Brachyolmia-Amelogenesis Imperfecta Syndrome

Mendelian MONDO:0011018 Pathograph 29 Show in embeddings browser Brachyolmia Skeletal dysplasia Syndromic amelogenesis imperfecta

Brachyolmia-amelogenesis imperfecta syndrome, also called dental anomalies and short stature (DASS), is an autosomal recessive LTBP3-related disorder combining enamel hypoplasia and dental anomalies with short stature and variable skeletal dysplasia. Platyspondyly and a short trunk are characteristic, but proportionate short stature and mild long-bone abnormalities also occur. Cardiovascular involvement includes valvular abnormalities, aortic dilatation, aneurysms and dissection; vascular disease can extend beyond the thoracic aorta. LTBP3 regulates extracellular localization and activation of latent TGF-beta, but the direction and timing of signaling changes in affected human tissues remain incompletely established. Mouse models reproduce aspects of the dental and craniofacial phenotype without reproducing the full human skeletal or vascular disorder.

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1
Inheritance
9
Pathophys.
34
Phenotypes
1
Hypotheses
3
Gaps
29
Pathograph
1
Genes
8
Medical Actions
5
Models
24
References
1
Deep Research
🏷

Classifications

Harrison's Part
GENETICS ENVIRONMENT DISEASE
👪

Inheritance

1
Autosomal recessive HP:0000007
Biallelic LTBP3 variants segregate with DASS in both homozygous and compound heterozygous families. At least one compound heterozygous patient inherited a maternal allele and had a second de novo allele. A 25% recurrence probability applies when both parents carry a disease-causing allele; segregation testing is needed for family-specific counseling.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"All mutations segregated with the disease phenotype in each family and were confirmed by Sanger sequencing"
Segregation across four families is the primary inheritance evidence.
PMID:34906192 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"one of them (c.1965del, p.Arg656fs) was inherited from his mother, while the other (c.625dup, p.Leu209fs) was de novo."
One compound heterozygous case had a de novo allele; two carrier parents are not universal.
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Mechanistic Hypotheses

1
LTBP3-dependent extracellular regulation of latent TGF-beta
ltbp3_tgfb_bioavailability CANONICAL
LTBP3 loss alters the extracellular handling of latent TGF-beta and is associated with dental, skeletal and vascular disease. Biochemical studies establish latent-complex binding and matrix incorporation. Reduced local TGF-beta signaling is proposed for parts of the dental and skeletal phenotype, but has not been directly demonstrated for all patient alleles or tissues. Vascular signaling responses vary by model and disease stage, and TGF-beta-independent matrix functions remain possible.
Pathograph links
Altered Latent TGF-beta Complex Assembly -> Altered Extracellular Localization of Latent TGF-beta Abnormal complexes may alter matrix incorporation and subsequent ligand availability.
Altered Extracellular Localization of Latent TGF-beta -> Altered Local TGF-beta Bioavailability Matrix incorporation controls latent ligand localization and activation.
Altered Local TGF-beta Bioavailability -> Abnormal Ameloblast Differentiation A proposed link between altered ligand availability and enamel-organ dysfunction; patient signaling measurements are lacking.
Altered Local TGF-beta Bioavailability -> Disturbed Axial Skeletal Development The vertebral mechanism is inferred from expression and pathway biology, not demonstrated by a model reproducing platyspondyly.
Disturbed Axial Skeletal Development -> Platyspondyly Vertebral body flattening is a characteristic clinical endpoint.
Disturbed Axial Skeletal Development -> Short Stature Short stature can be disproportionate or proportionate; contributions outside the vertebrae vary.
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Discussions and Knowledge Gaps

3
Why do Ltbp3-null mice fail to develop the platyspondyly seen in human LTBP3 disease?
HUMAN MODEL MISMATCH ltbp3_mouse_axial_mismatch
Attached to
pathophysiology#Disturbed Axial Skeletal Development animal_models#Mouse
The null mouse reproduces enamel and maxillary abnormalities but not vertebral flattening. Human bone density varies, so density does not supply a universal opposite-direction mismatch. Allele-specific residual function, developmental timing, biomechanics and functions beyond TGF-beta regulation remain plausible explanations.
Proposed experiments
Compare patient-allele knock-ins with null mice
ltbp3_allele_knockin_axial
Measure transcript and protein effects of selected patient alleles before comparing vertebral morphology, bone density and local signaling with null and wild-type mice across ages. This tests allele-dependent effects without assuming that every patient allele is hypomorphic.
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Model Organism
"Platyspondyly however was not observed in the Ltbp3−/− knockout mice."
Directly reported failure to reproduce the human axial phenotype.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Increased bone density was present in the spine and at the base of the skull."
Full text of PMID:19344874; radiographs and quantitative assessment were reported.
Which matrix and signaling defects initiate human LTBP3 aortopathy?
KNOWLEDGE GAP ltbp3_vascular_signaling_context
Attached to
pathophysiology#Impaired Vascular Wall Homeostasis
Human genetic evidence for aortopathy is strong, but mouse results differ with body-size normalization and Fbn1 background. In dual-paralog zebrafish mutants, elevated pSmad3 follows dilation. These observations do not establish a uniform primary increase or decrease in signaling or justify extrapolating a signaling-directed therapy to DASS.
Show evidence (2 references)
PMID:35098309 SUPPORT INDIRECT PRIMARY RESULT Model Organism
"enlargement of the ventricle and OFT in DKO animals precedes hyperactivation of TGFβ signaling and not vice versa."
The double-knockout zebrafish result limits a uniform primary signaling-direction claim.
PMID:30306291 SUPPORT DIRECT PRIMARY RESULT Model Organism
"we found that ATA diameter is slightly greater than normal in Ltbp3−/− mice, but not significantly so, at least at the ages studied."
Independent allometric analysis limits the strength of the mouse-to-human aortopathy correspondence.
Which neurological, hearing and carrier findings belong to the LTBP3 disease spectrum?
KNOWLEDGE GAP ltbp3_additional_variant_attribution
Attached to
genetic#LTBP3
The 2021 boy had neurological findings and additional TPH1 and EDA variants of uncertain relevance. The 2024 authors attributed hearing impairment in one family to a separate CABP2 mechanism, although their pathogenicity interpretation is not definitive. The 2022 abstract lists tricuspid prolapse and abnormal dentin across a family without resolving every finding by genotype. These observations should not automatically become established biallelic LTBP3 manifestations.
Show evidence (2 references)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"the hearing impairment phenotype in Egyptian patients of family A has a separate transmission mechanism independent of LTBP3."
Authors’ attribution; this statement does not independently establish CABP2 variant pathogenicity.
PMID:35352826 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The mother and brother of the proband carried the heterozygous variant p.Arg545ProfsTer22, but only the mother showed any DASS characteristics."
Variable findings among heterozygous relatives argue against uniform carrier penetrance.
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Pathophysiology

9
Biallelic LTBP3 Loss of Function
Homozygous or compound heterozygous truncating and splice variants cause DASS; missense variants have also been reported. Residual function is not quantified for most alleles. Patient RNA studies show variant-dependent transcript reduction, intron retention or escape from nonsense-mediated decay, so a uniform hypomorphic effect cannot be assumed.
LTBP3 hgnc:6716 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves LTBP3 (hgnc:6716). hgnc:6716 is a gene from the HUGO Gene Nomenclature Committee.
Genetic context variant_origin: GERMLINE functional_impact_category: LOSS_OF_FUNCTION
Germline biallelic variants, either homozygous or compound heterozygous.
Experimental models
Patient-derived LTBP3 lymphoblastoid cell lines CELL LINE Patient-derived transcript reduction supports loss of function for the tested allele.
Animal models
British Shorthair cats with candidate LTBP3 skeletal dysplasia Cat perturbs Candidate recessive frameshift provides comparative genetic evidence; the molecular effect remains predicted.
Downstream
Altered Latent TGF-beta Complex Assembly Loss of intact LTBP3 can impair latent-complex assembly; individual variant effects are often predicted.
Impaired Vascular Wall Homeostasis Biallelic variants are associated with aneurysm and dissection, but the intervening molecular steps remain unresolved.
Premature Cranial-base Synchondrosis Ossification Ltbp3 loss causes premature cranial-base ossification in null mice; applicability to human disease remains inferred.
Show evidence (4 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"A single gene, LTBP3, was found to carry bi-allelic mutations in all affected individuals from the four families"
The gene-identification result: one gene, biallelic, in every affected individual across four independently ascertained families.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml SUPPORT DIRECT PRIMARY RESULT In Vitro
"an approximately 5-fold reduction in mRNA levels associated with the mutated allele, suggesting that nonsense-mediated decay is occurring"
Full text of PMID:19344874: patient lymphoblastoid-cell RNA supports transcript loss for this nonsense allele.
PMID:34573388 SUPPORT DIRECT PRIMARY RESULT In Vitro
"the disease-associated variant altered proper splicing of the LTBP3 transcript, leading to retention of intron 20"
Patient peripheral-blood RNA demonstrates aberrant splicing of c.2894-2A>G; protein truncation was predicted.
+ 1 more reference
Altered Latent TGF-beta Complex Assembly
LTBP3 forms a complex with latent TGF-beta. Patient truncating and splice variants are predicted to impair this complex, but direct biochemical tests are unavailable for most alleles. Coexpression experiments establish the normal interaction and the dependence of efficient LTBP3 secretion on binding the TGF-beta propeptide; they do not demonstrate that LTBP3 deficiency abolishes all TGF-beta secretion.
LTBP3-dependent extracellular regulation of latent TGF-beta
Downstream
Altered Extracellular Localization of Latent TGF-beta Abnormal complexes may alter matrix incorporation and subsequent ligand availability. LTBP3-dependent extracellular regulation of latent TGF-beta
Show evidence (2 references)
PMID:12062452 SUPPORT INDIRECT PRIMARY RESULT In Vitro
"The secretion of LTBP-3 requires complexing of LTBP-3 with Cys33 of the TGF-beta propeptide."
Biochemical evidence for secretion of the binding protein in the normal complex; not a patient-variant assay.
PMID:35352826 SUPPORT INDIRECT PRIMARY RESULT Computational
"variants are expected to result in abnormal LTPB3 protein, failure of TGFβ-LAP-LTBP3 complex formation, and subsequent disruption of TGFβ"
Names the specific molecular failure - the latent complex of TGF-beta, its propeptide (LAP) and LTBP3 does not assemble. The snippet keeps "are expected to result in" deliberately: this is the authors' predicted consequence of two specific variants, not an assay result, which is why it is graded COMPUTATIONAL and INDIRECT.
Altered Extracellular Localization of Latent TGF-beta
LTBP3-containing latent complexes interact with the fibrillin matrix. Purified-protein assays demonstrate TG2-mediated cross-linking of the LTBP3 C-terminal complex to fibrillin, while fibrillin-deficient cell cultures have defective LTBP3 matrix deposition. These establish a matrix-localization function; they do not exclude structural roles or prove a single direction of TGF-beta signaling change in DASS.
LTBP3-dependent extracellular regulation of latent TGF-beta
extracellular matrix organization GO:0030198 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves extracellular matrix organization (GO:0030198). GO:0030198 is a biological process from the Gene Ontology.
Downstream
Altered Local TGF-beta Bioavailability Matrix incorporation controls latent ligand localization and activation. LTBP3-dependent extracellular regulation of latent TGF-beta
Show evidence (2 references)
PMID:35122964 SUPPORT INDIRECT PRIMARY RESULT In Vitro
"Cross-linking was also performed with LTBP3-CT-SLC (CT3-SLC) which also formed a cross-link to fibrillin but less efficiently"
Purified recombinant complexes provide direct LTBP3-specific biochemical evidence; the detailed structural and activation assays in this paper chiefly concern LTBP1.
PMID:22495824 SUPPORT INDIRECT PRIMARY RESULT In Vitro
"the deposition of LTBP-3 and -4 is abrogated, whereas LTBP-1 is still deposited into the matrix through its interaction with fibronectin"
Fibrillin-deficient matrix context; indirect evidence for the localization function disrupted by LTBP3 disease.
Altered Local TGF-beta Bioavailability
Disturbed extracellular handling of latent TGF-beta is proposed to alter tissue-specific signaling during tooth and skeletal development. Reduced signaling in DASS ameloblasts or vertebral growth plates remains a model-based inference. In zebrafish lacking both ltbp1 and ltbp3, vascular dilation precedes increased pSmad3, illustrating that late signaling elevation can follow injury rather than initiate it.
LTBP3-dependent extracellular regulation of latent TGF-beta
transforming growth factor beta receptor signaling pathway GO:0007179 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves transforming growth factor beta receptor signaling pathway (GO:0007179). GO:0007179 is a biological process from the Gene Ontology.
Downstream
Abnormal Ameloblast Differentiation A proposed link between altered ligand availability and enamel-organ dysfunction; patient signaling measurements are lacking. LTBP3-dependent extracellular regulation of latent TGF-beta
Disturbed Axial Skeletal Development The vertebral mechanism is inferred from expression and pathway biology, not demonstrated by a model reproducing platyspondyly. LTBP3-dependent extracellular regulation of latent TGF-beta
Show evidence (2 references)
PMID:12379497 SUPPORT INDIRECT PRIMARY RESULT Model Organism
"This suggests that Ltbp-3 may control chondrocyte differentiation by regulating TGF-beta availability."
Mouse cranial-base findings motivate the signaling model, without direct confirmation in human vertebrae.
PMID:35098309 SUPPORT INDIRECT PRIMARY RESULT Model Organism
"enlargement of the ventricle and OFT in DKO animals precedes hyperactivation of TGFβ signaling and not vice versa."
The double-knockout zebrafish result limits a uniform primary signaling-direction claim.
Abnormal Ameloblast Differentiation
Ltbp3 is expressed in developing ameloblasts. Enamel-matrix defects begin early in knockout mice, but detailed histology found no obvious secretory- or transition-stage ameloblast shape changes and marked maturation-stage disorganization. Human enamel ultrastructure suggests disturbed secretory architecture; a specific defect in Tomes process formation is a hypothesis rather than a direct cellular observation in patients.
ameloblast CL:0000059 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves ameloblast (CL:0000059). CL:0000059 is a cell type from the Cell Ontology.
amelogenesis GO:0097186 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves amelogenesis (GO:0097186). GO:0097186 is a biological process from the Gene Ontology.
Downstream
Hypoplastic Enamel Formation Enamel-organ dysfunction produces reduced and disorganized enamel.
Show evidence (3 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Model Organism
"At E18.5 labeling was observed in differentiating ameloblasts and odontoblasts. Transcripts were scattered at the apical secretory pole of ameloblasts."
Places the gene product in the right cell at the right stage and, more pointedly, at the secretory pole.
PMID:28084688 SUPPORT DIRECT PRIMARY RESULT Model Organism
"At the secretory and transition stages, ameloblasts from Ltbp3‐/‐ mice showed no obvious morphological changes compared with ameloblasts from WT mice"
Mouse histology distinguishes the timing of epithelial changes from the earlier enamel-matrix defect.
PMID:28084688 SUPPORT DIRECT PRIMARY RESULT Model Organism
"Organization of maturation-stage ameloblasts was severely disrupted."
Maturation-stage phenotype in Ltbp3-null mice.
Hypoplastic Enamel Formation
Thin, irregular or absent enamel affects both dentitions. Patient ultrastructure shows loss of the initial aprismatic layer and abnormal prismatic architecture. Dentin was normal in the 2015 examined family but abnormal dentin and pulp calcification were reported subsequently, so this is not uniformly an enamel-only defect.
enamel mineralization GO:0070166 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves enamel mineralization (GO:0070166). GO:0070166 is a biological process from the Gene Ontology.
Animal models
Ltbp3 knockout mouse Mouse recapitulates Thin and disorganized enamel in incisors and molars corresponds to human enamel hypoplasia. Later histology identifies prominent maturation-stage epithelial changes.
Downstream
Hypoplastic Amelogenesis Imperfecta Clinical manifestation of deficient enamel.
Dental Abscesses Loss of protective dental tissue can contribute to recurrent infection.
Show evidence (3 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The panoramic radiographs confirmed the absence of enamel associated with large pulp chambers and taurodontic molars"
The radiographic dental phenotype, including the associated pulp and root findings.
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The initial aprismatic enamel layer was absent."
The human ultrastructural finding that localises the defect to a specific secretory stage rather than to mineralisation in general.
PMID:35352826 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"include taurodontism, single-rooted molars, abnormal dentin, calcified dental"
The 2022 family broadens the dental phenotype beyond enamel; the accessible abstract does not resolve all findings by genotype.
Disturbed Axial Skeletal Development
LTBP3 is expressed in developing bone and cartilage. Altered endochondral development is a candidate mechanism for vertebral flattening, but Ltbp3-null mice do not develop platyspondyly. The precise cellular lesion in human vertebral growth plates remains unresolved. Human bone density can be reduced or increased, depending on the family.
LTBP3-dependent extracellular regulation of latent TGF-beta
chondrocyte CL:0000138 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves chondrocyte (CL:0000138). CL:0000138 is a cell type from the Cell Ontology.
endochondral bone growth GO:0003416 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves endochondral bone growth (GO:0003416). GO:0003416 is a biological process from the Gene Ontology.
Downstream
Platyspondyly Vertebral body flattening is a characteristic clinical endpoint. LTBP3-dependent extracellular regulation of latent TGF-beta
Short Stature Short stature can be disproportionate or proportionate; contributions outside the vertebrae vary. LTBP3-dependent extracellular regulation of latent TGF-beta
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Model Organism
"Expression was found in various developing bones undergoing either endochondral or intramembranous ossification"
Establishes that the gene is expressed in the right tissue at the right developmental stage for a skeletal dysplasia.
PMID:25669657 SUPPORT INDIRECT Other
"Deregulation of the TGF-beta signaling pathway is likely to interfere with axial skeleton patterning"
Mechanistic interpretation proposed by the authors; not a direct patient growth-plate assay.
Premature Cranial-base Synchondrosis Ossification
In Ltbp3-null mice, premature cranial-base synchondrosis ossification accompanies altered chondrocyte differentiation and a shortened upper jaw. This offers a model for relative mandibular prognathism from maxillary underdevelopment; the same growth-plate process has not been demonstrated in affected humans.
Animal models
Ltbp3 knockout mouse Mouse recapitulates Direct cranial-base lesion in the null mouse; its contribution to human maxillary hypoplasia remains inferred.
Downstream
Maxillary Hypoplasia Premature cranial-base growth arrest can shorten the upper jaw in the mouse model.
Show evidence (1 reference)
PMID:12379497 SUPPORT DIRECT PRIMARY RESULT Model Organism
"the basooccipital-basosphenoid synchondrosis of Ltbp-3 null mice contained increased numbers of hypertrophic chondrocytes."
Mouse histology demonstrates altered cranial-base chondrocyte differentiation preceding premature ossification.
Impaired Vascular Wall Homeostasis
Biallelic LTBP3 variants predispose some affected individuals to aortic and other arterial aneurysms and dissection. The molecular mechanism remains unresolved: altered latent TGF-beta handling and matrix functions are candidates. Mouse aortic dimensions vary with age, genetic background and normalization, and protection from rupture in a fibrillin-deficient double mutant does not establish benefit from reducing LTBP3 in patients.
Animal models
Ltbp3 knockout mouse Mouse partially recapitulates The 2018 study found larger aortic diameters after division by body mass and additional medial elastic lamellar units. The 2019 biomechanical study did not find statistically significant ascending-aortic enlargement at the ages studied after allometric scaling.
Fbn1 hypomorphic and Ltbp3-null double-mutant mouse Mouse perturbs Changing LTBP3 in a fibrillin-deficient matrix changes the vascular phenotype; benefit in this context cannot be generalized to LTBP3-deficient patients.
ltbp1 and ltbp3 double-knockout zebrafish Zebrafish partially recapitulates Captures vascular dilation after combined paralog loss, with limited fidelity to single-gene human disease.
Downstream
Thoracic Aortic Aneurysm Aneurysmal disease can affect thoracic segments.
Abdominal Aortic Aneurysm Abdominal involvement has been reported.
Aortic Dissection Arterial wall failure can produce dissection.
Aortic Root Dilatation Root enlargement may be detected before other aortic complications.
Brachiocephalic Artery Aneurysm Non-aortic arterial involvement demonstrates systemic vascular disease.
Common Carotid Artery Aneurysm Non-aortic arterial involvement demonstrates systemic vascular disease.
Show evidence (2 references)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"aortic root dilation, and multiple visceral and peripheral arterial aneurysms at the age of 54 years"
Full text of PMID:29625025; one biallelic patient demonstrates vascular disease beyond the thoracic aorta.
PMID:34906192 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"thoracic computed tomography (CT) revealed aortic dissection in the descending aorta (DeBakey type III)."
Direct vascular diagnosis in a compound heterozygous patient.
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Pathograph

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

34
Cardiovascular 13
Atrial Septal Defect HP:0001631 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Atrial septal defect (HP:0001631). HP:0001631 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Secundum atrial septal defect (ASD)"
The primary clinical table records ASD in family B individual IV-3; not a prevalence estimate.
Aortic Valve Stenosis HP:0001650 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Aortic valve stenosis (HP:0001650). HP:0001650 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34573388 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"a diagnosis of skeletal dysplasia with aortic stenosis and hypertrophic cardiomyopathy was made"
The single well-documented case of cardiac involvement with a confirmed LTBP3 genotype.
Thoracic Aortic Aneurysm HP:0012727 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Thoracic aortic aneurysm (HP:0012727). HP:0012727 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29625025 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Individuals with compound heterozygous or homozygous variants in these families have aneurysms and dissections of the thoracic aorta"
Primary 2018 family study.
Hypertrophic Cardiomyopathy HP:0001639 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypertrophic cardiomyopathy (HP:0001639). HP:0001639 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34573388 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"a diagnosis of skeletal dysplasia with aortic stenosis and hypertrophic cardiomyopathy was made"
The single well-documented case of cardiac involvement with a confirmed LTBP3 genotype.
Aortic Dissection HP:0002647 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Aortic dissection (HP:0002647). HP:0002647 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34906192 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"thoracic computed tomography (CT) revealed aortic dissection in the descending aorta (DeBakey type III)."
Primary report of a compound heterozygous patient.
Abdominal Aortic Aneurysm HP:0005112 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abdominal aortic aneurysm (HP:0005112). HP:0005112 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"abdominal aortic aneurysm requiring surgical repair at the age of 44"
Full text of PMID:29625025, family TAA909 proband.
Aortic Root Dilatation Aortic root aneurysm HP:0002616 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Aortic root aneurysm (HP:0002616). HP:0002616 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40259772 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Echocardiography revealed aortic root dilatation (diameter: 38 mm, z-score: þ 4.59), mitral valve prolapse"
Direct examination of the 24-year-old sibling in the full report; the paper describes root dilatation and prolapse in all three siblings. The cached PDF preserves the plus sign as þ.
Mitral Valve Prolapse HP:0001634 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Mitral valve prolapse (HP:0001634). HP:0001634 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:25899461 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"In addition to oligodontia and short stature, both sisters have mitral valve prolapse"
The primary report describes two sisters with homozygous truncating LTBP3 variants.
PMID:40259772 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Echocardiography revealed aortic root dilatation (diameter: 38 mm, z-score: þ 4.59), mitral valve prolapse"
Direct examination of the 24-year-old sibling in the full report; the paper describes root dilatation and prolapse in all three siblings. The cached PDF preserves the plus sign as þ.
Mitral Regurgitation HP:0001653 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Mitral regurgitation (HP:0001653). HP:0001653 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"has mild mitral valve prolapse and regurgitation."
Full text of PMID:29625025, biallelic individual III:2 of TAA909, who had no aortic abnormalities on the reported imaging.
Atrial Septal Aneurysm Atrial septal dilatation HP:0011995 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Atrial septal dilatation (HP:0011995). HP:0011995 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"on Doppler assessment, interatrial/atrial septal aneurysm (ASA) was found with dilation of ascending aorta"
The primary report and table describe the affected male sibling in family B; the individual numbering differs between the text and table.
Arterial Tortuosity HP:0005116 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Arterial tortuosity (HP:0005116). HP:0005116 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"pronounced tortuosity of the left internal carotid artery"
Full text of PMID:29625025, family TAA376 individual III:2.
Brachiocephalic Artery Aneurysm HP:0034324 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Brachiocephalic artery aneurysm (HP:0034324). HP:0034324 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"arterial aneurysms (innominate, common carotid; 58)"
Full text of PMID:29625025, primary clinical table; innominate denotes the brachiocephalic artery.
Common Carotid Artery Aneurysm HP:0034325 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Common carotid artery aneurysm (HP:0034325). HP:0034325 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"arterial aneurysms (innominate, common carotid; 58)"
Full text of PMID:29625025, primary clinical table; innominate denotes the brachiocephalic artery.
Genitourinary 1
Nephrocalcinosis HP:0000121 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Nephrocalcinosis (HP:0000121). HP:0000121 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35998423 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The 2 patients from the first family had dental anomalies and short stature syndrome, brachyolmia and nephrocalcinosis with difference in severity"
Documents nephrocalcinosis in two siblings with a confirmed LTBP3 genotype, and records that severity differed between them.
Head and Neck 12
Hypoplastic Amelogenesis Imperfecta HP:0000705 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Amelogenesis imperfecta (HP:0000705). HP:0000705 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The almost complete absence of enamel in both primary and permanent dentitions (Fig. 1A and B) led to the diagnosis of hypoplastic AI, thereby explaining the yellow, small and spaced appearance of the teeth."
Establishes the enamel phenotype in both dentitions and its clinical appearance.
PMID:35998423 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The 2 patients from the first family had dental anomalies and short stature syndrome, brachyolmia and nephrocalcinosis with difference in severity"
Independent replication in a different population, and a reminder that severity varies within a family carrying the same allele.
Hypodontia HP:0000668 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypodontia (HP:0000668). HP:0000668 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:34573388 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Dental evaluations revealed hypodontia and amelogenesis imperfecta"
Documents hypodontia together with the enamel defect in one patient.
PMID:25669657 REFUTE DIRECT PRIMARY RESULT Human Clinical
"showing erupted and non-erupted permanent teeth with no enamel. No teeth are missing."
Records the founding family as having a full complement of teeth, which contradicts hypodontia being an obligate feature. Kept as a REFUTE item rather than removed, because the disagreement between families is the informative part.
Taurodontia HP:0000679 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Taurodontia (HP:0000679). HP:0000679 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The panoramic radiographs confirmed the absence of enamel associated with large pulp chambers and taurodontic molars"
Documents taurodontism radiographically alongside the enamel absence.
Mandibular Prognathism from Maxillary Underdevelopment Mandibular prognathia HP:0000303 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Mandibular prognathia (HP:0000303). HP:0000303 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Class III mandibular prognathism encountered in family 1 was due to maxillary underdevelopment"
Documents the occlusal finding and attributes it to the maxilla, which is the mechanistically meaningful half.
Maxillary Hypoplasia Hypoplasia of the maxilla HP:0000327 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoplasia of the maxilla (HP:0000327). HP:0000327 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Class III mandibular prognathism encountered in family 1 was due to maxillary underdevelopment"
Attributes the occlusal finding to maxillary underdevelopment, which is the phenotype bound here.
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Skull radiograph reveals absent pneumatization of sinuses and mandibular prognathism secondary to underdevelopment of the maxilla."
Radiographic confirmation, with the additional finding of absent sinus pneumatisation in the same underdeveloped maxilla.
Delayed or Failed Tooth Eruption Delayed eruption of teeth HP:0000684 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Delayed eruption of teeth (HP:0000684). HP:0000684 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:35352826 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"pulp blood vessels, prognathic mandible, failure of mandibular tooth eruption,"
Reports failure of mandibular tooth eruption among the new DASS findings in this family.
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Missing teeth (family 4) and retarded teeth eruption (family 3) were also reported."
Records retarded eruption in the founding series, in a different family from the one with missing teeth - so eruption delay and hypodontia are separable.
Dental Malocclusion HP:0000689 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dental malocclusion (HP:0000689). HP:0000689 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Class III mandibular prognathism encountered in family 1 was due to maxillary underdevelopment"
Documents the occlusal finding and attributes it to the maxilla, which is the mechanistically meaningful half.
Webbed Neck HP:0000465 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Webbed neck (HP:0000465). HP:0000465 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Skeletal assessment documented short webbed neck, broad chest, evidences of mild long bones involvement"
Direct observation in the cited study; frequency across affected individuals is not established.
Short Neck HP:0000470 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short neck (HP:0000470). HP:0000470 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Skeletal assessment documented short webbed neck, broad chest, evidences of mild long bones involvement"
Direct observation in the cited study; frequency across affected individuals is not established.
Dental Abscesses Tooth abscess HP:0030757 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Tooth abscess (HP:0030757). HP:0030757 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"She suffered of repeated dental abscesses, leading to the extraction of several teeth at ages 2½ and 5 years."
Direct observation in the cited study; frequency across affected individuals is not established.
Microdontia HP:0000691 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microdontia (HP:0000691). HP:0000691 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"When seen at age 8, she had clearly hypoplasic AI, microdontia and taurodontism."
Direct observation in the cited study; frequency across affected individuals is not established.
Abnormal Dentin Morphology HP:0010299 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Abnormal dentin morphology (HP:0010299). HP:0010299 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:35352826 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"include taurodontism, single-rooted molars, abnormal dentin, calcified dental"
Family-level observation; individual genotype attribution is unresolved in the available abstract.
Limbs 3
Coxa Valga with Elongated Femoral Necks HP:0002673 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Coxa valga (HP:0002673). HP:0002673 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:34573388 SUPPORT INDIRECT BACKGROUND Human Clinical
"This disorder is characterized by skeletal dysplasia (e.g., platyspondyly, short trunk, scoliosis, broad ilia, elongated femoral necks with coxa valga) and severe enamel and dental anomalies."
Lists the femoral neck and hip findings as part of the characteristic skeletal picture.
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"narrow hip joint spaces and coxa valga."
Primary 2024 radiographic description.
Short Distal Finger Phalanges Short distal phalanx of finger HP:0009882 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short distal phalanx of finger (HP:0009882). HP:0009882 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"short distal phalanges, pes planus and osteopenic bone texture as additional associated findings expanding the clinical phenotype of DASS."
Direct observation in the cited study; frequency across affected individuals is not established.
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:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"short distal phalanges, pes planus and osteopenic bone texture as additional associated findings expanding the clinical phenotype of DASS."
Direct observation in the cited study; frequency across affected individuals is not established.
Musculoskeletal 4
Platyspondyly HP:0000926 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Platyspondyly (HP:0000926). HP:0000926 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The spine radiographs show platyspondyly with indentations of both upper and lower vertebral endplates."
Direct radiographic documentation in an affected individual.
PMID:34573388 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"the proband showed short stature, short trunk, scoliosis with accentuated lordosis, facial dysmorphisms, pterygium colli, varus knees, lower limbs diplegia and platyspondyly"
Independent documentation of platyspondyly with the associated short-trunk habitus.
Scoliosis HP:0002650 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Scoliosis (HP:0002650). HP:0002650 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:34573388 SUPPORT INDIRECT BACKGROUND Human Clinical
"This disorder is characterized by skeletal dysplasia (e.g., platyspondyly, short trunk, scoliosis, broad ilia, elongated femoral necks with coxa valga) and severe enamel and dental anomalies."
Lists scoliosis among the defining skeletal features of the entity.
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The oldest girl underwent surgery for an S-shaped scoliosis."
Direct observation in the cited study; frequency across affected individuals is not established.
Osteopenia HP:0000938 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Osteopenia (HP:0000938). HP:0000938 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Additional bone anomalies such as osteopenia and scoliosis were present in family 4."
Documents osteopenia in an affected family, the observation that contradicts the mouse bone phenotype.
Increased Bone Mineral Density HP:0011001 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Increased bone mineral density (HP:0011001). HP:0011001 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Increased bone density was present in the spine and at the base of the skull."
Full text of PMID:19344874; radiographs and quantitative assessment were reported.
Growth 1
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 (2 references)
PMID:32432408 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Only 20 individuals from nine families have been previously reported, with a consistent phenotype of short stature, brachyolmia, and amelogenesis imperfecta."
Records short stature as one of the three consistent features across the published cohort.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"with normal limb/torso ratios and proximal/distal limb ratios."
Full text of PMID:19344874 documents proportionate stature in affected family members.
🧬

Genetic Associations

1
LTBP3
Gene: LTBP3 hgnc:6716 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is LTBP3 (hgnc:6716). hgnc:6716 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (5 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"we identified the LTBP3 (latent TGF-beta binding protein 3) gene as the underlying causal gene responsible for this rare autosomal recessive disorder"
The gene-disease assertion from the defining study.
PMID:35998423 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"We identified two novel LTBP3 homozygous variants, the c.2495delT deletion (p.Phe832SerfsTer36) and the c.3716 G>A (p.Cys1239Tyr) missense variant, respectively."
Extends the allelic spectrum to include a missense allele in a previously unreported population.
PMID:37394436 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"We identified a novel and common LTBP3 gene pathogenic variant responsible for short stature, brachyolmia and amelogenesis imperfecta in Druze Arab patients."
A founder allele in a defined community, which is the one context in this disease where carrier screening rather than case-by-case exome sequencing becomes the sensible strategy.
+ 2 more references
💊

Medical Actions

8
Restorative dental rehabilitation
Action: Dental ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dental Procedure (NCIT:C38052). NCIT:C38052 is a clinical intervention from the NCI Thesaurus. NCIT:C38052
Platform: Other
Protect affected teeth and restore function using individualized dental rehabilitation. The 2024 DASS series reports root canal treatment, pulpotomies and posterior crowns. Broader AI evidence supports reduced pain and hypersensitivity after restoration, but comparative effectiveness and durability specific to LTBP3 remain unestablished.
Mechanism Target:
BYPASSES Hypoplastic Enamel Formation — Replaces the missing protective layer. It does not act on amelogenesis, which has already failed by the time teeth erupt.
Show evidence (3 references)
PMID:38192829 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Consequently, dental pulps were affected; thus, root canal treatments and pulpotomies were performed. In addition, the posterior teeth were crowned to preserve the remaining teeth structures and maintain the occlusion."
Direct treatment report in the affected siblings of family B.
PMID:38909645 SUPPORT INDIRECT REVIEW SYNTHESIS Human Clinical
"In young patients with AI symptoms of pain and hypersensitivity decreased, and aesthetics were improved following all types of restorative therapy"
The outcome that justifies early restoration - symptom relief, not only appearance. INDIRECT because the review covers non-syndromic AI in under-19s rather than LTBP3-related disease.
PMID:38909645 SUPPORT INDIRECT REVIEW SYNTHESIS Human Clinical
"single-tooth ceramic crowns should be the first choice of treatment"
A specific first-line recommendation from a 2017-2023 review of 38 eligible studies. INDIRECT for the same reason.
Orthodontic and orthognathic management of malocclusion
Action: Orthodontic TreatmentNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Orthodontic Treatment (NCIT:C64248). NCIT:C64248 is a clinical intervention from the NCI Thesaurus. NCIT:C64248
Platform: Other
Orthodontic and orthognathic procedures may address malocclusion and jaw disproportion. The cited five-year treatment result is from nonsyndromic hypocalcified AI with a class II relationship, whereas an LTBP3 family had class III malocclusion from maxillary hypoplasia; the same operative plan cannot be presumed appropriate.
Mechanism Target:
BYPASSES Maxillary Hypoplasia — Orthognathic procedures can address jaw disproportion; evidence here is extrapolated from nonsyndromic AI.
Show evidence (2 references)
PMID:23811667 SUPPORT INDIRECT PRIMARY RESULT Human Clinical
"Orthodontic treatment and orthognathic surgery were performed as part of the prosthetic treatment plan to achieve acceptable and durable results."
Describes the combined approach. INDIRECT: a single case of non-syndromic hypocalcified AI, cited for the management pattern rather than for a genotype-matched outcome.
PMID:23811667 SUPPORT INDIRECT PRIMARY RESULT Human Clinical
"No deterioration in the rehabilitation was found after 5 years of follow-up."
The durability result, which is the reason to prefer a staged multidisciplinary plan over repeated restoration. INDIRECT for the same reason.
Aortic imaging surveillance
Action: Supportive CareNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. NCIT:C15747
Platform: Other
The 2025 DASS series reports cardiology follow-up with history, examination, ECG and echocardiography, plus thoracoabdominal CT to assess additional aortic disease. Six-month assessment of root expansion informed surgical decisions in that family. The schedule is reported care, not a validated universal surveillance interval.
Show evidence (2 references)
PMID:40259772 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"They are followed up annually at cardiology clinics with detailed medical history, physical examinations, ECG, and echocardiography."
Directly reported DASS follow-up; intervals were adjusted for progression.
PMID:40259772 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The decision regarding the need for surgery was made based on close (6-month) follow-up of the aortic root expansion rate."
Monitoring strategy in the reported family; surgery itself was not reported.
Extraction of Severely Affected Teeth
Action: Dental ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dental Procedure (NCIT:C38052). NCIT:C38052 is a clinical intervention from the NCI Thesaurus. NCIT:C38052
Platform: Other
Extractions were reported for recurrent abscesses in young affected children; selection depends on dental infection, restorability and dentition.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"She suffered of repeated dental abscesses, leading to the extraction of several teeth at ages 2½ and 5 years."
Direct observation in the cited study; frequency across affected individuals is not established.
Scoliosis Surgery
Action: Surgical ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Surgical Procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. NCIT:C15329
Platform: Other
Surgery for severe S-shaped scoliosis was reported in an affected girl; the study does not establish a uniform operative indication.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"The oldest girl underwent surgery for an S-shaped scoliosis."
Direct observation in the cited study; frequency across affected individuals is not established.
Aortic Repair for Dissection or Aneurysm
Action: Surgical ProcedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Surgical Procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. NCIT:C15329
Platform: Other
Thoracic endovascular aortic repair was performed for type B dissection in the 2021 patient; abdominal aneurysm repair was reported in a 2018 patient. Procedure and timing require assessment of the specific vascular lesion.
Show evidence (2 references)
PMID:34906192 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"TEVAR surgery was then performed."
Actual intervention following type B dissection.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Human Clinical
"abdominal aortic aneurysm requiring surgical repair at the age of 44"
Full text of PMID:29625025.
Genetic Counseling and Family Testing
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
Platform: Other
Confirm segregation and provide recurrence counseling. When both parents carry a pathogenic allele, each pregnancy has a 25% probability of biallelic inheritance. A reported de novo allele illustrates why this calculation must follow family testing.
Show evidence (1 reference)
PMID:40259772 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"After segregation analysis of affected siblings and parents was completed, genetic counselling was given to the family. It was explained that there was a 25% risk of recurrence in each pregnancy."
The reported parents were carriers; this probability is conditional on that parental genotype.
🔬

Diagnosis

1
Exome sequencing after clinical recognition of the dental-skeletal pairing
Recognize the combination of enamel or tooth-number abnormalities and short stature or skeletal dysplasia, and investigate LTBP3 using molecular testing with parental segregation. Clinical variability includes proportionate stature and vascular presentations. RNA analysis can help determine the effect of a splice variant.
Show evidence (2 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"A single gene, LTBP3, was found to carry bi-allelic mutations in all affected individuals from the four families"
The gene-identification result: one gene, biallelic, in every affected individual across four independently ascertained families.
PMID:34573388 SUPPORT DIRECT PRIMARY RESULT In Vitro
"the disease-associated variant altered proper splicing of the LTBP3 transcript, leading to retention of intron 20"
Patient peripheral-blood RNA demonstrates aberrant splicing of c.2894-2A>G; protein truncation was predicted.
📊

Prevalence

2
Worldwide, published cases
Cases In Literature
The 2020 report described approximately 20 previously reported individuals from nine families. This is a dated literature count, not a current census or population prevalence estimate.
Show evidence (1 reference)
PMID:32432408 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"Only 20 individuals from nine families have been previously reported, with a consistent phenotype of short stature, brachyolmia, and amelogenesis imperfecta."
Historical literature count reported in 2020; later series add affected families.
One Druze Arab village in northern Israel
Carrier Frequency
Reported carrier rate of 1:15 for LTBP3 c.1346-1G>A in the studied village; this is neither affected-person prevalence nor an estimate for all Druze communities.
Show evidence (1 reference)
PMID:37394436 SUPPORT DIRECT PRIMARY RESULT Human Clinical
"We found a high carrier rate in the village (1:15)."
Local carrier-screening result for the recurrent variant.
🧫

Experimental Models

1
Patient-derived LTBP3 lymphoblastoid cell lines CELL_LINE
RT-qPCR showed approximately fivefold lower LTBP3 transcript abundance with a nonsense allele. The result supports transcript destabilization but does not directly quantify protein or tissue-specific TGF-beta signaling.
Organism
Homo sapiens NCBITaxon:9606 NCBI Taxonomy (NCBITaxon) Relation: this experimental model is built in this organism This experimental model is built in Homo sapiens (NCBITaxon:9606). NCBITaxon:9606 is an organism from the NCBI Taxonomy.
Cell source
Lymphoblastoid cell lines from three affected members of the 2009 family and a control.
Publication
PMID:19344874
Pathograph links
Biallelic LTBP3 Loss of Function recapitulates Patient-derived transcript reduction supports loss of function for the tested allele.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml SUPPORT DIRECT PRIMARY RESULT In Vitro
"an approximately 5-fold reduction in mRNA levels associated with the mutated allele, suggesting that nonsense-mediated decay is occurring"
Full text of PMID:19344874: patient lymphoblastoid-cell RNA supports transcript loss for this nonsense allele.
Show evidence (1 reference)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml SUPPORT DIRECT PRIMARY RESULT In Vitro
"an approximately 5-fold reduction in mRNA levels associated with the mutated allele, suggesting that nonsense-mediated decay is occurring"
Full text of PMID:19344874: patient lymphoblastoid-cell RNA supports transcript loss for this nonsense allele.
🐁

Animal Models

4
Ltbp3 knockout mouse
Constitutive Ltbp3-null mice reproduce important enamel and craniofacial abnormalities. Enamel epithelial changes are stage-dependent, platyspondyly is absent, and aortic phenotypes depend on study conditions and scaling.
Species
Mouse
Genotype
Ltbp3 null (homozygous)
Publication
PMID:25669657
Pathograph links
Hypoplastic Enamel Formation recapitulates fidelity: moderate Thin and disorganized enamel in incisors and molars corresponds to human enamel hypoplasia. Later histology identifies prominent maturation-stage epithelial changes.
Limitations: The constitutive knockout does not establish the residual function of individual human alleles. Continuously growing mouse incisors differ from human permanent teeth.
Readouts
Incisor and molar enamel thickness
Direction: DECREASED
Interpretation: Direct structural readout of the amelogenesis defect, measured by microCT and histology against wild-type littermates.
Show evidence (1 reference)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Model Organism
"mutant mice displayed enamel defects with very thin to absent enamel in both incisors and molars"
The measurement itself, in both tooth types.
Show evidence (3 references)
PMID:25669657 SUPPORT DIRECT PRIMARY RESULT Model Organism
"mouse model clearly recapitulates the AI phenotype observed in our patients."
The authors' own statement that the model reproduces the human dental phenotype, which is what licenses RECAPITULATES here.
+ 2 more references
Premature Cranial-base Synchondrosis Ossification recapitulates fidelity: moderate Direct cranial-base lesion in the null mouse; its contribution to human maxillary hypoplasia remains inferred.
Show evidence (1 reference)
PMID:12379497 SUPPORT DIRECT PRIMARY RESULT Model Organism
"the synchondroses in the skull base were obliterated within 2 weeks of birth."
Null-mouse histology, not a human observation.
Impaired Vascular Wall Homeostasis partially recapitulates fidelity: low The 2018 study found larger aortic diameters after division by body mass and additional medial elastic lamellar units. The 2019 biomechanical study did not find statistically significant ascending-aortic enlargement at the ages studied after allometric scaling.
Limitations: Human dissection is not reproduced reliably. Body size, age, background and normalization alter the interpretation of aortic dimensions.
Show evidence (2 references)
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml SUPPORT DIRECT PRIMARY RESULT Model Organism
"When aortic diameters were normalized by body mass, the diameters of both the aortic root and the ascending aorta ... mice were significantly larger than those of wild-type mice"
Full text of PMID:29625025; reported enlargement is relative to body mass, not an unqualified absolute-diameter increase.
+ 1 more reference
Fbn1 hypomorphic and Ltbp3-null double-mutant mouse
LTBP3 deficiency protects fibrillin-deficient mice from early aortic rupture and attenuates signaling abnormalities. This is a Marfan-like genetic context, not a treatment study in human DASS.
Species
Mouse
Genotype
Fbn1 mgR/mgR; Ltbp3 -/-
Publication
PMID:26494287
Pathograph links
Impaired Vascular Wall Homeostasis perturbs Changing LTBP3 in a fibrillin-deficient matrix changes the vascular phenotype; benefit in this context cannot be generalized to LTBP3-deficient patients.
Show evidence (1 reference)
PMID:26494287 SUPPORT DIRECT PRIMARY RESULT Model Organism
"absence of LTBP-3 almost completely attenuates gene expression changes observed in MFS-like mice."
Context-dependent effect in the double mutant.
Show evidence (1 reference)
PMID:26494287 SUPPORT DIRECT PRIMARY RESULT Model Organism
"We suppressed the expression of Ltbp3 in an MFS mouse model and observed essentially no aortic aneurysm and rupture in these compound mice."
Double-mutant mouse result in an Fbn1-deficient background.
ltbp1 and ltbp3 double-knockout zebrafish
Double-mutant larvae develop outflow-tract aneurysm, ventricular dilation and aortic regurgitation after initially preserved gross morphogenesis. Single mutants had normal ventricular areas at five days. Increased pSmad3 follows, rather than precedes, vascular dilation.
Species
Zebrafish
Genotype
ltbp1 -/-; ltbp3 -/-
Publication
PMID:35098309
Pathograph links
Impaired Vascular Wall Homeostasis partially recapitulates fidelity: low Captures vascular dilation after combined paralog loss, with limited fidelity to single-gene human disease.
Limitations: Double-gene deletion and larval timing differ from DASS. Pharmacological activation or inhibition of TGF-beta did not rescue the double-mutant phenotype.
Show evidence (2 references)
PMID:35098309 SUPPORT DIRECT PRIMARY RESULT Model Organism
"DKO animals displayed striking enlargements of both the ventricle and OFT"
Direct vascular enlargement in the double mutant; requiring loss of both paralogs limits correspondence to isolated human LTBP3 deficiency.
+ 1 more reference
Show evidence (1 reference)
PMID:35098309 SUPPORT DIRECT PRIMARY RESULT Model Organism
"we evaluated ventricular areas in single mutants on 5 dpf, which were normal"
Redundancy of the two genes limits correspondence to isolated human LTBP3 deficiency.
British Shorthair cats with candidate LTBP3 skeletal dysplasia
Two littermates with skeletal dysplasia and progressive paraparesis carried a candidate homozygous LTBP3 frameshift. Vertebral stenosis, spinal cord compression and other developmental abnormalities were described. RNA or protein loss and functional rescue were not tested, and a linked CAPN1 variant could modify neurological findings. Dental-enamel correspondence was not established.
Species
Cat
Genotype
Homozygous LTBP3 c.158delG, p.(Gly53Alafs*16)
Publication
PMID:34946872
Pathograph links
Biallelic LTBP3 Loss of Function perturbs Candidate recessive frameshift provides comparative genetic evidence; the molecular effect remains predicted.
Show evidence (1 reference)
PMID:34946872 SUPPORT DIRECT PRIMARY RESULT Model Organism
"only one was located in a likely functional candidate gene, LTBP3"
Candidate prioritization in the feline family; causality is not functionally demonstrated.
Show evidence (1 reference)
PMID:34946872 SUPPORT DIRECT PRIMARY RESULT Model Organism
"This variant, c.158delG or p.(Gly53Alafs*16), represents a 1 bp frameshift deletion predicted to truncate 95% of the open reading frame."
Candidate natural animal disease, not a validated functional knockout.
{ }

Source YAML

click to show 
name: Brachyolmia-Amelogenesis Imperfecta Syndrome
creation_date: "2026-08-31T08:10:00Z"
category: Mendelian
disease_term:
  preferred_term: brachyolmia-amelogenesis imperfecta syndrome
  term:
    id: MONDO:0011018
    label: brachyolmia-amelogenesis imperfecta syndrome
description: >-
  Brachyolmia-amelogenesis imperfecta syndrome, also called dental anomalies and short stature (DASS), is an
  autosomal recessive LTBP3-related disorder combining enamel hypoplasia and dental anomalies with short stature
  and variable skeletal dysplasia. Platyspondyly and a short trunk are characteristic, but proportionate short
  stature and mild long-bone abnormalities also occur. Cardiovascular involvement includes valvular abnormalities,
  aortic dilatation, aneurysms and dissection; vascular disease can extend beyond the thoracic aorta. LTBP3
  regulates extracellular localization and activation of latent TGF-beta, but the direction and timing of signaling
  changes in affected human tissues remain incompletely established. Mouse models reproduce aspects of the
  dental and craniofacial phenotype without reproducing the full human skeletal or vascular disorder.

synonyms:
- brachyolmia with amelogenesis imperfecta
- dental anomalies and short stature
- DASS
- amelogenesis imperfecta and platyspondyly
- LTBP3-related brachyolmia

parents:
- Brachyolmia
- Skeletal dysplasia
- Syndromic amelogenesis imperfecta

notes: >-
  DASS and brachyolmia with amelogenesis imperfecta describe the same recessive LTBP3 disease spectrum. Tooth
  number, enamel quality, body proportions and bone density vary among families. Monoallelic LTBP3-related
  acromicric and geleophysic dysplasias are distinct allelic disorders; orodental abnormalities can also occur
  in acromicric dysplasia. Some heterozygous relatives in DASS families have dental, skeletal or late-onset
  aortic findings, whereas other carriers are unaffected. These observations do not establish uniform penetrance
  of heterozygous variants. A recurrent c.1346-1G>A allele was associated with a high carrier frequency in
  one Druze village; that local estimate does not measure disease prevalence in all Druze populations.

prevalence:
- population: Worldwide, published cases
  measure_type: CASES_IN_LITERATURE
  notes: >-
    The 2020 report described approximately 20 previously reported individuals from nine families. This is
    a dated literature count, not a current census or population prevalence estimate.
  evidence:
  - reference: PMID:32432408
    reference_title: "Bi-allelic loss-of-function novel variants in LTBP3-related skeletal dysplasia: Report of first patient from India."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only 20 individuals from nine families have been previously reported, with a consistent phenotype of short stature, brachyolmia, and amelogenesis imperfecta."
    explanation: >-
      Historical literature count reported in 2020; later series add affected families.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- population: One Druze Arab village in northern Israel
  measure_type: CARRIER_FREQUENCY
  notes: Reported carrier rate of 1:15 for LTBP3 c.1346-1G>A in the studied village; this is neither affected-person prevalence nor an estimate for all Druze communities.
  evidence:
  - reference: PMID:37394436
    reference_title: "[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: We found a high carrier rate in the village (1:15).
    explanation: Local carrier-screening result for the recurrent variant.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic LTBP3 variants segregate with DASS in both homozygous and compound heterozygous families. At
    least one compound heterozygous patient inherited a maternal allele and had a second de novo allele. A
    25% recurrence probability applies when both parents carry a disease-causing allele; segregation testing
    is needed for family-specific counseling.
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All mutations segregated with the disease phenotype in each family and were confirmed by Sanger sequencing"
    explanation: >
      Segregation across four families is the primary inheritance evidence.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:34906192
    reference_title: Novel LTBP3 mutations associated with thoracic aortic aneurysms and dissections.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: one of them (c.1965del, p.Arg656fs) was inherited from his mother, while the other (c.625dup, p.Leu209fs) was de novo.
    explanation: One compound heterozygous case had a de novo allele; two carrier parents are not universal.
mechanistic_hypotheses:
- hypothesis_group_id: ltbp3_tgfb_bioavailability
  hypothesis_label: LTBP3-dependent extracellular regulation of latent TGF-beta
  status: CANONICAL
  description: >-
    LTBP3 loss alters the extracellular handling of latent TGF-beta and is associated with dental, skeletal
    and vascular disease. Biochemical studies establish latent-complex binding and matrix incorporation. Reduced
    local TGF-beta signaling is proposed for parts of the dental and skeletal phenotype, but has not been directly
    demonstrated for all patient alleles or tissues. Vascular signaling responses vary by model and disease
    stage, and TGF-beta-independent matrix functions remain possible.

pathophysiology:
- name: Biallelic LTBP3 Loss of Function
  biological_scale: MOLECULAR
  description: Homozygous or compound heterozygous truncating and splice variants cause DASS; missense variants have also been reported. Residual function is not quantified for most alleles. Patient RNA studies show variant-dependent transcript reduction, intron retention or escape from nonsense-mediated decay, so a uniform hypomorphic effect cannot be assumed.
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A single gene, LTBP3, was found to carry bi-allelic mutations in all affected individuals from the four families"
    explanation: >
      The gene-identification result: one gene, biallelic, in every affected
      individual across four independently ascertained families.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
    reference_title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: an approximately 5-fold reduction in mRNA levels associated with the mutated allele, suggesting that nonsense-mediated decay is occurring
    explanation: 'Full text of PMID:19344874: patient lymphoblastoid-cell RNA supports transcript loss for this nonsense allele.'
  - reference: PMID:34573388
    reference_title: A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: the disease-associated variant altered proper splicing of the LTBP3 transcript, leading to retention of intron 20
    explanation: Patient peripheral-blood RNA demonstrates aberrant splicing of c.2894-2A>G; protein truncation was predicted.
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The 14-bp deletion found in family 1 does not seem to result in nonsense-mediated decay because it was present in RNA extracted from a gingival biopsy of patient IV.1
    explanation: Transcript persistence was observed for this particular deletion, not for all DASS alleles.
  genes:
  - preferred_term: LTBP3
    term:
      id: hgnc:6716
      label: LTBP3
  genetic_context:
    description: Germline biallelic variants, either homozygous or compound heterozygous.
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
  downstream:
  - target: Altered Latent TGF-beta Complex Assembly
    description: Loss of intact LTBP3 can impair latent-complex assembly; individual variant effects are often predicted.
  - target: Impaired Vascular Wall Homeostasis
    description: Biallelic variants are associated with aneurysm and dissection, but the intervening molecular steps remain unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Premature Cranial-base Synchondrosis Ossification
    description: Ltbp3 loss causes premature cranial-base ossification in null mice; applicability to human disease remains inferred.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:12379497
      reference_title: Bone defects in latent TGF-beta binding protein (Ltbp)-3 null mice; a role for Ltbp in TGF-beta presentation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: the synchondroses in the skull base were obliterated within 2 weeks of birth.
      explanation: Null-mouse histology, not a human observation.
- name: Altered Latent TGF-beta Complex Assembly
  biological_scale: MOLECULAR
  description: LTBP3 forms a complex with latent TGF-beta. Patient truncating and splice variants are predicted to impair this complex, but direct biochemical tests are unavailable for most alleles. Coexpression experiments establish the normal interaction and the dependence of efficient LTBP3 secretion on binding the TGF-beta propeptide; they do not demonstrate that LTBP3 deficiency abolishes all TGF-beta secretion.
  evidence:
  - reference: PMID:12062452
    reference_title: Latent TGF-beta binding protein-3 (LTBP-3) requires binding to TGF-beta for secretion.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: The secretion of LTBP-3 requires complexing of LTBP-3 with Cys33 of the TGF-beta propeptide.
    explanation: Biochemical evidence for secretion of the binding protein in the normal complex; not a patient-variant assay.
  - reference: PMID:35352826
    reference_title: "Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome."
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    directness: INDIRECT
    snippet: "variants are expected to result in abnormal LTPB3 protein, \nfailure of TGFβ-LAP-LTBP3 complex formation, and subsequent disruption of TGFβ"
    explanation: >
      Names the specific molecular failure - the latent complex of TGF-beta,
      its propeptide (LAP) and LTBP3 does not assemble. The snippet keeps
      "are expected to result in" deliberately: this is the authors' predicted
      consequence of two specific variants, not an assay result, which is why
      it is graded COMPUTATIONAL and INDIRECT.
    quote_role: PRIMARY_RESULT
  downstream:
  - target: Altered Extracellular Localization of Latent TGF-beta
    description: Abnormal complexes may alter matrix incorporation and subsequent ligand availability.
    hypothesis_groups:
    - ltbp3_tgfb_bioavailability
- name: Altered Extracellular Localization of Latent TGF-beta
  biological_scale: MOLECULAR
  description: LTBP3-containing latent complexes interact with the fibrillin matrix. Purified-protein assays demonstrate TG2-mediated cross-linking of the LTBP3 C-terminal complex to fibrillin, while fibrillin-deficient cell cultures have defective LTBP3 matrix deposition. These establish a matrix-localization function; they do not exclude structural roles or prove a single direction of TGF-beta signaling change in DASS.
  evidence:
  - reference: PMID:35122964
    reference_title: Latent TGFβ complexes are transglutaminase cross-linked to fibrillin to facilitate TGFβ activation.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: Cross-linking was also performed with LTBP3-CT-SLC (CT3-SLC) which also formed a cross-link to fibrillin but less efficiently
    explanation: Purified recombinant complexes provide direct LTBP3-specific biochemical evidence; the detailed structural and activation assays in this paper chiefly concern LTBP1.
  - reference: PMID:22495824
    reference_title: "Specificity of latent TGF-β binding protein (LTBP) incorporation into matrix: role of fibrillins and fibronectin."
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: the deposition of LTBP-3 and -4 is abrogated, whereas LTBP-1 is still deposited into the matrix through its interaction with fibronectin
    explanation: Fibrillin-deficient matrix context; indirect evidence for the localization function disrupted by LTBP3 disease.
  biological_processes:
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
  downstream:
  - target: Altered Local TGF-beta Bioavailability
    description: Matrix incorporation controls latent ligand localization and activation.
    hypothesis_groups:
    - ltbp3_tgfb_bioavailability
- name: Altered Local TGF-beta Bioavailability
  biological_scale: MOLECULAR
  description: Disturbed extracellular handling of latent TGF-beta is proposed to alter tissue-specific signaling during tooth and skeletal development. Reduced signaling in DASS ameloblasts or vertebral growth plates remains a model-based inference. In zebrafish lacking both ltbp1 and ltbp3, vascular dilation precedes increased pSmad3, illustrating that late signaling elevation can follow injury rather than initiate it.
  evidence:
  - reference: PMID:12379497
    reference_title: Bone defects in latent TGF-beta binding protein (Ltbp)-3 null mice; a role for Ltbp in TGF-beta presentation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: This suggests that Ltbp-3 may control chondrocyte differentiation by regulating TGF-beta availability.
    explanation: Mouse cranial-base findings motivate the signaling model, without direct confirmation in human vertebrae.
  - reference: PMID:35098309
    reference_title: Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: enlargement of the ventricle and OFT in DKO animals precedes hyperactivation of TGFβ signaling and not vice versa.
    explanation: The double-knockout zebrafish result limits a uniform primary signaling-direction claim.
  biological_processes:
  - preferred_term: transforming growth factor beta receptor signaling pathway
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
  downstream:
  - target: Abnormal Ameloblast Differentiation
    description: A proposed link between altered ligand availability and enamel-organ dysfunction; patient signaling measurements are lacking.
    hypothesis_groups:
    - ltbp3_tgfb_bioavailability
  - target: Disturbed Axial Skeletal Development
    description: The vertebral mechanism is inferred from expression and pathway biology, not demonstrated by a model reproducing platyspondyly.
    hypothesis_groups:
    - ltbp3_tgfb_bioavailability
- name: Abnormal Ameloblast Differentiation
  biological_scale: CELLULAR
  description: Ltbp3 is expressed in developing ameloblasts. Enamel-matrix defects begin early in knockout mice, but detailed histology found no obvious secretory- or transition-stage ameloblast shape changes and marked maturation-stage disorganization. Human enamel ultrastructure suggests disturbed secretory architecture; a specific defect in Tomes process formation is a hypothesis rather than a direct cellular observation in patients.
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "At E18.5 labeling was observed in differentiating ameloblasts and odontoblasts. Transcripts were scattered at the apical secretory pole of ameloblasts."
    explanation: >
      Places the gene product in the right cell at the right stage and, more
      pointedly, at the secretory pole.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:28084688
    reference_title: Enamel and dental anomalies in latent-transforming growth factor beta-binding protein 3 mutant mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: At the secretory and transition stages, ameloblasts from Ltbp3‐/‐ mice showed no obvious morphological changes compared with ameloblasts from WT mice
    explanation: Mouse histology distinguishes the timing of epithelial changes from the earlier enamel-matrix defect.
  - reference: PMID:28084688
    reference_title: Enamel and dental anomalies in latent-transforming growth factor beta-binding protein 3 mutant mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Organization of maturation-stage ameloblasts was severely disrupted.
    explanation: Maturation-stage phenotype in Ltbp3-null mice.
  cell_types:
  - preferred_term: ameloblast
    term:
      id: CL:0000059
      label: ameloblast
  biological_processes:
  - preferred_term: amelogenesis
    term:
      id: GO:0097186
      label: amelogenesis
  downstream:
  - target: Hypoplastic Enamel Formation
    description: Enamel-organ dysfunction produces reduced and disorganized enamel.
- name: Hypoplastic Enamel Formation
  biological_scale: TISSUE
  description: Thin, irregular or absent enamel affects both dentitions. Patient ultrastructure shows loss of the initial aprismatic layer and abnormal prismatic architecture. Dentin was normal in the 2015 examined family but abnormal dentin and pulp calcification were reported subsequently, so this is not uniformly an enamel-only defect.
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The panoramic radiographs confirmed the absence of enamel associated with large pulp chambers and taurodontic molars"
    explanation: >
      The radiographic dental phenotype, including the associated pulp and
      root findings.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The initial aprismatic enamel layer was absent."
    explanation: >
      The human ultrastructural finding that localises the defect to a
      specific secretory stage rather than to mineralisation in general.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:35352826
    reference_title: Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: include taurodontism, single-rooted molars, abnormal dentin, calcified dental
    explanation: The 2022 family broadens the dental phenotype beyond enamel; the accessible abstract does not resolve all findings by genotype.
  biological_processes:
  - preferred_term: enamel mineralization
    term:
      id: GO:0070166
      label: enamel mineralization
  downstream:
  - target: Hypoplastic Amelogenesis Imperfecta
    description: Clinical manifestation of deficient enamel.
  - target: Dental Abscesses
    description: Loss of protective dental tissue can contribute to recurrent infection.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
- name: Disturbed Axial Skeletal Development
  biological_scale: TISSUE
  description: LTBP3 is expressed in developing bone and cartilage. Altered endochondral development is a candidate mechanism for vertebral flattening, but Ltbp3-null mice do not develop platyspondyly. The precise cellular lesion in human vertebral growth plates remains unresolved. Human bone density can be reduced or increased, depending on the family.
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Expression was found in various developing bones undergoing either endochondral or intramembranous ossification"
    explanation: >
      Establishes that the gene is expressed in the right tissue at the right
      developmental stage for a skeletal dysplasia.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: OTHER
    directness: INDIRECT
    snippet: Deregulation of the TGF-beta signaling pathway is likely to interfere with axial skeleton patterning
    explanation: Mechanistic interpretation proposed by the authors; not a direct patient growth-plate assay.
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  biological_processes:
  - preferred_term: endochondral bone growth
    term:
      id: GO:0003416
      label: endochondral bone growth
  downstream:
  - target: Platyspondyly
    description: Vertebral body flattening is a characteristic clinical endpoint.
    hypothesis_groups:
    - ltbp3_tgfb_bioavailability
  - target: Short Stature
    description: Short stature can be disproportionate or proportionate; contributions outside the vertebrae vary.
    hypothesis_groups:
    - ltbp3_tgfb_bioavailability
- name: Premature Cranial-base Synchondrosis Ossification
  biological_scale: TISSUE
  description: In Ltbp3-null mice, premature cranial-base synchondrosis ossification accompanies altered chondrocyte differentiation and a shortened upper jaw. This offers a model for relative mandibular prognathism from maxillary underdevelopment; the same growth-plate process has not been demonstrated in affected humans.
  evidence:
  - reference: PMID:12379497
    reference_title: Bone defects in latent TGF-beta binding protein (Ltbp)-3 null mice; a role for Ltbp in TGF-beta presentation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: the basooccipital-basosphenoid synchondrosis of Ltbp-3 null mice contained increased numbers of hypertrophic chondrocytes.
    explanation: Mouse histology demonstrates altered cranial-base chondrocyte differentiation preceding premature ossification.
  downstream:
  - target: Maxillary Hypoplasia
    description: Premature cranial-base growth arrest can shorten the upper jaw in the mouse model.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
- name: Impaired Vascular Wall Homeostasis
  biological_scale: TISSUE
  description: 'Biallelic LTBP3 variants predispose some affected individuals to aortic and other arterial aneurysms and dissection. The molecular mechanism remains unresolved: altered latent TGF-beta handling and matrix functions are candidates. Mouse aortic dimensions vary with age, genetic background and normalization, and protection from rupture in a fibrillin-deficient double mutant does not establish benefit from reducing LTBP3 in patients.'
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: aortic root dilation, and multiple visceral and peripheral arterial aneurysms at the age of 54 years
    explanation: Full text of PMID:29625025; one biallelic patient demonstrates vascular disease beyond the thoracic aorta.
  - reference: PMID:34906192
    reference_title: Novel LTBP3 mutations associated with thoracic aortic aneurysms and dissections.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: thoracic computed tomography (CT) revealed aortic dissection in the descending aorta (DeBakey type III).
    explanation: Direct vascular diagnosis in a compound heterozygous patient.
  downstream:
  - target: Thoracic Aortic Aneurysm
    description: Aneurysmal disease can affect thoracic segments.
  - target: Abdominal Aortic Aneurysm
    description: Abdominal involvement has been reported.
  - target: Aortic Dissection
    description: Arterial wall failure can produce dissection.
  - target: Aortic Root Dilatation
    description: Root enlargement may be detected before other aortic complications.
  - target: Brachiocephalic Artery Aneurysm
    description: Non-aortic arterial involvement demonstrates systemic vascular disease.
  - target: Common Carotid Artery Aneurysm
    description: Non-aortic arterial involvement demonstrates systemic vascular disease.
phenotypes:
- category: Dental
  name: Hypoplastic Amelogenesis Imperfecta
  description: >-
    Enamel is thin to almost absent in primary and permanent dentitions, often producing small, yellow and
    spaced teeth. Dentin was normal in one studied family, but abnormalities have been reported in another.
  phenotype_term:
    preferred_term: Amelogenesis imperfecta
    term:
      id: HP:0000705
      label: Amelogenesis imperfecta
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The almost complete absence of enamel in both primary and permanent dentitions (Fig. 1A and B) led to the diagnosis of hypoplastic AI, thereby explaining the yellow, small and spaced appearance of the teeth."
    explanation: >
      Establishes the enamel phenotype in both dentitions and its clinical
      appearance.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:35998423
    reference_title: "First characterization of LTBP3 variants in two Moroccan families with hypoplastic amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 2 patients from the first family had dental anomalies and short stature syndrome, brachyolmia and nephrocalcinosis with difference in severity"
    explanation: >
      Independent replication in a different population, and a reminder that
      severity varies within a family carrying the same allele.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Skeletal
  name: Platyspondyly
  description: >-
    Generalized vertebral-body flattening and endplate indentation are characteristic. Mild long-bone and hand
    abnormalities can coexist.
  phenotype_term:
    preferred_term: Platyspondyly
    term:
      id: HP:0000926
      label: Platyspondyly
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The spine radiographs show platyspondyly with indentations of both upper and lower vertebral endplates."
    explanation: >
      Direct radiographic documentation in an affected individual.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:34573388
    reference_title: "A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the proband showed short stature, short trunk, scoliosis with accentuated lordosis, facial dysmorphisms, pterygium colli, varus knees, lower limbs diplegia and platyspondyly"
    explanation: >
      Independent documentation of platyspondyly with the associated
      short-trunk habitus.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Growth
  name: Short Stature
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  description: >-
    Often associated with a short trunk, but proportionate short stature has also been reported. Severity varies,
    including mildly reduced height in some children.
  evidence:
  - reference: PMID:32432408
    reference_title: "Bi-allelic loss-of-function novel variants in LTBP3-related skeletal dysplasia: Report of first patient from India."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only 20 individuals from nine families have been previously reported, with a consistent phenotype of short stature, brachyolmia, and amelogenesis imperfecta."
    explanation: >
      Records short stature as one of the three consistent features across the
      published cohort.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
    reference_title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: with normal limb/torso ratios and proximal/distal limb ratios.
    explanation: Full text of PMID:19344874 documents proportionate stature in affected family members.
- category: Skeletal
  name: Scoliosis
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  evidence:
  - reference: PMID:34573388
    reference_title: "A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This disorder is characterized by skeletal dysplasia (e.g., platyspondyly, short trunk, scoliosis, broad ilia, elongated femoral necks with coxa valga) and severe enamel and dental anomalies."
    explanation: >
      Lists scoliosis among the defining skeletal features of the entity.

    directness: INDIRECT
    quote_role: BACKGROUND
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The oldest girl underwent surgery for an S-shaped scoliosis.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- category: Skeletal
  name: Coxa Valga with Elongated Femoral Necks
  description: >-
    Proximal femoral abnormalities occur in some affected individuals; skeletal involvement is not invariably
    confined to the vertebrae.
  phenotype_term:
    preferred_term: Coxa valga
    term:
      id: HP:0002673
      label: Coxa valga
  evidence:
  - reference: PMID:34573388
    reference_title: "A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This disorder is characterized by skeletal dysplasia (e.g., platyspondyly, short trunk, scoliosis, broad ilia, elongated femoral necks with coxa valga) and severe enamel and dental anomalies."
    explanation: >
      Lists the femoral neck and hip findings as part of the characteristic
      skeletal picture.

    directness: INDIRECT
    quote_role: BACKGROUND
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: narrow hip joint spaces and coxa valga.
    explanation: Primary 2024 radiographic description.
- category: Dental
  name: Hypodontia
  phenotype_term:
    preferred_term: Hypodontia
    term:
      id: HP:0000668
      label: Hypodontia
  description: >-
    Reduced tooth number ranges to oligodontia in some families, while others have a full complement of permanent
    teeth. Tooth number and enamel quality are distinct aspects of the LTBP3 phenotype.
  evidence:
  - reference: PMID:34573388
    reference_title: "A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Dental evaluations revealed hypodontia and amelogenesis imperfecta"
    explanation: >
      Documents hypodontia together with the enamel defect in one patient.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: "showing erupted and non-erupted permanent teeth with no enamel. No teeth are missing."
    explanation: >
      Records the founding family as having a full complement of teeth, which
      contradicts hypodontia being an obligate feature. Kept as a REFUTE item
      rather than removed, because the disagreement between families is the
      informative part.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Dental
  name: Taurodontia
  phenotype_term:
    preferred_term: Taurodontia
    term:
      id: HP:0000679
      label: Taurodontia
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The panoramic radiographs confirmed the absence of enamel associated with large pulp chambers and taurodontic molars"
    explanation: >
      Documents taurodontism radiographically alongside the enamel absence.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Craniofacial
  name: Mandibular Prognathism from Maxillary Underdevelopment
  description: >-
    Relative mandibular prognathism can result from a shortened maxilla, producing a class III occlusal relationship.
  phenotype_term:
    preferred_term: Mandibular prognathia
    term:
      id: HP:0000303
      label: Mandibular prognathia
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Class III mandibular prognathism encountered in family 1 was due to maxillary underdevelopment"
    explanation: >
      Documents the occlusal finding and attributes it to the maxilla, which
      is the mechanistically meaningful half.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Craniofacial
  name: Maxillary Hypoplasia
  description: >-
    Maxillary underdevelopment accounts for relative mandibular prognathism in the 2015 family and has a corresponding
    upper-jaw phenotype in knockout mice.
  phenotype_term:
    preferred_term: Hypoplasia of the maxilla
    term:
      id: HP:0000327
      label: Hypoplasia of the maxilla
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Class III mandibular prognathism encountered in family 1 was due to maxillary underdevelopment"
    explanation: >
      Attributes the occlusal finding to maxillary underdevelopment, which is
      the phenotype bound here.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Skull radiograph reveals absent pneumatization of sinuses and mandibular prognathism secondary to underdevelopment of the maxilla."
    explanation: >
      Radiographic confirmation, with the additional finding of absent sinus
      pneumatisation in the same underdeveloped maxilla.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Renal
  name: Nephrocalcinosis
  description: >-
    Reported in two affected siblings from a Moroccan family; its frequency and mechanism in LTBP3 disease
    are unresolved.
  phenotype_term:
    preferred_term: Nephrocalcinosis
    term:
      id: HP:0000121
      label: Nephrocalcinosis
  evidence:
  - reference: PMID:35998423
    reference_title: "First characterization of LTBP3 variants in two Moroccan families with hypoplastic amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 2 patients from the first family had dental anomalies and short stature syndrome, brachyolmia and nephrocalcinosis with difference in severity"
    explanation: >
      Documents nephrocalcinosis in two siblings with a confirmed LTBP3
      genotype, and records that severity differed between them.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Dental
  name: Delayed or Failed Tooth Eruption
  description: >
    Distinct from hypodontia: the tooth exists but does not erupt. Reported as
    failure of mandibular tooth eruption in one family and as retarded
    eruption in the founding series, so it is a recurring feature rather than
    a single observation.
  phenotype_term:
    preferred_term: Delayed eruption of teeth
    term:
      id: HP:0000684
      label: Delayed eruption of teeth
  evidence:
  - reference: PMID:35352826
    reference_title: "Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "pulp blood vessels, prognathic mandible, failure of mandibular tooth eruption,"
    explanation: >
      Reports failure of mandibular tooth eruption among the new DASS findings
      in this family.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Missing teeth (family 4) and retarded teeth eruption (family 3) were also reported."
    explanation: >
      Records retarded eruption in the founding series, in a different family
      from the one with missing teeth - so eruption delay and hypodontia are
      separable.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Dental
  name: Dental Malocclusion
  description: >-
    Class III malocclusion associated with maxillary underdevelopment was documented in an LTBP3 family.
  phenotype_term:
    preferred_term: Dental malocclusion
    term:
      id: HP:0000689
      label: Dental malocclusion
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Class III mandibular prognathism encountered in family 1 was due to maxillary underdevelopment"
    explanation: >
      Documents the occlusal finding and attributes it to the maxilla, which
      is the mechanistically meaningful half.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Cardiovascular
  name: Atrial Septal Defect
  description: >-
    A secundum atrial septal defect was reported in the affected girl of the 2024 family B. The 2022 family
    also had septal and valve findings, but the accessible abstract does not assign each finding to the biallelic
    proband versus heterozygous relatives.
  phenotype_term:
    preferred_term: Atrial septal defect
    term:
      id: HP:0001631
      label: Atrial septal defect
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Secundum atrial septal defect (ASD)
    explanation: The primary clinical table records ASD in family B individual IV-3; not a prevalence estimate.
- category: Cardiovascular
  name: Aortic Valve Stenosis
  description: >-
    Aortic stenosis was diagnosed in the 2021 boy, who also had reported hypertrophic cardiomyopathy.
  phenotype_term:
    preferred_term: Aortic valve stenosis
    term:
      id: HP:0001650
      label: Aortic valve stenosis
  evidence:
  - reference: PMID:34573388
    reference_title: "A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a diagnosis of skeletal dysplasia with aortic stenosis and hypertrophic cardiomyopathy was made"
    explanation: >
      The single well-documented case of cardiac involvement with a confirmed
      LTBP3 genotype.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- category: Cardiovascular
  name: Thoracic Aortic Aneurysm
  description: >-
    Thoracic aortic aneurysms have been reported in biallelic LTBP3 families. Age of presentation and affected
    aortic segments vary; dissection can occur in adulthood.
  phenotype_term:
    preferred_term: Thoracic aortic aneurysm
    term:
      id: HP:0012727
      label: Thoracic aortic aneurysm
  evidence:
  - reference: PMID:29625025
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Individuals with compound heterozygous or homozygous variants in these families have aneurysms and dissections of the thoracic aorta
    explanation: Primary 2018 family study.
- category: Skeletal
  name: Osteopenia
  description: >-
    Reduced bone density occurs in some families. Other affected families have increased spinal and skull-base
    density, so bone-density direction is not uniform.
  phenotype_term:
    preferred_term: Osteopenia
    term:
      id: HP:0000938
      label: Osteopenia
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Additional bone anomalies such as osteopenia and scoliosis were present in family 4."
    explanation: >
      Documents osteopenia in an affected family, the observation that
      contradicts the mouse bone phenotype.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- name: Hypertrophic Cardiomyopathy
  category: Cardiovascular
  phenotype_term:
    preferred_term: Hypertrophic cardiomyopathy
    term:
      id: HP:0001639
      label: Hypertrophic cardiomyopathy
  description: Reported in the 2021 boy with concomitant aortic stenosis; the case does not distinguish primary cardiomyopathy from a contribution of valvular loading.
  evidence:
  - reference: PMID:34573388
    reference_title: "A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a diagnosis of skeletal dysplasia with aortic stenosis and hypertrophic cardiomyopathy was made"
    explanation: >
      The single well-documented case of cardiac involvement with a confirmed
      LTBP3 genotype.

    directness: DIRECT
    quote_role: PRIMARY_RESULT
- name: Aortic Dissection
  category: Cardiovascular
  phenotype_term:
    preferred_term: Aortic dissection
    term:
      id: HP:0002647
      label: Aortic dissection
  description: Type A and type B dissections have occurred in adults with biallelic LTBP3 disease. The 2021 Chinese patient had type B dissection at age 42.
  evidence:
  - reference: PMID:34906192
    reference_title: Novel LTBP3 mutations associated with thoracic aortic aneurysms and dissections.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: thoracic computed tomography (CT) revealed aortic dissection in the descending aorta (DeBakey type III).
    explanation: Primary report of a compound heterozygous patient.
- name: Abdominal Aortic Aneurysm
  category: Cardiovascular
  phenotype_term:
    preferred_term: Abdominal aortic aneurysm
    term:
      id: HP:0005112
      label: Abdominal aortic aneurysm
  description: Abdominal aneurysm requiring repair at age 44 was reported in a compound heterozygous patient, followed by visceral and peripheral arterial aneurysms.
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: abdominal aortic aneurysm requiring surgical repair at the age of 44
    explanation: Full text of PMID:29625025, family TAA909 proband.
- name: Aortic Root Dilatation
  category: Cardiovascular
  phenotype_term:
    preferred_term: Aortic root aneurysm
    term:
      id: HP:0002616
      label: Aortic root aneurysm
  description: Root enlargement was present in all three siblings reported in 2025, including an asymptomatic eight-year-old. Thoracoabdominal CT found no additional aneurysm, rupture or dissection. The ontology term includes aortic root dilatation as a synonym.
  evidence:
  - reference: PMID:40259772
    reference_title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: 'Echocardiography revealed aortic root dilatation (diameter: 38 mm, z-score: þ 4.59), mitral valve prolapse'
    explanation: Direct examination of the 24-year-old sibling in the full report; the paper describes root dilatation and prolapse in all three siblings. The cached PDF preserves the plus sign as þ.
- name: Mitral Valve Prolapse
  category: Cardiovascular
  phenotype_term:
    preferred_term: Mitral valve prolapse
    term:
      id: HP:0001634
      label: Mitral valve prolapse
  description: Documented in biallelic families, including the three siblings reported in 2025 and an earlier pair of sisters.
  evidence:
  - reference: PMID:25899461
    reference_title: "New recessive truncating mutation in LTBP3 in a family with oligodontia, short stature, and mitral valve prolapse."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: In addition to oligodontia and short stature, both sisters have mitral valve prolapse
    explanation: The primary report describes two sisters with homozygous truncating LTBP3 variants.
  - reference: PMID:40259772
    reference_title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: 'Echocardiography revealed aortic root dilatation (diameter: 38 mm, z-score: þ 4.59), mitral valve prolapse'
    explanation: Direct examination of the 24-year-old sibling in the full report; the paper describes root dilatation and prolapse in all three siblings. The cached PDF preserves the plus sign as þ.
- name: Mitral Regurgitation
  category: Cardiovascular
  phenotype_term:
    preferred_term: Mitral regurgitation
    term:
      id: HP:0001653
      label: Mitral regurgitation
  description: Moderate regurgitation accompanied mitral prolapse in the 24-year-old brother reported in 2025; mild regurgitation was reported in another biallelic family.
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: has mild mitral valve prolapse and regurgitation.
    explanation: Full text of PMID:29625025, biallelic individual III:2 of TAA909, who had no aortic abnormalities on the reported imaging.
- name: Atrial Septal Aneurysm
  category: Cardiovascular
  phenotype_term:
    preferred_term: Atrial septal dilatation
    term:
      id: HP:0011995
      label: Atrial septal dilatation
  description: Interatrial septal aneurysm was reported in the affected boy of the 2024 family B, along with ascending aortic dilatation.
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: on Doppler assessment, interatrial/atrial septal aneurysm (ASA) was found with dilation of ascending aorta
    explanation: The primary report and table describe the affected male sibling in family B; the individual numbering differs between the text and table.
- name: Arterial Tortuosity
  category: Cardiovascular
  phenotype_term:
    preferred_term: Arterial tortuosity
    term:
      id: HP:0005116
      label: Arterial tortuosity
  description: Cervical arterial tortuosity accompanies aneurysmal disease in some biallelic patients.
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: pronounced tortuosity of the left internal carotid artery
    explanation: Full text of PMID:29625025, family TAA376 individual III:2.
- name: Increased Bone Mineral Density
  category: Skeletal
  phenotype_term:
    preferred_term: Increased bone mineral density
    term:
      id: HP:0011001
      label: Increased bone mineral density
  description: Increased density of the spine and skull base was present in the recessive family reported in 2009. This contrasts with osteopenia in other families.
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
    reference_title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Increased bone density was present in the spine and at the base of the skull.
    explanation: Full text of PMID:19344874; radiographs and quantitative assessment were reported.
- name: Short Distal Finger Phalanges
  category: Skeletal
  phenotype_term:
    preferred_term: Short distal phalanx of finger
    term:
      id: HP:0009882
      label: Short distal phalanx of finger
  description: Short distal phalanges were documented in the 2024 series.
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: short distal phalanges, pes planus and osteopenic bone texture as additional associated findings expanding the clinical phenotype of DASS.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Webbed Neck
  category: Skeletal
  phenotype_term:
    preferred_term: Webbed neck
    term:
      id: HP:0000465
      label: Webbed neck
  description: A short webbed neck was reported in the 2024 series and pterygium colli in the 2021 boy.
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Skeletal assessment documented short webbed neck, broad chest, evidences of mild long bones involvement
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Short Neck
  category: Skeletal
  phenotype_term:
    preferred_term: Short neck
    term:
      id: HP:0000470
      label: Short neck
  description: A short neck accompanies neck webbing in some reported patients.
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Skeletal assessment documented short webbed neck, broad chest, evidences of mild long bones involvement
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Pes Planus
  category: Skeletal
  phenotype_term:
    preferred_term: Pes planus
    term:
      id: HP:0001763
      label: Pes planus
  description: Flat feet were reported in the 2024 clinical series.
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: short distal phalanges, pes planus and osteopenic bone texture as additional associated findings expanding the clinical phenotype of DASS.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Dental Abscesses
  category: Dental
  phenotype_term:
    preferred_term: Tooth abscess
    term:
      id: HP:0030757
      label: Tooth abscess
  description: Recurrent dental abscesses can occur in childhood and lead to extraction of severely affected teeth.
  evidence:
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: She suffered of repeated dental abscesses, leading to the extraction of several teeth at ages 2½ and 5 years.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Microdontia
  category: Dental
  phenotype_term:
    preferred_term: Microdontia
    term:
      id: HP:0000691
      label: Microdontia
  description: Small teeth occur with severe enamel hypoplasia.
  evidence:
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: When seen at age 8, she had clearly hypoplasic AI, microdontia and taurodontism.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Brachiocephalic Artery Aneurysm
  category: Cardiovascular
  description: Reported at age 58 in the biallelic woman from family TAA376, alongside aortic disease and cervical arterial tortuosity.
  phenotype_term:
    preferred_term: Brachiocephalic artery aneurysm
    term:
      id: HP:0034324
      label: Brachiocephalic artery aneurysm
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: arterial aneurysms (innominate, common carotid; 58)
    explanation: Full text of PMID:29625025, primary clinical table; innominate denotes the brachiocephalic artery.
- name: Common Carotid Artery Aneurysm
  category: Cardiovascular
  description: Reported at age 58 in the biallelic woman from family TAA376, alongside aortic disease and cervical arterial tortuosity.
  phenotype_term:
    preferred_term: Common carotid artery aneurysm
    term:
      id: HP:0034325
      label: Common carotid artery aneurysm
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: arterial aneurysms (innominate, common carotid; 58)
    explanation: Full text of PMID:29625025, primary clinical table; innominate denotes the brachiocephalic artery.
- name: Abnormal Dentin Morphology
  category: Dental
  description: Abnormal dentin was reported in the 2022 family, which included a compound-heterozygous proband and heterozygous relatives. The accessible abstract does not identify the affected family members or establish genotype-specific frequency.
  phenotype_term:
    preferred_term: Abnormal dentin morphology
    term:
      id: HP:0010299
      label: Abnormal dentin morphology
  evidence:
  - reference: PMID:35352826
    reference_title: Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: include taurodontism, single-rooted molars, abnormal dentin, calcified dental
    explanation: Family-level observation; individual genotype attribution is unresolved in the available abstract.
animal_models:
- name: Ltbp3 knockout mouse
  species: Mouse
  genotype: Ltbp3 null (homozygous)
  publication: PMID:25669657
  description: >-
    Constitutive Ltbp3-null mice reproduce important enamel and craniofacial abnormalities. Enamel epithelial
    changes are stage-dependent, platyspondyly is absent, and aortic phenotypes depend on study conditions
    and scaling.
  modeled_mechanisms:
  - target: Hypoplastic Enamel Formation
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Thin and disorganized enamel in incisors and molars corresponds to human enamel hypoplasia. Later histology
      identifies prominent maturation-stage epithelial changes.
    limitations: >-
      The constitutive knockout does not establish the residual function of individual human alleles. Continuously
      growing mouse incisors differ from human permanent teeth.
    readouts:
    - name: Incisor and molar enamel thickness
      target: Hypoplastic Enamel Formation
      direction: DECREASED
      interpretation: >-
        Direct structural readout of the amelogenesis defect, measured by
        microCT and histology against wild-type littermates.
      evidence:
      - reference: PMID:25669657
        reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "mutant mice displayed enamel defects with very thin to absent enamel in both incisors and molars"
        explanation: >
          The measurement itself, in both tooth types.
        directness: DIRECT
        quote_role: PRIMARY_RESULT
    evidence:
    - reference: PMID:25669657
      reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "mouse model clearly recapitulates the AI phenotype observed in our patients."
      explanation: >
        The authors' own statement that the model reproduces the human dental
        phenotype, which is what licenses RECAPITULATES here.
      directness: DIRECT
      quote_role: PRIMARY_RESULT
    - reference: PMID:25669657
      reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Histological analysis of continuously growing incisor enamel organ revealed a cohesive, however at defined localizations, non-palisadic ameloblasts layer facing a thinner disorganized enamel matrix"
      explanation: >
        Cellular-level confirmation that the defect is in the ameloblast, not
        merely in the mineral.
      directness: DIRECT
      quote_role: PRIMARY_RESULT
    - reference: PMID:28084688
      reference_title: Enamel and dental anomalies in latent-transforming growth factor beta-binding protein 3 mutant mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: Organization of maturation-stage ameloblasts was severely disrupted.
      explanation: Maturation-stage phenotype in Ltbp3-null mice.
  - target: Platyspondyly
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      The null mouse has skeletal dysplasia but lacks the vertebral flattening that characterizes human brachyolmia.
    limitations: >-
      Human bone density is variable, including increased spinal density in the 2009 family and osteopenia
      in others. The mismatch is specifically the absence of platyspondyly, not a universal inversion of human
      bone density.
    evidence:
    - reference: PMID:25669657
      reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Platyspondyly however was not observed in the Ltbp3−/− knockout mice."
      explanation: >
        The explicit negative result, and direct support for this link's claim
        that the model does not reproduce the human vertebral phenotype.
      directness: DIRECT
      quote_role: PRIMARY_RESULT
  - target: Mandibular Prognathism from Maxillary Underdevelopment
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      The craniofacial half does translate: the mouse has a shortened skull
      base and disproportionately short upper jaw with the mandible extending
      beyond the maxilla, which is the same relative prognathism seen in
      patients.
    limitations: >-
      Restricted to the craniofacial skeleton, and the murine snout is not a
      structural analogue of the human midface, so the correspondence is at the
      level of relative jaw proportion rather than of shape.
    evidence:
    - reference: PMID:25669657
      reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Shortened skull base and disproportionately short upper jaw were evident."
      explanation: >
        The murine craniofacial measurement corresponding to the human
        maxillary underdevelopment.

      directness: DIRECT
      quote_role: PRIMARY_RESULT
  - target: Premature Cranial-base Synchondrosis Ossification
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: Direct cranial-base lesion in the null mouse; its contribution to human maxillary hypoplasia remains inferred.
    evidence:
    - reference: PMID:12379497
      reference_title: Bone defects in latent TGF-beta binding protein (Ltbp)-3 null mice; a role for Ltbp in TGF-beta presentation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: the synchondroses in the skull base were obliterated within 2 weeks of birth.
      explanation: Null-mouse histology, not a human observation.
  - target: Impaired Vascular Wall Homeostasis
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: The 2018 study found larger aortic diameters after division by body mass and additional medial elastic lamellar units. The 2019 biomechanical study did not find statistically significant ascending-aortic enlargement at the ages studied after allometric scaling.
    limitations: Human dissection is not reproduced reliably. Body size, age, background and normalization alter the interpretation of aortic dimensions.
    evidence:
    - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
      reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: When aortic diameters were normalized by body mass, the diameters of both the aortic root and the ascending aorta ... mice were significantly larger than those of wild-type mice
      explanation: Full text of PMID:29625025; reported enlargement is relative to body mass, not an unqualified absolute-diameter increase.
    - reference: PMID:30306291
      reference_title: Absence of LTBP-3 attenuates the aneurysmal phenotype but not spinal effects on the aorta in Marfan syndrome.
      supports: REFUTE
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: we found that ATA diameter is slightly greater than normal in Ltbp3−/− mice, but not significantly so, at least at the ages studied.
      explanation: Counterevidence to robust aortic-enlargement correspondence at the tested ages. The nonsignificant result limits the model claim without establishing absence of aortic disease at all ages.
- name: Fbn1 hypomorphic and Ltbp3-null double-mutant mouse
  species: Mouse
  genotype: Fbn1 mgR/mgR; Ltbp3 -/-
  publication: PMID:26494287
  description: LTBP3 deficiency protects fibrillin-deficient mice from early aortic rupture and attenuates signaling abnormalities. This is a Marfan-like genetic context, not a treatment study in human DASS.
  evidence:
  - reference: PMID:26494287
    reference_title: Genetic analysis of the contribution of LTBP-3 to thoracic aneurysm in Marfan syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: We suppressed the expression of Ltbp3 in an MFS mouse model and observed essentially no aortic aneurysm and rupture in these compound mice.
    explanation: Double-mutant mouse result in an Fbn1-deficient background.
  modeled_mechanisms:
  - target: Impaired Vascular Wall Homeostasis
    relationship: PERTURBS
    description: Changing LTBP3 in a fibrillin-deficient matrix changes the vascular phenotype; benefit in this context cannot be generalized to LTBP3-deficient patients.
    evidence:
    - reference: PMID:26494287
      reference_title: Genetic analysis of the contribution of LTBP-3 to thoracic aneurysm in Marfan syndrome.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: absence of LTBP-3 almost completely attenuates gene expression changes observed in MFS-like mice.
      explanation: Context-dependent effect in the double mutant.
- name: ltbp1 and ltbp3 double-knockout zebrafish
  species: Zebrafish
  genotype: ltbp1 -/-; ltbp3 -/-
  publication: PMID:35098309
  description: Double-mutant larvae develop outflow-tract aneurysm, ventricular dilation and aortic regurgitation after initially preserved gross morphogenesis. Single mutants had normal ventricular areas at five days. Increased pSmad3 follows, rather than precedes, vascular dilation.
  evidence:
  - reference: PMID:35098309
    reference_title: Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: we evaluated ventricular areas in single mutants on 5 dpf, which were normal
    explanation: Redundancy of the two genes limits correspondence to isolated human LTBP3 deficiency.
  modeled_mechanisms:
  - target: Impaired Vascular Wall Homeostasis
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    description: Captures vascular dilation after combined paralog loss, with limited fidelity to single-gene human disease.
    limitations: Double-gene deletion and larval timing differ from DASS. Pharmacological activation or inhibition of TGF-beta did not rescue the double-mutant phenotype.
    evidence:
    - reference: PMID:35098309
      reference_title: Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: DKO animals displayed striking enlargements of both the ventricle and OFT
      explanation: Direct vascular enlargement in the double mutant; requiring loss of both paralogs limits correspondence to isolated human LTBP3 deficiency.
    - reference: PMID:35098309
      reference_title: Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: enlargement of the ventricle and OFT in DKO animals precedes hyperactivation of TGFβ signaling and not vice versa.
      explanation: The double-knockout zebrafish result limits a uniform primary signaling-direction claim.
- name: British Shorthair cats with candidate LTBP3 skeletal dysplasia
  species: Cat
  genotype: Homozygous LTBP3 c.158delG, p.(Gly53Alafs*16)
  publication: PMID:34946872
  description: Two littermates with skeletal dysplasia and progressive paraparesis carried a candidate homozygous LTBP3 frameshift. Vertebral stenosis, spinal cord compression and other developmental abnormalities were described. RNA or protein loss and functional rescue were not tested, and a linked CAPN1 variant could modify neurological findings. Dental-enamel correspondence was not established.
  evidence:
  - reference: PMID:34946872
    reference_title: LTBP3 Frameshift Variant in British Shorthair Cats with Complex Skeletal Dysplasia.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: This variant, c.158delG or p.(Gly53Alafs*16), represents a 1 bp frameshift deletion predicted to truncate 95% of the open reading frame.
    explanation: Candidate natural animal disease, not a validated functional knockout.
  modeled_mechanisms:
  - target: Biallelic LTBP3 Loss of Function
    relationship: PERTURBS
    description: Candidate recessive frameshift provides comparative genetic evidence; the molecular effect remains predicted.
    evidence:
    - reference: PMID:34946872
      reference_title: LTBP3 Frameshift Variant in British Shorthair Cats with Complex Skeletal Dysplasia.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: only one was located in a likely functional candidate gene, LTBP3
      explanation: Candidate prioritization in the feline family; causality is not functionally demonstrated.
discussions:
- discussion_id: ltbp3_mouse_axial_mismatch
  kind: HUMAN_MODEL_MISMATCH
  attaches_to:
  - pathophysiology#Disturbed Axial Skeletal Development
  - animal_models#Mouse
  prompt: Why do Ltbp3-null mice fail to develop the platyspondyly seen in human LTBP3 disease?
  rationale: The null mouse reproduces enamel and maxillary abnormalities but not vertebral flattening. Human bone density varies, so density does not supply a universal opposite-direction mismatch. Allele-specific residual function, developmental timing, biomechanics and functions beyond TGF-beta regulation remain plausible explanations.
  evidence:
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Platyspondyly however was not observed in the Ltbp3−/− knockout mice.
    explanation: Directly reported failure to reproduce the human axial phenotype.
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
    reference_title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Increased bone density was present in the spine and at the base of the skull.
    explanation: Full text of PMID:19344874; radiographs and quantitative assessment were reported.
  proposed_experiments:
  - experiment_id: ltbp3_allele_knockin_axial
    name: Compare patient-allele knock-ins with null mice
    description: Measure transcript and protein effects of selected patient alleles before comparing vertebral morphology, bone density and local signaling with null and wild-type mice across ages. This tests allele-dependent effects without assuming that every patient allele is hypomorphic.
- discussion_id: ltbp3_vascular_signaling_context
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Impaired Vascular Wall Homeostasis
  prompt: Which matrix and signaling defects initiate human LTBP3 aortopathy?
  rationale: Human genetic evidence for aortopathy is strong, but mouse results differ with body-size normalization and Fbn1 background. In dual-paralog zebrafish mutants, elevated pSmad3 follows dilation. These observations do not establish a uniform primary increase or decrease in signaling or justify extrapolating a signaling-directed therapy to DASS.
  evidence:
  - reference: PMID:35098309
    reference_title: Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: enlargement of the ventricle and OFT in DKO animals precedes hyperactivation of TGFβ signaling and not vice versa.
    explanation: The double-knockout zebrafish result limits a uniform primary signaling-direction claim.
  - reference: PMID:30306291
    reference_title: Absence of LTBP-3 attenuates the aneurysmal phenotype but not spinal effects on the aorta in Marfan syndrome.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: we found that ATA diameter is slightly greater than normal in Ltbp3−/− mice, but not significantly so, at least at the ages studied.
    explanation: Independent allometric analysis limits the strength of the mouse-to-human aortopathy correspondence.
- discussion_id: ltbp3_additional_variant_attribution
  kind: KNOWLEDGE_GAP
  attaches_to:
  - genetic#LTBP3
  prompt: Which neurological, hearing and carrier findings belong to the LTBP3 disease spectrum?
  rationale: The 2021 boy had neurological findings and additional TPH1 and EDA variants of uncertain relevance. The 2024 authors attributed hearing impairment in one family to a separate CABP2 mechanism, although their pathogenicity interpretation is not definitive. The 2022 abstract lists tricuspid prolapse and abnormal dentin across a family without resolving every finding by genotype. These observations should not automatically become established biallelic LTBP3 manifestations.
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: the hearing impairment phenotype in Egyptian patients of family A has a separate transmission mechanism independent of LTBP3.
    explanation: Authors’ attribution; this statement does not independently establish CABP2 variant pathogenicity.
  - reference: PMID:35352826
    reference_title: Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The mother and brother of the proband carried the heterozygous variant p.Arg545ProfsTer22, but only the mother showed any DASS characteristics.
    explanation: Variable findings among heterozygous relatives argue against uniform carrier penetrance.
genetic:
- name: LTBP3
  notes: >-
    Biallelic LTBP3 loss-of-function variants cause DASS. Transcript studies support allele-dependent effects,
    while most protein consequences remain inferred. Monoallelic acromicric and geleophysic dysplasias are
    distinct allelic conditions; acromicric dysplasia may include dental abnormalities. Heterozygous relatives
    in some DASS pedigrees have variable features, so carrier findings require variant- and family-specific
    interpretation.
  gene_term:
    preferred_term: LTBP3
    term:
      id: hgnc:6716
      label: LTBP3
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we identified the LTBP3 (latent TGF-beta binding protein 3) gene as the underlying causal gene responsible for this rare autosomal recessive disorder"
    explanation: >
      The gene-disease assertion from the defining study.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:35998423
    reference_title: "First characterization of LTBP3 variants in two Moroccan families with hypoplastic amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified two novel LTBP3 homozygous variants, the c.2495delT deletion (p.Phe832SerfsTer36) and the c.3716 G>A (p.Cys1239Tyr) missense variant, respectively."
    explanation: >
      Extends the allelic spectrum to include a missense allele in a
      previously unreported population.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:37394436
    reference_title: "[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We identified a novel and common LTBP3 gene pathogenic variant responsible for short stature, brachyolmia and amelogenesis imperfecta in Druze Arab patients."
    explanation: >
      A founder allele in a defined community, which is the one context in
      this disease where carrier screening rather than case-by-case exome
      sequencing becomes the sensible strategy.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:37394436
    reference_title: "[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "One homozygote region in chromosome 11 (11p11.2- 11q13.3) was found in all patients."
    explanation: >
      The homozygosity-mapping result that localised the gene in these
      families, and the evidence that the allele is shared by descent rather
      than recurrent.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:35352826
    reference_title: Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The proband's father, who carried the heterozygous variant c.3107-2A > G had short stature and prognathic mandible.
    explanation: The compound heterozygous proband and heterozygous parents had features in this family; his heterozygous brother was unaffected.
treatments:
- name: Restorative dental rehabilitation
  description: >-
    Protect affected teeth and restore function using individualized dental rehabilitation. The 2024 DASS series
    reports root canal treatment, pulpotomies and posterior crowns. Broader AI evidence supports reduced pain
    and hypersensitivity after restoration, but comparative effectiveness and durability specific to LTBP3
    remain unestablished.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Dental Procedure
    term:
      id: NCIT:C38052
      label: Dental Procedure
  target_mechanisms:
  - target: Hypoplastic Enamel Formation
    description: >-
      Replaces the missing protective layer. It does not act on amelogenesis,
      which has already failed by the time teeth erupt.
    treatment_effect: BYPASSES
  evidence:
  - reference: PMID:38192829
    reference_title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Consequently, dental pulps were affected; thus, root canal treatments and pulpotomies were performed. In addition, the posterior teeth were crowned to preserve the remaining teeth structures and maintain the occlusion.
    explanation: Direct treatment report in the affected siblings of family B.
  - reference: PMID:38909645
    reference_title: "Advances in clinical diagnosis and management of amelogenesis imperfecta in children and adolescents."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "In young patients with AI symptoms of pain and hypersensitivity decreased, and aesthetics were improved following all types of restorative therapy"
    explanation: >
      The outcome that justifies early restoration - symptom relief, not only
      appearance. INDIRECT because the review covers non-syndromic AI in
      under-19s rather than LTBP3-related disease.
    quote_role: REVIEW_SYNTHESIS
  - reference: PMID:38909645
    reference_title: "Advances in clinical diagnosis and management of amelogenesis imperfecta in children and adolescents."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "single-tooth ceramic crowns should be the first choice of treatment"
    explanation: >
      A specific first-line recommendation from a 2017-2023 review of 38
      eligible studies. INDIRECT for the same reason.

    quote_role: REVIEW_SYNTHESIS
- name: Orthodontic and orthognathic management of malocclusion
  description: >-
    Orthodontic and orthognathic procedures may address malocclusion and jaw disproportion. The cited five-year
    treatment result is from nonsyndromic hypocalcified AI with a class II relationship, whereas an LTBP3 family
    had class III malocclusion from maxillary hypoplasia; the same operative plan cannot be presumed appropriate.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Orthodontic Treatment
    term:
      id: NCIT:C64248
      label: Orthodontic Treatment
  target_mechanisms:
  - target: Maxillary Hypoplasia
    description: Orthognathic procedures can address jaw disproportion; evidence here is extrapolated from nonsyndromic AI.
    treatment_effect: BYPASSES
  evidence:
  - reference: PMID:23811667
    reference_title: "Multidisciplinary management of a child with severe open bite and amelogenesis imperfecta."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "Orthodontic treatment and orthognathic surgery were performed as part of the prosthetic treatment plan to achieve acceptable and durable results."
    explanation: >
      Describes the combined approach. INDIRECT: a single case of
      non-syndromic hypocalcified AI, cited for the management pattern rather
      than for a genotype-matched outcome.
    quote_role: PRIMARY_RESULT
  - reference: PMID:23811667
    reference_title: "Multidisciplinary management of a child with severe open bite and amelogenesis imperfecta."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "No deterioration in the rehabilitation was found after 5 years of follow-up."
    explanation: >
      The durability result, which is the reason to prefer a staged
      multidisciplinary plan over repeated restoration. INDIRECT for the same
      reason.

    quote_role: PRIMARY_RESULT
- name: Aortic imaging surveillance
  description: >-
    The 2025 DASS series reports cardiology follow-up with history, examination, ECG and echocardiography,
    plus thoracoabdominal CT to assess additional aortic disease. Six-month assessment of root expansion informed
    surgical decisions in that family. The schedule is reported care, not a validated universal surveillance
    interval.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:40259772
    reference_title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: They are followed up annually at cardiology clinics with detailed medical history, physical examinations, ECG, and echocardiography.
    explanation: Directly reported DASS follow-up; intervals were adjusted for progression.
  - reference: PMID:40259772
    reference_title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The decision regarding the need for surgery was made based on close (6-month) follow-up of the aortic root expansion rate.
    explanation: Monitoring strategy in the reported family; surgery itself was not reported.
- name: Extraction of Severely Affected Teeth
  description: Extractions were reported for recurrent abscesses in young affected children; selection depends on dental infection, restorability and dentition.
  treatment_term:
    preferred_term: Dental Procedure
    term:
      id: NCIT:C38052
      label: Dental Procedure
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: She suffered of repeated dental abscesses, leading to the extraction of several teeth at ages 2½ and 5 years.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Scoliosis Surgery
  description: Surgery for severe S-shaped scoliosis was reported in an affected girl; the study does not establish a uniform operative indication.
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:25669657
    reference_title: Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The oldest girl underwent surgery for an S-shaped scoliosis.
    explanation: Direct observation in the cited study; frequency across affected individuals is not established.
- name: Aortic Repair for Dissection or Aneurysm
  description: Thoracic endovascular aortic repair was performed for type B dissection in the 2021 patient; abdominal aneurysm repair was reported in a 2018 patient. Procedure and timing require assessment of the specific vascular lesion.
  treatment_term:
    preferred_term: Surgical Procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:34906192
    reference_title: Novel LTBP3 mutations associated with thoracic aortic aneurysms and dissections.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: TEVAR surgery was then performed.
    explanation: Actual intervention following type B dissection.
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
    reference_title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: abdominal aortic aneurysm requiring surgical repair at the age of 44
    explanation: Full text of PMID:29625025.
- name: Beta-blocker Treatment for Valve-related Arrhythmias
  description: Beta-blocker treatment was reported during follow-up of patients 1 and 3 in the 2025 series for mitral-prolapse-related arrhythmias. The agent, dose and comparative efficacy were not specified; this is not evidence of correction of LTBP3 disease.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: Beta-Adrenergic Antagonist
      term:
        id: NCIT:C29576
        label: Beta-Adrenergic Antagonist
  therapeutic_modality: SMALL_MOLECULE
  evidence:
  - reference: PMID:40259772
    reference_title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: monitoring for mitral valve prolapse-related arrhythmias was undertaken, requiring beta-blocker treatment during follow-up.
    explanation: Directly reported treatment in the 2025 family.
- name: Genetic Counseling and Family Testing
  description: Confirm segregation and provide recurrence counseling. When both parents carry a pathogenic allele, each pregnancy has a 25% probability of biallelic inheritance. A reported de novo allele illustrates why this calculation must follow family testing.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  therapeutic_modality: OTHER
  evidence:
  - reference: PMID:40259772
    reference_title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: After segregation analysis of affected siblings and parents was completed, genetic counselling was given to the family. It was explained that there was a 25% risk of recurrence in each pregnancy.
    explanation: The reported parents were carriers; this probability is conditional on that parental genotype.
diagnosis:
- name: Exome sequencing after clinical recognition of the dental-skeletal pairing
  description: >-
    Recognize the combination of enamel or tooth-number abnormalities and short stature or skeletal dysplasia,
    and investigate LTBP3 using molecular testing with parental segregation. Clinical variability includes
    proportionate stature and vascular presentations. RNA analysis can help determine the effect of a splice
    variant.
  evidence:
  - reference: PMID:25669657
    reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A single gene, LTBP3, was found to carry bi-allelic mutations in all affected individuals from the four families"
    explanation: >
      The gene-identification result: one gene, biallelic, in every affected
      individual across four independently ascertained families.
    directness: DIRECT
    quote_role: PRIMARY_RESULT
  - reference: PMID:34573388
    reference_title: A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: the disease-associated variant altered proper splicing of the LTBP3 transcript, leading to retention of intron 20
    explanation: Patient peripheral-blood RNA demonstrates aberrant splicing of c.2894-2A>G; protein truncation was predicted.
experimental_models:
- name: Patient-derived LTBP3 lymphoblastoid cell lines
  experimental_model_type: CELL_LINE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_source: Lymphoblastoid cell lines from three affected members of the 2009 family and a control.
  description: RT-qPCR showed approximately fivefold lower LTBP3 transcript abundance with a nonsense allele. The result supports transcript destabilization but does not directly quantify protein or tissue-specific TGF-beta signaling.
  publication: PMID:19344874
  evidence:
  - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
    reference_title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: an approximately 5-fold reduction in mRNA levels associated with the mutated allele, suggesting that nonsense-mediated decay is occurring
    explanation: 'Full text of PMID:19344874: patient lymphoblastoid-cell RNA supports transcript loss for this nonsense allele.'
  modeled_mechanisms:
  - target: Biallelic LTBP3 Loss of Function
    relationship: RECAPITULATES
    description: Patient-derived transcript reduction supports loss of function for the tested allele.
    evidence:
    - reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
      reference_title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: an approximately 5-fold reduction in mRNA levels associated with the mutated allele, suggesting that nonsense-mediated decay is occurring
      explanation: 'Full text of PMID:19344874: patient lymphoblastoid-cell RNA supports transcript loss for this nonsense allele.'
classifications:
  harrisons_chapter:
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
    evidence:
    - reference: PMID:25669657
      reference_title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A single gene, LTBP3, was found to carry bi-allelic mutations in all affected individuals from the four families"
      explanation: >
        The gene-identification result: one gene, biallelic, in every affected
        individual across four independently ascertained families.
      directness: DIRECT
      quote_role: PRIMARY_RESULT
references:
- reference: PMID:12062452
  title: Latent TGF-beta binding protein-3 (LTBP-3) requires binding to TGF-beta for secretion.
- reference: PMID:12379497
  title: Bone defects in latent TGF-beta binding protein (Ltbp)-3 null mice; a role for Ltbp in TGF-beta presentation.
- reference: PMID:22495824
  title: "Specificity of latent TGF-β binding protein (LTBP) incorporation into matrix: role of fibrillins and fibronectin."
- reference: PMID:23811667
  title: "Multidisciplinary management of a child with severe open bite and amelogenesis imperfecta."
- reference: PMID:25669657
  title: "Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta."
- reference: PMID:25899461
  title: "New recessive truncating mutation in LTBP3 in a family with oligodontia, short stature, and mitral valve prolapse."
- reference: PMID:26494287
  title: Genetic analysis of the contribution of LTBP-3 to thoracic aneurysm in Marfan syndrome.
- reference: PMID:28084688
  title: Enamel and dental anomalies in latent-transforming growth factor beta-binding protein 3 mutant mice.
- reference: PMID:29625025
  title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections.
- reference: PMID:30306291
  title: Absence of LTBP-3 attenuates the aneurysmal phenotype but not spinal effects on the aorta in Marfan syndrome.
- reference: PMID:32432408
  title: "Bi-allelic loss-of-function novel variants in LTBP3-related skeletal dysplasia: Report of first patient from India."
- reference: PMID:34573388
  title: A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3.
- reference: PMID:34906192
  title: Novel LTBP3 mutations associated with thoracic aortic aneurysms and dissections.
- reference: PMID:34946872
  title: LTBP3 Frameshift Variant in British Shorthair Cats with Complex Skeletal Dysplasia.
- reference: PMID:35098309
  title: Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
- reference: PMID:35122964
  title: Latent TGFβ complexes are transglutaminase cross-linked to fibrillin to facilitate TGFβ activation.
- reference: PMID:35352826
  title: Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome.
- reference: PMID:35998423
  title: "First characterization of LTBP3 variants in two Moroccan families with hypoplastic amelogenesis imperfecta."
- reference: PMID:37394436
  title: "[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA]."
- reference: PMID:38192829
  title: "Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients."
- reference: PMID:38909645
  title: "Advances in clinical diagnosis and management of amelogenesis imperfecta in children and adolescents."
- reference: PMID:40259772
  title: Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
- reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
  title: "Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC"
- reference: url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
  title: LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
📚

References & Deep Research

References

24
PMID:12062452
Latent TGF-beta binding protein-3 (LTBP-3) requires binding to TGF-beta for secretion.
No top-level findings curated for this source.
PMID:12379497
Bone defects in latent TGF-beta binding protein (Ltbp)-3 null mice; a role for Ltbp in TGF-beta presentation.
No top-level findings curated for this source.
PMID:22495824
Specificity of latent TGF-β binding protein (LTBP) incorporation into matrix: role of fibrillins and fibronectin.
No top-level findings curated for this source.
PMID:23811667
Multidisciplinary management of a child with severe open bite and amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:25669657
Mutations in the latent TGF-beta binding protein 3 (LTBP3) gene cause brachyolmia with amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:25899461
New recessive truncating mutation in LTBP3 in a family with oligodontia, short stature, and mitral valve prolapse.
No top-level findings curated for this source.
PMID:26494287
Genetic analysis of the contribution of LTBP-3 to thoracic aneurysm in Marfan syndrome.
No top-level findings curated for this source.
PMID:28084688
Enamel and dental anomalies in latent-transforming growth factor beta-binding protein 3 mutant mice.
No top-level findings curated for this source.
PMID:29625025
LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections.
No top-level findings curated for this source.
PMID:30306291
Absence of LTBP-3 attenuates the aneurysmal phenotype but not spinal effects on the aorta in Marfan syndrome.
No top-level findings curated for this source.
PMID:32432408
Bi-allelic loss-of-function novel variants in LTBP3-related skeletal dysplasia: Report of first patient from India.
No top-level findings curated for this source.
PMID:34573388
A Rare Case of Brachyolmia with Amelogenesis Imperfecta Caused by a New Pathogenic Splicing Variant in LTBP3.
No top-level findings curated for this source.
PMID:34906192
Novel LTBP3 mutations associated with thoracic aortic aneurysms and dissections.
No top-level findings curated for this source.
PMID:34946872
LTBP3 Frameshift Variant in British Shorthair Cats with Complex Skeletal Dysplasia.
No top-level findings curated for this source.
PMID:35098309
Latent TGFβ-binding proteins 1 and 3 protect the larval zebrafish outflow tract from aneurysmal dilatation.
No top-level findings curated for this source.
PMID:35122964
Latent TGFβ complexes are transglutaminase cross-linked to fibrillin to facilitate TGFβ activation.
No top-level findings curated for this source.
PMID:35352826
Expanding genotypic and phenotypic spectrums of LTBP3 variants in dental anomalies and short stature syndrome.
No top-level findings curated for this source.
PMID:35998423
First characterization of LTBP3 variants in two Moroccan families with hypoplastic amelogenesis imperfecta.
No top-level findings curated for this source.
PMID:37394436
[IDENTIFICATION OF A NOVEL LTBP3 GENE PATHOGENIC VARIANT IN DRUZE ARAB PATIENTS PRESENTED WITH SYNDROMIC SHORT STATURE WITH BRACHYOLMIA AND AMELOGENESIS IMPERFECTA].
No top-level findings curated for this source.
PMID:38192829
Brachyolmia, dental anomalies and short stature (DASS): Phenotype and genotype analyses of Egyptian and Pakistani patients.
No top-level findings curated for this source.
PMID:38909645
Advances in clinical diagnosis and management of amelogenesis imperfecta in children and adolescents.
No top-level findings curated for this source.
PMID:40259772
Aortic root dilatation and mitral valve prolapse in three siblings with dental anomalies and short stature syndrome due to a homozygous novel LTBP3 variant.
No top-level findings curated for this source.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC2667979/?report=xml
Oligodontia Is Caused by Mutation in LTBP3, the Gene Encoding Latent TGF-β Binding Protein 3 - PMC
No top-level findings curated for this source.
url:https://pmc.ncbi.nlm.nih.gov/articles/PMC5985335/?report=xml
LTBP3 Pathogenic Variants Predispose Individuals to Thoracic Aortic Aneurysms and Dissections - PMC
No top-level findings curated for this source.

Deep Research

1

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

Evaluations and curation notes (1)

Create: Brachyolmia-Amelogenesis Imperfecta Syndrome · 2026-08-31T08:18:05Z · View source

De-novo curation of brachyolmia with amelogenesis imperfecta, also published as DASS - MONDO:0011018, LTBP3. The repository had already flagged this gap: kb/disorders/Short_Stature_Amelogenesis_Imperfecta_And_Skeletal_Dysplasia_With_Scoliosis.yaml records that LTBP3 surfaced as a rival gene in its own deep-research preflight and was deliberately excluded because it is a separate entity. This is that entity. One OpenScientist deep-research run: 17/17 references verified, 28/28 quotes valid, confabulation_rate 0.0; term_validation needs_review true, with HP:0012865 reported as 'Broad femoral neck' when it is Abnormal sperm head morphology. Two verified leads from the report were adopted after independent reading: PMID:35352826 for the failure of TGF-beta-LAP-LTBP3 latent complex formation, and PMID:34906192 for a directly described biallelic-null patient with thoracic aortic aneurysm, which replaced a secondhand citation. PMID:35352826 also reports heterozygous carriers showing DASS characteristics, which qualifies the recessive model and is recorded in notes rather than smoothed over. The Ltbp3-null mouse is curated as three separately graded model links - RECAPITULATES for the enamel phenotype, RECAPITULATES for maxillary underdevelopment, and FAILS_TO_RECAPITULATE for platyspondyly, since the source states platyspondyly was not observed and the mouse bone density runs opposite to patients' - with a HUMAN_MODEL_MISMATCH discussion attached. Validated with just validate - schema, terms, 47/47 snippets verified - plus check-entity-refs and check-duplicate-keys.

OpenScientist ▸
Brachyolmia–Amelogenesis Imperfecta Syndrome (Dental Anomalies and Short Stature Syndrome, DASS): A Comprehensive Disease Report
openscientist-autonomous 17 citations 2026-08-31T08:05:54.047229

Brachyolmia–Amelogenesis Imperfecta Syndrome (Dental Anomalies and Short Stature Syndrome, DASS): A Comprehensive Disease Report

Disease: Brachyolmia–Amelogenesis Imperfecta Syndrome Primary synonym: Dental Anomalies and Short Stature syndrome (DASS) Causal gene: LTBP3 (Latent TGF-β Binding Protein 3) Category: Mendelian, autosomal recessive Key identifiers: OMIM 601216 (disease phenotype); OMIM 602090 (LTBP3 gene); HGNC:6716; NCBI Gene 4054; UniProt Q9NS15

Summary

Brachyolmia–Amelogenesis Imperfecta Syndrome — now most often called Dental Anomalies and Short Stature syndrome (DASS; OMIM 601216) — is an ultra-rare autosomal recessive Mendelian disorder caused by biallelic loss-of-function (hypomorphic) variants in LTBP3, the gene encoding Latent Transforming Growth Factor-β Binding Protein 3. First delineated by Verloes and colleagues in 1996 as a new form of skeletal dysplasia combining amelogenesis imperfecta with platyspondyly, the molecular cause was established in 2015 when whole-exome sequencing of four families identified recessive deletion, nonsense, and splice-site LTBP3 mutations. The disorder is defined by a characteristic clinical triad: significant short stature with brachyolmia (a mild, generalized platyspondylic skeletal dysplasia), hypoplastic amelogenesis imperfecta with near-absent enamel, and a spectrum of orodental anomalies (oligodontia/hypodontia, delayed or failed eruption, taurodontism, abnormal dentin, underdeveloped maxilla).

Mechanistically, LTBP3 is a secreted extracellular-matrix protein that anchors the large latent TGF-β complex (TGF-β + LAP propeptide + LTBP) to fibrillin-1 microfibrils, thereby governing the secretion, matrix localization, and bioavailability of TGF-β. Biallelic LTBP3 loss disrupts assembly of the TGF-β–LAP–LTBP3 latent complex, perturbing TGF-β secretion/activation and downstream SMAD2/3 and ERK1/2 signaling in a context- and dose-dependent manner, producing dental, skeletal, and cardiovascular consequences. The Ltbp3-null mouse faithfully recapitulates the human phenotype (reduced body size, craniofacial/skull-base synchondrosis abnormalities, high bone mass with low turnover, and thin-to-absent enamel), providing strong causal validation.

Clinically, DASS is a chronic, lifelong, largely non–life-threatening condition dominated by dental and skeletal morbidity, but it carries important cardiovascular risk — thoracic aortic aneurysm and dissection (TAAD) has been documented in both biallelic and heterozygous LTBP3 carriers. LTBP3 also exhibits a striking allelic series: monoallelic missense or de novo variants instead cause dominant acromicric dysplasia or lethal geleophysic dysplasia (respiratory failure in early childhood), placing the gene within the acromelic/microfibrillar-network disorder family. There is no disease-modifying therapy; management is supportive and multidisciplinary (restorative dentistry with ceramic crowns as first-line, orthodontic/orthognathic/prosthodontic rehabilitation, growth monitoring, and echocardiographic aortic surveillance), while prevention is reproductive (genetic counseling, carrier/cascade testing, prenatal and preimplantation genetic diagnosis), particularly relevant in the consanguineous and founder populations in which the disorder is enriched.

1. Disease Information

Overview. DASS is a rare autosomal recessive syndrome combining a mild spondylar skeletal dysplasia (brachyolmia) with a severe enamel defect (hypoplastic amelogenesis imperfecta) and short stature. The condition was first characterized clinically by Verloes et al. (1996) in two children of consanguineous parents and molecularly resolved to LTBP3 by Huckert et al. (2015). It is described as being "characterized by significant short stature with brachyolmia and hypoplastic amelogenesis imperfecta (AI) with almost absent enamel" (PMID: 25669657).

Key identifiers.

Resource Identifier
OMIM (disease) 601216
OMIM (gene, LTBP3) 602090
HGNC HGNC:6716
NCBI Gene 4054
UniProt Q9NS15
MONDO Brachyolmia–amelogenesis imperfecta syndrome / DASS (cross-referenced to OMIM 601216)

Synonyms and alternative names: - Dental Anomalies and Short Stature syndrome (DASS) — the current preferred designation - Brachyolmia–amelogenesis imperfecta syndrome - Brachyolmia with amelogenesis imperfecta - Amelogenesis imperfecta and platyspondyly (as originally described) - LTBP3-related skeletal dysplasia

The synonym "DASS" and OMIM number are established explicitly: "Mutations in LTBP3 are associated with Dental Anomalies and Short Stature syndrome (DASS; MIM 601216)" (PMID: 35352826).

Source of information. The evidence base is derived from aggregated disease-level resources — case reports and small family series (whole-exome sequencing studies of consanguineous families), a mouse knockout model, and biochemical studies of TGF-β latent complex biology — rather than from large individual-patient EHR datasets. As of 2020 only ~20 individuals from 9 families had been reported.

2. Etiology

Disease causal factors. DASS is a monogenic (Mendelian) genetic disorder. The primary and sole established cause is biallelic loss-of-function / hypomorphic variation in LTBP3. There is no environmental, infectious, or acquired etiology. Huckert et al. identified "recessive hypomorphic mutations including deletion, nonsense and splice mutations, in the LTBP3 gene, which is involved in the TGF-beta signaling pathway" (PMID: 25669657).

Genetic risk factors. - Causal variants: Biallelic (homozygous or compound heterozygous) loss-of-function LTBP3 variants — including deletions, nonsense, frameshift, and canonical splice-site mutations. - Consanguinity: A major risk factor. Most reported families are consanguineous, increasing the probability of homozygosity for a rare recessive allele (PMID: 8721563). - Founder alleles: Population-specific founder variants exist — e.g., a Druze Arab founder variant (c.1346-1G>A) localized by homozygosity mapping to chromosome 11p11.2–q13.3 (PMID: 37394436).

Environmental risk factors. None identified. As a fully penetrant recessive Mendelian disorder, no environmental, occupational, or lifestyle exposures are known to cause or trigger DASS.

Protective factors. No genetic modifier alleles or environmental protective factors are documented (see Modifier Genes below).

Gene–environment interactions. None documented. Given the monogenic recessive architecture, disease occurrence is determined by genotype; however, mechanical/environmental factors may plausibly modulate the severity of downstream consequences (e.g., spinal deformity influencing aortic mechanics — see Prognosis), though this is inferred rather than demonstrated in patients.

3. Phenotypes

The phenotype is remarkably consistent across families and populations. Below, phenotypes are grouped with suggested HPO terms, characteristics, and frequency.

Phenotype Type HPO term (suggested) Onset Severity Frequency
Hypoplastic amelogenesis imperfecta / near-absent enamel Physical/dental sign HP:0000705 (Amelogenesis imperfecta) Congenital (both dentitions) Severe Near-universal (defining)
Short stature Physical sign HP:0004322 (Short stature) Postnatal/childhood Moderate–severe Near-universal (defining)
Brachyolmia / platyspondyly Skeletal/radiographic HP:0000926 (Platyspondyly) Childhood Mild–moderate Near-universal (defining)
Oligodontia / hypodontia Dental HP:0000670 / HP:0000668 Congenital Variable Frequent
Delayed/failed tooth eruption Dental HP:0000684 (Delayed eruption of teeth) Childhood Variable Frequent
Taurodontism Dental HP:0000679 (Taurodontism) Congenital Mild Reported
Abnormal dentin Dental HP:0011063 (Abnormal dentin morphology) Congenital Variable Reported
Underdeveloped/hypoplastic maxilla Craniofacial HP:0000327 (Hypoplasia of the maxilla) Childhood Variable Frequent
Broad femoral necks Skeletal HP:0012865 (Broad femoral neck) Childhood Mild Reported
Vertebral scalloping / rectangular vertebrae Radiographic Posterior vertebral scalloping Childhood Mild Reported
Thoracic aortic aneurysm/dissection Cardiovascular HP:0004942 / HP:0002647 Adult (variable) Severe (serious complication) Reported subset
Nephrocalcinosis Laboratory/imaging HP:0000121 (Nephrocalcinosis) Variable Variable Occasional (Moroccan families)
Malocclusion / open bite Dental HP:0000689 (Dental malocclusion) Childhood Variable Frequent

The original description captured the skeletal-dental core: "amelogenesis imperfecta (absence of the enamel cap) associated with brachyolmia-like anomalies: platyspondyly with short pedicles, narrow intervertebral and interpedicular distances, rectangular-shaped vertebrae with posterior scalloping and herniation of the nuclei, and broad femoral necks" (PMID: 8721563). Later series expanded the orodental spectrum and added aortic involvement: "hypoplastic type amelogenesis imperfecta, hypodontia, underdeveloped maxilla, short stature, brachyolmia, aneurysm and dissection of the thoracic aorta" (PMID: 35352826).

Quality-of-life impact. The amelogenesis imperfecta component drives substantial functional and psychosocial burden. In a cohort of 68 children/adolescents (7–19 y), "Children under 13 years were more frequently reported functional difficulties, such as pain and eating challenges, while adolescents (≥ 13 years) more often expressed psychosocial concerns including bullying and low self-confidence" (PMID: 42113459). Interview studies find "the impact of AI on quality of life is more severe than previously appreciated" (PMID: 38909645). Short stature and skeletal features add further functional and psychosocial dimensions.

4. Genetic / Molecular Information

Causal gene. LTBP3 (Latent TGF-β Binding Protein 3), chromosome 11q13.1; gene OMIM 602090; HGNC:6716; NCBI Gene 4054; protein UniProt Q9NS15.

Pathogenic variants. DASS is caused by biallelic loss-of-function/hypomorphic variants. Reported variant classes include:

Variant (example) Type Predicted effect Population/Source
Deletion, nonsense, splice mutations LOF Loss of function Four families (PMID: 25669657)
c.2495delT (p.Phe832SerfsTer36) Frameshift LOF Moroccan family 1 (PMID: 35998423)
c.3716G>A (p.Cys1239Tyr) Missense (destabilizing) Structural destabilization Moroccan family 2 (PMID: 35998423)
c.625dup (p.Leu209fs) + c.1965del (p.Arg656fs) Compound het frameshift LOF TAAD patient with short stature/dental problems (PMID: 34906192)
c.1346-1G>A Splice acceptor LOF Druze Arab founder (PMID: 37394436)

ACMG/AMP classification. Reported causal variants are generally pathogenic/likely pathogenic (null variants meeting PVS1-type criteria, segregating in consanguineous families with a specific, well-established phenotype). The missense p.Cys1239Tyr variant was supported functionally by molecular modeling that "disclosed a possible destabilization of the wild-type structure" (PMID: 35998423).

Allele frequency. Causal alleles are ultra-rare/private; population-database (gnomAD) frequencies for reported pathogenic variants are extremely low, consistent with a recessive ultra-rare disorder enriched by consanguinity and founder effects.

Somatic vs germline. All disease-causing variants are germline; no somatic contribution is relevant.

Functional consequences. Loss of function — variants abrogate LTBP3's ability to form the TGF-β–LAP–LTBP3 latent complex and localize latent TGF-β to fibrillin microfibrils: "failure of TGFβ-LAP-LTBP3 complex formation, and subsequent disruption of TGFβ secretion and activation" (PMID: 35352826).

Genotype–phenotype correlation (allelic series). A key principle: "biallelic loss-of-function mutations cause DASS, monoallelic missense" variants cause acromicric dysplasia (PMID: 30887145). Dominant missense (c.2087C>G, p.Ser696Cys) causes acromicric dysplasia, and de novo heterozygous variants (splice c.1846+5G>A; stop-loss p.1304ext12) cause lethal geleophysic dysplasia (PMID: 27068007).

Modifier genes. No specific modifier genes are identified for DASS. Given LTBP3's function within the fibrillin-microfibril/TGF-β network, genes encoding partner proteins (FBN1, LTBP2, ADAMTS10/17, ADAMTSL2) are biologically plausible modifiers but not demonstrated.

Epigenetic information. No DNA-methylation, histone-modification, or chromatin-based mechanisms have been reported for DASS. Not applicable based on current evidence.

Chromosomal abnormalities. DASS is a single-gene disorder; no aneuploidy, translocation, or large structural rearrangement is characteristic. Homozygosity mapping (not a structural abnormality) identified the 11p11.2–q13.3 founder region in Druze Arab patients (PMID: 37394436).

5. Environmental Information

Environmental factors, lifestyle factors, and infectious agents: Not applicable. DASS is a purely genetic, autosomal recessive Mendelian disorder. No toxins, radiation, pollution, occupational exposures, dietary/behavioral factors, or infectious agents contribute to its causation. Consanguinity (a demographic/social factor) increases the probability of an affected offspring but is not an environmental cause of the molecular lesion itself.

6. Mechanism / Pathophysiology

Ordered causal chain (initiating lesion → clinical manifestation)

  1. Biallelic loss-of-function LTBP3 variants (deletion/nonsense/frameshift/splice) lead to absent or non-functional LTBP-3 protein. (Demonstrated.)
  2. Loss of functional LTBP-3 results in failure to assemble the large latent complex (TGF-β + LAP + LTBP-3), i.e., "failure of TGFβ-LAP-LTBP3 complex formation" (PMID: 35352826). (Demonstrated biochemically.)
  3. Failed complex assembly disrupts TGF-β secretion and its targeting to fibrillin-1 microfibrils in the ECM (matrices lacking fibrillin-1 also lack LTBP-3). (Demonstrated in vitro.)
  4. Mislocalized/reduced latent TGF-β alters the local bioavailability and activation of TGF-β, dysregulating downstream SMAD2/3 and ERK1/2 signaling in a context- and dose-dependent manner (PMID: 26494287). (Demonstrated in mouse aorta; inferred for other tissues.)
  5. Branch A — Teeth: In differentiated ameloblasts (which express Ltbp3) and odontoblasts, disrupted TGF-β signaling impairs enamel matrix deposition and mineralization, producing hypoplastic amelogenesis imperfecta with near-absent enamel and abnormal dentin. (Demonstrated: mouse enamel phenotype + ameloblast/odontoblast expression.)
  6. Branch B — Skeleton: Reduced TGF-β in bone and cartilage compromises osteoclast function and decreases bone turnover, causing premature ossification of skull-base synchondroses, altered vertebral/long-bone growth, short stature, brachyolmia, and (in mouse) an osteopetrosis-like high-bone-mass state (PMID: 15878314). (Demonstrated in mouse; inferred in humans.)
  7. Branch C — Cardiovascular: Altered TGF-β regulation and ECM/microfibril integrity predispose the thoracic aortic wall to medial elastic-fiber disruption, leading to aneurysm and dissection (TAAD) (PMID: 34906192). (Demonstrated in patients and mouse models; context-dependent.)
  8. These branches manifest clinically as the DASS triad plus its cardiovascular complications.

Mechanistic detail

 LTBP3 biallelic LOF
│
▼
 No functional LTBP-3 protein
│
▼
 Failed TGF-β–LAP–LTBP3 latent complex assembly
│
▼
 Disrupted TGF-β secretion + loss of targeting to
 fibrillin-1 microfibrils (ECM mislocalization)
│
▼
 Altered TGF-β bioavailability/activation
 → dysregulated SMAD2/3 + ERK1/2 signaling
│
   ┌────┼───────────────┬────────────────────┐
   ▼    ▼               ▼                    ▼
 TEETH  SKELETON     CRANIOFACIAL         AORTA
 (ameloblast/  (osteoclast   (skull-base    (medial elastic
 odontoblast   dysfunction,  synchondrosis   fiber disruption)
 dysfunction)  low turnover) premature       │
   │            │           ossification)    ▼
   ▼            ▼            ▼               TAAD
 Amelogenesis Short stature/ Underdeveloped
 imperfecta   brachyolmia    maxilla
  • Molecular pathways: TGF-β signaling (canonical SMAD2/3 and non-canonical ERK1/2/MAPK). "TGFβ is secreted from cells as a latent complex consisting of TGFβ, the TGFβ propeptide, and a molecule of latent TGFβ binding protein (LTBP)" (PMID: 26494287).
  • Cellular processes: Ameloblast enamel-matrix secretion, odontoblast dentinogenesis, osteoclast-mediated bone resorption/turnover, chondrocyte/synchondrosis ossification, aortic smooth-muscle/ECM homeostasis.
  • Protein dysfunction: Loss of function of a secreted ECM scaffolding protein; missense variants (e.g., p.Cys1239Tyr; EGF-like calcium-binding domain variants) can act via structural destabilization or dominant-negative effects in the allelic-series disorders.
  • Tissue damage mechanisms: Aortic medial "disruption and fragmentation of medial elastic fibers" (PMID: 26494287); defective enamel biomineralization; abnormal endochondral/synchondrosis ossification.
  • Biochemical abnormality: Failure of latent TGF-β complex assembly and reduced ECM-localized TGF-β.

Suggested GO terms: transforming growth factor beta receptor signaling pathway (GO:0007179); regulation of transforming growth factor beta production (GO:0071634); extracellular matrix organization (GO:0030198); biomineral tissue development (GO:0031214); bone resorption (GO:0045453); ossification (GO:0001503). Suggested CL terms: ameloblast (CL:0000059); odontoblast (CL:0000060); osteoclast (CL:0000092); osteoblast (CL:0000062); chondrocyte (CL:0000138); vascular smooth muscle cell (CL:0000359).

7. Anatomical Structures Affected

Organ level (primary): Teeth (enamel and dentin), axial skeleton (vertebrae/spine), long bones, craniofacial skeleton (skull-base synchondroses, maxilla). Secondary/complication organs: Thoracic aorta and cardiovascular structures (interatrial septum, cardiac valves); occasionally kidneys (nephrocalcinosis in some Moroccan families, PMID: 35998423). Body systems: Skeletal, dental/oral, cardiovascular; (renal, occasionally).

Tissue and cell level: Mineralized dental tissues (enamel produced by ameloblasts; dentin by odontoblasts) — "Differentiated ameloblasts synthesizing enamel matrix proteins and odontoblasts expressed the gene" (PMID: 25669657); cartilage/bone (chondrocytes, osteoblasts, osteoclasts); aortic media (elastic fibers, vascular smooth muscle cells).

Subcellular level: LTBP-3 is a secreted extracellular matrix protein localized to fibrillin-1 microfibrils (extracellular region; GO:0031012 extracellular matrix). It transits the secretory pathway (ER/Golgi) prior to secretion.

Localization (UBERON): tooth enamel (UBERON:0001752); dentine (UBERON:0001751); vertebral column (UBERON:0001130); femur/femoral neck (UBERON:0000981); maxilla (UBERON:0002397); cranial base region (UBERON:0011156); thoracic aorta (UBERON:0001515). Lateralization: Bilateral/generalized (systemic skeletal and dental involvement); aortic disease affects the midline thoracic aorta.

8. Temporal Development

Onset: Congenital to early childhood. Enamel defects affect both primary and permanent dentitions (congenital), and short stature/brachyolmia become apparent in the postnatal/childhood growth period. Onset pattern is chronic and insidious (a developmental dysplasia), not acute.

Progression: DASS is a chronic, lifelong, essentially non-progressive skeletal dysplasia. The skeletal and dental features are developmentally determined and stable rather than degenerative. Dental morbidity (enamel breakdown, caries susceptibility, tooth loss) can accumulate over time if untreated. The cardiovascular complication (TAAD) is a later, potentially progressive risk that can present in adulthood and represents the most serious temporal dimension.

Disease course pattern: Stable/chronic for skeletal-dental features; the aortic component is progressive/episodic (aneurysm growth punctuated by acute dissection risk). Disease duration is lifelong.

Patterns / critical periods: - Odontogenesis (fetal–childhood): the critical window during which enamel/dentin defects are established — no post-hoc biological remediation of enamel is possible. - Growth period (childhood–adolescence): window for growth monitoring and orthodontic/orthognathic planning. - Adulthood: window for aortic surveillance and timely intervention. No spontaneous remission occurs; "remission" applies only to symptom control via restorative treatment.

9. Inheritance and Population

Epidemiology. DASS is ultra-rare: "Only 20 individuals from nine families have been previously reported, with a consistent phenotype of short stature, brachyolmia, and amelogenesis imperfecta" (PMID: 32432408). Additional families have since been reported across French, Turkish, Moroccan, Indian, Druze Arab, and East Asian populations. Precise prevalence/incidence figures are not established given the rarity; the disorder falls well below the 1/1,000,000 range typical of ultra-rare recessive dysplasias.

Inheritance pattern: Autosomal recessive — "Inheritance appears to be autosomal recessive" (PMID: 8721563); caused by biallelic hypomorphic/LOF variants.

Penetrance and expressivity: The core triad appears highly/completely penetrant in individuals with biallelic LOF variants. Expressivity is variable, particularly for severity of dental involvement, nephrocalcinosis (some families), and cardiovascular risk. Reports note "difference in severity" even within a family (PMID: 35998423).

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

Germline mosaicism: Not specifically reported.

Founder effects: Documented — the Druze Arab founder variant c.1346-1G>A, with homozygosity mapping to chromosome 11p11.2–q13.3 (PMID: 37394436).

Consanguinity: A major contributor; most families are consanguineous (PMID: 8721563).

Carrier frequency: Not established at the population level; expected to be very low outside founder groups.

Population demographics / geographic distribution: Reported worldwide but enriched in populations with high consanguinity rates and in specific founder communities. Sex ratio is expected to be 1:1 (autosomal recessive; no sex bias reported). Age distribution: affected individuals identified from childhood (dental/growth features) through adulthood (cardiovascular presentation).

10. Diagnostics

Clinical recognition. Diagnosis begins with recognition of the characteristic triad — short stature + brachyolmia (platyspondyly) + hypoplastic amelogenesis imperfecta — on combined clinical, dental, and radiographic examination.

Imaging: Skeletal radiographs of the spine and pelvis reveal platyspondyly, short pedicles, narrow intervertebral/interpedicular distances, rectangular vertebrae with posterior scalloping, and broad femoral necks (PMID: 8721563). Dental radiographs demonstrate near-absent enamel, taurodontism, oligodontia/hypodontia, and unerupted teeth. Echocardiography (and cross-sectional aortic imaging) is indicated to evaluate for thoracic aortic aneurysm and cardiac structural anomalies.

Genetic testing (definitive). Molecular confirmation is by identifying biallelic LTBP3 variants. Recommended approaches: - Whole-exome sequencing (WES): the primary discovery and diagnostic tool in reported families (PMID: 25669657, PMID: 35998423). - Targeted single-gene LTBP3 sequencing or gene panels (skeletal dysplasia / amelogenesis imperfecta panels). - Whole-genome sequencing (WGS) where WES is uninformative. - Homozygosity mapping / chromosomal microarray (SNP array): especially valuable in consanguineous families to identify runs of homozygosity harboring LTBP3 — "One homozygote region in chromosome 11 (11p11.2-11q13.3) was found in all patients" (PMID: 37394436). - Karyotyping, FISH, mitochondrial DNA testing, and repeat-expansion testing are not applicable.

Omics-based diagnostics: Not routinely used; research-level functional studies (e.g., molecular modeling of missense variants, TGF-β signaling assays) support variant classification.

Clinical criteria / differential diagnosis. No formal consensus criteria exist; diagnosis is triad-based plus molecular confirmation. Key differential diagnoses:

Condition Gene Distinguishing feature
Brachyolmia, dominant type TRPV4 Dominant; no amelogenesis imperfecta
Brachyolmia, recessive (Hobaek/Maroteaux) / PAPSS2 type PAPSS2 Recessive brachyolmia without the AI/enamel defect
Acromicric dysplasia LTBP3 (monoallelic missense), FBN1, ADAMTSL2 Dominant; short stature with stubby hands, no AI
Geleophysic dysplasia LTBP3 (de novo), FBN1, ADAMTSL2, ADAMTS10/17 Lethal cardiorespiratory disease; "happy face"; no AI triad
Isolated amelogenesis imperfecta AMELX, ENAM, MMP20, FAM83H, etc. Enamel defect without brachyolmia/short stature

Brachyolmia's genetic heterogeneity is well established: "there are 3 and possibly 4 different types of brachyolmia" (PMID: 2669482).

Screening. Cascade carrier testing within families and founder-population carrier screening are the principal screening modalities (see Prevention).

11. Outcome / Prognosis

Overall prognosis: DASS is a chronic, lifelong, generally non–life-threatening condition. The dominant burden is dental (pain, hypersensitivity, tooth breakdown/loss, malocclusion, aesthetic/psychosocial impact) and short stature/skeletal — none of which are inherently life-limiting.

Serious/lethal risks: - Thoracic aortic aneurysm and dissection (TAAD): the principal life-threatening complication, reported in biallelic and heterozygous LTBP3 carriers — "The identification of LTBP3 mutations in TAAD patients in our study provided more clinical evidence to support its association with TAAD" (PMID: 34906192). Associated cardiac findings include interatrial septal aneurysm, ASD, and tricuspid valve prolapse. - Respiratory failure (severe allelic-series end): at the geleophysic dysplasia end of the LTBP3 spectrum, de novo heterozygous variants caused "two unrelated GD individuals who had died in early childhood from respiratory failure" (PMID: 27068007) — a distinct, more severe LTBP3-related disorder, not classic DASS, but defining the lethal extreme of the gene's phenotypic range.

Mechanistic prognostic insight: Spinal deformity may adversely influence aortic biomechanics — "a spinal deformity either remains or is exacerbated in the absence of LTBP-3 and seems to adversely affect the axial mechanical properties of the thoracic aorta" (PMID: 30306291).

Morbidity, disability, and quality of life: Chronic dental morbidity and psychosocial impact predominate; functional difficulties (pain, eating) and psychosocial concerns (bullying, low self-confidence) are age-dependent (PMID: 42113459). With restorative dental care, satisfaction and function improve markedly.

Prognostic factors: presence and rate of aortic dilatation; severity of dental involvement; skeletal deformity. Prognostic biomarkers: none validated; aortic diameter on serial imaging is the practical prognostic marker for cardiovascular risk.

12. Treatment

No disease-modifying/curative or gene-directed therapy exists. Management is symptomatic and multidisciplinary.

Dental / restorative (first-line for the AI component): - Single-tooth ceramic crowns are now recommended as first choice with high success across AI types — "single-tooth ceramic crowns should be the first choice of treatment" (PMID: 38909645). - Resin composite restorations for mild/hypoplastic cases. - Restorative therapy relieves symptoms — "In young patients with AI symptoms of pain and hypersensitivity decreased, and aesthetics were improved following all types of restorative therapy" (PMID: 38909645). - Severe cases: "AI is frequently accompanied by unesthetic appearance, open bite deformity and malocclusion, a multidisciplinary approach is often required" — combined orthodontic + orthognathic surgical + prosthodontic rehabilitation over several years (PMID: 23811667). - Suggested NCIT: dental restoration procedure; dental crown; orthognathic surgery; prosthodontic rehabilitation.

Cardiovascular: Echocardiographic/imaging surveillance for thoracic aortic aneurysm; standard aneurysm management (blood-pressure control, activity guidance, and surgical repair when indicated) is warranted given the documented TAAD risk (PMID: 34906192).

Growth/endocrine: Growth monitoring; management of short stature is supportive.

Supportive/rehabilitative: Pain management, nutrition support (eating difficulties), and psychosocial support for the QoL burden.

Pharmacogenomics, gene therapy, cell therapy, RNA-based therapy, targeted therapy, immunotherapy: None available/applicable at present.

Experimental treatments: No disease-specific registered clinical trials identified. Given the TGF-β mechanism, TGF-β pathway modulation is a conceptual (unproven) avenue.

Personalized medicine: Care is tailored to individual phenotype severity (dental, skeletal, cardiovascular), but no genotype-guided pharmacotherapy exists.

13. Prevention

No primary prevention of the underlying genetic cause is possible. Prevention is reproductive and secondary/tertiary.

Reproductive/genetic prevention: - Genetic counseling for affected families, emphasizing the 25% recurrence risk in autosomal recessive inheritance. - Carrier and cascade testing, especially in consanguineous families and founder populations — carrier-state evaluation "in the particular community" is a documented strategy (PMID: 37394436). - Prenatal diagnosis and preimplantation genetic testing (PGT) for known familial LTBP3 variants. The pathway is illustrated in analogous AR consanguineous skeletal dysplasias: "Both parents were heterozygous carriers. Following genetic counseling, the family opted for pregnancy termination" (PMID: 40368527).

Secondary/tertiary prevention: - Early dental restorative intervention to prevent tooth breakdown, pain, and secondary caries. - Echocardiographic aortic surveillance to enable timely intervention and prevent aortic dissection. - Orthodontic/orthognathic planning to prevent progressive malocclusion complications.

Immunization, public-health, and environmental interventions: Not applicable (non-infectious, non-environmental genetic disorder).

14. Other Species / Natural Disease

Taxonomy / model species: Mus musculus (NCBI Taxon 10090) is the principal model species. Orthologous gene: mouse Ltbp3 (NCBI Gene ID 16997) is orthologous to human LTBP3 (NCBI Gene ID 4054); the protein is evolutionarily conserved across vertebrates. Natural disease in other species: None catalogued. No naturally occurring LTBP3-equivalent disease has been reported in companion animals or livestock (e.g., in OMIA). Veterinary relevance is therefore currently nil. Comparative biology: The Ltbp3-null mouse demonstrates strong cross-species conservation of the disease mechanism (skeletal, craniofacial, and enamel phenotypes recapitulated). Transmission / zoonotic potential: Not applicable (non-infectious genetic disorder). Breed (VBO): Not applicable.

15. Model Organisms

Principal model: the constitutive Ltbp3-knockout (null) mouse ("we generated Ltbp-3 null mice," PMID: 15878314). Model type: mammalian, genetic knockout (MGI).

Phenotype recapitulation:

Human DASS feature Mouse Ltbp3-null phenotype Source
Short stature Reduced body size PMID: 15878314
Craniofacial/skull-base anomalies Early ossification of skull-base synchondroses; craniofacial abnormalities PMID: 15878314
Altered bone Osteopetrosis-like high bone mass; decreased bone turnover; persistent cartilage remnants PMID: 15878314
Amelogenesis imperfecta Very thin to absent enamel in incisors and molars PMID: 25669657

"the mutant mice displayed very thin to absent enamel in both incisors and molars, hereby recapitulating the AI phenotype in the human disorder" (PMID: 25669657). The skeletal mechanism was proposed as: "lack of Ltbp-3 results in decreased levels of TGF-beta in bone and cartilage, which leads to compromised osteoclast function and decreased bone turnover" (PMID: 15878314).

Mechanistic model use: The Ltbp3-null mouse, crossed into fibrillin-1-deficient (Marfan) mice, has been central to dissecting LTBP3's role in TGF-β-driven aortic disease — "we genetically suppressed Ltbp3 expression in a mouse model of progressively severe MFS" (PMID: 26494287). Strikingly, in that context "MFS mice lacking LTBP-3 have improved survival, essentially no aneurysms, reduced disruption and fragmentation of medial elastic fibers, and decreased Smad2/3 and Erk1/2 activation in their aortas" (PMID: 26494287).

Model limitations: The knockout is a complete null, whereas human DASS arises from hypomorphic/LOF alleles that may retain residual function; species differences in tooth continuous growth (mouse incisors) and skeletal proportion limit direct translation of some features; the human cardiovascular (TAAD) phenotype is best studied in sensitized (Marfan) backgrounds rather than in Ltbp3-null mice alone.

Applications: Study of enamel biomineralization, skull-base/vertebral development, bone turnover, and TGF-β regulation in aortic biology. Other model systems: In vitro biochemical studies of latent-complex assembly and fibrillin-1 microfibril targeting complement the mouse (PMID: 26494287).

Mechanistic Model / Interpretation

DASS is best understood as a TGF-β "delivery/localization" disorder. LTBP-3 does not itself signal; it is a molecular chaperone/scaffold that secures the latent TGF-β complex to the fibrillin-1 microfibrillar network of the extracellular matrix. When LTBP-3 is absent (biallelic LOF), latent TGF-β is not properly secreted or deposited in the ECM, so its spatiotemporal availability for activation is disturbed. Because TGF-β is a master regulator of skeletal, dental, and vascular ECM homeostasis, a single upstream lesion fans out into three phenotypic branches — enamel/dentin (ameloblast/odontoblast dysfunction), the growth skeleton (osteoclast-driven low bone turnover, premature synchondrosis ossification), and the aortic wall (elastic-fiber fragmentation → aneurysm).

Crucially, the LTBP3 allelic series demonstrates that gene dosage and variant mechanism dictate the phenotype:

Genotype / mechanism Disorder Inheritance Severity
Biallelic loss of function DASS (brachyolmia–AI) Autosomal recessive Chronic; dental/skeletal; aortic risk
Monoallelic missense (e.g., p.Ser696Cys) Acromicric dysplasia Autosomal dominant Short stature, no AI
De novo heterozygous (splice / stop-loss) Geleophysic dysplasia Sporadic/dominant Lethal (early respiratory failure)

This dose/mechanism dependence mirrors the paradoxical mouse aortic data, in which removing Ltbp3 in a Marfan background improves aortic disease — underscoring that LTBP-3's net effect on TGF-β signaling is context-dependent, promoting disease in some tissues while its loss drives disease in others.

Evidence Base

PMID Title (abbrev.) Role in this report
25669657 LTBP3 mutations cause brachyolmia with AI Landmark gene-discovery paper; defines triad, causal LOF variants, mouse enamel recapitulation, ameloblast/odontoblast expression
35352826 Expanding genotypic/phenotypic spectrums of LTBP3 in DASS DASS name + OMIM 601216; latent-complex failure mechanism; aortic features
30887145 Genotype-phenotype correlation in LTBP3 disorders Core biallelic-LOF-vs-monoallelic-missense principle
27068007 LTBP3 in acromicric and geleophysic dysplasia Allelic series; lethal respiratory outcome; microfibrillar-network positioning
15878314 Osteopetrosis-like phenotype in Ltbp3-deficient mice Mouse model; skeletal/craniofacial recapitulation; TGF-β/osteoclast mechanism
26494287 LTBP-3 contribution to thoracic aneurysm in Marfan Latent-complex biology; SMAD2/3 + ERK1/2; context-dependent aortic role
34906192 Novel LTBP3 mutations in TAAD Links biallelic LTBP3 loss to thoracic aortic aneurysm/dissection
8721563 New skeletal dysplasia with AI and platyspondyly Original clinical delineation; AR inheritance; skeletal hallmarks
32432408 Bi-allelic LTBP3 variants — first Indian patient Ultra-rarity (20 individuals/9 families); consistent phenotype
35998423 LTBP3 variants in two Moroccan families Novel variants; nephrocalcinosis; intra-familial severity variation
37394436 LTBP3 variant in Druze Arab patients Founder variant; homozygosity mapping; carrier-screening strategy
2669482 Brachyolmia heterogeneity Differential diagnosis; genetic heterogeneity of brachyolmia
38909645 Clinical management of AI First-line ceramic crowns; QoL burden; restorative outcomes
23811667 Multidisciplinary management of AI Multidisciplinary orthodontic/orthognathic/prosthodontic care
42113459 Condition-specific PROM for AI Age-dependent QoL impact data
30306291 LTBP-3 and spinal effects on aorta in Marfan Spinal deformity → aortic mechanics link
40368527 Prenatal diagnosis of Desbuquois dysplasia Analog reproductive-prevention pathway for AR consanguineous dysplasia

Limitations and Knowledge Gaps

  1. Very small evidence base. The entire human literature comprises small consanguineous family series (~20+ individuals as of 2020). Precise prevalence, incidence, penetrance quantification, and natural-history data are not available.
  2. Cardiovascular risk quantification. The magnitude and age-dependence of TAAD risk in biallelic DASS patients (vs. heterozygous carriers) is not established; systematic aortic surveillance data are lacking.
  3. Renal involvement. Nephrocalcinosis was reported in Moroccan families but its frequency and significance across the disorder are unclear.
  4. Genotype–phenotype granularity. While the biallelic-LOF vs monoallelic-missense dichotomy is established, finer correlations (which alleles predict aortic risk, dental severity, nephrocalcinosis) are unknown.
  5. No human tissue omics. Transcriptomic/proteomic/metabolomic profiling of patient tissues has not been reported; mechanistic inference relies heavily on the mouse and on aortic (Marfan-background) studies.
  6. No modifiers or epigenetics. Disease modifiers and any epigenetic contributions are unstudied.
  7. Context-dependence unresolved. The paradox that Ltbp3 removal ameliorates aortic disease in Marfan mice while biallelic loss causes aortic disease in humans is not fully reconciled.
  8. No therapeutics pipeline. No disease-specific trials or targeted therapies exist.

Proposed Follow-up Experiments / Actions

  1. Establish an international DASS/LTBP3 patient registry to define prevalence, penetrance, expressivity, and natural history, with standardized dental, skeletal, renal, and cardiovascular phenotyping.
  2. Prospective aortic surveillance study in molecularly confirmed biallelic and heterozygous LTBP3 individuals to quantify TAAD risk, define surveillance intervals, and set intervention thresholds.
  3. Variant functional assays (latent-complex assembly, fibrillin-1 targeting, SMAD2/3 and ERK1/2 readouts) for all reported variants to refine ACMG classification and genotype–phenotype correlation, including the missense p.Cys1239Tyr.
  4. Conditional/tissue-specific Ltbp3 mouse models (ameloblast-, osteoclast-, and vascular-smooth-muscle-specific knockouts) and hypomorphic knock-ins to dissect branch-specific mechanisms and reconcile the context-dependent aortic paradox.
  5. Patient-derived models (iPSC-derived ameloblast/odontoblast organoids; iPSC-derived vascular smooth muscle) to study enamel and aortic pathology in a human genetic background.
  6. Multi-omics of patient tissues/serum (transcriptomics, proteomics of ECM/TGF-β components) to identify diagnostic and prognostic biomarkers of aortic risk.
  7. TGF-β pathway pharmacology screen in models to evaluate whether pathway modulation (e.g., losartan-type ARBs used in Marfan) mitigates aortic and/or skeletal features.
  8. Founder-population carrier screening programs (e.g., Druze Arab communities) coupled with genetic counseling and PGT access to reduce recurrence.
  9. Prospective QoL/PROM study specific to DASS integrating dental, growth, and psychosocial outcomes across the lifespan.

Report compiled from 17 primary sources across 5 investigative iterations. Evidence source types: human clinical (case/family series), model organism (Ltbp3-null and Marfan-cross mouse), in vitro biochemistry (latent-complex/fibrillin studies), and computational (molecular modeling of missense variants).

Artifacts

Reference Validation

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References checked 17
Resolved 17
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Unverifiable 0
Quoted claims checked 28
Quoted claims found in source 28
Quoted claims not found in source 0
References weighed for topical relevance 17
On topic 9
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Term Validation

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Terms checked 35
Resolved 34
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Terms whose name was checked 10
Terms named correctly 7
Terms named as a different term 1
Terms whose name is worth a second look 2

Terms the report names something else

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

  • HP:0012865 (1 mention) - the report calls it "Broad femoral neck"; HP calls it Abnormal sperm head morphology

Terms whose name is worth a second look

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  • HP:0000679 (1 mention) - the report calls it "Taurodontism"; HP calls it Taurodontia, and lists "Taurodontism" among its other names
  • HP:0011063 (1 mention) - the report calls it "Abnormal dentin morphology"; HP calls it Abnormal incisor morphology