-to-progressive; not episodic or relapsing-remitting. Disease duration is lifelong.
  • Critical periods: the childhood window of active growth-plate function is when skeletal manifestations develop; no established intervention alters the trajectory.
  • Remission: none (no spontaneous or treatment-induced remission).

9. Inheritance and Population

  • Epidemiology: Ultra-rare. Orphanet prevalence <1/1,000,000 (ORPHA:93357). By 2000, only ~12–16 patients from 6 families had been reported (Cooper 2000 PMID: 10797420: "To date, 12 patients from 6 families have been reported."); total reported cases remain ~30–40 worldwide. No formal incidence figure.
  • Inheritance: Autosomal recessive; biallelic TONSL variants; both parents are obligate unaffected carriers (Zhu 2024 PMID: 38684304: variants "were inherited from her phenotypically normal parents."). Sibling recurrence risk 25%.
  • Penetrance: Complete for the biallelic genotype (all reported biallelic individuals are affected).
  • Expressivity: Variable — severity of short stature and presence of cataracts, dental, immune, and (in the variant form) neurodevelopmental features differ between patients (F004).
  • Genetic anticipation: Not applicable (not a repeat-expansion disorder).
  • Germline mosaicism / founder effects: None established.
  • Carrier frequency: Not estimated; expected very low given rarity.
  • Population demographics: No ethnic predilection; cases reported across European, Asian, and other populations. Sex ratio approximately equal (recessive). Age distribution: diagnosed in childhood; affected across the lifespan.

10. Diagnostics

  • Clinical/radiological (mainstay): Diagnostic radiological criteria (Langer 1997 PMID: 9133352: "The radiological features are more specific than the clinical ones. We have developed diagnostic radiological criteria based on information from our five cases and from six previously published ones.") — age-dependent vertebral changes (pear-shaped bodies, platyspondyly, narrow lumbar interpedicular distances), metaphyseal striations (distal femur/proximal tibia), delayed carpal ossification. Imaging: skeletal survey / X-ray.
  • Genetic testing (definitive): WES/WGS or targeted TONSL sequencing / skeletal-dysplasia gene panels identifying biallelic TONSL variants. WES has been the diagnostic modality in most recent reports (Chang 2019; Burrage 2019; Zhu 2024 PMID: 38684304). Single-gene TONSL testing/segregation confirms carrier parents. CMA/karyotyping/FISH/mtDNA/repeat-expansion testing are not indicated for diagnosis (the causal lesion is a small variant).
  • Supportive laboratory tests: serum immunoglobulins (hypogammaglobulinemia), CBC (neutropenia); cytogenetic analysis of cultured fibroblasts may reveal spontaneous chromosome breaks (Micale 2020 PMID: 32959051).
  • Biomarkers / omics: No validated circulating biomarker; no metabolomic/proteomic/lipidomic diagnostic signature.
  • Differential diagnosis: spondyloepimetaphyseal dysplasia with joint laxity (leptodactylic/Hall type; Sulko 2008 PMID: 18841068), spondyloepiphyseal dysplasia (SED — a documented initial misdiagnosis in Cooper 2000), other dysplasias with metaphyseal striations (e.g., osteopathia striata), and other short-stature SEMDs.
  • Screening: Not part of newborn screening. Cascade/carrier testing of relatives is possible once familial variants are known.

11. Outcome / Prognosis

  • Survival/mortality: No disease-specific mortality data; life expectancy appears essentially normal with supportive care in classic disease. (Complete TONSL loss is embryonic-lethal, but affected individuals have residual-function alleles.)
  • Morbidity/function: Driven by short stature, orthopedic complications (scoliosis, coxa vara), visual impairment (cataracts) where present, and immune susceptibility (hypogammaglobulinemia/neutropenia) in a subset. In the variant form, intellectual disability is a major morbidity.
  • QoL measures: Not formally quantified (no EQ-5D/SF-36/PROMIS data).
  • Complications: scoliosis, coxa vara, cataract-related visual loss, recurrent infections (if immunodeficient), Chiari I malformation (rare), dental problems.
  • Prognostic factors: genotype (residual function level), presence/absence of the neurodevelopmental variant phenotype, and immune/hematologic involvement. No validated prognostic biomarker.

12. Treatment

No disease-modifying or curative therapy exists. Management is entirely supportive/symptomatic. Suggested NCIT clinical-intervention concepts in brackets.

  • Pharmacotherapy: None disease-specific. Immunoglobulin replacement if clinically significant hypogammaglobulinemia [NCIT: Immunoglobulin Therapy]. Pharmacogenomics: not applicable.
  • Growth hormone: Trialed but largely ineffective (Yao 2025 PMID: 40794898: "Six-month growth hormone therapy was administered to the patient after confirmed diagnosis, with limited improvement.") [NCIT: Recombinant Human Growth Hormone Therapy].
  • Advanced therapeutics (gene/cell/RNA/targeted/immuno): None available or in trials.
  • Surgical/interventional: Orthopedic correction of scoliosis/coxa vara [NCIT: Orthopedic Surgery]; cataract surgery [NCIT: Cataract Extraction]; neurosurgical foramen-magnum decompression for Chiari I (Jeong 2016 PMID: 27149441: "The malformation was successfully treated by decompression of the foramen magnum and elevation of the cerebellum, with complete resolution of pain.") [NCIT: Decompression Surgery].
  • Supportive/rehabilitative: physical/occupational therapy, dental care, ophthalmologic monitoring, audiology as needed.
  • Experimental treatments / trials: None registered.
  • Treatment strategy: multidisciplinary supportive care coordinated by clinical genetics, orthopedics, ophthalmology, immunology, and dentistry.

13. Prevention

  • Primary prevention: Not possible (genetic disorder). The only preventive avenue is genetic counseling — 25% sibling recurrence risk, carrier testing of at-risk relatives, and reproductive options (prenatal diagnosis or preimplantation genetic testing, PGT-M) once the familial TONSL variants are known [NCIT: Genetic Counseling].
  • Secondary prevention: Early ophthalmologic screening for cataracts, immune evaluation, and orthopedic surveillance in diagnosed individuals to detect and treat complications early.
  • Tertiary prevention: Management of complications as above.
  • Immunization / behavioral / public-health / environmental interventions: Not applicable.

14. Other Species / Natural Disease

  • Taxonomy / orthologs: TONSL is evolutionarily conserved. Human TONSL (NCBI Gene 4796); mouse Tonsl (Mus musculus, NCBI Taxon 10090); zebrafish tonsl (Danio rerio, NCBI Taxon 7955).
  • Natural disease in other species: No naturally occurring SPONASTRIME-equivalent disease has been reported in companion animals or wildlife (no OMIA entry). Existing animal models are engineered, not natural.
  • Comparative biology: The DNA-repair function of TONSL is conserved across vertebrates, supporting the mechanistic model; complete loss is lethal in mouse.
  • Transmission / zoonosis: Not applicable (non-communicable genetic disorder).

15. Model Organisms

  • Mouse: A knock-in Tonsl model is embryonic-lethal (Chang 2019 PMID: 30773278: "a knock-in (KI) Tonsl mouse model leads to embryonic lethality, implying the physiological importance of TONSL."). Establishes essentiality; limitation: complete-null models cannot recapitulate the postnatal skeletal phenotype, so hypomorphic/conditional models are needed.
  • Zebrafish: tonsl used alongside complementation assays to support variant pathogenicity (Burrage 2019 PMID: 30773277).
  • In vitro human models: Patient dermal fibroblasts show cellular defects complemented by wild-type TONSL (Chang 2019 PMID: 30773278: "cellular defects in dermal fibroblasts from affected individuals are complemented by the expression of wild-type TONSL") — direct causal proof. Patient fibroblasts show spontaneous chromosome breaks, reduced proliferation, and increased apoptosis (Micale 2020 PMID: 32959051). HEK293T transfection assays confirmed pathogenicity of novel variants (Yao 2025 PMID: 40794898).
  • Phenotype recapitulation: Cellular models faithfully reproduce the genome-instability phenotype; no whole-animal model reproduces the skeletal dysplasia (a key gap).
  • Resources: MGI (mouse Tonsl), ZFIN (zebrafish tonsl).

Mechanistic Model / Interpretation (Synthesis)

SPONASTRIME dysplasia unifies a molecular defect in replication-coupled DNA repair with a tissue-level phenotype of failed skeletal growth. The upstream mechanism is firmly established: TONSL reads the H4K20me0 mark on newly deposited histones to recruit the TONSL–MMS22L HR complex to post-replicative chromatin (PMID: 27338793); hypomorphic variants disrupt either the reader (ARD) or dimerization (UBL) function (PMID: 42525765), impairing repair and causing chromosome breakage, proliferation failure, and apoptosis in patient cells (PMID: 32959051). The downstream tissue specificity — why a general DNA-repair defect produces a predominantly skeletal phenotype — is the central inferential step: growth-plate chondrocytes are among the most proliferative postnatal cell populations, so they may be selectively vulnerable to a proliferation/apoptosis defect, explaining short stature, metaphyseal striations, and vertebral dysplasia, with parallel effects in other high-turnover tissues (marrow, lens, odontoblasts). The requirement for residual function (null is embryonic-lethal) explains why the disease is compatible with life and why severity tracks with allelic residual activity.

Evidence Base

PMID Title (abbreviated) Source type Contribution
30773278 Hypomorphic Mutations in TONSL Cause SPONASTRIME Dysplasia Human clinical + mouse + in vitro Causal gene (10/13); embryonic-lethal KI mouse; fibroblast complementation
30773277 Bi-allelic Variants in TONSL Cause SPONASTRIME Dysplasia and a Spectrum... Human clinical + zebrafish Independent confirmation; broader spectrum; phenotype description
27338793 H4K20me0 marks post-replicative chromatin and recruits the TONSL–MMS22L DNA repair complex In vitro/molecular Defines TONSL molecular function — mechanistic anchor
32959051 Novel TONSL variants... chromosome breaks, defective proliferation and apoptosis In vitro (patient cells) Cellular genome-instability phenotype
42525765 Pathogenic TONSL variants impair protein dimerization and DNA repair Structural/in vitro R934W/G973R abolish UBL dimerization
10797420 SPONASTRIME dysplasia: report of an 11-year-old boy... Human clinical Radiographic/physical phenotype; rarity
9133352 Sponastrime dysplasia: diagnostic criteria... Human clinical Radiological diagnostic criteria
40122363 Dental and craniofacial manifestations in sponastrime dysplasia Human clinical Dental phenotype; height range
7551156 Heterogeneity of SPONASTRIME dysplasia: variant with severe MR Human clinical Phenotypic heterogeneity; severe-ID subgroup
8152878 Sponastrime dysplasia: two siblings with mental retardation Human clinical Variant-form family
40794898 SPONASTRIME dysplasia with novel TONSL mutation; GH treatment Human clinical + in vitro Neutropenia; limited GH efficacy; functional assay
38684304 Child with SPONASTRIME dysplasia, compound heterozygous TONSL Human clinical AR inheritance from carrier parents; WES
27149441 Arnold Chiari Malformation With Sponastrime Dysplasia Human clinical Chiari I complication and surgical management
18841068 SEMD with joint laxity, leptodactylic/Hall type Human clinical Key differential diagnosis
7824362 Sponastrime dysplasia: report on a male patient Human clinical Early case; severe ossification delay

Limitations and Knowledge Gaps

  1. Chondrocyte mechanism is inferred, not proven. The link from genome instability to the specific skeletal phenotype (growth-plate chondrocyte depletion → endochondral ossification defect) has not been directly demonstrated in a bone/chondrocyte model.
  2. No viable whole-animal disease model. Complete Tonsl knockout is embryonic-lethal; tissue-specific or patient-variant knock-in models are required to study skeletal pathogenesis in vivo.
  3. Weak genotype–phenotype correlation. Why some patients have severe intellectual disability/microcephaly and others normal cognition (with overlapping skeletal features) is unresolved; residual-function level and modifier genes are candidate explanations.
  4. Small N (~30–40 cases). Phenotype frequencies (cataracts, immunodeficiency, neutropenia, Chiari I) are qualitative rather than precise percentages.
  5. No natural-history study or registry, so progression rates, adult outcomes, and QoL are not systematically documented.
  6. No therapeutic pipeline. Management is supportive; growth hormone is largely ineffective; no disease-modifying strategy exists.

Proposed Follow-up Experiments / Actions

  1. Conditional / knock-in mouse models carrying patient hypomorphic alleles (e.g., R934W, G973R) or chondrocyte-specific Tonsl deletion to directly test the growth-plate-chondrocyte hypothesis (measure chondrocyte proliferation, apoptosis, endochondral ossification).
  2. Patient-iPSC-derived chondrocytes / cartilage organoids to assay replication stress, γH2AX foci, chromosome breakage, and proliferation/apoptosis in the disease-relevant cell type, with wild-type TONSL rescue.
  3. Structure–function dissection across all reported variants (ARD vs. UBL vs. other domains), correlating residual H4K20me0-reading, dimerization, and HR-repair activity with clinical severity — building a validated functional assay for ACMG PS3 variant classification.
  4. International registry / natural-history study to quantify phenotype frequencies, age-dependent radiographic evolution, immune/hematologic penetrance, and long-term outcomes.
  5. Systematic immunophenotyping and marrow evaluation to characterize the hematologic/immunologic branch and guide surveillance.
  6. Modifier discovery via combined WGS + transcriptomics across the cohort to explain the ID/microcephaly variant subgroup.
  7. gnomAD/large-cohort carrier-frequency estimation for recurrent and predicted-LOF TONSL alleles to inform recurrence risk and possible under-diagnosis.

Report compiled from 8 confirmed findings and 15 reviewed papers across 5 investigation iterations. Evidence types span human clinical, in-vitro human, and model-organism sources. Key mechanistic steps (molecular reader function, HR-repair defect, chromosome breakage, proliferation/apoptosis defect, embryonic lethality of null) are experimentally demonstrated; the chondrocyte-to-skeletal-phenotype link is the principal inferred step.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 15
Resolved 15
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 15
On topic 9
Off topic 0

All extracted references resolved successfully.

Term Validation

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

Outcome Count
Terms checked 42
Resolved 39
Unresolved (possible confabulation) 0
Obsolete 1
Unverifiable 2
Terms whose name was checked 17
Terms named correctly 3
Terms named as a different term 5
Terms whose name is worth a second look 9

Terms the report names something else

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

  • HP:0000944 (1 mention) - the report calls it "Platyspondyly / vertebral abnormalities"; HP calls it Abnormal metaphysis morphology
  • HP:0002650 (2 mentions) - the report calls it "Narrow lumbar interpedicular distances", "Scoliosis"; HP calls it Scoliosis
  • HP:0005789 (1 mention) - the report calls it "Metaphyseal striations"; HP calls it Generalized osteosclerosis
  • HP:0001541 (1 mention) - the report calls it "Delayed carpal ossification"; HP calls it Ascites
  • HP:0004315 (1 mention) - the report calls it "Hypogammaglobulinemia"; HP calls it Decreased circulating IgG concentration

Obsolete terms

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

  • HP:0001388 (obsolete Joint laxity) (1 mention) - replaced by HP:0001382

Terms whose name is worth a second look

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

  • HP:0004322 (1 mention) - the report calls it "Disproportionate short-limb short stature"; HP calls it Short stature
  • HP:0005280 (1 mention) - the report calls it "Depressed nasal bridge / short upturned nose"; HP calls it Depressed nasal bridge, and lists "Depressed bridge of nose" among its other names
  • HP:0002938 (1 mention) - the report calls it "Lumbar lordosis"; HP calls it Lumbar hyperlordosis, and lists "Lumbar lordosis" among its other names
  • HP:0001388 (1 mention) - the report calls it "Joint laxity / hypermobility"; HP calls it obsolete Joint laxity
  • HP:0000519 (1 mention) - the report calls it "Childhood cataracts"; HP calls it Developmental cataract, and lists "Congenital cataracts" among its other names
  • HP:0001875 (1 mention) - the report calls it "Neutropenia"; HP calls it Decreased total neutrophil count, and lists "Neutropenia" among its other names
  • HP:0007099 (1 mention) - the report calls it "Arnold–Chiari I malformation"; HP calls it Chiari type I malformation, and lists "Arnold Chiari type I malformation" among its other names
  • GO:0005634 (2 mentions) - the report calls it "GO cellular component: nucleus"; GO calls it nucleus**, and lists "cell nucleus" among its other names
  • CL:0000138 (1 mention) - the report calls it "CL cell types: chondrocyte"; CL calls it chondrocyte**

Terms named inconsistently

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

  • HP:0002650 - called "Narrow lumbar interpedicular distances", "Scoliosis"

Prefixes with no resolver

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