3-M Syndrome

Mendelian MONDO:0007477 Pathograph 41 Show in embeddings browser Autosomal recessive disease Primordial dwarfism

3-M syndrome is an autosomal recessive primordial growth disorder caused by biallelic loss-of-function variants in any one of three genes - CUL7, OBSL1 or CCDC8 - whose products assemble a single plasma-membrane-localized E3 ubiquitin ligase, the "3-M complex". Growth restriction begins in utero and never catches up, giving severe pre- and postnatal growth deficiency with a final height around five standard deviations below the mean, a distinctive facies (relative macrocephaly, triangular face, midface retrusion, fleshy nasal tip, long philtrum, pointed chin) and characteristic slender long bones and tall vertebral bodies. What sets 3-M apart from most other microcephalic primordial dwarfisms is what is *absent*: intelligence is normal and there is no major organ-system involvement beyond the skeleton, so the disorder is close to a pure growth phenotype. The three genes are mutated in a mutually exclusive manner and produce a clinically near-indistinguishable phenotype, with a severity gradient (CUL7 shortest, CCDC8 mildest) rather than qualitatively different diseases.

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1
Inheritance
6
Pathophys.
27
Phenotypes
41
Pathograph
3
Genes
4
Medical Actions
3
Subtypes
3
Models
11
References
1
Deep Research
🏷

Classifications

Harrison's Part
GENETICS ENVIRONMENT DISEASE
ISDS Skeletal Nosology
primordial dwarfism and slender bones
👪

Inheritance

1
Autosomal recessive HP:0000007
Biallelic (homozygous or compound heterozygous) pathogenic variants in CUL7, OBSL1 or CCDC8; heterozygous carriers are unaffected. Consanguinity and founder alleles are common in reported families.
Autosomal recessive inheritance Penetrance: COMPLETE
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"3-M syndrome is inherited in an autosomal recessive manner"
GeneReviews states the inheritance pattern directly.
◆

Subtypes

3
3-M syndrome type 1 (CUL7-related) MONDO:0010117
CUL7 hgnc:21024 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in CUL7 (hgnc:21024). hgnc:21024 is a gene from the HUGO Gene Nomenclature Committee.
The commonest form, accounting for roughly 70% of molecularly solved cases, and on average the most severe - CUL7-mutated individuals are significantly shorter than those with OBSL1 or CCDC8 variants. Corresponds to ISDS NOS 21-0010 and OMIM 273750.
3-M syndrome type 2 (OBSL1-related) MONDO:0013039
OBSL1 hgnc:29092 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in OBSL1 (hgnc:29092). hgnc:29092 is a gene from the HUGO Gene Nomenclature Committee.
Roughly a quarter of cases. Clinically and radiographically indistinguishable from CUL7-related disease, but with a somewhat greater final height. Corresponds to ISDS NOS 21-0020 and OMIM 612921.
3-M syndrome type 3 (CCDC8-related) MONDO:0013627
CCDC8 hgnc:25367 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in CCDC8 (hgnc:25367). hgnc:25367 is a gene from the HUGO Gene Nomenclature Committee.
The rarest form, under a tenth of cases, and on average the mildest. Corresponds to ISDS NOS 21-0030 and OMIM 614205.
⚙

Pathophysiology

6
Loss of a 3-M Ubiquitin Ligase Complex Component
Biallelic loss-of-function variants in CUL7, OBSL1 or CCDC8 remove one subunit of a single shared E3 ubiquitin ligase. CUL7 is the cullin scaffold, assembling an SCF-like complex with Skp1, FBXW8 and ROC1/RBX1; OBSL1 is a cytoskeletal adaptor required to maintain CUL7 protein levels; CCDC8 is the membrane-anchored partner. Because the three act in one pathway, mutations are mutually exclusive and any one of them produces the same disease.
CUL7 hgnc:21024 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves CUL7 (hgnc:21024). hgnc:21024 is a gene from the HUGO Gene Nomenclature Committee. OBSL1 hgnc:29092 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves OBSL1 (hgnc:29092). hgnc:29092 is a gene from the HUGO Gene Nomenclature Committee. CCDC8 hgnc:25367 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves CCDC8 (hgnc:25367). hgnc:25367 is a gene from the HUGO Gene Nomenclature Committee.
ubiquitin protein ligase activity GO:0061630 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves ubiquitin protein ligase activity (GO:0061630), qualified as loss of function. GO:0061630 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Cul7-RING ubiquitin ligase complex GO:0031467 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves Cul7-RING ubiquitin ligase complex (GO:0031467). GO:0031467 is a cellular component from the Gene Ontology.
Downstream
Failed Membrane Assembly of the 3-M Ligase
Show evidence (4 references)
PMID:16142236 SUPPORT In Vitro
"CUL7 assembles an E3 ubiquitin ligase complex containing Skp1, Fbx29 (also called Fbw8) and ROC1 and promotes ubiquitination"
Establishes CUL7 as the scaffold of an SCF-like E3 ligase, the molecular function lost in 3M1.
PMID:16142236 SUPPORT In Vitro
"the 3-M-associated CUL7 nonsense and missense mutations R1445X and H1464P, respectively, render CUL7 deficient in recruiting ROC1"
Shows patient variants act by preventing assembly of a catalytically competent ligase, not merely by reducing CUL7 abundance.
PMID:19481195 SUPPORT In Vitro
"loss of OBSL1 leads to downregulation of CUL7, implying a role for OBSL1 in the maintenance of CUL7 protein levels"
Explains why an OBSL1 null phenocopies a CUL7 null: OBSL1 loss collapses CUL7 levels, so both converge on the same ligase.
+ 1 more reference
Failed Membrane Assembly of the 3-M Ligase
CCDC8 localizes exclusively to the plasma membrane and is phosphorylated by CK2 and GSK3; that phosphorylation nucleates binding first of OBSL1 and then of CUL7, assembling the ligase at the membrane. Patient-derived mutations in any of the three genes disrupt this membrane localization, and the ligase substrate LL5-beta - a plasma-membrane protein that regulates cell migration - accumulates instead of being degraded.
protein ubiquitination GO:0016567 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased protein ubiquitination (GO:0016567). GO:0016567 is a biological process from the Gene Ontology. ↓ DECREASED
ubiquitin-protein transferase activity GO:0004842 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased ubiquitin-protein transferase activity (GO:0004842). GO:0004842 is a molecular function from the Gene Ontology. ↓ DECREASED
plasma membrane GO:0005886 Gene Ontology (GO) Relation: this pathophysiological event involves this cellular component This pathophysiological event involves plasma membrane (GO:0005886). GO:0005886 is a cellular component from the Gene Ontology.
Downstream
Impaired Cell Migration and Placental Development
Disordered GH-IGF Growth Factor Signalling
Show evidence (2 references)
PMID:31343991 SUPPORT In Vitro
"Phosphorylation of CCDC8 resulted in its binding first with OBSL1, and then CUL7, leading to the membrane assembly of the 3-M E3 ubiquitin ligase complex."
Establishes the ordered, phosphorylation-dependent assembly of the ligase at the plasma membrane.
PMID:31343991 SUPPORT In Vitro
"patient-derived mutations in 3-M genes disrupted membrane localization of the 3-M complex and accumulated LL5"
Shows the disease alleles act by mislocalizing the complex, with failure to turn over its substrate as the readout.
Impaired Cell Migration and Placental Development
Accumulation of the migration regulator LL5-beta impairs cell migration. In mice, deleting Ccdc8 impairs trophoblast migration and placental development, producing intrauterine growth restriction - a mechanism that explains the prenatal onset of the human growth failure rather than merely accompanying it. Cul7-null mice are independently runted with defective trophoblast differentiation and abnormal placental vasculature.
trophoblast cell CL:0000351 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves trophoblast cell (CL:0000351). CL:0000351 is a cell type from the Cell Ontology.
trophoblast cell migration GO:0061450 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased trophoblast cell migration (GO:0061450). GO:0061450 is a biological process from the Gene Ontology. ↓ DECREASED placenta development GO:0001890 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased placenta development (GO:0001890). GO:0001890 is a biological process from the Gene Ontology. ↓ DECREASED
Animal models
Ccdc8 knockout mouse Mouse recapitulates Establishes that deleting a 3-M gene impairs trophoblast migration and placental development and produces intrauterine growth restriction.
Constitutive Cul7 (p185) knockout mouse Mouse partially recapitulates Converges on the same placental trophoblast defect from a different 3-M gene.
Downstream
Severe Pre- and Postnatal Growth Restriction
Intrauterine growth restriction Placental trophoblast migration failure is the prenatal arm of the growth deficit.
Show evidence (3 references)
PMID:31343991 SUPPORT Model Organism
"Deletion of Ccdc8 in mice impaired trophoblast migration and placental development, resulting in intrauterine growth restriction and perinatal lethality."
Directly links loss of a 3-M gene to trophoblast migration failure and intrauterine growth restriction in vivo.
PMID:12904573 SUPPORT Model Organism
"placentas show defects in the differentiation of the trophoblast lineage with an abnormal vascular structure"
An independent 3-M gene knockout converges on the same placental trophoblast defect.
PMID:16142236 SUPPORT INDIRECT Human Clinical
"These results suggest that impaired ubiquitination may have a role in the pathogenesis of intrauterine growth retardation in humans."
The original CUL7 paper proposes, but does not demonstrate, the link from impaired ubiquitination to human intrauterine growth retardation - hence INDIRECT.
Disordered GH-IGF Growth Factor Signalling
3-M children usually have normal peak serum GH and normal or low IGF-1, yet respond poorly to growth hormone - the pattern of resistance rather than deficiency. Patient fibroblasts dysregulate IGF binding protein generation and show gene-specific signalling defects: CUL7-null cells have impaired IGF1-driven AKT activation with normal GH responses, CCDC8-null cells the converse, and OBSL1-null cells are impaired in both. This is the cellular reason growth hormone therapy is only modestly effective.
dermal fibroblast CL:0000057 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves dermal fibroblast, annotated with fibroblast (CL:0000057). CL:0000057 is a cell type from the Cell Ontology.
insulin-like growth factor receptor signaling pathway GO:0048009 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased insulin-like growth factor receptor signaling pathway (GO:0048009). GO:0048009 is a biological process from the Gene Ontology. ↓ DECREASED growth hormone receptor signaling pathway GO:0060396 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased growth hormone receptor signaling pathway (GO:0060396). GO:0060396 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Growth Plate Chondrocyte Proliferation Defect
Show evidence (4 references)
PMID:23018678 SUPPORT In Vitro
"the CUL7(-/-) cells showed impaired IGF1 signalling, CCDC8(-/-) cells showed impaired GH signalling and the OBSL1(-/-) cells showed impairment in both pathways"
Documents the gene-specific split of the signalling defect across the three 3-M genotypes.
PMID:23018678 SUPPORT Human Clinical
"Dysregulation of the GH-IGF-IGF binding protein axis is a feature of 3-M syndrome."
States the axis-level conclusion this node asserts.
PMID:22624670 SUPPORT Human Clinical
"serum GH levels are usually normal and IGF-I normal or low, while growth response to rhGH therapy is variable but typically poor. All these features suggest a degree of resistance in the GH-IGF axis"
Gives the clinical endocrine pattern - resistance, not deficiency - that this node explains.
+ 1 more reference
Growth Plate Chondrocyte Proliferation Defect
Cartilage-specific Cul7 knockout mice have abnormally short and deformed limbs with thickened growth plates, disorderly chondrocyte columns, fewer cells in the proliferative zone and disordered metaphyseal trabecular bone - implicating both chondrocyte proliferation and endochondral ossification as the proximate tissue mechanism of the skeletal growth failure.
growth plate chondrocyte CL:0000138 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves growth plate chondrocyte, annotated with chondrocyte (CL:0000138). CL:0000138 is a cell type from the Cell Ontology.
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 endochondral bone morphogenesis GO:0060350 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased endochondral bone morphogenesis (GO:0060350). GO:0060350 is a biological process from the Gene Ontology. ↓ DECREASED
growth plate cartilage UBERON:0004129 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in growth plate cartilage (UBERON:0004129). UBERON:0004129 is an anatomical location from the Uberon multi-species anatomy ontology.
Animal models
Cartilage-specific Cul7 knockout mouse Mouse recapitulates Reproduces the growth-plate lesion proposed to underlie the human skeletal growth failure.
Downstream
Severe Pre- and Postnatal Growth Restriction
Short thorax Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Short neck Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Pectus deformity Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Pectus excavatum Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Winged scapulae Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Thoracic kyphoscoliosis Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Hyperlordosis Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Spina bifida occulta Axial skeletal patterning defect; grouped with the other vertebral findings, though the specific route from the growth-plate lesion to a neural-arch closure defect is not established.
Clinodactyly of the fifth fingers Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Prominent heels Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Pes planus Growth-plate and skeletal consequence of the chondrocyte proliferation defect.
Dolichocephaly Craniofacial skeletal consequence; the cranial vault is bone whose growth depends on the same proliferation defect.
Midface retrusion Craniofacial skeletal consequence of impaired bone growth.
Pointed chin Craniofacial skeletal consequence of impaired mandibular growth.
Triangular face Craniofacial skeletal consequence; the triangular gestalt follows from relative sparing of the calvarium against midface and mandibular hypoplasia.
Slender long bones A growth-plate proliferation defect that spares periosteal apposition gives long bones that are elongated and narrow with a constricted diaphysis - the characteristic 3-M radiographic appearance.
Tall vertebral bodies The vertebral expression of the same disproportion between longitudinal growth and cross-sectional growth.
Fleshy nasal tip Part of the craniofacial gestalt, grouped with the other midface features; no route from the chondrocyte defect to soft-tissue nasal morphology is established.
Long philtrum Grouped with the other midface features; the route is not established.
Thick eyebrows Grouped with the craniofacial gestalt; no mechanism is established, and this is a soft-tissue rather than skeletal feature.
Joint hypermobility Grouped with the connective-tissue findings. CUL7 and OBSL1 act on cytoskeletal and extracellular-matrix substrates, so a shared connective-tissue basis is plausible, but it has not been shown.
Dislocated hips Downstream of the joint laxity together with the acetabular geometry that follows abnormal endochondral growth.
Hypogonadism in males Reported in males with 3-M; no mechanism links the ubiquitin-ligase defect to gonadal function.
Hypospadias An occasional finding in affected males, grouped as a developmental anomaly with no established route.
Show evidence (2 references)
PMID:38367951 SUPPORT Model Organism
"increased thickness of growth plate, the disorderly arranged chondrocyte columns, decreased number of cells in the proliferation zone"
Documents the growth-plate histology in a cartilage-specific Cul7 knockout.
PMID:38367951 SUPPORT Model Organism
"The knockout of Cul7 gene may affect both the proliferation of chondrocytes and the endochondral osteogenesis"
States the two-process conclusion this node asserts.
Severe Pre- and Postnatal Growth Restriction
The organism-level endpoint: growth restriction that begins before birth and continues without a catch-up phase, giving a final height about five standard deviations below the mean, together with the characteristic facies and skeletal findings, and with intelligence spared.
Downstream
Severe pre- and postnatal growth deficiency The organism-level growth endpoint measured as final height.
Relative macrocephaly Head circumference is spared while body size is not, so the relative macrocephaly is a consequence of the body-growth deficit rather than of head overgrowth.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"3-M syndrome is characterized by severe pre- and postnatal growth deficiency (final height five standard deviations below the mean)"
GeneReviews quantifies the growth endpoint.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for 3-M Syndrome Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

27
Endocrine 1
Hypogonadism in males OCCASIONAL HP:0000135 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypogonadism (males), annotated with Hypogonadism (HP:0000135). HP:0000135 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"Males with 3-M syndrome can have hypogonadism and occasionally hypospadias."
GeneReviews records hypogonadism as a male-restricted feature.
Genitourinary 1
Hypospadias OCCASIONAL HP:0000047 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypospadias (HP:0000047). HP:0000047 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"Males with 3-M syndrome can have hypogonadism and occasionally hypospadias."
GeneReviews records hypospadias as an occasional male finding.
Head and Neck 7
Relative macrocephaly FREQUENT HP:0004482 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Relative macrocephaly (HP:0004482). HP:0004482 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
GeneReviews lists relative macrocephaly among the characteristic facial features.
Triangular face FREQUENT HP:0000325 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Triangular face (HP:0000325). HP:0000325 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
Listed by GeneReviews among the characteristic facial features.
Midface retrusion 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.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
Listed by GeneReviews among the characteristic facial features.
Fleshy nasal tip Bulbous nose HP:0000414 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Fleshy (bulbous) nasal tip, annotated with Bulbous nose (HP:0000414). HP:0000414 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
Listed by GeneReviews among the characteristic facial features.
Long philtrum HP:0000343 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Long philtrum (HP:0000343). HP:0000343 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"thick eyebrows, fleshy nasal tip, long philtrum"
Listed by GeneReviews among the characteristic facial features.
Pointed chin HP:0000307 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pointed chin (HP:0000307). HP:0000307 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"thick vermilion of the upper and low lips, and pointed chin"
Listed by GeneReviews among the characteristic facial features.
Short neck HP:0000470 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short, broad neck, annotated with Short neck (HP:0000470). HP:0000470 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"Additional features of 3-M syndrome include short, broad neck, prominent trapezii"
Listed by GeneReviews among the additional skeletal features.
Limbs 2
Dislocated hips Congenital hip dislocation HP:0001374 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dislocated hips, annotated with Congenital hip dislocation (HP:0001374). HP:0001374 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"clinodactyly of the fifth fingers, generalized or distal joint hypermobility, dislocated hips"
Listed by GeneReviews among the additional skeletal features.
Pes planus HP:0001763 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pes planus (HP:0001763). HP:0001763 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"dislocated hips, prominent heels, and pes planus"
Listed by GeneReviews among the additional skeletal features.
Musculoskeletal 5
Pectus deformity Pectus carinatum HP:0000768 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pectus carinatum (HP:0000768). HP:0000768 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
GeneReviews records pectus carinatum or excavatum; carinatum is bound here and excavatum is curated as its own phenotype.
Pectus excavatum HP:0000767 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Pectus excavatum (HP:0000767). HP:0000767 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
The alternative chest-wall deformity recorded by GeneReviews.
Thoracic kyphoscoliosis HP:0002751 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Thoracic kyphoscoliosis, annotated with Kyphoscoliosis (HP:0002751), qualified as course progressive. HP:0002751 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"thoracic kyphoscoliosis, hyperlordosis, spina bifida occulta"
Listed by GeneReviews among the additional skeletal features.
Hyperlordosis HP:0003307 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyperlordosis (HP:0003307). HP:0003307 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"thoracic kyphoscoliosis, hyperlordosis, spina bifida occulta"
Listed by GeneReviews among the additional skeletal features.
Joint hypermobility HP:0001382 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Generalized or distal joint hypermobility, annotated with Joint hypermobility (HP:0001382). HP:0001382 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"clinodactyly of the fifth fingers, generalized or distal joint hypermobility, dislocated hips"
Listed by GeneReviews among the additional skeletal features.
Growth 2
Severe pre- and postnatal growth deficiency VERY_FREQUENT Short stature HP:0004322 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short stature (HP:0004322). HP:0004322 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"3-M syndrome is characterized by severe pre- and postnatal growth deficiency (final height five standard deviations below the mean)"
The defining feature, quantified by GeneReviews.
Intrauterine growth restriction VERY_FREQUENT Intrauterine growth retardation HP:0001511 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intrauterine growth retardation (HP:0001511). HP:0001511 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:19481195 SUPPORT Human Clinical
"3-M syndrome is an autosomal-recessive primordial growth disorder characterized by significant intrauterine and postnatal growth restriction"
Prenatal onset is what makes 3-M a primordial rather than a postnatal growth disorder.
Other 9
Dolichocephaly HP:0000268 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dolichocephaly (HP:0000268). HP:0000268 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
Listed by GeneReviews among the characteristic facial features.
Thick eyebrows HP:0000574 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Thick eyebrow (HP:0000574). HP:0000574 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"thick eyebrows, fleshy nasal tip, long philtrum"
Listed by GeneReviews among the characteristic facial features.
Slender long bones VERY_FREQUENT HP:0003100 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Slender long bones, annotated with Slender long bone (HP:0003100). HP:0003100 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:11665997 SUPPORT Human Clinical
"3-M syndrome can be differentiated from other types of dwarfism by clinical criteria and by the demonstration of characteristically slender long bones and foreshortened vertebral bodies."
States the radiographic finding and its diagnostic role, which is why this phenotype is flagged diagnostic.
PMID:41437277 SUPPORT Human Clinical
"X-rays of patient 1 at birth: slender and elongated long bones, with diaphyseal constriction and cortical thickening (C); tall vertebrae, with reduced anteroposterior diameter (A, B); thin metacarpals and phalanges (E)."
A contemporary molecularly confirmed case with the detailed radiographic description, including the diaphyseal constriction and cortical thickening this phenotype's description asserts.
Tall vertebral bodies FREQUENT Increased vertebral height HP:0004570 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tall vertebral bodies with reduced anteroposterior diameter, annotated with Increased vertebral height (HP:0004570). HP:0004570 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:41437277 SUPPORT Human Clinical
"3-M syndrome (OMIM# 273750, 612921, 614205) is a rare autosomal recessive disease characterized by severe pre- and post-natal growth retardation, bulbous nose, short thorax, prominent abdomen, slight slender tubular bones, tall vertebral bodies, and normal intelligence."
Names tall vertebral bodies among the defining features of the disorder.
Short thorax HP:0010306 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short thorax (HP:0010306). HP:0010306 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
Listed by GeneReviews among the additional skeletal features.
Winged scapulae Scapular winging HP:0003691 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Winged scapulae, annotated with Scapular winging (HP:0003691). HP:0003691 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
Listed by GeneReviews among the additional skeletal features.
Spina bifida occulta HP:0003298 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Spina bifida occulta (HP:0003298). HP:0003298 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"thoracic kyphoscoliosis, hyperlordosis, spina bifida occulta"
Listed by GeneReviews among the additional skeletal features.
Clinodactyly of the fifth fingers Clinodactyly of the 5th finger HP:0004209 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Clinodactyly of the 5th finger (HP:0004209). HP:0004209 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"clinodactyly of the fifth fingers, generalized or distal joint hypermobility, dislocated hips"
Listed by GeneReviews among the additional skeletal features.
Prominent heels Prominent calcaneus HP:0012428 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Prominent heels, annotated with Prominent calcaneus (HP:0012428). HP:0012428 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"dislocated hips, prominent heels, and pes planus"
Listed by GeneReviews among the additional skeletal features.
🧬

Genetic Associations

3
CUL7
Gene: CUL7 hgnc:21024 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is CUL7 (hgnc:21024). hgnc:21024 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:16142236 SUPPORT Human Clinical
"we first mapped the underlying gene to chromosome 6p21.1 and then identified 25 distinct mutations in the gene cullin 7 (CUL7)"
The mapping and mutation study that established CUL7 as the first 3-M gene.
OBSL1
Gene: OBSL1 hgnc:29092 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is OBSL1 (hgnc:29092). hgnc:29092 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:19481195 SUPPORT Human Clinical
"we subsequently discovered seven distinct null mutations from 10 families within the gene OBSL1"
The locus-mapping and mutation study that established OBSL1 as the second 3-M gene.
CCDC8
Gene: CCDC8 hgnc:25367 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is CCDC8 (hgnc:25367). hgnc:25367 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:21737058 SUPPORT Human Clinical
"Exome sequencing now identifies mutations in CCDC8 as a cause of 3-M syndrome."
The exome study that established CCDC8 as the third 3-M gene.
💊

Medical Actions

4
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.
Referral to a paediatric endocrinologist for consideration of growth hormone in prepubertal children. The response is characteristically modest: 3-M is a GH-resistant rather than GH-deficient state, so the drug is working against a downstream signalling block. Set expectations accordingly rather than escalating dose indefinitely.
Mechanism Target:
Disordered GH-IGF Growth Factor Signalling — Exogenous GH acts on the axis this node describes; the node's signalling block is why the response is limited.
Show evidence (2 references)
PMID:20301654 SUPPORT Human Clinical
"Referral to pediatric endocrinologist for consideration of growth hormone in prepubertal children."
GeneReviews management recommendation.
PMID:23018678 SUPPORT Human Clinical
"3-M patients typically have a modest response to GH treatment, but the mechanism is unknown."
Documents the limited efficacy that qualifies this treatment - PARTIAL because the statement is about a modest rather than an absent response.
Orthopedic Management
Action: orthopedic surgical procedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is orthopedic surgical procedure (NCIT:C16186). NCIT:C16186 is a clinical intervention from the NCI Thesaurus. Ontology label: Orthopedic Surgical Procedure NCIT:C16186
Orthopedic evaluation for hip dislocation, scoliosis and significant joint laxity. Surgical limb lengthening may be an option.
Target Phenotypes: Dislocated hips HP:0001374 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Dislocated hips, annotated with Congenital hip dislocation (HP:0001374). HP:0001374 is a phenotype from the Human Phenotype Ontology. Thoracic kyphoscoliosis HP:0002751 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Thoracic kyphoscoliosis, annotated with Kyphoscoliosis (HP:0002751). HP:0002751 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"Orthopedic evaluation in individuals with hip dislocation, scoliosis, and significant joint laxity is essential."
GeneReviews management recommendation.
Physical and Occupational Therapy
Action: physical therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is physical therapy (NCIT:C15302). NCIT:C15302 is a clinical intervention from the NCI Thesaurus. Ontology label: Physical Therapy NCIT:C15302
Physical therapy, occupational therapy and community child health services to put adaptations for short stature in place and maximize access to the environment.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"Physical therapy, occupational therapy, and community child health services are important in ensuring necessary adaptations for short stature are put in place"
GeneReviews management recommendation.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Autosomal recessive counseling: a 25% recurrence risk for each sib once both parents are known carriers, with carrier testing and prenatal or preimplantation genetic testing possible after the familial variants are identified.
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being a carrier"
GeneReviews genetic counseling guidance.
🔬

Diagnosis

2
Molecular genetic testing of CUL7, OBSL1 and CCDC8 (Biallelic pathogenic variants in CUL7, OBSL1 or CCDC8)
Either arm is sufficient - GeneReviews establishes the diagnosis on the clinical and radiographic picture *and/or* biallelic variants - but in practice the molecular result is what distinguishes 3-M from the other primordial dwarfisms and assigns the subtype. Roughly 70% of solved cases are CUL7.
molecular genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:20301654 SUPPORT Human Clinical
"The diagnosis of 3-M syndrome is established in a proband with prenatal-onset persistent growth deficiency and the characteristic clinical and radiographic features and/or biallelic pathogenic variants in CCDC8, CUL7, or OBSL1 identified by molecular genetic testing."
The GeneReviews diagnostic criterion, naming both the clinical route and the three genes.
Skeletal radiography (Slender long bones with tall vertebral bodies, on a background of prenatal-onset growth deficiency)
The radiographic pair is what historically separated 3-M from other dwarfisms. Timing matters: the findings are clearest in the newborn period and become progressively less distinctive with age, so a normal-looking survey in an older child does not exclude the diagnosis.
clinical and radiographic evaluation NCIT:C124351 NCI Thesaurus (NCIT)
Show evidence (2 references)
PMID:11665997 SUPPORT Human Clinical
"3-M syndrome can be differentiated from other types of dwarfism by clinical criteria and by the demonstration of characteristically slender long bones and foreshortened vertebral bodies."
States the differentiating radiographic findings.
PMID:41437277 SUPPORT Human Clinical
"Our paper highlights how the clinical diagnosis of 3-M is easier in the first months of life, while in older children the phenotype becomes increasingly nuanced."
The age-dependence caveat, which is why molecular testing carries more of the diagnostic weight in an older child.
📊

Prevalence

1
Worldwide
Cases In Literature Not yet documented
No population prevalence or incidence estimate has been published. 3-M syndrome is known from case series rather than population surveillance; ascertainment is clinical and then genotype-confirmed, so published case counts are not a rate. Founder alleles enrich the disorder in specific populations (Yakut, Maghrebian/Tunisian, Turkish).
🐁

Animal Models

3
Cartilage-specific Cul7 knockout mouse
A conditional, cartilage-restricted Cul7 knockout that survives past birth, unlike the constitutive null, and so allows the growth plate to be studied directly.
Species
Mouse
Genotype
Cul7fl/fl;Col2a1-CreERT2
Publication
PMID:38367951
Pathograph links
Growth Plate Chondrocyte Proliferation Defect recapitulates fidelity: moderate Reproduces the growth-plate lesion proposed to underlie the human skeletal growth failure.
Limitations: Cartilage-restricted and tamoxifen-induced, so it models the postnatal skeletal component only; it cannot speak to the placental/prenatal arm of the mechanism, and it addresses CUL7 alone rather than the OBSL1 and CCDC8 genotypes.
Readouts
Proliferative-zone chondrocyte number
Direction: DECREASED
Interpretation: Direct cellular correlate of the proliferation defect this node asserts.
Show evidence (1 reference)
PMID:38367951 SUPPORT Model Organism
"decreased number of cells in the proliferation zone"
The measured reduction in proliferative-zone cellularity.
Limb length
Direction: DECREASED
Interpretation: Organ-level consequence of the growth-plate lesion.
Show evidence (1 reference)
PMID:38367951 SUPPORT Model Organism
"mice had abnormally short and deformed limbs"
The gross skeletal readout of the model.
Show evidence (1 reference)
PMID:38367951 SUPPORT Model Organism
"The knockout of Cul7 gene may affect both the proliferation of chondrocytes and the endochondral osteogenesis"
Supports treating this model as informative for the growth-plate node.
Ccdc8 knockout mouse
Constitutive Ccdc8 deletion, used to test whether loss of a 3-M gene is sufficient to cause intrauterine growth restriction through the placenta.
Species
Mouse
Genotype
Ccdc8 null
Publication
PMID:31343991
Pathograph links
Impaired Cell Migration and Placental Development recapitulates fidelity: moderate Establishes that deleting a 3-M gene impairs trophoblast migration and placental development and produces intrauterine growth restriction.
Limitations: Perinatally lethal in the mouse, whereas human CCDC8-related 3-M is the mildest of the three genotypes and compatible with adult life - so the model overstates severity and cannot address postnatal growth.
Readouts
Fetal growth
Direction: DECREASED
Interpretation: Intrauterine growth restriction as the in vivo endpoint of placental failure.
Show evidence (1 reference)
PMID:31343991 SUPPORT Model Organism
"resulting in intrauterine growth restriction and perinatal lethality"
The measured growth outcome in the knockout.
Show evidence (1 reference)
PMID:31343991 SUPPORT Model Organism
"Deletion of Ccdc8 in mice impaired trophoblast migration and placental development"
Supports treating this model as informative for the placental node.
Constitutive Cul7 (p185) knockout mouse
The original Cul7 null, runted and perinatally lethal from respiratory distress, with defective trophoblast differentiation and abnormal placental vasculature.
Species
Mouse
Genotype
Cul7 (p185) null
Publication
PMID:12904573
Pathograph links
Impaired Cell Migration and Placental Development partially recapitulates fidelity: moderate Converges on the same placental trophoblast defect from a different 3-M gene.
Limitations: Perinatally lethal, so it does not model the viable human disease; the reported emphasis is vascular morphogenesis rather than the migration defect later shown for the 3-M ligase.
Readouts
Placental trophoblast differentiation
Direction: ALTERED
Interpretation: Histological correlate of the placental node.
Show evidence (1 reference)
PMID:12904573 SUPPORT Model Organism
"placentas show defects in the differentiation of the trophoblast lineage with an abnormal vascular structure"
The measured placental phenotype.
Show evidence (1 reference)
PMID:12904573 SUPPORT Model Organism
"embryos are runted and die immediately after birth because of respiratory distress"
Supports treating this model as informative for prenatal growth failure, while its perinatal lethality is the limitation recorded above.
{ }

Source YAML

click to show 
name: 3-M Syndrome
creation_date: "2026-08-27T01:40:00Z"
category: Mendelian
synonyms:
- 3M syndrome
- Miller-McKusick-Malvaux syndrome
- Le Merrer syndrome
- gloomy face syndrome
- Yakut short stature syndrome
- dolichospondylic dysplasia
description: >-
  3-M syndrome is an autosomal recessive primordial growth disorder caused by
  biallelic loss-of-function variants in any one of three genes - CUL7, OBSL1 or
  CCDC8 - whose products assemble a single plasma-membrane-localized E3
  ubiquitin ligase, the "3-M complex". Growth restriction begins in utero and
  never catches up, giving severe pre- and postnatal growth deficiency with a
  final height around five standard deviations below the mean, a distinctive
  facies (relative macrocephaly, triangular face, midface retrusion, fleshy
  nasal tip, long philtrum, pointed chin) and characteristic slender long bones
  and tall vertebral bodies. What sets 3-M apart from most other microcephalic
  primordial dwarfisms is what is *absent*: intelligence is normal and there is
  no major organ-system involvement beyond the skeleton, so the disorder is
  close to a pure growth phenotype. The three genes are mutated in a mutually
  exclusive manner and produce a clinically near-indistinguishable phenotype,
  with a severity gradient (CUL7 shortest, CCDC8 mildest) rather than
  qualitatively different diseases.
disease_term:
  preferred_term: 3-M syndrome
  term:
    id: MONDO:0007477
    label: 3-M syndrome
parents:
- Autosomal recessive disease
- Primordial dwarfism
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  isds_skeletal_category:
  - classification_value: primordial_dwarfism_and_slender_bones
    notes: >-
      ISDS Nosology of Genetic Skeletal Disorders, 2023 revision (Unger et al.,
      PMID:36779427), group 21 "Primordial dwarfism and slender bone
      dysplasias". The nosology splits 3-M by gene into three rows - NOS 21-0010
      "3-M syndrome, CUL7-related" (OMIM 273750), NOS 21-0020 "3-M syndrome,
      OBSL1-related" (612921) and NOS 21-0030 "3-M syndrome, CCDC8-related"
      (614205) - all in this one group. This entry lumps all three, matching how
      the literature treats them: the genes are mutated mutually exclusively,
      act in one pathway, and give a phenotype that differs in severity rather
      than in kind. The three nosology rows are curated here as `has_subtypes`
      so the split remains queryable.
has_subtypes:
- name: 3M1
  subtype_term:
    preferred_term: 3M syndrome 1
    term:
      id: MONDO:0010117
      label: 3M syndrome 1
  display_name: 3-M syndrome type 1 (CUL7-related)
  description: >-
    The commonest form, accounting for roughly 70% of molecularly solved cases,
    and on average the most severe - CUL7-mutated individuals are significantly
    shorter than those with OBSL1 or CCDC8 variants. Corresponds to
    ISDS NOS 21-0010 and OMIM 273750.
  genes:
  - preferred_term: CUL7
    term:
      id: hgnc:21024
      label: CUL7
- name: 3M2
  subtype_term:
    preferred_term: 3M syndrome 2
    term:
      id: MONDO:0013039
      label: 3M syndrome 2
  display_name: 3-M syndrome type 2 (OBSL1-related)
  description: >-
    Roughly a quarter of cases. Clinically and radiographically
    indistinguishable from CUL7-related disease, but with a somewhat greater
    final height. Corresponds to ISDS NOS 21-0020 and OMIM 612921.
  genes:
  - preferred_term: OBSL1
    term:
      id: hgnc:29092
      label: OBSL1
- name: 3M3
  subtype_term:
    preferred_term: 3M syndrome 3
    term:
      id: MONDO:0013627
      label: 3M syndrome 3
  display_name: 3-M syndrome type 3 (CCDC8-related)
  description: >-
    The rarest form, under a tenth of cases, and on average the mildest.
    Corresponds to ISDS NOS 21-0030 and OMIM 614205.
  genes:
  - preferred_term: CCDC8
    term:
      id: hgnc:25367
      label: CCDC8
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >-
    No population prevalence or incidence estimate has been published. 3-M
    syndrome is known from case series rather than population surveillance;
    ascertainment is clinical and then genotype-confirmed, so published case
    counts are not a rate. Founder alleles enrich the disorder in specific
    populations (Yakut, Maghrebian/Tunisian, Turkish).
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  penetrance: COMPLETE
  description: >-
    Biallelic (homozygous or compound heterozygous) pathogenic variants in
    CUL7, OBSL1 or CCDC8; heterozygous carriers are unaffected. Consanguinity
    and founder alleles are common in reported families.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome is inherited in an autosomal recessive manner"
    explanation: >-
      GeneReviews states the inheritance pattern directly.
genetic:
- name: CUL7
  gene_term:
    preferred_term: CUL7
    term:
      id: hgnc:21024
      label: CUL7
  relationship_type: CAUSATIVE
  subtype: 3M1
  notes: >-
    CUL7 (6p21.1) encodes a large cullin-family scaffold that assembles an
    SCF-like E3 ubiquitin ligase with Skp1, FBXW8 (Fbx29/Fbw8) and ROC1/RBX1.
    Nonsense, frameshift and canonical splice variants predominate; missense
    variants cluster in the region required to recruit ROC1.
  case_fractions:
  - population: 3-M families with an identified mutation (Hanson et al. cohort)
    case_fraction_percent: 69.0
    notes: Most frequently mutated of the three 3-M genes.
    evidence:
    - reference: PMID:23018678
      reference_title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The prevalence of 3-M mutations was 69% CUL7, 23% OBSL1 and 8% CCDC8."
      explanation: >-
        Quantifies the CUL7 share of molecularly solved 3-M cases in this
        cohort.
  evidence:
  - reference: PMID:16142236
    reference_title: "Identification of mutations in CUL7 in 3-M syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we first mapped the underlying gene to chromosome 6p21.1 and then identified 25 distinct mutations in the gene cullin 7 (CUL7)"
    explanation: >-
      The mapping and mutation study that established CUL7 as the first 3-M
      gene.
- name: OBSL1
  gene_term:
    preferred_term: OBSL1
    term:
      id: hgnc:29092
      label: OBSL1
  relationship_type: CAUSATIVE
  subtype: 3M2
  notes: >-
    OBSL1 (2q35) encodes a putative cytoskeletal adaptor of the obscurin
    family that localizes to the nuclear envelope. Reported disease alleles are
    null variants.
  case_fractions:
  - population: 3-M families with an identified mutation (Hanson et al. cohort)
    case_fraction_percent: 23.0
    evidence:
    - reference: PMID:23018678
      reference_title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The prevalence of 3-M mutations was 69% CUL7, 23% OBSL1 and 8% CCDC8."
      explanation: >-
        Quantifies the OBSL1 share of molecularly solved 3-M cases.
  evidence:
  - reference: PMID:19481195
    reference_title: "The primordial growth disorder 3-M syndrome connects ubiquitination to the cytoskeletal adaptor OBSL1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we subsequently discovered seven distinct null mutations from 10 families within the gene OBSL1"
    explanation: >-
      The locus-mapping and mutation study that established OBSL1 as the second
      3-M gene.
- name: CCDC8
  gene_term:
    preferred_term: CCDC8
    term:
      id: hgnc:25367
      label: CCDC8
  relationship_type: CAUSATIVE
  subtype: 3M3
  notes: >-
    CCDC8 (19q13.32) is a single-exon gene derived from a retrotransposon Gag
    protein in placental mammals; it is disrupted almost exclusively by
    truncating variants.
  case_fractions:
  - population: 3-M families with an identified mutation (Hanson et al. cohort)
    case_fraction_percent: 8.0
    evidence:
    - reference: PMID:23018678
      reference_title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The prevalence of 3-M mutations was 69% CUL7, 23% OBSL1 and 8% CCDC8."
      explanation: >-
        Quantifies the CCDC8 share of molecularly solved 3-M cases.
  evidence:
  - reference: PMID:21737058
    reference_title: "Exome sequencing identifies CCDC8 mutations in 3-M syndrome, suggesting that CCDC8 contributes in a pathway with CUL7 and OBSL1 to control human growth."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Exome sequencing now identifies mutations in CCDC8 as a cause of 3-M syndrome."
    explanation: >-
      The exome study that established CCDC8 as the third 3-M gene.
pathophysiology:
- name: Loss of a 3-M Ubiquitin Ligase Complex Component
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    Biallelic loss-of-function variants in CUL7, OBSL1 or CCDC8 remove one
    subunit of a single shared E3 ubiquitin ligase. CUL7 is the cullin scaffold,
    assembling an SCF-like complex with Skp1, FBXW8 and ROC1/RBX1; OBSL1 is a
    cytoskeletal adaptor required to maintain CUL7 protein levels; CCDC8 is the
    membrane-anchored partner. Because the three act in one pathway, mutations
    are mutually exclusive and any one of them produces the same disease.
  genes:
  - preferred_term: CUL7
    term:
      id: hgnc:21024
      label: CUL7
  - preferred_term: OBSL1
    term:
      id: hgnc:29092
      label: OBSL1
  - preferred_term: CCDC8
    term:
      id: hgnc:25367
      label: CCDC8
  molecular_functions:
  - preferred_term: ubiquitin protein ligase activity
    term:
      id: GO:0061630
      label: ubiquitin protein ligase activity
    modifier: LOSS_OF_FUNCTION
  cellular_components:
  - preferred_term: Cul7-RING ubiquitin ligase complex
    term:
      id: GO:0031467
      label: Cul7-RING ubiquitin ligase complex
  downstream:
  - target: Failed Membrane Assembly of the 3-M Ligase
  evidence:
  - reference: PMID:16142236
    reference_title: "Identification of mutations in CUL7 in 3-M syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "CUL7 assembles an E3 ubiquitin ligase complex containing Skp1, Fbx29 (also called Fbw8) and ROC1 and promotes ubiquitination"
    explanation: >-
      Establishes CUL7 as the scaffold of an SCF-like E3 ligase, the molecular
      function lost in 3M1.
  - reference: PMID:16142236
    reference_title: "Identification of mutations in CUL7 in 3-M syndrome."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the 3-M-associated CUL7 nonsense and missense mutations R1445X and H1464P, respectively, render CUL7 deficient in recruiting ROC1"
    explanation: >-
      Shows patient variants act by preventing assembly of a catalytically
      competent ligase, not merely by reducing CUL7 abundance.
  - reference: PMID:19481195
    reference_title: "The primordial growth disorder 3-M syndrome connects ubiquitination to the cytoskeletal adaptor OBSL1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "loss of OBSL1 leads to downregulation of CUL7, implying a role for OBSL1 in the maintenance of CUL7 protein levels"
    explanation: >-
      Explains why an OBSL1 null phenocopies a CUL7 null: OBSL1 loss collapses
      CUL7 levels, so both converge on the same ligase.
  - reference: PMID:21737058
    reference_title: "Exome sequencing identifies CCDC8 mutations in 3-M syndrome, suggesting that CCDC8 contributes in a pathway with CUL7 and OBSL1 to control human growth."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "coimmunoprecipitation indicates a physical interaction between CCDC8 and OBSL1 but not CUL7"
    explanation: >-
      Places CCDC8 in the same physical complex via OBSL1, completing the
      three-gene pathway.
- name: Failed Membrane Assembly of the 3-M Ligase
  biological_scale: MOLECULAR
  description: >-
    CCDC8 localizes exclusively to the plasma membrane and is phosphorylated by
    CK2 and GSK3; that phosphorylation nucleates binding first of OBSL1 and then
    of CUL7, assembling the ligase at the membrane. Patient-derived mutations in
    any of the three genes disrupt this membrane localization, and the ligase
    substrate LL5-beta - a plasma-membrane protein that regulates cell migration
    - accumulates instead of being degraded.
  molecular_functions:
  - preferred_term: ubiquitin-protein transferase activity
    term:
      id: GO:0004842
      label: ubiquitin-protein transferase activity
    modifier: DECREASED
  biological_processes:
  - preferred_term: protein ubiquitination
    term:
      id: GO:0016567
      label: protein ubiquitination
    modifier: DECREASED
  cellular_components:
  - preferred_term: plasma membrane
    term:
      id: GO:0005886
      label: plasma membrane
  downstream:
  - target: Impaired Cell Migration and Placental Development
  - target: Disordered GH-IGF Growth Factor Signalling
  evidence:
  - reference: PMID:31343991
    reference_title: "Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Phosphorylation of CCDC8 resulted in its binding first with OBSL1, and then CUL7, leading to the membrane assembly of the 3-M E3 ubiquitin ligase complex."
    explanation: >-
      Establishes the ordered, phosphorylation-dependent assembly of the ligase
      at the plasma membrane.
  - reference: PMID:31343991
    reference_title: "Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "patient-derived mutations in 3-M genes disrupted membrane localization of the 3-M complex and accumulated LL5"
    explanation: >-
      Shows the disease alleles act by mislocalizing the complex, with failure
      to turn over its substrate as the readout.
- name: Impaired Cell Migration and Placental Development
  biological_scale: TISSUE
  description: >-
    Accumulation of the migration regulator LL5-beta impairs cell migration.
    In mice, deleting Ccdc8 impairs trophoblast migration and placental
    development, producing intrauterine growth restriction - a mechanism that
    explains the prenatal onset of the human growth failure rather than merely
    accompanying it. Cul7-null mice are independently runted with defective
    trophoblast differentiation and abnormal placental vasculature.
  cell_types:
  - preferred_term: trophoblast cell
    term:
      id: CL:0000351
      label: trophoblast cell
  biological_processes:
  - preferred_term: trophoblast cell migration
    term:
      id: GO:0061450
      label: trophoblast cell migration
    modifier: DECREASED
  - preferred_term: placenta development
    term:
      id: GO:0001890
      label: placenta development
    modifier: DECREASED
  downstream:
  - target: Severe Pre- and Postnatal Growth Restriction
  - target: Intrauterine growth restriction
    description: >-
      Placental trophoblast migration failure is the prenatal arm of the
      growth deficit.
  evidence:
  - reference: PMID:31343991
    reference_title: "Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Deletion of Ccdc8 in mice impaired trophoblast migration and placental development, resulting in intrauterine growth restriction and perinatal lethality."
    explanation: >-
      Directly links loss of a 3-M gene to trophoblast migration failure and
      intrauterine growth restriction in vivo.
  - reference: PMID:12904573
    reference_title: "Targeted disruption of p185/Cul7 gene results in abnormal vascular morphogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "placentas show defects in the differentiation of the trophoblast lineage with an abnormal vascular structure"
    explanation: >-
      An independent 3-M gene knockout converges on the same placental
      trophoblast defect.
  - reference: PMID:16142236
    reference_title: "Identification of mutations in CUL7 in 3-M syndrome."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "These results suggest that impaired ubiquitination may have a role in the pathogenesis of intrauterine growth retardation in humans."
    explanation: >-
      The original CUL7 paper proposes, but does not demonstrate, the link from
      impaired ubiquitination to human intrauterine growth retardation - hence
      INDIRECT.
- name: Disordered GH-IGF Growth Factor Signalling
  biological_scale: CELLULAR
  description: >-
    3-M children usually have normal peak serum GH and normal or low IGF-1, yet
    respond poorly to growth hormone - the pattern of resistance rather than
    deficiency. Patient fibroblasts dysregulate IGF binding protein generation
    and show gene-specific signalling defects: CUL7-null cells have impaired
    IGF1-driven AKT activation with normal GH responses, CCDC8-null cells the
    converse, and OBSL1-null cells are impaired in both. This is the cellular
    reason growth hormone therapy is only modestly effective.
  cell_types:
  - preferred_term: dermal fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  biological_processes:
  - preferred_term: insulin-like growth factor receptor signaling pathway
    term:
      id: GO:0048009
      label: insulin-like growth factor receptor signaling pathway
    modifier: DECREASED
  - preferred_term: growth hormone receptor signaling pathway
    term:
      id: GO:0060396
      label: growth hormone receptor signaling pathway
    modifier: DECREASED
  downstream:
  - target: Growth Plate Chondrocyte Proliferation Defect
  evidence:
  - reference: PMID:23018678
    reference_title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the CUL7(-/-) cells showed impaired IGF1 signalling, CCDC8(-/-) cells showed impaired GH signalling and the OBSL1(-/-) cells showed impairment in both pathways"
    explanation: >-
      Documents the gene-specific split of the signalling defect across the
      three 3-M genotypes.
  - reference: PMID:23018678
    reference_title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dysregulation of the GH-IGF-IGF binding protein axis is a feature of 3-M syndrome."
    explanation: >-
      States the axis-level conclusion this node asserts.
  - reference: PMID:22624670
    reference_title: "Exploring the spectrum of 3-M syndrome, a primordial short stature disorder of disrupted ubiquitination."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "serum GH levels are usually normal and IGF-I normal or low, while growth response to rhGH therapy is variable but typically poor. All these features suggest a degree of resistance in the GH-IGF axis"
    explanation: >-
      Gives the clinical endocrine pattern - resistance, not deficiency - that
      this node explains.
  - reference: PMID:22624670
    reference_title: "Exploring the spectrum of 3-M syndrome, a primordial short stature disorder of disrupted ubiquitination."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "CUL7 acts an ubiquitin ligase and is known to interact with p53, cyclin D-1 and the growth factor signalling molecule IRS-1, the link with the latter may contribute to the GH-IGF resistance"
    explanation: >-
      Proposes IRS-1, a shared node of the GH, insulin and IGF-1 pathways, as
      the substrate connecting ligase loss to growth-factor resistance. The
      source states this as a possible contribution, so support is PARTIAL.
- name: Growth Plate Chondrocyte Proliferation Defect
  biological_scale: TISSUE
  description: >-
    Cartilage-specific Cul7 knockout mice have abnormally short and deformed
    limbs with thickened growth plates, disorderly chondrocyte columns, fewer
    cells in the proliferative zone and disordered metaphyseal trabecular bone -
    implicating both chondrocyte proliferation and endochondral ossification as
    the proximate tissue mechanism of the skeletal growth failure.
  cell_types:
  - preferred_term: growth plate chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  locations:
  - preferred_term: growth plate cartilage
    term:
      id: UBERON:0004129
      label: growth plate cartilage
  biological_processes:
  - preferred_term: chondrocyte proliferation
    term:
      id: GO:0035988
      label: chondrocyte proliferation
    modifier: DECREASED
  - preferred_term: endochondral bone morphogenesis
    term:
      id: GO:0060350
      label: endochondral bone morphogenesis
    modifier: DECREASED
  downstream:
  - target: Severe Pre- and Postnatal Growth Restriction
  - target: Short thorax
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Short neck
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Pectus deformity
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Pectus excavatum
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Winged scapulae
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Thoracic kyphoscoliosis
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Hyperlordosis
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Spina bifida occulta
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Axial skeletal patterning defect; grouped with the other vertebral
      findings, though the specific route from the growth-plate lesion to a
      neural-arch closure defect is not established.
  - target: Clinodactyly of the fifth fingers
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Prominent heels
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Pes planus
    description: >-
      Growth-plate and skeletal consequence of the chondrocyte proliferation
      defect.
  - target: Dolichocephaly
    description: >-
      Craniofacial skeletal consequence; the cranial vault is bone whose
      growth depends on the same proliferation defect.
  - target: Midface retrusion
    description: >-
      Craniofacial skeletal consequence of impaired bone growth.
  - target: Pointed chin
    description: >-
      Craniofacial skeletal consequence of impaired mandibular growth.
  - target: Triangular face
    description: >-
      Craniofacial skeletal consequence; the triangular gestalt follows from
      relative sparing of the calvarium against midface and mandibular
      hypoplasia.
  - target: Slender long bones
    description: >-
      A growth-plate proliferation defect that spares periosteal apposition
      gives long bones that are elongated and narrow with a constricted
      diaphysis - the characteristic 3-M radiographic appearance.
  - target: Tall vertebral bodies
    description: >-
      The vertebral expression of the same disproportion between longitudinal
      growth and cross-sectional growth.
  - target: Fleshy nasal tip
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Part of the craniofacial gestalt, grouped with the other midface
      features; no route from the chondrocyte defect to soft-tissue nasal
      morphology is established.
  - target: Long philtrum
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the other midface features; the route is not established.
  - target: Thick eyebrows
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the craniofacial gestalt; no mechanism is established, and
      this is a soft-tissue rather than skeletal feature.
  - target: Joint hypermobility
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Grouped with the connective-tissue findings. CUL7 and OBSL1 act on
      cytoskeletal and extracellular-matrix substrates, so a shared
      connective-tissue basis is plausible, but it has not been shown.
  - target: Dislocated hips
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Downstream of the joint laxity together with the acetabular geometry
      that follows abnormal endochondral growth.
  - target: Hypogonadism in males
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Reported in males with 3-M; no mechanism links the ubiquitin-ligase
      defect to gonadal function.
  - target: Hypospadias
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      An occasional finding in affected males, grouped as a developmental
      anomaly with no established route.
  evidence:
  - reference: PMID:38367951
    reference_title: "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "increased thickness of growth plate, the disorderly arranged chondrocyte columns, decreased number of cells in the proliferation zone"
    explanation: >-
      Documents the growth-plate histology in a cartilage-specific Cul7
      knockout.
  - reference: PMID:38367951
    reference_title: "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The knockout of Cul7 gene may affect both the proliferation of chondrocytes and the endochondral osteogenesis"
    explanation: >-
      States the two-process conclusion this node asserts.
- name: Severe Pre- and Postnatal Growth Restriction
  biological_scale: ORGANISM
  role: consequence
  description: >-
    The organism-level endpoint: growth restriction that begins before birth and
    continues without a catch-up phase, giving a final height about five
    standard deviations below the mean, together with the characteristic facies
    and skeletal findings, and with intelligence spared.
  downstream:
  - target: Severe pre- and postnatal growth deficiency
    description: >-
      The organism-level growth endpoint measured as final height.
  - target: Relative macrocephaly
    description: >-
      Head circumference is spared while body size is not, so the relative
      macrocephaly is a consequence of the body-growth deficit rather than of
      head overgrowth.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome is characterized by severe pre- and postnatal growth deficiency (final height five standard deviations below the mean)"
    explanation: >-
      GeneReviews quantifies the growth endpoint.
phenotypes:
- category: Growth
  name: Severe pre- and postnatal growth deficiency
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome is characterized by severe pre- and postnatal growth deficiency (final height five standard deviations below the mean)"
    explanation: >-
      The defining feature, quantified by GeneReviews.
- category: Growth
  name: Intrauterine growth restriction
  phenotype_term:
    preferred_term: Intrauterine growth retardation
    term:
      id: HP:0001511
      label: Intrauterine growth retardation
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:19481195
    reference_title: "The primordial growth disorder 3-M syndrome connects ubiquitination to the cytoskeletal adaptor OBSL1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome is an autosomal-recessive primordial growth disorder characterized by significant intrauterine and postnatal growth restriction"
    explanation: >-
      Prenatal onset is what makes 3-M a primordial rather than a postnatal
      growth disorder.
- category: Craniofacial
  name: Relative macrocephaly
  phenotype_term:
    preferred_term: Relative macrocephaly
    term:
      id: HP:0004482
      label: Relative macrocephaly
  frequency: FREQUENT
  description: >-
    Head circumference is normal for age against a markedly reduced body size,
    so the head appears relatively large. This is the opposite of the
    microcephaly seen in most other group-21 primordial dwarfisms and is a
    useful discriminator.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      GeneReviews lists relative macrocephaly among the characteristic facial
      features.
- category: Craniofacial
  name: Triangular face
  phenotype_term:
    preferred_term: Triangular face
    term:
      id: HP:0000325
      label: Triangular face
  frequency: FREQUENT
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Craniofacial
  name: Dolichocephaly
  phenotype_term:
    preferred_term: Dolichocephaly
    term:
      id: HP:0000268
      label: Dolichocephaly
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Craniofacial
  name: Midface retrusion
  phenotype_term:
    preferred_term: Midface retrusion
    term:
      id: HP:0011800
      label: Midface retrusion
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Craniofacial
  name: Fleshy nasal tip
  phenotype_term:
    preferred_term: Fleshy (bulbous) nasal tip
    term:
      id: HP:0000414
      label: Bulbous nose
  description: >-
    Together with short stature, the most durable diagnostic clue: most other
    dysmorphic and radiographic features attenuate with age.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facies (relative macrocephaly, dolichocephaly, triangular face, midface retrusion, thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Craniofacial
  name: Thick eyebrows
  phenotype_term:
    preferred_term: Thick eyebrow
    term:
      id: HP:0000574
      label: Thick eyebrow
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Craniofacial
  name: Long philtrum
  phenotype_term:
    preferred_term: Long philtrum
    term:
      id: HP:0000343
      label: Long philtrum
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thick eyebrows, fleshy nasal tip, long philtrum"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Craniofacial
  name: Pointed chin
  phenotype_term:
    preferred_term: Pointed chin
    term:
      id: HP:0000307
      label: Pointed chin
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thick vermilion of the upper and low lips, and pointed chin"
    explanation: >-
      Listed by GeneReviews among the characteristic facial features.
- category: Skeletal
  name: Slender long bones
  phenotype_term:
    preferred_term: Slender long bones
    term:
      id: HP:0003100
      label: Slender long bone
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >-
    The radiographic finding that places 3-M in the slender-bone half of ISDS
    group 21, and one of the two features classically used to separate it from
    other dwarfisms. The bones are slender and elongated with diaphyseal
    constriction and cortical thickening. It is most obvious in the newborn
    period; the 2025 phenotype-evolution report notes the radiographic picture
    becomes progressively less distinctive with age, which is a practical
    caveat for diagnosing an older child.
  evidence:
  - reference: PMID:11665997
    reference_title: "3-M syndrome: description of six new patients with review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome can be differentiated from other types of dwarfism by clinical criteria and by the demonstration of characteristically slender long bones and foreshortened vertebral bodies."
    explanation: >-
      States the radiographic finding and its diagnostic role, which is why
      this phenotype is flagged diagnostic.
  - reference: PMID:41437277
    reference_title: "3-M syndrome: evolution of the phenotype over time."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "X-rays of patient 1 at birth: slender and elongated long bones, with diaphyseal constriction and cortical thickening (C); tall vertebrae, with reduced anteroposterior diameter (A, B); thin metacarpals and phalanges (E)."
    explanation: >-
      A contemporary molecularly confirmed case with the detailed radiographic
      description, including the diaphyseal constriction and cortical
      thickening this phenotype's description asserts.
- category: Skeletal
  name: Tall vertebral bodies
  phenotype_term:
    preferred_term: Tall vertebral bodies with reduced anteroposterior diameter
    term:
      id: HP:0004570
      label: Increased vertebral height
  frequency: FREQUENT
  description: >-
    The spinal counterpart of the slender long bones, and the second half of
    the classic radiographic pair. Note the older literature describes the
    vertebral bodies as "foreshortened" - referring to the reduced
    anteroposterior diameter, not to reduced height, which is increased.
  evidence:
  - reference: PMID:41437277
    reference_title: "3-M syndrome: evolution of the phenotype over time."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome (OMIM# 273750, 612921, 614205) is a rare autosomal recessive disease characterized by severe pre- and post-natal growth retardation, bulbous nose, short thorax, prominent abdomen, slight slender tubular bones, tall vertebral bodies, and normal intelligence."
    explanation: >-
      Names tall vertebral bodies among the defining features of the disorder.
- category: Skeletal
  name: Short neck
  phenotype_term:
    preferred_term: Short, broad neck
    term:
      id: HP:0000470
      label: Short neck
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional features of 3-M syndrome include short, broad neck, prominent trapezii"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Short thorax
  phenotype_term:
    preferred_term: Short thorax
    term:
      id: HP:0010306
      label: Short thorax
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Pectus deformity
  phenotype_term:
    preferred_term: Pectus carinatum
    term:
      id: HP:0000768
      label: Pectus carinatum
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
    explanation: >-
      GeneReviews records pectus carinatum or excavatum; carinatum is bound
      here and excavatum is curated as its own phenotype.
- category: Skeletal
  name: Pectus excavatum
  phenotype_term:
    preferred_term: Pectus excavatum
    term:
      id: HP:0000767
      label: Pectus excavatum
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
    explanation: >-
      The alternative chest-wall deformity recorded by GeneReviews.
- category: Skeletal
  name: Winged scapulae
  phenotype_term:
    preferred_term: Winged scapulae
    term:
      id: HP:0003691
      label: Scapular winging
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pectus carinatum/excavatum, short thorax, square shoulders, winged scapulae"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Thoracic kyphoscoliosis
  phenotype_term:
    preferred_term: Thoracic kyphoscoliosis
    term:
      id: HP:0002751
      label: Kyphoscoliosis
    clinical_course: PROGRESSIVE
  description: >-
    GeneReviews recommends annual assessment, so this is a surveillance target
    rather than a static finding.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thoracic kyphoscoliosis, hyperlordosis, spina bifida occulta"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Hyperlordosis
  phenotype_term:
    preferred_term: Hyperlordosis
    term:
      id: HP:0003307
      label: Hyperlordosis
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thoracic kyphoscoliosis, hyperlordosis, spina bifida occulta"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Spina bifida occulta
  phenotype_term:
    preferred_term: Spina bifida occulta
    term:
      id: HP:0003298
      label: Spina bifida occulta
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "thoracic kyphoscoliosis, hyperlordosis, spina bifida occulta"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Clinodactyly of the fifth fingers
  phenotype_term:
    preferred_term: Clinodactyly of the 5th finger
    term:
      id: HP:0004209
      label: Clinodactyly of the 5th finger
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "clinodactyly of the fifth fingers, generalized or distal joint hypermobility, dislocated hips"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Joint hypermobility
  phenotype_term:
    preferred_term: Generalized or distal joint hypermobility
    term:
      id: HP:0001382
      label: Joint hypermobility
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "clinodactyly of the fifth fingers, generalized or distal joint hypermobility, dislocated hips"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Dislocated hips
  phenotype_term:
    preferred_term: Dislocated hips
    term:
      id: HP:0001374
      label: Congenital hip dislocation
  description: >-
    GeneReviews recommends assessment at every infant visit, particularly where
    walking is delayed.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "clinodactyly of the fifth fingers, generalized or distal joint hypermobility, dislocated hips"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Prominent heels
  phenotype_term:
    preferred_term: Prominent heels
    term:
      id: HP:0012428
      label: Prominent calcaneus
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dislocated hips, prominent heels, and pes planus"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Skeletal
  name: Pes planus
  phenotype_term:
    preferred_term: Pes planus
    term:
      id: HP:0001763
      label: Pes planus
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dislocated hips, prominent heels, and pes planus"
    explanation: >-
      Listed by GeneReviews among the additional skeletal features.
- category: Endocrine
  name: Hypogonadism in males
  phenotype_term:
    preferred_term: Hypogonadism (males)
    term:
      id: HP:0000135
      label: Hypogonadism
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Males with 3-M syndrome can have hypogonadism and occasionally hypospadias."
    explanation: >-
      GeneReviews records hypogonadism as a male-restricted feature.
- category: Genitourinary
  name: Hypospadias
  phenotype_term:
    preferred_term: Hypospadias
    term:
      id: HP:0000047
      label: Hypospadias
  frequency: OCCASIONAL
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Males with 3-M syndrome can have hypogonadism and occasionally hypospadias."
    explanation: >-
      GeneReviews records hypospadias as an occasional male finding.
diagnosis:
- name: Molecular genetic testing of CUL7, OBSL1 and CCDC8
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  presence: Biallelic pathogenic variants in CUL7, OBSL1 or CCDC8
  description: >-
    Either arm is sufficient - GeneReviews establishes the diagnosis on the
    clinical and radiographic picture *and/or* biallelic variants - but in
    practice the molecular result is what distinguishes 3-M from the other
    primordial dwarfisms and assigns the subtype. Roughly 70% of solved cases
    are CUL7.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of 3-M syndrome is established in a proband with prenatal-onset persistent growth deficiency and the characteristic clinical and radiographic features and/or biallelic pathogenic variants in CCDC8, CUL7, or OBSL1 identified by molecular genetic testing."
    explanation: >-
      The GeneReviews diagnostic criterion, naming both the clinical route and
      the three genes.
- name: Skeletal radiography
  diagnosis_term:
    preferred_term: clinical and radiographic evaluation
    term:
      id: NCIT:C124351
      label: Clinical Evaluation
  presence: Slender long bones with tall vertebral bodies, on a background of prenatal-onset growth deficiency
  description: >-
    The radiographic pair is what historically separated 3-M from other
    dwarfisms. Timing matters: the findings are clearest in the newborn period
    and become progressively less distinctive with age, so a normal-looking
    survey in an older child does not exclude the diagnosis.
  evidence:
  - reference: PMID:11665997
    reference_title: "3-M syndrome: description of six new patients with review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M syndrome can be differentiated from other types of dwarfism by clinical criteria and by the demonstration of characteristically slender long bones and foreshortened vertebral bodies."
    explanation: >-
      States the differentiating radiographic findings.
  - reference: PMID:41437277
    reference_title: "3-M syndrome: evolution of the phenotype over time."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Our paper highlights how the clinical diagnosis of 3-M is easier in the first months of life, while in older children the phenotype becomes increasingly nuanced."
    explanation: >-
      The age-dependence caveat, which is why molecular testing carries more of
      the diagnostic weight in an older child.
treatments:
- name: Growth Hormone Therapy
  description: >-
    Referral to a paediatric endocrinologist for consideration of growth hormone
    in prepubertal children. The response is characteristically modest: 3-M is a
    GH-resistant rather than GH-deficient state, so the drug is working against
    a downstream signalling block. Set expectations accordingly rather than
    escalating dose indefinitely.
  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_mechanisms:
  - target: Disordered GH-IGF Growth Factor Signalling
    description: >-
      Exogenous GH acts on the axis this node describes; the node's signalling
      block is why the response is limited.
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Referral to pediatric endocrinologist for consideration of growth hormone in prepubertal children."
    explanation: >-
      GeneReviews management recommendation.
  - reference: PMID:23018678
    reference_title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "3-M patients typically have a modest response to GH treatment, but the mechanism is unknown."
    explanation: >-
      Documents the limited efficacy that qualifies this treatment - PARTIAL
      because the statement is about a modest rather than an absent response.
- name: Orthopedic Management
  description: >-
    Orthopedic evaluation for hip dislocation, scoliosis and significant joint
    laxity. Surgical limb lengthening may be an option.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: orthopedic surgical procedure
    term:
      id: NCIT:C16186
      label: Orthopedic Surgical Procedure
  target_phenotypes:
  - preferred_term: Dislocated hips
    term:
      id: HP:0001374
      label: Congenital hip dislocation
  - preferred_term: Thoracic kyphoscoliosis
    term:
      id: HP:0002751
      label: Kyphoscoliosis
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Orthopedic evaluation in individuals with hip dislocation, scoliosis, and significant joint laxity is essential."
    explanation: >-
      GeneReviews management recommendation.
- name: Physical and Occupational Therapy
  description: >-
    Physical therapy, occupational therapy and community child health services
    to put adaptations for short stature in place and maximize access to the
    environment.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: physical therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Physical therapy, occupational therapy, and community child health services are important in ensuring necessary adaptations for short stature are put in place"
    explanation: >-
      GeneReviews management recommendation.
- name: Genetic Counseling
  description: >-
    Autosomal recessive counseling: a 25% recurrence risk for each sib once both
    parents are known carriers, with carrier testing and prenatal or
    preimplantation genetic testing possible after the familial variants are
    identified.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301654
    reference_title: "3-M Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being a carrier"
    explanation: >-
      GeneReviews genetic counseling guidance.
animal_models:
- name: Cartilage-specific Cul7 knockout mouse
  species: Mouse
  genotype: Cul7fl/fl;Col2a1-CreERT2
  publication: PMID:38367951
  description: >-
    A conditional, cartilage-restricted Cul7 knockout that survives past birth,
    unlike the constitutive null, and so allows the growth plate to be studied
    directly.
  modeled_mechanisms:
  - target: Growth Plate Chondrocyte Proliferation Defect
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reproduces the growth-plate lesion proposed to underlie the human skeletal
      growth failure.
    limitations: >-
      Cartilage-restricted and tamoxifen-induced, so it models the postnatal
      skeletal component only; it cannot speak to the placental/prenatal arm of
      the mechanism, and it addresses CUL7 alone rather than the OBSL1 and
      CCDC8 genotypes.
    readouts:
    - name: Proliferative-zone chondrocyte number
      target: Growth Plate Chondrocyte Proliferation Defect
      direction: DECREASED
      interpretation: >-
        Direct cellular correlate of the proliferation defect this node asserts.
      evidence:
      - reference: PMID:38367951
        reference_title: "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "decreased number of cells in the proliferation zone"
        explanation: >-
          The measured reduction in proliferative-zone cellularity.
    - name: Limb length
      target: Growth Plate Chondrocyte Proliferation Defect
      direction: DECREASED
      interpretation: >-
        Organ-level consequence of the growth-plate lesion.
      evidence:
      - reference: PMID:38367951
        reference_title: "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "mice had abnormally short and deformed limbs"
        explanation: >-
          The gross skeletal readout of the model.
    evidence:
    - reference: PMID:38367951
      reference_title: "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The knockout of Cul7 gene may affect both the proliferation of chondrocytes and the endochondral osteogenesis"
      explanation: >-
        Supports treating this model as informative for the growth-plate node.
- name: Ccdc8 knockout mouse
  species: Mouse
  genotype: Ccdc8 null
  publication: PMID:31343991
  description: >-
    Constitutive Ccdc8 deletion, used to test whether loss of a 3-M gene is
    sufficient to cause intrauterine growth restriction through the placenta.
  modeled_mechanisms:
  - target: Impaired Cell Migration and Placental Development
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Establishes that deleting a 3-M gene impairs trophoblast migration and
      placental development and produces intrauterine growth restriction.
    limitations: >-
      Perinatally lethal in the mouse, whereas human CCDC8-related 3-M is the
      mildest of the three genotypes and compatible with adult life - so the
      model overstates severity and cannot address postnatal growth.
    readouts:
    - name: Fetal growth
      target: Impaired Cell Migration and Placental Development
      direction: DECREASED
      interpretation: >-
        Intrauterine growth restriction as the in vivo endpoint of placental
        failure.
      evidence:
      - reference: PMID:31343991
        reference_title: "Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "resulting in intrauterine growth restriction and perinatal lethality"
        explanation: >-
          The measured growth outcome in the knockout.
    evidence:
    - reference: PMID:31343991
      reference_title: "Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Deletion of Ccdc8 in mice impaired trophoblast migration and placental development"
      explanation: >-
        Supports treating this model as informative for the placental node.
- name: Constitutive Cul7 (p185) knockout mouse
  species: Mouse
  genotype: Cul7 (p185) null
  publication: PMID:12904573
  description: >-
    The original Cul7 null, runted and perinatally lethal from respiratory
    distress, with defective trophoblast differentiation and abnormal placental
    vasculature.
  modeled_mechanisms:
  - target: Impaired Cell Migration and Placental Development
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Converges on the same placental trophoblast defect from a different 3-M
      gene.
    limitations: >-
      Perinatally lethal, so it does not model the viable human disease; the
      reported emphasis is vascular morphogenesis rather than the migration
      defect later shown for the 3-M ligase.
    readouts:
    - name: Placental trophoblast differentiation
      target: Impaired Cell Migration and Placental Development
      direction: ALTERED
      interpretation: >-
        Histological correlate of the placental node.
      evidence:
      - reference: PMID:12904573
        reference_title: "Targeted disruption of p185/Cul7 gene results in abnormal vascular morphogenesis."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "placentas show defects in the differentiation of the trophoblast lineage with an abnormal vascular structure"
        explanation: >-
          The measured placental phenotype.
    evidence:
    - reference: PMID:12904573
      reference_title: "Targeted disruption of p185/Cul7 gene results in abnormal vascular morphogenesis."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "embryos are runted and die immediately after birth because of respiratory distress"
      explanation: >-
        Supports treating this model as informative for prenatal growth failure,
        while its perinatal lethality is the limitation recorded above.
references:
- reference: PMID:20301654
  title: "3-M Syndrome."
  tags:
  - GeneReviews
- reference: PMID:16142236
  title: "Identification of mutations in CUL7 in 3-M syndrome."
- reference: PMID:19481195
  title: "The primordial growth disorder 3-M syndrome connects ubiquitination to the cytoskeletal adaptor OBSL1."
- reference: PMID:21737058
  title: "Exome sequencing identifies CCDC8 mutations in 3-M syndrome, suggesting that CCDC8 contributes in a pathway with CUL7 and OBSL1 to control human growth."
- reference: PMID:23018678
  title: "Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling."
- reference: PMID:22624670
  title: "Exploring the spectrum of 3-M syndrome, a primordial short stature disorder of disrupted ubiquitination."
- reference: PMID:11665997
  title: "3-M syndrome: description of six new patients with review of the literature."
- reference: PMID:41437277
  title: "3-M syndrome: evolution of the phenotype over time."
- reference: PMID:31343991
  title: "Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development."
- reference: PMID:38367951
  title: "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice."
- reference: PMID:12904573
  title: "Targeted disruption of p185/Cul7 gene results in abnormal vascular morphogenesis."
📚

References & Deep Research

References

11
PMID:20301654
3-M Syndrome.
No top-level findings curated for this source.
PMID:16142236
Identification of mutations in CUL7 in 3-M syndrome.
No top-level findings curated for this source.
PMID:19481195
The primordial growth disorder 3-M syndrome connects ubiquitination to the cytoskeletal adaptor OBSL1.
No top-level findings curated for this source.
PMID:21737058
Exome sequencing identifies CCDC8 mutations in 3-M syndrome, suggesting that CCDC8 contributes in a pathway with CUL7 and OBSL1 to control human growth.
No top-level findings curated for this source.
PMID:23018678
Mutations in CUL7, OBSL1 and CCDC8 in 3-M syndrome lead to disordered growth factor signalling.
No top-level findings curated for this source.
PMID:22624670
Exploring the spectrum of 3-M syndrome, a primordial short stature disorder of disrupted ubiquitination.
No top-level findings curated for this source.
PMID:11665997
3-M syndrome: description of six new patients with review of the literature.
No top-level findings curated for this source.
PMID:41437277
3-M syndrome: evolution of the phenotype over time.
No top-level findings curated for this source.
PMID:31343991
Impaired plasma membrane localization of ubiquitin ligase complex underlies 3-M syndrome development.
No top-level findings curated for this source.
PMID:38367951
Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice.
No top-level findings curated for this source.
PMID:12904573
Targeted disruption of p185/Cul7 gene results in abnormal vascular morphogenesis.
No top-level findings curated for this source.

Deep Research

1
Claude Code ▸
3-M Syndrome: Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 20 citations 2026-08-27T01:45:22.080316

3-M Syndrome: Comprehensive Research Report

1. Disease Information

Overview. 3-M syndrome (also written "3M syndrome," "Miller-McKusick-Malvaux syndrome," "Le Merrer syndrome," or "Gloomy face syndrome") is a rare autosomal recessive primordial growth disorder — meaning growth restriction begins prenatally and persists throughout life without a "catch-up" phase — characterized by severe pre- and postnatal growth deficiency, a distinctive facial gestalt, characteristic skeletal/radiographic findings, and normal intelligence. The name derives from the surnames of the three physicians (Miller, McKusick, Malvaux) who first described it in 1975.

Key identifiers: - OMIM: 3M syndrome 1 (#273750, CUL7), 3M syndrome 2 (#612921, OBSL1), 3M syndrome 3 (#614205, CCDC8) OMIM #273750; OMIM #612921; OMIM #614205 - Orphanet: ORPHA2616 (Orphanet: 3M syndrome) - MONDO: MONDO:0007477 (3M syndrome 1); related MONDO terms exist per subtype - Disease Ontology: DOID:0060241 - GeneReviews: NBK1481 (Cormier-Daire, Huber, et al., updated periodically) - GTR/MeSH/ICD: Listed under primordial dwarfism / short stature syndromes; no dedicated ICD-10-CM code beyond the general short-stature syndrome category

Synonyms: 3M syndrome; Miller-McKusick-Malvaux syndrome; Le Merrer syndrome; Gloomy face syndrome (historical, now discouraged); Dolichospondylic dysplasia; Yakut short stature syndrome (population-specific CUL7 founder-variant form).

Data derivation: Information is drawn predominantly from aggregated case-series/cohort literature (fewer than ~250 molecularly confirmed cases reported worldwide as of 2025) rather than large-scale EHR/registry data, reflecting the disorder's rarity. GeneReviews and the recent 2025 natural-history literature review (217 pooled cases from 36 publications) are the most authoritative aggregate sources.

2. Etiology

Disease causal factors — genetic. 3-M syndrome is caused by biallelic (homozygous or compound heterozygous) loss-of-function variants in one of three genes encoding components of a single molecular complex:

Subtype OMIM Gene Locus Approx. proportion of cases
3M1 #273750 CUL7 (Cullin-7) 6p21.1 ~65–75%
3M2 #612921 OBSL1 (Obscurin-like 1) 2q35 ~28–34%
3M3 #614205 CCDC8 (Coiled-coil domain containing 8) 19q13.32 ~1–5%

Approximately 1% of clinically diagnosed cases remain molecularly unresolved, suggesting additional causative genes or loci may exist (GeneReviews NBK1481).

  • CUL7 variants: predominance of null variants (nonsense, splice-site; missense also frequent); ~50% of pathogenic variants localize to the cullin domain critical for ROC1 anchoring.
  • OBSL1 variants: most pathogenic variants occur within the first 8 exons, affecting all known isoforms, predominantly loss-of-function.
  • CCDC8: a single-exon gene; pathogenic variants lead to truncation and loss of function.

Founder variants (population-specific risk factors): - Yakut population (Siberia): CUL7 c.4581dupT (also reported as 4582_4583insT), described by Maksimova et al. 2007, associated with a distinctive phenotype of high neonatal respiratory distress but comparatively few bone abnormalities (PMC2652813). - Maghrebian/Tunisian population: CUL7 c.4451_4452delTG. - Turkish population: OBSL1 c.1273dupA (emerging founder variant).

Risk factors: - Genetic: Consanguinity substantially raises risk given the autosomal recessive inheritance and regional founder alleles; carrier parents (heterozygotes) are asymptomatic. - Environmental: No environmental, toxin, infectious, or lifestyle risk factors have been identified — this is a purely monogenic Mendelian disorder. - Modifier genes: None formally established, though phenotypic variability (e.g., milder stature in CCDC8-related disease vs. more severe in CUL7-related disease) suggests gene-specific and possibly allele-specific modulation of severity.

Protective factors: None described; this is a fully penetrant recessive disorder once biallelic pathogenic variants are present.

Gene-environment interactions: Not applicable/not reported — no environmental modifiers of penetrance or expressivity have been documented in the literature.

3. Phenotypes

Growth phenotype

  • Severe pre- and postnatal growth deficiency: final adult height typically ~5 SD below the mean (range roughly 115–150 cm in adults). Birth length typically 40–42 cm with normal head circumference for gestational age (giving the appearance of relative macrocephaly).
  • No catch-up growth occurs; short stature is proportionate. HPO: HP:0004322 (Short stature), HP:0001511 (Intrauterine growth retardation).

Craniofacial features

Characteristic facies including: relative macrocephaly (HP:0004482 / HP:0000256 macrocephaly-adjacent terms), dolichocephaly (HP:0000268), triangular face (HP:0000325), midface retrusion (HP:0011800), thick eyebrows (HP:0000574), fleshy/bulbous nasal tip (HP:0000455-adjacent), long philtrum (HP:0000343), thick vermilion of upper and lower lips (HP:0012471), pointed chin (HP:0000307). Infants may show facial nevus simplex and infraorbital fullness that fade with age. Facial appearance is most diagnostic in infancy and becomes progressively subtler through childhood into adolescence, per a 2025 natural-history review of 217 cases (Ital J Pediatr, PMID 41437277, DOI 10.1186/s13052-025-02172-8).

Musculoskeletal features

Short broad neck, prominent trapezii, pectus carinatum/excavatum (HP:0000768/HP:0000767), short thorax, square shoulders, winged scapulae, thoracic kyphoscoliosis (HP:0002751), hyperlordosis (HP:0002938), spina bifida occulta, clinodactyly of the fifth finger (HP:0004209), joint hypermobility (HP:0001382), hip dislocation, prominent heels, pes planus (HP:0001763).

Radiographic (skeletal) hallmark features

  • Slender long bones with diaphyseal constriction and flared metaphyses — the primary distinguishing radiologic sign.
  • Tall vertebral bodies with reduced anteroposterior and transverse diameters, especially lumbar.
  • Elevated metacarpal and vertebral indices.
  • Small pelvic bones. These become "increasingly vague" with age, per the 2025 natural-history review, so radiographic diagnosis is most reliable in infancy.

Neurodevelopmental

Normal intelligence is a defining and diagnostically important feature that distinguishes 3-M syndrome from many other severe short-stature/primordial-dwarfism syndromes (e.g., Seckel syndrome, microcephalic primordial dwarfism).

Endocrine/reproductive

Males may have hypogonadism and occasionally hypospadias (HP:0000047); a 2024 JCEM Case Reports paper documented a CUL7-variant male with bifid scrotum and perineal hypospadias at birth, spontaneous but incomplete pubertal maturation, and progressive gonadal failure in adolescence (declining testicular volume, rising gonadotropins, low-normal testosterone) (PMID 38847008, PMC11154130). Female gonadal function appears normal. Endocrine (thyroid, adrenal) function is otherwise generally normal.

Cardiac

Aortic root dilatation reported in some individuals — a rationale for periodic echocardiographic surveillance.

Respiratory

Some neonates, particularly in the Yakut founder-variant population, experience significant neonatal respiratory distress (~41% in that population), sometimes requiring NICU care.

Quality of life

Not formally quantified with standardized instruments (EQ-5D/SF-36) in the literature reviewed; qualitatively, impact centers on short-stature-related psychosocial and functional issues (adaptive equipment needs, orthopedic complications) rather than cognitive/behavioral burden, since intelligence and daily function are largely preserved.

4. Genetic/Molecular Information

Causal genes: CUL7 (HGNC:16290, OMIM 609577), OBSL1 (HGNC:15738, OMIM 610991), CCDC8 (HGNC:17086, OMIM *614145).

Pathogenic variant classification: Per ACMG/AMP framework, disease-causing alleles are classified as pathogenic/likely pathogenic biallelic loss-of-function or damaging missense variants; heterozygous carriers are unaffected. ClinVar/ClinGen entries exist for known recurrent and founder variants.

Variant types: - Nonsense, frameshift, and canonical splice-site variants predominate for CUL7 and OBSL1 (loss-of-function mechanism). - Missense variants also occur in CUL7, frequently clustering in the cullin domain required for ROC1 (RBX1) anchoring within the SCF-like complex. - CCDC8, being single-exon, is disrupted almost exclusively by truncating variants causing loss of function.

Allele frequency: No individual pathogenic variant reaches appreciable frequency in general population databases (gnomAD) outside specific founder populations (Yakut, Maghrebian/Tunisian, Turkish), consistent with an ultra-rare recessive disorder.

Origin: Germline, biallelic — not somatic; both alleles inherited from heterozygous, unaffected parents (or occasionally uniparental disomy/de novo events, though these are not prominently reported for this condition).

Functional consequence — molecular mechanism: CUL7 is a member of the Cullin family and forms the scaffold of an SCF-like (Skp1–Cullin–F-box) E3 ubiquitin ligase complex localized to the Golgi apparatus. This complex: - Physically interacts with OBSL1 and CCDC8 to form the "3-M E3 complex," which regulates microtubule dynamics and ubiquitinates the membrane-associated protein LL5β, impacting cell migration and cytoskeletal regulation (Hanson et al. 2009, Am J Hum Genet, PMC2694976; PMID 19481195). - Is implicated in proteasomal degradation of IRS-1 (insulin receptor substrate-1) and cyclin D1. CUL7 interacts with IRS-1, a downstream signaling node shared by insulin, IGF-1, and GH receptor pathways. Loss of CUL7 function leads to IRS-1 accumulation (impaired proteasomal turnover), and downstream reduced IGF-1-mediated activation of Akt and reduced cell proliferation (Endocrine Abstracts EA0021P232). - Loss of CUL7 also reduces OBSL1 transcription, tying the three genes into a single interdependent pathway — consistent with all three genes producing a convergent, largely indistinguishable phenotype (CUL7- and OBSL1-related disease are "clinically and radiographically indistinguishable," per GeneReviews, though CUL7-related disease tends to produce shorter final stature). - A separate mechanistic axis: 3-M fibroblasts show an epigenetic gene-expression signature of reduced IGF2 expression and increased H19 expression, resembling the imprinting profile of Silver-Russell syndrome, with markedly reduced IGF-II secretion in conditioned culture medium (10.2±2.9 ng/mL control vs. 0.6±0.9 ng/mL 3-M fibroblasts, P<0.01) — implicating IGF2 silencing as a contributing, gene-network-level (not primary genetic-imprinting) mechanism (Meyer et al. 2013, Endocr Connect, PMID 24148222, PMC3847915).

Modifier genes: None formally established; phenotype-genotype correlation is largely gene-specific (CUL7 > OBSL1 > CCDC8 severity gradient) rather than driven by known secondary modifiers.

Epigenetic information: The IGF2/H19 imprinting-like expression signature above is the principal epigenetic finding; it appears to be a downstream transcriptional consequence of E3-complex disruption rather than a primary imprinting defect.

Chromosomal abnormalities: 3-M syndrome is not caused by large structural chromosomal rearrangements; it is a single-gene (biallelic small-variant) disorder. No characteristic CNV/translocation etiology has been reported.

5. Environmental Information

3-M syndrome is a monogenic Mendelian disorder with no identified environmental, toxin, infectious, or lifestyle contributing factors. It is not associated with teratogen exposure, maternal illness, or infectious triggers. The only population-level "risk factor" beyond genetics is consanguinity, which increases the probability of biallelic inheritance of a rare recessive allele, and geographic/ethnic founder-variant enrichment (Yakut, Maghrebian, Turkish populations).

6. Mechanism / Pathophysiology

Causal chain (upstream → downstream):

  1. Molecular trigger: Biallelic loss-of-function variant in CUL7, OBSL1, or CCDC8 → loss of function of one component of the Golgi-localized 3-M E3 ubiquitin ligase complex.
  2. Complex disruption: CUL7, OBSL1, and CCDC8 normally physically interact to form the joint 3-M E3 complex, which is critical for microtubule regulation and ubiquitination of the membrane-associated protein LL5β (cell migration regulator). Loss of any one component destabilizes the complex.
  3. Impaired proteostasis of growth-signaling intermediates: Failure of ubiquitin-mediated proteasomal degradation of IRS-1 (and cyclin D1) → IRS-1 accumulation.
  4. Blunted IGF-1/insulin/GH signal transduction: Because IRS-1 is a shared downstream node of insulin, IGF-1, and GH receptor pathways, its dysregulated turnover produces reduced IGF-1-mediated Akt activation and reduced cellular proliferative response to growth-factor stimulation.
  5. Cell-cycle/cytoskeletal defects: Mitotic and cytokinesis abnormalities from loss of CUL7 function are proposed contributors to short stature; reduced OBSL1 transcription follows loss of CUL7, reinforcing pathway interdependence.
  6. Epigenetic-level convergence: A gene-expression signature of reduced IGF2 and elevated H19 (Silver-Russell-like) further suppresses IGF-II bioavailability, compounding the growth-signaling deficit.
  7. Tissue-level consequence — growth plate dysfunction: Cartilage-specific Cul7 knockout mice show abnormally short/deformed limbs, thickened growth plates, disorganized chondrocyte columns, decreased proliferative-zone cell numbers, and disordered trabecular bone at the metaphysis — implicating both chondrocyte proliferation defects and disrupted endochondral ossification as the proximate tissue mechanism of skeletal growth failure (Longitudinal skeletal growth study, PMID 38367951, ScienceDirect).
  8. Organism-level phenotype: Severe proportionate pre-/postnatal growth restriction, characteristic facial dysmorphism, skeletal (long-bone/vertebral) abnormalities, and (in a subset) gonadal, cardiac, and respiratory involvement, with sparing of cognitive development.

Molecular pathways involved: Ubiquitin-proteasome system (SCF/Cullin-RING E3 ligase pathway); insulin/IGF-1/GH-IRS1-Akt signaling axis; microtubule/cytoskeletal regulation via LL5β.

Cellular processes: Impaired cell proliferation, disrupted mitosis/cytokinesis, altered cell migration (cytoskeletal), disrupted chondrocyte proliferation and endochondral ossification.

Protein dysfunction: Loss-of-function of CUL7 (scaffold protein of Golgi-localized E3 ligase), OBSL1 (cytoskeletal adaptor), CCDC8 (coiled-coil complex partner); consequent failure of substrate (IRS-1, cyclin D1, LL5β) ubiquitination/degradation.

Suggested ontology terms: - GO (biological process): GO:0016567 (protein ubiquitination), GO:0043161 (proteasome-mediated ubiquitin-dependent protein catabolic process), GO:0043410 (positive regulation of MAPK cascade)/IGF signaling-related terms, GO:0001501 (skeletal system development), GO:0060350 (endochondral bone morphogenesis) - GO (molecular function): GO:0031625 (ubiquitin protein ligase binding), GO:0004842 (ubiquitin-protein transferase activity) - CL (cell types): CL:0000138 (chondrocyte), CL:0000057 (fibroblast, used in in vitro studies) - UBERON: UBERON:0002102 (growth plate cartilage), UBERON:0001474 (bone element)

7. Anatomical Structures Affected

Organ/system level: - Skeletal system (primary): long bones, vertebral column, pelvis, ribs, hands/feet — UBERON:0001434 (skeletal system) - Craniofacial skeleton and soft tissue: skull shape, facial structure — UBERON:0000033 (head) - Reproductive system (males): testes, scrotum, penile/urethral development (hypospadias) — UBERON:0000473 (testis) - Cardiovascular system: aortic root — UBERON:0002049 (aorta) - Respiratory system: neonatal lung maturation/distress in some populations — UBERON:0002048 (lung) - CNS: spared (normal intelligence)

Tissue/cell level: Growth plate chondrocytes (proliferative zone), cortical/trabecular bone, dermal fibroblasts (used for functional IGF2/H19 studies), Golgi-associated cellular machinery broadly (since CUL7 localizes to the Golgi apparatus).

Subcellular level: Golgi apparatus (site of the 3-M E3 ligase complex) — GO:0005794 (Golgi apparatus); microtubule cytoskeleton — GO:0005874 (microtubule); ubiquitin-proteasome machinery — GO:0000502 (proteasome complex).

Localization/laterality: Findings are generally bilateral and symmetric (proportionate short stature, symmetric limb involvement) — this symmetry is a key differentiator from Silver-Russell syndrome, which classically shows limb-length asymmetry.

8. Temporal Development

Onset: Prenatal — intrauterine growth restriction is evident before birth (low birth weight/length with normal-for-age head circumference), making this a primordial (prenatal-onset) growth disorder rather than a postnatal-onset condition.

Progression: Persistent, non-progressive, lifelong short stature without catch-up growth. The disorder is generally stable rather than degenerative — final adult height is reached without further mechanistic deterioration, though secondary orthopedic (kyphoscoliosis, joint laxity) and endocrine (pubertal, gonadal) complications can evolve over time.

Phenotype evolution with age (per the 2025 natural-history review of 217 cases, PMID 41437277): - Infancy is the period of clearest diagnostic signal — short length/thorax, protuberant abdomen, prominent heels, bulbous/fleshy nasal tip, and the most distinct radiographic long-bone/vertebral findings. - Childhood through adolescence: most dysmorphic and radiographic features progressively attenuate/become "increasingly vague"; short stature and the characteristic nasal appearance persist as the most durable diagnostic clues. - Puberty/adulthood: some males show initially normal pubertal onset followed by secondary (progressive) gonadal failure in adolescence/young adulthood (declining testicular volume, rising gonadotropins) — a later-emerging, evolving feature rather than a static congenital one.

Critical periods: Infancy/early childhood is the critical window for clinical/radiographic diagnosis and for initiating growth hormone trials, given diminishing diagnostic specificity of physical signs with age.

9. Inheritance and Population

Epidemiology: - Prevalence: Not formally established; fewer than ~250 molecularly confirmed cases reported in the literature worldwide since the first description in 1975 (GeneReviews NBK1481); Orphanet lists it as "very rare" with prevalence unknown/<1/1,000,000. - Incidence: Not reported at a population level (too rare for standard surveillance-based incidence estimation).

Inheritance pattern: Autosomal recessive for all three subtypes (3M1/CUL7, 3M2/OBSL1, 3M3/CCDC8). Sibling recurrence risk when both parents are carriers: 25% affected, 50% carrier, 25% unaffected/non-carrier.

Penetrance: Complete (biallelic pathogenic variants are consistently associated with the phenotype).

Expressivity: Variable — facial/skeletal severity and final height vary by gene (CUL7 generally associated with the shortest stature; CCDC8-related disease tends to be milder with relatively higher final height) and to some extent by specific allele (e.g., the Yakut CUL7 founder variant produces a distinct sub-phenotype with high neonatal respiratory distress but comparatively fewer bone abnormalities).

Genetic anticipation: Not applicable/not reported (not a repeat-expansion disorder).

Germline mosaicism: Not specifically documented in the reviewed literature, though standard recessive-disorder recurrence counseling applies.

Founder effects: - Yakut (Sakha) population, Siberia: CUL7 c.4581dupT — described in 43 affected individuals (Maksimova et al. 2007, PMC2652813); associated with high neonatal respiratory distress (~41%) and fewer skeletal anomalies than typical CUL7-related disease. - Maghrebian/Tunisian population: CUL7 c.4451_4452delTG. - Turkish population: OBSL1 c.1273dupA (emerging founder allele).

Consanguinity role: Strongly associated with increased case frequency, as expected for an ultra-rare autosomal recessive disorder; many reported cohorts (e.g., recent Chinese and Middle Eastern case series) note parental consanguinity.

Carrier frequency: Not established at a population level outside founder populations.

Population demographics: Reported cases span diverse ethnic groups (European, Middle Eastern/Maghrebian, East Asian [Chinese, Japanese], Siberian/Yakut, Turkish), consistent with panethnic occurrence with regional founder-variant clustering. No formal sex-ratio skew is reported (autosomal recessive, so no inherent sex bias, aside from male-specific gonadal manifestations being clinically more apparent in males).

10. Diagnostics

Diagnostic criteria (GeneReviews): Diagnosis established in a proband with prenatal-onset persistent growth deficiency plus characteristic clinical and radiographic features, and/or identification of biallelic pathogenic variants in CCDC8, CUL7, or OBSL1 by molecular genetic testing. No formally published consensus clinical scoring criteria exist.

Clinical tests: - Imaging: Skeletal radiographic survey — long bones (slender diaphyses, flared metaphyses), spine (tall vertebral bodies), pelvis (small pelvic bones); echocardiography for aortic root assessment. - Laboratory: IGF-1 levels (monitored during GH trials); gonadotropin/testosterone panel in pubertal/adult males for hypogonadism surveillance. - Prenatal ultrasound: Short long bones and other skeletal findings can be detected as early as 24 weeks' gestation, though findings are not pathognomonic on their own.

Genetic testing: - Recommended approach: multigene panel covering CUL7, OBSL1, CCDC8 (and relevant differential-diagnosis genes), or exome/genome sequencing given phenotypic overlap with other growth-restriction syndromes. - Single-gene sequential testing (starting with CUL7, the most frequently implicated gene) is an alternative in resource-limited settings or when a founder variant is suspected by ancestry. - Prenatal and preimplantation genetic testing are available once familial pathogenic variants are identified (demonstrated in a 2023 Chinese family case, PMC10767403).

Clinical criteria / differential diagnosis (per GeneReviews): - Silver-Russell syndrome: often shows limb-length asymmetry and relative macrocephaly at birth; lacks the classic 3-M long-bone/vertebral radiologic signature; notably, 3-M syndrome shares an IGF2/H19 expression signature with SRS at the molecular level despite distinct genetic causes. - Mulibrey nanism: less severe IUGR; distinct facial gestalt (high forehead, "pseudohydrocephalic" skull). - IGF1R haploinsufficiency/deficiency: microcephaly and intellectual disability common in severe cases (contrasts with normal head size/intelligence in 3-M). - Dubowitz syndrome: microcephaly, eczema, intellectual disability. - Fetal alcohol syndrome: acquired, with microcephaly and nail hypoplasia — important to exclude given overlapping growth restriction/facial features.

Screening: No population-based newborn screening program exists (disorder too rare and non-treatable via early biochemical intervention); diagnosis is clinically/radiographically or genetically triggered rather than screened.

11. Outcome/Prognosis

  • Survival/mortality: Life expectancy is generally normal. No characteristic disease-specific mortality has been documented outside of population-specific neonatal respiratory distress risk (e.g., Yakut founder variant) and rare complete-knockout-lethal equivalents in constitutive animal models (not applicable to human heterozygous-viable genotypes, since humans with the disease are, by definition, live-born survivors of hypomorphic/partial-loss-of-function alleles).
  • Morbidity: Primarily orthopedic (kyphoscoliosis, hip dysplasia/dislocation, joint hypermobility-related complications, potential early arthritis), endocrine (progressive gonadal failure in some males), and cardiovascular (aortic root dilatation) morbidity, layered onto lifelong short stature.
  • Cognitive/functional outcome: Normal intelligence and generally preserved functional independence, distinguishing 3-M syndrome prognostically from many other severe growth-restriction syndromes.
  • Complications: Neonatal respiratory distress (population-dependent), hip dislocation, scoliosis, joint laxity/early arthritis risk, hypospadias (surgical correction), progressive hypogonadism in some males, aortic root dilation.
  • Prognostic factors: Causal gene (CUL7 > OBSL1 > CCDC8 in terms of severity/short stature), specific founder variant (e.g., Yakut variant → higher respiratory risk), and timing/response to growth hormone trial.
  • Recovery potential: Height deficit is not "recovered" — it is a fixed, non-progressive trait once adult stature is reached; management is supportive/adaptive rather than curative.

12. Treatment

Pharmacotherapy — Growth hormone (GH): - Standard of care approach: referral to pediatric endocrinology for a trial of recombinant human growth hormone, particularly in prepubertal children, with close monitoring of growth velocity and IGF-1 levels. - Response is variable: some children show meaningful improvement in growth velocity; others show poor response. A well-documented case (novel CUL7 mutation, associated with neonatal respiratory distress) showed a good response to GH therapy (PMID from PMC4418346, Endocrinol Diabetes Metab Case Rep); another 18-year follow-up case documented 3-M syndrome co-occurring with growth hormone deficiency responding to treatment (PMC3608257, Ital J Pediatr 2013). - One reported individual with CUL7-related disease treated with recombinant human IGF-1 showed a poor response and significant side effects — IGF-1 therapy is not generally favored. - NCIT term: NCIT:C15986 (Pharmacotherapy) as the general treatment_term, with growth hormone as therapeutic_agent (e.g., somatropin, CHEBI-bindable).

Surgical/interventional: - Orthopedic surgery for hip dysplasia/dislocation and progressive kyphoscoliosis (NCIT:C16186, Orthopedic Surgical Procedure). - Surgical limb lengthening is an option for selected patients seeking increased stature (NCIT:C15329, Surgical Procedure). - Urological surgery for hypospadias correction in affected males (NCIT:C15329).

Supportive/rehabilitative: - Physical therapy (NCIT:C15302) and occupational therapy to maximize function and address joint hypermobility/adaptive needs. - Environmental/community adaptations (adaptive equipment, community child-health services) for short stature.

Endocrine management: Monitoring and, where indicated, hormone replacement for males with progressive hypogonadism (testosterone/gonadotropin-guided management by endocrinology).

Surveillance/monitoring protocol (from GeneReviews):

System Evaluation Suggested frequency
Growth Growth chart/velocity Every 6–12 months
Musculoskeletal Joint hypermobility, kyphoscoliosis assessment Annually
Hip Dislocation screening Each visit in infancy, especially if walking delayed
Cardiac Echocardiogram (aortic root) Consider in adolescence

Experimental/investigational: No gene therapy, RNA-based therapy, or targeted molecular therapy has been developed or trialed for 3-M syndrome; management remains supportive/symptomatic rather than mechanism-targeted, reflecting the structural (ubiquitin-ligase complex assembly) nature of the defect, which is not straightforwardly druggable. No relevant ClinicalTrials.gov interventional trials specific to 3-M syndrome were identified in this search.

Treatment outcomes / adverse events: GH therapy is generally well tolerated in the reported cases with variable efficacy; IGF-1 therapy in the one reported case caused significant side effects with poor efficacy.

13. Prevention

  • Primary prevention: Not applicable in the traditional sense (no modifiable environmental cause); the only "primary prevention" lever is reproductive/genetic counseling for known carrier couples, particularly in consanguineous unions or founder-variant populations (Yakut, Maghrebian, Turkish).
  • Secondary prevention (early detection): Prenatal ultrasound surveillance (skeletal findings detectable from ~24 weeks in at-risk pregnancies) and, where familial variants are known, prenatal diagnosis and preimplantation genetic testing (PGT) — demonstrated in a 2023 Chinese family case using novel biallelic CUL7 variants (PMC10767403).
  • Genetic counseling: Central to prevention/family planning — carrier detection in relatives once the familial variant(s) are known; counseling on the 25% recurrence risk for future pregnancies of carrier couples; sibling evaluation for undiagnosed short stature.
  • Screening programs: No population-based newborn or carrier screening program exists given extreme rarity, though targeted carrier screening is reasonable in founder populations with known high local carrier frequency.
  • Tertiary prevention: Surveillance protocol above (orthopedic, cardiac, endocrine) aims to prevent/mitigate secondary complications (scoliosis progression, hip damage, aortic complications, missed hypogonadism) rather than the primary disease process.

14. Other Species / Natural Disease

Naturally occurring veterinary disease: - Sheep (Ovis aries): A recessively inherited disorder in Australian Poll Merino/Merino sheep called Brachygnathia, Cardiomegaly and Renal Hypoplasia Syndrome (BCRHS) was found to be caused by a frameshift variant in OBSL1 (p.(Val573Trpfs119)), representing a naturally occurring ovine model of human 3M syndrome-2. Identification enabled improved breeding management of the affected flock via carrier detection (BMC Genomic Data 2020; OMIA:001595-9940, "Growth disorder, syndromic, OBSL1-related," in Ovis aries*).

Comparative biology / model organisms: - Mouse (Mus musculus), Cul7 knockout: Constitutive Cul7−/− mice are perinatal lethal — severe growth retardation in late gestation and respiratory distress after birth; some models show abnormal bone mineralization, decreased body weight, and reduced bone mineral density; others show severe fetal growth restriction and perinatal death (multiple studies cited in PMC10423707 background). To circumvent lethality, a cartilage-specific conditional knockout (Cul7^fl/fl;Col2a1-CreERT2) was generated: these mice show short/deformed limbs, thickened growth plates, disorganized proliferative-zone chondrocyte columns, and disordered metaphyseal trabecular bone — implicating defective chondrocyte proliferation and endochondral ossification (PMID 38367951, ScienceDirect, "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice"). - Mouse, CCDC8 knockout: A 2023 study (Molecular Biomedicine, PMID 37574524, PMC10423707) established a Ccdc8−/− mouse model; knockout was highly lethal (only 4 live-born knockouts from 410 mice bred, <1% success rate), with placental developmental disorder, intrauterine growth retardation, intrauterine death, and perinatal death closely paralleling Cul7 knockout embryo phenotypes — supporting the shared-pathway model of CUL7/OBSL1/CCDC8 function. - OBSL1 knockout studies (Hanson et al. 2009, PMC2694976) established the direct physical and functional link between OBSL1 and the CUL7-containing E3 ligase complex, foundational to the current mechanistic model.

Cross-species relevance: These animal models (sheep OBSL1, mouse Cul7/Ccdc8) confirm cross-species conservation of the 3-M E3 complex's essential role in fetal/perinatal growth and support their use for mechanistic and (potentially) therapeutic research, though the severe perinatal lethality of constitutive knockouts limits their use to conditional/tissue-specific systems for postnatal phenotyping.

Zoonotic potential: None — this is a purely genetic (non-infectious) disorder; no transmission risk.

15. Model Organisms

Model Type Key features Reference
Cul7−/− mouse (constitutive) Genetic knockout, mammalian Perinatal lethal; late-gestation growth retardation, respiratory distress at birth; some lines show abnormal bone mineralization and reduced BMD Cited in PMC10423707 background
Cul7^fl/fl;Col2a1-CreERT2 mouse Conditional/tissue-specific (cartilage) knockout Short/deformed limbs, thickened growth plate, disorganized proliferative chondrocytes, disordered metaphyseal trabecular bone; viable, enabling postnatal skeletal phenotyping PMID 38367951
Ccdc8−/− mouse Constitutive knockout Highly lethal (<1% live-birth rate of homozygotes); placental defects, IUGR, intrauterine/perinatal death mirroring Cul7 knockouts PMID 37574524 / PMC10423707
Merino/Poll Merino sheep, OBSL1 frameshift Naturally occurring animal model BCRHS: brachygnathia, cardiomegaly, renal hypoplasia; ovine model of human 3M syndrome-2; enabled breeding-based carrier management BMC Genomic Data 2020 / OMIA:001595-9940
Human dermal fibroblasts (patient-derived) Cellular/in vitro Reduced IGF2 expression, increased H19 expression, reduced IGF-II secretion vs. controls; used to demonstrate the IGF2-silencing mechanism PMID 24148222

Applications: These models collectively support study of (a) the shared CUL7-OBSL1-CCDC8 E3-ligase-complex biology, (b) chondrocyte/growth-plate-specific consequences of complex loss, (c) placental/perinatal growth-restriction mechanisms, and (d) potential future therapeutic-target validation (e.g., IGF-1/Akt pathway modulation), though no model has yet been used for interventional (drug) testing specific to 3-M syndrome in the literature surveyed.

Model limitations: Constitutive knockouts in mouse (Cul7, Ccdc8) are embryonic/perinatal lethal and thus do not recapitulate the live-born, postnatal phenotype seen in humans (who carry hypomorphic/partial-loss-of-function alleles rather than complete null states compatible only with lethality) — a clear human-model mismatch: conditional/tissue-specific knockouts were required to generate a viable, phenotypically informative postnatal model. The sheep OBSL1 model, by contrast, is a naturally occurring, viable (in appropriate genotype/zygosity) large-animal model that may better approximate the human postnatal skeletal phenotype, though comparative fidelity has not been formally characterized against the human 3-M radiographic signature.

Summary Table: Suggested Ontology Bindings

Category Term
Disease MONDO:0007477 (3M syndrome 1); OMIM #273750/#612921/#614205; ORPHA:2616
Genes hgnc CUL7, hgnc OBSL1, hgnc CCDC8 (verify current HGNC IDs before curation)
Phenotypes (HP) HP:0004322 Short stature; HP:0001511 IUGR; HP:0002938 Hyperlordosis; HP:0001382 Joint hypermobility; HP:0002751 Kyphoscoliosis; HP:0000047 Hypospadias; HP:0000268 Dolichocephaly; HP:0011800 Midface retrusion
GO (BP) GO:0016567 protein ubiquitination; GO:0060350 endochondral bone morphogenesis
GO (CC) GO:0005794 Golgi apparatus
CL CL:0000138 chondrocyte
UBERON UBERON:0002102 growth plate cartilage
NCIT (treatment) NCIT:C15986 Pharmacotherapy (GH); NCIT:C16186 Orthopedic Surgical Procedure; NCIT:C15302 Physical Therapy

Sources

  • 3-M Syndrome – GeneReviews (NBK1481)
  • OMIM #273750 – THREE M SYNDROME 1
  • OMIM #612921 – THREE M SYNDROME 2
  • OMIM #614205 – THREE M SYNDROME 3
  • Orphanet: 3M syndrome (ORPHA2616)
  • NORD: Three M Syndrome
  • Hanson D et al., "The Primordial Growth Disorder 3-M Syndrome Connects Ubiquitination to the Cytoskeletal Adaptor OBSL1," Am J Hum Genet 2009, PMID 19481195 — PMC2694976
  • Meyer R et al., "3-M syndrome: a growth disorder associated with IGF2 silencing," Endocr Connect 2013, PMID 24148222 — PMC3847915
  • Maksimova N et al., "Clinical, molecular and histopathological features of short stature syndrome with novel CUL7 mutation in Yakuts," 2007 — PMC2652813
  • "3-M syndrome: evolution of the phenotype over time," Ital J Pediatr, Dec 2025, PMID 41437277, DOI 10.1186/s13052-025-02172-8 — PMC12838503
  • "Establishment of the 3M syndrome animal model in CCDC8 knockout mice," Mol Biomed 2023, PMID 37574524 — PMC10423707
  • "Longitudinal skeletal growth and growth plate morphological characteristics of chondro-tissue specific CUL7 knockout mice," PMID 38367951 — ScienceDirect
  • "Molecular basis of a new ovine model for human 3M syndrome-2," BMC Genomic Data 2020 — Springer; PMC7493961
  • Aldhoon-Hainerová I et al., "Gonadal Failure in a Male With 3-M Syndrome," JCEM Case Rep 2024, PMID 38847008 — PMC11154130
  • "Chinese patients with 3M syndrome: clinical manifestations and two novel pathogenic variants," Front Genet 2023 — Frontiers
  • "3-M syndrome: a novel CUL7 mutation associated with respiratory distress and a good response to GH therapy" — PMC4418346
  • "3-M syndrome associated with growth hormone deficiency: 18 year follow-up of a patient," Ital J Pediatr 2013 — PMC3608257
  • "Prenatal diagnosis and preimplantation genetics testing of 3M syndrome in a Chinese family with novel biallelic variants of CUL7" — PMC10767403
  • Society for Endocrinology, "Loss of the Golgi localised E3 ubiquitin ligase containing Cullin 7 in 3-M syndrome leads to reduced cell proliferation and reduced IGF1 mediated activation of Akt" — Endocrine Abstracts

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