Osteogenesis Imperfecta Type IV

Mendelian MONDO:0008148 Pathograph 3 Osteogenesis imperfecta

Osteogenesis imperfecta type IV represents moderate severity OI, intermediate between the mild type I and severe type III. Caused by dominant-negative mutations in COL1A1 or COL1A2, affected individuals have moderate bone fragility, variable short stature, normal or near-normal scleral hue (distinguishing it from type I), and may have dentinogenesis imperfecta. Phenotypic severity is highly variable, overlapping with both milder and more severe forms.

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1
Inheritance
3
Pathophys.
10
Phenotypes
3
Pathograph
1
Genes
3
Treatments
1
Datasets
22
References
2
Deep Research
👪

Inheritance

1
Autosomal Dominant
Autosomal dominant inheritance. Both inherited and de novo mutations occur. Variable expressivity is common even within families.
Show evidence (1 reference)
PMID:6822598 SUPPORT Human Clinical
"Most patients with dominantly inherited osteogenesis imperfecta have blue sclerae and relatively mild symptoms. However, in a small group of families the patients have normal sclerae and this disorder has been classified as Type 4 osteogenesis imperfecta."
This classic type IV cohort explicitly describes the subtype as a dominantly inherited form of osteogenesis imperfecta.
⚙

Pathophysiology

3
Procollagen Processing and Intracellular Trafficking Defect
Structural collagen I mutations disrupt procollagen folding, chaperone-assisted processing, and transport from the endoplasmic reticulum to the Golgi before abnormal collagen reaches the extracellular matrix.
Osteoblast link
Protein folding link
Downstream
Defective Collagen Matrix Assembly
Show evidence (1 reference)
DOI:10.1007/s00439-021-02302-2 SUPPORT Other
"The production of collagen entails a complex process, starting from the production of the collagen Iα1 and collagen Iα2 chains in the endoplasmic reticulum, during and after which procollagen is subjected to a plethora of posttranslational modifications by chaperones. After reaching the Golgi..."
This review supports a proximal osteoblast defect in procollagen folding, chaperone-assisted processing, and ER-to-Golgi trafficking in OI.
Defective Collagen Matrix Assembly
Abnormal collagen that escapes intracellular quality-control is poorly secreted and disrupts extracellular matrix assembly and mineralization, weakening bone matrix integrity.
Osteoblast link
Collagen Fibril Organization link Bone Mineralization link
Downstream
Dysregulated Bone Remodeling
Show evidence (1 reference)
PMID:16786509 SUPPORT Human Clinical
"Most patients with a clinical diagnosis of OI type I-IV have a mutation in the COL1A1 or COL1A2 genes which encode the two alpha chains of type I collagen, the major component of the bone matrix."
This type I-IV mutation-analysis cohort directly links classical OI, including type IV, to COL1A1/COL1A2 defects in type I collagen, the major bone matrix component, avoiding reliance on a perinatal lethal type II review for this mechanism.
Dysregulated Bone Remodeling
Secondary signaling and resorption abnormalities further amplify fragility, with excessive TGF-beta signaling and increased osteoclast-related bone turnover superimposed on the abnormal collagen matrix.
Osteoblast link Osteoclast link
TGF-beta receptor signaling link Bone remodeling link
Show evidence (2 references)
PMID:24793237 SUPPORT Model Organism
"Here, we show that excessive transforming growth factor-β (TGF-β) signaling is a mechanism of OI in both recessive (Crtap(-/-)) and dominant (Col1a2(tm1.1Mcbr)) OI mouse models. In the skeleton, we find higher expression of TGF-β target genes, higher ratio of phosphorylated Smad2 to total Smad2..."
This dominant OI model supports excess TGF-beta/SMAD signaling as a downstream disease mechanism relevant to collagen I structural disease.
PMID:39372603 SUPPORT Human Clinical
"Bone histomorphometry demonstrated the trends for higher osteoclast numbers (1.16; CI: -0.22, 2.55) and osteoclast surface (0.43; CI: -0.63, 1.49), and significantly higher eroded surface (3.24; CI: 0.51, 5.96) compared with age-matched controls."
This patient meta-analysis supports increased osteoclast-associated bone turnover as part of OI pathophysiology.
⬡

Pathograph

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

Phenotypes

10
Ear 1
Hearing Impairment Hearing impairment (HP:0000365)
Show evidence (1 reference)
PMID:10923226 SUPPORT Human Clinical
"Two sporadic OI cases with conductive hearing loss were ascertained (4.4%): An 11-year-old girl with type IV OI with a PTA0.5-2 kHz of 35/40 dB HL and a 15-year-old boy with type IV OI with a PTA0.5-2 kHz of 27/18 dB HL."
This pediatric hearing cohort directly documents type IV OI cases with conductive hearing loss.
Eye 1
Normal Scleral Hue EXCLUDED Blue sclerae (HP:0000592)
Show evidence (1 reference)
PMID:6822598 SUPPORT Human Clinical
"However, in a small group of families the patients have normal sclerae and this disorder has been classified as Type 4 osteogenesis imperfecta."
This classic clinical description identifies normal sclerae as a defining feature of OI type IV.
Head and Neck 2
Dentinogenesis Imperfecta Dentinogenesis imperfecta (HP:0000703)
Show evidence (2 references)
PMID:6822598 SUPPORT Human Clinical
"In Type 4 the first fracture more commonly occurs at birth, dentinogenesis imperfecta is more frequent than in Type 1 and bruising and nose-bleeds are less common."
This type IV cohort directly reports dentinogenesis imperfecta as a more frequent feature in type IV than in type I OI.
PMID:20384825 SUPPORT Human Clinical
"A total of ten patients had abnormal discolourations referable to DI: four patients were affected by OI type I, three patients by OI type III, and three patients by OI type IV. The discolourations, yellow/brown or opalescent grey, could not be related to the different types of OI."
This pediatric dental cohort directly documents dentinogenesis imperfecta with discolored teeth in children with OI type IV.
Wormian Bones Wormian bones (HP:0002645)
Show evidence (1 reference)
PMID:16961127 SUPPORT Human Clinical
"These three abnormalities and wormian bones were predominantly found in OI Types III and IV as well as in patients exhibiting dentinal abnormality."
This OI cohort directly associates wormian bones with the type III/IV classical deforming phenotypes.
Limbs 1
Bowing of the Long Bones Bowing of the long bones (HP:0006487)
Show evidence (1 reference)
PMID:38752190 SUPPORT Human Clinical
"The bone fragility and repeated fractures produce deformities of the long bones especially in femur and tibia. However, neck of femur (NOF) fractures in OI are rarely described. A 11-year-old male patient known to have OI (Sillence type IV) sustained a NOF fracture after a fall. He also had..."
This type IV case report directly documents long-bone bowing and femoral deformity.
Musculoskeletal 2
Recurrent Fractures Recurrent fractures (HP:0002757)
Show evidence (2 references)
PMID:29970925 SUPPORT Human Clinical
"PURPOSE: Osteogenesis imperfecta (OI) predisposes people to recurrent fractures, bone deformities, and short stature."
This large OI cohort explicitly identifies recurrent fractures as a core feature of the disorder, including individuals with type IV OI.
PMID:6822598 SUPPORT Human Clinical
"The two types are similar in usually causing a mild disease but with a wide range of severity, and in both types the rate of fracture declines in adolescence."
This classic type IV cohort supports the typical decline in fracture rate during adolescence.
Scoliosis FREQUENT Scoliosis (HP:0002650)
Show evidence (1 reference)
PMID:26927310 SUPPORT Human Clinical
"The prevalence of scoliosis was highest in OI type III (89%), followed by OI type IV (61%) and OI type I (36%)."
This large COL1A1/COL1A2 cohort shows that scoliosis is frequent in OI type IV.
Nervous System 1
Delayed Gross Motor Development Delayed gross motor development (HP:0002194)
Show evidence (1 reference)
PMID:10968241 SUPPORT Human Clinical
"In OI type IV, a retardation in motor development developed after the milestone 'sitting without support' was achieved."
This motor-development cohort directly documents delayed gross motor progression in children with OI type IV.
Growth 1
Moderate Short Stature Short stature (HP:0004322)
Show evidence (1 reference)
PMID:29970925 SUPPORT Human Clinical
"In children, the median z-scores for height in OI types I, III, and IV were -0.66, -6.91, and -2.79, respectively. Growth velocity was diminished in OI types III and IV."
This multicenter cohort directly quantifies short stature and reduced growth velocity in children with OI type IV.
Other 1
Basilar Invagination Basilar invagination (HP:0012366)
Show evidence (1 reference)
PMID:16961127 SUPPORT Human Clinical
"As a sign of basilar invagination the odontoid process protruded into the foramen magnum or reached the foramen magnum level in 22.2% of the patients with OI, whereas none of the controls showed this feature."
This cephalometric OI cohort shows that basilar invagination is a clinically relevant cranial complication; the same study noted these skull base abnormalities were predominantly found in types III and IV.
🧬

Genetic Associations

1
COL1A1/COL1A2 Mutations (Causative)
Show evidence (1 reference)
PMID:16786509 SUPPORT Human Clinical
"Analysis of COL1A1 and COL1A2 in a cohort of 83 unrelated patients with OI type I-IV identified a total of 62 mutations."
This cohort directly supports COL1A1/COL1A2 variants as the molecular basis for clinically diagnosed OI type I-IV, including type IV.
💊

Treatments

3
Bisphosphonate Therapy
Action: Bisphosphonate therapy Ontology label: bisphosphonate agent therapy MAXO:0000954
Bisphosphonates can improve vertebral density and vertebral shape in childhood, but short-term functional benefit and long-bone fracture reduction are inconsistent.
Show evidence (2 references)
PMID:15883638 SUPPORT Human Clinical
"Bisphosphonates have been widely administered to children with OI based on observational trials. A randomized controlled trial of q3m intravenous pamidronate in children with types III and IV OI yielded positive vertebral changes in DXA and geometry after 1 year of treatment, but no further..."
This randomized trial supports vertebral benefit from pamidronate in type III/IV OI but not consistent short-term functional or long-bone fracture improvement.
DOI:10.1007/s00223-024-01202-7 SUPPORT Human Clinical
"Children currently receive off-label treatment with bisphosphonates, without any consistent approach to dose, drug or route of administration."
Confirms that bisphosphonates remain widely used off-label in pediatric OI, despite nonstandardized drug, dose, and route choices.
Orthopedic Management
Action: Orthopedic surgery Ontology label: surgical procedure MAXO:0000004
Fracture treatment and corrective surgery for deformities as needed. Intramedullary rodding for severe cases.
Show evidence (1 reference)
PMID:11127846 SUPPORT Human Clinical
"An aggressive rehabilitative approach is indicated to optimise functional ability and walking capacity; appropriately timed surgery to insert intramedullary rods provides improved function of extremities."
Practical treatment guidelines explicitly support intramedullary rodding and related orthopedic surgery to improve function in OI.
Physical Therapy
Action: Physical therapy Ontology label: physical therapy MAXO:0000011
Physical therapy and rehabilitation to optimize mobility, walking capacity, and overall function.
Show evidence (1 reference)
PMID:11127846 SUPPORT Human Clinical
"Three types of treatment are available: nonsurgical management (physical therapy, rehabilitation, bracing and splinting), surgery (intramedullary rod positioning, spinal and basilar impression surgery), and drugs to increase the strength of bone and decrease the number of fractures."
Practical treatment guidelines explicitly include physical therapy and rehabilitation as standard nonsurgical management in OI.
📊

Related Datasets

1
Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV. PMID:16786509
Human clinical molecular cohort of 83 unrelated patients diagnosed with OI types I-IV, identifying COL1A1 and COL1A2 variants relevant to classical collagen-related OI including type IV.
human VARIANT DATABASE n=83
Conditions: osteogenesis imperfecta type I-IV COL1A1/COL1A2 pathogenic variants
PMID:16786509
Show evidence (1 reference)
PMID:16786509 SUPPORT Human Clinical
"Analysis of COL1A1 and COL1A2 in a cohort of 83 unrelated patients with OI type I-IV identified a total of 62 mutations."
This abstract defines a reusable human variant cohort for classical OI types I-IV and documents the sample count and mutation yield.
{ }

Source YAML

click to show 
name: Osteogenesis Imperfecta Type IV
creation_date: '2026-02-06T03:25:37Z'
updated_date: '2026-04-24T15:48:08Z'
category: Mendelian
description: >
  Osteogenesis imperfecta type IV represents moderate severity OI, intermediate
  between the mild type I and severe type III. Caused by dominant-negative
  mutations in COL1A1 or COL1A2, affected individuals have moderate bone fragility,
  variable short stature, normal or near-normal scleral hue (distinguishing it
  from type I), and may have dentinogenesis imperfecta. Phenotypic severity is
  highly variable, overlapping with both milder and more severe forms.
disease_term:
  preferred_term: Osteogenesis imperfecta type IV
  term:
    id: MONDO:0008148
    label: osteogenesis imperfecta type 4
parents:
- Osteogenesis imperfecta
inheritance:
- name: Autosomal Dominant
  description: >
    Autosomal dominant inheritance. Both inherited and de novo mutations occur.
    Variable expressivity is common even within families.
  evidence:
  - reference: PMID:6822598
    reference_title: "Osteogenesis imperfecta with dominant inheritance and normal sclerae."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most patients with dominantly inherited osteogenesis imperfecta have blue
      sclerae and relatively mild symptoms. However, in a small group of
      families the patients have normal sclerae and this disorder has been
      classified as Type 4 osteogenesis imperfecta.
    explanation: >-
      This classic type IV cohort explicitly describes the subtype as a
      dominantly inherited form of osteogenesis imperfecta.
prevalence:
- population: Swedish pediatric osteogenesis imperfecta population
  percentage: 1.35 per 100,000
  notes: >-
    In a near-complete Swedish pediatric ascertainment study, type IV was the
    most prevalent non-type-I classical subtype.
  evidence:
  - reference: PMID:25944380
    reference_title: "Genetic epidemiology, prevalence, and genotype-phenotype correlations in the Swedish population with osteogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The prevalence of OI types I, III, and IV was 5.16, 0.89, and 1.35/100 000, respectively (7.40/100 000 overall), corresponding to what has been estimated but not unequivocally proven in any population."
    explanation: This population-based Swedish study directly estimates pediatric prevalence of OI type IV at 1.35 per 100,000.
pathophysiology:
- name: Procollagen Processing and Intracellular Trafficking Defect
  description: >
    Structural collagen I mutations disrupt procollagen folding,
    chaperone-assisted processing, and transport from the endoplasmic
    reticulum to the Golgi before abnormal collagen reaches the extracellular
    matrix.
  cell_types:
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: Protein folding
    term:
      id: GO:0006457
      label: protein folding
  evidence:
  - reference: DOI:10.1007/s00439-021-02302-2
    reference_title: Collagen transport and related pathways in Osteogenesis Imperfecta
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The production of collagen entails a complex process, starting from the
      production of the collagen Iα1 and collagen Iα2 chains in the
      endoplasmic reticulum, during and after which procollagen is subjected
      to a plethora of posttranslational modifications by chaperones. After
      reaching the Golgi organelle, procollagen is destined to the
      extracellular matrix where it forms collagen fibrils.
    explanation: >-
      This review supports a proximal osteoblast defect in procollagen folding,
      chaperone-assisted processing, and ER-to-Golgi trafficking in OI.
  downstream:
  - target: Defective Collagen Matrix Assembly
- name: Defective Collagen Matrix Assembly
  description: >
    Abnormal collagen that escapes intracellular quality-control is poorly
    secreted and disrupts extracellular matrix assembly and mineralization,
    weakening bone matrix integrity.
  cell_types:
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: Collagen Fibril Organization
    term:
      id: GO:0030199
      label: collagen fibril organization
  - preferred_term: Bone Mineralization
    term:
      id: GO:0030282
      label: bone mineralization
  evidence:
  - reference: PMID:16786509
    reference_title: "Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Most patients with a clinical diagnosis of OI type I-IV have a mutation in
      the COL1A1 or COL1A2 genes which encode the two alpha chains of type I
      collagen, the major component of the bone matrix.
    explanation: >-
      This type I-IV mutation-analysis cohort directly links classical OI,
      including type IV, to COL1A1/COL1A2 defects in type I collagen, the major
      bone matrix component, avoiding reliance on a perinatal lethal type II
      review for this mechanism.
  downstream:
  - target: Dysregulated Bone Remodeling
- name: Dysregulated Bone Remodeling
  description: >
    Secondary signaling and resorption abnormalities further amplify fragility,
    with excessive TGF-beta signaling and increased osteoclast-related bone
    turnover superimposed on the abnormal collagen matrix.
  cell_types:
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  - preferred_term: Osteoclast
    term:
      id: CL:0000092
      label: osteoclast
  biological_processes:
  - preferred_term: TGF-beta receptor signaling
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
  - preferred_term: Bone remodeling
    term:
      id: GO:0046849
      label: bone remodeling
  evidence:
  - reference: PMID:24793237
    reference_title: Excessive transforming growth factor-β signaling is a common mechanism in osteogenesis imperfecta.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we show that excessive transforming growth factor-β (TGF-β)
      signaling is a mechanism of OI in both recessive (Crtap(-/-)) and
      dominant (Col1a2(tm1.1Mcbr)) OI mouse models. In the skeleton, we find
      higher expression of TGF-β target genes, higher ratio of phosphorylated
      Smad2 to total Smad2 protein and higher in vivo Smad2 reporter activity.
    explanation: >-
      This dominant OI model supports excess TGF-beta/SMAD signaling as a
      downstream disease mechanism relevant to collagen I structural disease.
  - reference: PMID:39372603
    reference_title: "Osteoclast indices in osteogenesis imperfecta: systematic review and meta-analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Bone histomorphometry demonstrated the trends for higher osteoclast
      numbers (1.16; CI: -0.22, 2.55) and osteoclast surface (0.43; CI: -0.63,
      1.49), and significantly higher eroded surface (3.24; CI: 0.51, 5.96)
      compared with age-matched controls.
    explanation: >-
      This patient meta-analysis supports increased osteoclast-associated bone
      turnover as part of OI pathophysiology.
genetic:
- name: COL1A1/COL1A2 Mutations
  association: Causative
  notes: >
    Structural mutations including glycine substitutions and splice site
    mutations. Mutations in COL1A2 are more common in type IV than in
    type III, possibly explaining the milder phenotype given the
    2:1 ratio of alpha1 to alpha2 chains in type I collagen.
  evidence:
  - reference: PMID:16786509
    reference_title: "Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Analysis of COL1A1 and COL1A2 in a cohort of 83 unrelated patients with OI
      type I-IV identified a total of 62 mutations.
    explanation: >-
      This cohort directly supports COL1A1/COL1A2 variants as the molecular basis
      for clinically diagnosed OI type I-IV, including type IV.
phenotypes:
- name: Moderate Short Stature
  description: >
    Short stature is common, with reduced growth velocity during childhood and
    variable severity across affected individuals.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:29970925
    reference_title: "Growth characteristics in individuals with osteogenesis imperfecta in North America: results from a multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In children, the median z-scores for height in OI types I, III, and IV
      were -0.66, -6.91, and -2.79, respectively. Growth velocity was
      diminished in OI types III and IV.
    explanation: >-
      This multicenter cohort directly quantifies short stature and reduced
      growth velocity in children with OI type IV.
- name: Recurrent Fractures
  description: >
    Recurrent fractures are a core clinical feature, with fracture burden often
    declining during adolescence.
  phenotype_term:
    preferred_term: Recurrent fractures
    term:
      id: HP:0002757
      label: Recurrent fractures
  evidence:
  - reference: PMID:29970925
    reference_title: "Growth characteristics in individuals with osteogenesis imperfecta in North America: results from a multicenter study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PURPOSE: Osteogenesis imperfecta (OI) predisposes people to recurrent
      fractures, bone deformities, and short stature.
    explanation: >-
      This large OI cohort explicitly identifies recurrent fractures as a core
      feature of the disorder, including individuals with type IV OI.
  - reference: PMID:6822598
    reference_title: "Osteogenesis imperfecta with dominant inheritance and normal sclerae."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The two types are similar in usually causing a mild disease but with a
      wide range of severity, and in both types the rate of fracture declines
      in adolescence.
    explanation: >-
      This classic type IV cohort supports the typical decline in fracture rate
      during adolescence.
- name: Normal Scleral Hue
  description: >
    Normal or near-normal sclerae are characteristic of type IV and help
    distinguish it from type I osteogenesis imperfecta.
  phenotype_term:
    preferred_term: Blue sclerae
    term:
      id: HP:0000592
      label: Blue sclerae
  frequency: EXCLUDED
  evidence:
  - reference: PMID:6822598
    reference_title: "Osteogenesis imperfecta with dominant inheritance and normal sclerae."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      However, in a small group of families the patients have normal sclerae
      and this disorder has been classified as Type 4 osteogenesis imperfecta.
    explanation: >-
      This classic clinical description identifies normal sclerae as a defining
      feature of OI type IV.
- name: Dentinogenesis Imperfecta
  description: >
    Variable dentinogenesis imperfecta, sometimes with yellow-brown or
    opalescent gray tooth discoloration.
  phenotype_term:
    preferred_term: Dentinogenesis imperfecta
    term:
      id: HP:0000703
      label: Dentinogenesis imperfecta
  evidence:
  - reference: PMID:6822598
    reference_title: "Osteogenesis imperfecta with dominant inheritance and normal sclerae."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In Type 4 the first fracture more commonly occurs at birth,
      dentinogenesis imperfecta is more frequent than in Type 1 and bruising
      and nose-bleeds are less common.
    explanation: >-
      This type IV cohort directly reports dentinogenesis imperfecta as a more
      frequent feature in type IV than in type I OI.
  - reference: PMID:20384825
    reference_title: "Dentinogenesis imperfecta in children with osteogenesis imperfecta: a clinical and ultrastructural study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A total of ten patients had abnormal discolourations referable to DI:
      four patients were affected by OI type I, three patients by OI type III,
      and three patients by OI type IV. The discolourations, yellow/brown or
      opalescent grey, could not be related to the different types of OI.
    explanation: >-
      This pediatric dental cohort directly documents dentinogenesis imperfecta
      with discolored teeth in children with OI type IV.
- name: Bowing of the Long Bones
  description: >
    Long-bone bowing can occur in type IV OI, particularly in the femur.
  phenotype_term:
    preferred_term: Bowing of the long bones
    term:
      id: HP:0006487
      label: Bowing of the long bones
  evidence:
  - reference: PMID:38752190
    reference_title: "Management of Combined Fracture Neck of Femur and Femoral Deformity in Osteogenesis Imperfecta Patient: A Case Report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The bone fragility and repeated fractures produce deformities of the long
      bones especially in femur and tibia. However, neck of femur (NOF)
      fractures in OI are rarely described. A 11-year-old male patient known to
      have OI (Sillence type IV) sustained a NOF fracture after a fall. He also
      had proximal femoral anterolateral bowing proximally and over an
      intramedullary (IM) rod inserted 4 years back.
    explanation: >-
      This type IV case report directly documents long-bone bowing and femoral
      deformity.
- name: Scoliosis
  description: >
    Scoliosis is a frequent spinal complication in type IV OI and may progress
    during growth.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: FREQUENT
  evidence:
  - reference: PMID:26927310
    reference_title: "Scoliosis in osteogenesis imperfecta caused by COL1A1/COL1A2 mutations - genotype-phenotype correlations and effect of bisphosphonate treatment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The prevalence of scoliosis was highest in OI type III (89%), followed by
      OI type IV (61%) and OI type I (36%).
    explanation: >-
      This large COL1A1/COL1A2 cohort shows that scoliosis is frequent in OI
      type IV.
- name: Delayed Gross Motor Development
  description: >
    Gross motor development may become delayed after unsupported sitting is
    achieved.
  phenotype_term:
    preferred_term: Delayed gross motor development
    term:
      id: HP:0002194
      label: Delayed gross motor development
  evidence:
  - reference: PMID:10968241
    reference_title: "Osteogenesis imperfecta: profiles of motor development as assessed by a postal questionnaire."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In OI type IV, a retardation in motor development developed after the
      milestone 'sitting without support' was achieved.
    explanation: >-
      This motor-development cohort directly documents delayed gross motor
      progression in children with OI type IV.
- name: Hearing Impairment
  description: >
    Conductive hearing impairment can occur in childhood in some patients.
  phenotype_term:
    preferred_term: Hearing impairment
    term:
      id: HP:0000365
      label: Hearing impairment
  evidence:
  - reference: PMID:10923226
    reference_title: "Hearing loss in children with osteogenesis imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Two sporadic OI cases with conductive hearing loss were ascertained (4.4%):
      An 11-year-old girl with type IV OI with a PTA0.5-2 kHz of 35/40 dB HL
      and a 15-year-old boy with type IV OI with a PTA0.5-2 kHz of 27/18 dB HL.
    explanation: >-
      This pediatric hearing cohort directly documents type IV OI cases with
      conductive hearing loss.
- name: Basilar Invagination
  description: >
    Skull-base invagination can occur in type IV OI and warrants radiographic
    surveillance when craniovertebral junction disease is suspected.
  phenotype_term:
    preferred_term: Basilar invagination
    term:
      id: HP:0012366
      label: Basilar invagination
  evidence:
  - reference: PMID:16961127
    reference_title: "Skull base abnormalities in osteogenesis imperfecta: a cephalometric evaluation of 54 patients and 108 control volunteers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As a sign of basilar invagination the odontoid process protruded into the
      foramen magnum or reached the foramen magnum level in 22.2% of the
      patients with OI, whereas none of the controls showed this feature.
    explanation: >-
      This cephalometric OI cohort shows that basilar invagination is a
      clinically relevant cranial complication; the same study noted these skull
      base abnormalities were predominantly found in types III and IV.
- name: Wormian Bones
  description: >
    Wormian bones are a recognized cranial radiographic feature in the more
    deforming classical OI subtypes, including type IV.
  phenotype_term:
    preferred_term: Wormian bones
    term:
      id: HP:0002645
      label: Wormian bones
  evidence:
  - reference: PMID:16961127
    reference_title: "Skull base abnormalities in osteogenesis imperfecta: a cephalometric evaluation of 54 patients and 108 control volunteers."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These three abnormalities and wormian bones were predominantly found in
      OI Types III and IV as well as in patients exhibiting dentinal
      abnormality.
    explanation: >-
      This OI cohort directly associates wormian bones with the type III/IV
      classical deforming phenotypes.
diagnosis:
- name: Clinical, Radiographic, and Molecular Diagnosis
  description: >-
    Osteogenesis imperfecta type IV (now described in GeneReviews as common
    variable OI with normal sclerae) is diagnosed from variable bone
    fragility and short stature with characteristic radiographic findings,
    and confirmed by identification of a heterozygous COL1A1 or COL1A2
    variant on molecular genetic testing.
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: MAXO:0000533
      label: molecular genetic testing
  evidence:
  - reference: PMID:20301472
    reference_title: "COL1A1- and COL1A2-Related Osteogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of COL1A1/COL1A2-OI is established in a proband with clinical and radiographic manifestations of OI by identification of a heterozygous in COL1A1 or COL1A2 by molecular genetic testing."
    explanation: >-
      GeneReviews defines the combined clinical/radiographic and molecular diagnostic criteria for COL1A1/COL1A2-related OI, including the moderate type IV form.
  - reference: PMID:20301472
    reference_title: "COL1A1- and COL1A2-Related Osteogenesis Imperfecta."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "common variable OI with normal sclerae (previously OI type IV)"
    explanation: >-
      GeneReviews maps the legacy Sillence type IV label to the modern descriptive nomenclature.
treatments:
- name: Bisphosphonate Therapy
  description: >
    Bisphosphonates can improve vertebral density and vertebral shape in
    childhood, but short-term functional benefit and long-bone fracture
    reduction are inconsistent.
  treatment_term:
    preferred_term: Bisphosphonate therapy
    term:
      id: MAXO:0000954
      label: bisphosphonate agent therapy
  evidence:
  - reference: PMID:15883638
    reference_title: "Controlled trial of pamidronate in children with types III and IV osteogenesis imperfecta confirms vertebral gains but not short-term functional improvement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Bisphosphonates have been widely administered to children with OI based
      on observational trials. A randomized controlled trial of q3m
      intravenous pamidronate in children with types III and IV OI yielded
      positive vertebral changes in DXA and geometry after 1 year of
      treatment, but no further significant improvement during extended
      treatment. The treated group did not experience significantly decreased
      pain or long bone fractures or have increased motor function or muscle
      strength.
    explanation: >-
      This randomized trial supports vertebral benefit from pamidronate in
      type III/IV OI but not consistent short-term functional or long-bone
      fracture improvement.
  - reference: DOI:10.1007/s00223-024-01202-7
    reference_title: "Medical Management for Fracture Prevention in Children with Osteogenesis Imperfecta"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Children currently receive off-label treatment with bisphosphonates,
      without any consistent approach to dose, drug or route of administration.
    explanation: >-
      Confirms that bisphosphonates remain widely used off-label in pediatric
      OI, despite nonstandardized drug, dose, and route choices.
- name: Orthopedic Management
  description: >
    Fracture treatment and corrective surgery for deformities as needed.
    Intramedullary rodding for severe cases.
  treatment_term:
    preferred_term: Orthopedic surgery
    term:
      id: MAXO:0000004
      label: surgical procedure
  evidence:
  - reference: PMID:11127846
    reference_title: "Osteogenesis imperfecta: practical treatment guidelines."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      An aggressive rehabilitative approach is indicated to optimise functional
      ability and walking capacity; appropriately timed surgery to insert
      intramedullary rods provides improved function of extremities.
    explanation: >-
      Practical treatment guidelines explicitly support intramedullary rodding
      and related orthopedic surgery to improve function in OI.
- name: Physical Therapy
  description: >
    Physical therapy and rehabilitation to optimize mobility, walking capacity,
    and overall function.
  treatment_term:
    preferred_term: Physical therapy
    term:
      id: MAXO:0000011
      label: physical therapy
  evidence:
  - reference: PMID:11127846
    reference_title: "Osteogenesis imperfecta: practical treatment guidelines."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Three types of treatment are available: nonsurgical management (physical
      therapy, rehabilitation, bracing and splinting), surgery
      (intramedullary rod positioning, spinal and basilar impression surgery),
      and drugs to increase the strength of bone and decrease the number of
      fractures.
    explanation: >-
      Practical treatment guidelines explicitly include physical therapy and
      rehabilitation as standard nonsurgical management in OI.
datasets:
- accession: PMID:16786509
  title: Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV.
  description: >-
    Human clinical molecular cohort of 83 unrelated patients diagnosed with OI
    types I-IV, identifying COL1A1 and COL1A2 variants relevant to classical
    collagen-related OI including type IV.
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  data_type: VARIANT_DATABASE
  sample_count: 83
  conditions:
  - osteogenesis imperfecta type I-IV
  - COL1A1/COL1A2 pathogenic variants
  publication: PMID:16786509
  evidence:
  - reference: PMID:16786509
    reference_title: "Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Analysis of COL1A1 and COL1A2 in a cohort of 83 unrelated patients with OI
      type I-IV identified a total of 62 mutations.
    explanation: >-
      This abstract defines a reusable human variant cohort for classical OI
      types I-IV and documents the sample count and mutation yield.
references:
- reference: PMID:20301472
  title: "COL1A1- and COL1A2-Related Osteogenesis Imperfecta."
  tags:
  - GeneReviews
  findings: []
- reference: PMID:10923226
  title: Hearing loss in children with osteogenesis imperfecta.
  findings: []
- reference: PMID:10968241
  title: "Osteogenesis imperfecta: profiles of motor development as assessed by a postal questionnaire."
  findings: []
- reference: PMID:11127846
  title: "Osteogenesis imperfecta: practical treatment guidelines."
  findings: []
- reference: PMID:15883638
  title: Controlled trial of pamidronate in children with types III and IV osteogenesis imperfecta confirms vertebral gains but not short-term functional improvement.
  findings: []
- reference: PMID:16786509
  title: Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV.
  findings: []
- reference: PMID:16961127
  title: "Skull base abnormalities in osteogenesis imperfecta: a cephalometric evaluation of 54 patients and 108 control volunteers."
  findings: []
- reference: PMID:20384825
  title: "Dentinogenesis imperfecta in children with osteogenesis imperfecta: a clinical and ultrastructural study."
  findings: []
- reference: PMID:24793237
  title: Excessive transforming growth factor-β signaling is a common mechanism in osteogenesis imperfecta.
  findings: []
- reference: PMID:26927310
  title: Scoliosis in osteogenesis imperfecta caused by COL1A1/COL1A2 mutations - genotype-phenotype correlations and effect of bisphosphonate treatment.
  findings: []
- reference: PMID:29970925
  title: "Growth characteristics in individuals with osteogenesis imperfecta in North America: results from a multicenter study."
  findings: []
- reference: PMID:38752190
  title: "Management of Combined Fracture Neck of Femur and Femoral Deformity in Osteogenesis Imperfecta Patient: A Case Report."
  findings: []
- reference: PMID:39372603
  title: "Osteoclast indices in osteogenesis imperfecta: systematic review and meta-analysis."
  findings: []
- reference: PMID:6822598
  title: Osteogenesis imperfecta with dominant inheritance and normal sclerae.
  findings: []
- reference: DOI:10.1007/s00223-024-01202-7
  title: Medical Management for Fracture Prevention in Children with Osteogenesis Imperfecta
  findings: []
- reference: DOI:10.1007/s00223-024-01248-7
  title: A Dyadic Nosology for Osteogenesis Imperfecta and Bone Fragility Syndromes 2024
  findings: []
- reference: DOI:10.1007/s00439-021-02302-2
  title: Collagen transport and related pathways in Osteogenesis Imperfecta
  findings: []
- reference: DOI:10.1186/s13023-023-02849-5
  title: Pathogenic mechanisms of osteogenesis imperfecta, evidence for classification
  findings: []
- reference: DOI:10.1297/cpe.2025-0009
  title: 'Osteogenesis imperfecta: pathogenesis, classification, and          treatment'
  findings: []
- reference: DOI:10.1515/jpem-2024-0512
  title: 'Osteogenesis imperfecta: shifting paradigms in pathophysiology and care in children'
  findings: []
- reference: DOI:10.3892/wasj.2024.284
  title: 'Beyond brittle bones: Genetic mechanisms underlying osteogenesis imperfecta (Review)'
  findings: []
- reference: DOI:10.56294/saludcyt2024894
  title: 'The Role of Denosumab and Bisphosphonate in Osteogenesis Imperfecta: A Literature Review'
  findings: []
📚

References & Deep Research

References

22
PMID:20301472
COL1A1- and COL1A2-Related Osteogenesis Imperfecta.
No top-level findings curated for this source.
PMID:10923226
Hearing loss in children with osteogenesis imperfecta.
No top-level findings curated for this source.
PMID:10968241
Osteogenesis imperfecta: profiles of motor development as assessed by a postal questionnaire.
No top-level findings curated for this source.
PMID:11127846
Osteogenesis imperfecta: practical treatment guidelines.
No top-level findings curated for this source.
PMID:15883638
Controlled trial of pamidronate in children with types III and IV osteogenesis imperfecta confirms vertebral gains but not short-term functional improvement.
No top-level findings curated for this source.
PMID:16786509
Mutation analysis of COL1A1 and COL1A2 in patients diagnosed with osteogenesis imperfecta type I-IV.
No top-level findings curated for this source.
PMID:16961127
Skull base abnormalities in osteogenesis imperfecta: a cephalometric evaluation of 54 patients and 108 control volunteers.
No top-level findings curated for this source.
PMID:20384825
Dentinogenesis imperfecta in children with osteogenesis imperfecta: a clinical and ultrastructural study.
No top-level findings curated for this source.
PMID:24793237
Excessive transforming growth factor-β signaling is a common mechanism in osteogenesis imperfecta.
No top-level findings curated for this source.
PMID:26927310
Scoliosis in osteogenesis imperfecta caused by COL1A1/COL1A2 mutations - genotype-phenotype correlations and effect of bisphosphonate treatment.
No top-level findings curated for this source.
PMID:29970925
Growth characteristics in individuals with osteogenesis imperfecta in North America: results from a multicenter study.
No top-level findings curated for this source.
PMID:38752190
Management of Combined Fracture Neck of Femur and Femoral Deformity in Osteogenesis Imperfecta Patient: A Case Report.
No top-level findings curated for this source.
PMID:39372603
Osteoclast indices in osteogenesis imperfecta: systematic review and meta-analysis.
No top-level findings curated for this source.
PMID:6822598
Osteogenesis imperfecta with dominant inheritance and normal sclerae.
No top-level findings curated for this source.
DOI:10.1007/s00223-024-01202-7
Medical Management for Fracture Prevention in Children with Osteogenesis Imperfecta
No top-level findings curated for this source.
DOI:10.1007/s00223-024-01248-7
A Dyadic Nosology for Osteogenesis Imperfecta and Bone Fragility Syndromes 2024
No top-level findings curated for this source.
DOI:10.1007/s00439-021-02302-2
Collagen transport and related pathways in Osteogenesis Imperfecta
No top-level findings curated for this source.
DOI:10.1186/s13023-023-02849-5
Pathogenic mechanisms of osteogenesis imperfecta, evidence for classification
No top-level findings curated for this source.
DOI:10.1297/cpe.2025-0009
Osteogenesis imperfecta: pathogenesis, classification, and treatment
No top-level findings curated for this source.
DOI:10.1515/jpem-2024-0512
Osteogenesis imperfecta: shifting paradigms in pathophysiology and care in children
No top-level findings curated for this source.
DOI:10.3892/wasj.2024.284
Beyond brittle bones: Genetic mechanisms underlying osteogenesis imperfecta (Review)
No top-level findings curated for this source.
DOI:10.56294/saludcyt2024894
The Role of Denosumab and Bisphosphonate in Osteogenesis Imperfecta: A Literature Review
No top-level findings curated for this source.

Deep Research

2
Disorder ▸

Disorder

  • Name: Osteogenesis Imperfecta Type IV
  • Category: Mendelian
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 12

Key Pathophysiology Nodes

  • Moderate Collagen Structural Defect
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1007/s00223-024-01202-7
  • DOI:10.1007/s00223-024-01248-7
  • DOI:10.1007/s00223-024-01293-2
  • DOI:10.1007/s00439-021-02302-2
  • DOI:10.1186/s13023-023-02849-5
  • DOI:10.1297/cpe.2025-0009
  • DOI:10.1515/jpem-2024-0512
  • DOI:10.3390/jcm13041065
  • DOI:10.3892/wasj.2024.284
  • DOI:10.56294/saludcyt2024894
Falcon ▸
Disease Pathophysiology Research Report
Edison Scientific Literature 28 citations 2026-02-04T19:41:35.310639

Disease Pathophysiology Research Report

Target Disease - Disease Name: Osteogenesis Imperfecta Type IV (OI type IV) - MONDO ID: Not definitively identified in the evidence retrieved here; OI is a Mendelian collagen type I disorder predominantly due to COL1A1/COL1A2 variants (classification updates noted below). (sillence2024adyadicnosology pages 8-9) - Category: Mendelian

Plan (concise) - Define scope and taxonomy (OI type IV within Sillence/ISDS dyadic nosology). (sillence2024adyadicnosology pages 8-9) - Synthesize core molecular/cellular pathophysiology and dysregulated pathways. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) - Enumerate key molecular players (genes/proteins, cell types, tissues; chemicals relevant to management). (claeys2021collagentransportand pages 1-2, kresnadi2024theroleof pages 2-5, sillence2024adyadicnosology pages 8-9) - Map biological processes and cellular components (GO-aligned). (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) - Outline disease progression from mutation to phenotype with representative HPO-style phenotypes. (yu2023pathogenicmechanismsof pages 1-2, khan2024beyondbrittlebones pages 2-3) - Summarize 2023–2024 developments (nosology updates, management evidence, dentition data). (sillence2024adyadicnosology pages 8-9, kresnadi2024theroleof pages 2-5, ventura2024dentalabnormalitiesin pages 1-2) - Assemble evidence with URLs and dates.

Pathophysiology description - Core concept: OI type IV sits in the classical Sillence I–IV spectrum, typically caused by autosomal dominant COL1A1 or COL1A2 variants that either reduce type I collagen quantity (haploinsufficiency) or alter collagen structure (dominant-negative glycine substitutions in the Gly-X-Y repeats), impairing extracellular matrix assembly and bone material quality. “Qualitative and quantitative defects in type I collagen polypeptides were postulated to account for the genetic heterogeneity in OI,” and type 4 historically reflects a moderate severity phenotype in this spectrum. (sillence2024adyadicnosology pages 8-9) - Molecular mechanisms: Mechanistic classes relevant to type IV include defects in type I collagen synthesis, post-translational modification, folding, and cross-linking; bone mineralization defects; and osteoblast differentiation/function abnormalities. The review explicitly proposes mechanistic classification across these axes for OI, with COL1A1/COL1A2 in the collagen-defect class underpinning classical types including type IV. (yu2023pathogenicmechanismsof pages 1-2) - Cellular and pathway dysregulation: The collagen I lifecycle spans ER synthesis and folding, chaperone-assisted post-translational modification, ER–Golgi transport, extracellular processing, and fibrillogenesis. Disruptions at any stage weaken the ECM. Emerging contributors include retrograde ER–Golgi transport components and WNT signaling, with osteoblast and osteocyte signaling networks broadly altered. (claeys2021collagentransportand pages 1-2) - Bone remodeling signaling: Recent reviews emphasize TGF-β/SMAD signaling in OI pathogenesis and its interplay with osteoblast/osteoclast balance; WNT pathway perturbations (e.g., sclerostin/DKK1) modulate osteogenesis and are therapeutic targets. (yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9)

Key molecular players and affected biology - Genes/Proteins (HGNC): - COL1A1 (HGNC:2197) and COL1A2 (HGNC:2198) encode the type I collagen chains; missense glycine substitutions often cause structural defects (dominant-negative), while nonsense/frameshift/splice variants usually cause haploinsufficiency. Type IV commonly arises from these mechanisms. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) - Locus heterogeneity and modifiers: ISDS/2024 nosology recognizes >24 OI/bone fragility entities, with additional AD/AR/X-linked loci and reports of digenic contributions (e.g., variants affecting WNT signaling), which may influence expressivity in “type 4-like” phenotypes. (sillence2024adyadicnosology pages 8-9) - Variant classes typical for type IV and consequences: - Glycine substitutions in the collagen triple helix (qualitative defects) lead to delayed triple-helix folding, overmodification, ER stress, abnormal fibrillogenesis, and brittle matrix—consistent with moderate severity type IV phenotypes. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) - Quantitative defects (COL1A1 LOF) more often produce type I; however, phenotypic overlap between types I and IV is common, and intrafamilial variability is recognized. (sillence2024adyadicnosology pages 8-9) - Cell types (CL): Osteoblasts (matrix production), osteocytes (mechanosensing; transcriptome dysregulation), and osteoclasts (resorption). In dentition, odontoblasts are affected, explaining DI. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, ventura2024dentalabnormalitiesin pages 1-2) - Tissues/organs (UBERON): Bone element (skeleton) is primary; teeth/dentin and periodontal ligament, sclera, and auditory structures (cochlea/ossicles) can be involved, reflecting type I collagen distribution. (claeys2021collagentransportand pages 1-2, khan2024beyondbrittlebones pages 2-3, ventura2024dentalabnormalitiesin pages 1-2) - Chemical entities (CHEBI) relevant to management: Bisphosphonates (e.g., pamidronate, zoledronic acid) and anabolic teriparatide are commonly discussed in OI care and trials. (kresnadi2024theroleof pages 2-5, hasegawa2025osteogenesisimperfectapathogenesis pages 1-2)

Biological processes (for GO annotation) and cellular components - Processes: extracellular matrix organization; collagen fibril organization; bone mineralization; TGF-β signaling pathway; WNT signaling pathway; osteoblast differentiation and osteoclast regulation. These processes capture the major axes of dysregulation in OI type IV. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) - Cellular components: endoplasmic reticulum (collagen synthesis/folding), Golgi apparatus (procollagen processing/trafficking), and extracellular matrix (mature fibrils). (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2)

Ontology-mapped summary (embed) | Category | Entity | Ontology ID | Role / Relevance | Representative sources | |---|---|---:|---|---| | Gene / Protein | COL1A1 (pro-alpha1(I)) | HGNC:2197 | Encodes type I collagen α1 chain; dominant glycine substitutions or haploinsufficiency underlie many OI type IV cases and disrupt triple-helix formation. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) | | Gene / Protein | COL1A2 (pro-alpha2(I)) | HGNC:2198 | Encodes type I collagen α2 chain; variants (glycine substitutions) frequently cause structural collagen defects and associate with DI in some cases. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9, ventura2024dentalabnormalitiesin pages 1-2) | | Biological Process | Extracellular matrix organization | GO:0030198 | Disrupted ECM assembly and collagen deposition reduce bone matrix integrity and increase fragility. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) | | Biological Process | Collagen fibril organization | GO:0030199 | Abnormal fibrillogenesis from mutant collagen (glycine substitutions) alters fibril structure and mechanical properties. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) | | Biological Process | Bone mineralization | GO:0030282 | Impaired mineral deposition and matrix mineralization contribute to low BMD and fractures in OI. | (yu2023pathogenicmechanismsof pages 1-2, ventura2024dentalabnormalitiesin pages 1-2) | | Biological Process | TGF‑beta signaling pathway | GO:0007179 | Upregulated TGF‑β signaling implicated in altered bone turnover, osteoblast/osteoclast imbalance and skeletal deformities. | (yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9, kresnadi2024theroleof pages 2-5) | | Biological Process | Wnt signaling pathway | GO:0016055 | Regulates osteoblast activity; pathway targeted by sclerostin/DKK1 modulators under investigation for OI. | (claeys2021collagentransportand pages 1-2, sillence2024adyadicnosology pages 8-9, dinulescu2024newperspectivesof pages 1-2) | | Cellular Component | Endoplasmic reticulum | GO:0005783 | Site of collagen chain synthesis and folding; mutant collagen causes ER stress and chaperone pathway involvement. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) | | Cellular Component | Golgi apparatus | GO:0005794 | Procollagen processing and trafficking; transport defects (ER‑Golgi) can contribute to OI pathogenesis. | (claeys2021collagentransportand pages 1-2) | | Cellular Component | Extracellular matrix | GO:0031012 | Location of mature type I collagen fibrils; structural defects here directly weaken bone and dentin. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) | | Cell Type | Osteoblast | CL:0000062 | Collagen‑producing bone‑forming cells; impaired secretion/function leads to defective matrix formation. | (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) | | Cell Type | Osteocyte | CL:0000138 | Long‑lived mechanosensors; transcriptome dysregulation in OI models indicates altered signaling and bone homeostasis. | (claeys2021collagentransportand pages 2-4, yu2023pathogenicmechanismsof pages 1-2) | | Cell Type | Osteoclast | CL:0000092 | Bone‑resorbing cells; activity modulated by RANK/RANKL and TGF‑β—contributes to turnover imbalance in OI. | (yu2023pathogenicmechanismsof pages 1-2, kresnadi2024theroleof pages 2-5) | | Cell Type | Odontoblast | CL:0000067 | Dentin‑forming cells affected by collagen I defects, producing dentinogenesis imperfecta (DI) phenotypes. | (ventura2024dentalabnormalitiesin pages 1-2) | | Anatomical Location | Bone element | UBERON:0001474 | Primary organ system affected: low bone mass, fractures, deformity. | (claeys2021collagentransportand pages 1-2, sillence2024adyadicnosology pages 8-9) | | Anatomical Location | Dentin | UBERON:0001752 | Tissue with high collagen I content; explains DI prevalence in OI (approx. 20–48% reported). | (ventura2024dentalabnormalitiesin pages 1-2) | | Anatomical Location | Sclera | UBERON:0001772 | Altered collagen in sclera produces blue/gray sclerae in many OI patients (variable by subtype). | (khan2024beyondbrittlebones pages 2-3, sillence2024adyadicnosology pages 8-9) | | Anatomical Location | Cochlea | UBERON:0002247 | Auditory structures can be affected leading to hearing impairment in OI. | (khan2024beyondbrittlebones pages 2-3) | | Chemical Entity | Zoledronic acid | CHEBI:101277 | Intravenous bisphosphonate antiresorptive used in OI management to increase BMD and reduce bone pain/fractures. | (hasegawa2025osteogenesisimperfectapathogenesis pages 1-2, kresnadi2024theroleof pages 2-5) | | Chemical Entity | Pamidronate | CHEBI:8069 | Pediatric bisphosphonate commonly used off‑label to treat children with OI. | (hasegawa2025osteogenesisimperfectapathogenesis pages 1-2, kresnadi2024theroleof pages 2-5) | | Chemical Entity | Teriparatide | CHEBI:38763 | PTH(1‑34) anabolic agent under investigation (adult OI trials) as a bone‑forming therapy. | (dinulescu2024newperspectivesof pages 1-2, kresnadi2024theroleof pages 2-5) |

Table: Compact ontology‑mapped summary of key genes, processes, components, cell types, anatomical sites and management chemicals relevant to Osteogenesis Imperfecta Type IV, with representative supporting sources (pqac IDs). This table is useful for integrating mechanistic annotations into knowledge bases and for rapid literature-linked reference.

Disease progression and sequence of events - Initiating trigger: Pathogenic variants in COL1A1 or COL1A2 (often glycine substitutions) impair triple-helix formation and/or reduce collagen I quantity. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) - Intracellular consequences: Delayed folding and overmodification of procollagen chains in the ER, increased chaperone engagement, ER stress; impaired ER–Golgi trafficking; abnormal secretion. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) - Extracellular consequences: Disordered fibrillogenesis and aberrant collagen cross-linking; altered mineralization; compromised microarchitecture. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2) - Tissue-level remodeling: Dysregulated TGF-β and WNT signaling in bone remodeling skews osteoblast/osteoclast coupling, compounding fragility and deformity. (yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) - Clinical manifestations: Moderately severe bone fragility with recurrent long-bone fractures, variable deformities, short stature, scoliosis/kyphosis, and variable extraskeletal features (teeth, sclerae, hearing). Type IV often has normal or gray sclerae and can present with DI; phenotypic overlap with types I/III exists and intrafamilial variability is common. (sillence2024adyadicnosology pages 8-9, khan2024beyondbrittlebones pages 2-3, ventura2024dentalabnormalitiesin pages 1-2)

Phenotypic manifestations (HPO-style, representative) - Fragile bones/recurrent fractures; skeletal deformities (e.g., scoliosis/kyphosis); short stature; dentinogenesis imperfecta type I (variable, 20–48% across OI collectively; more frequent in severe skeletal types including III/IV); hearing impairment in some. “Those with a more severe skeletal phenotype (OI type III/IV) exhibited more dental abnormalities than those with a milder skeletal phenotype (OI type I).” (ventura2024dentalabnormalitiesin pages 1-2)

Recent developments and latest research (prioritizing 2023–2024) - Nosology update (ISDS-informed, 2024): The “dyadic nosology” links genomic co-descriptors to Sillence phenotypes, acknowledging >24 loci and significant heterogeneity and overlap; it emphasizes integrating clinical severity with genotype for entities such as “type 4” and warns about historical misinterpretations of Sillence categories. (sillence2024adyadicnosology pages 8-9) - Management in children (2024 expert review): Bisphosphonates remain widely used off-label in pediatric OI, but meta-analyses show equivocal anti-fracture efficacy; standardized dosing and long-term outcome data are needed. Targeted antibody therapies developed for osteoporosis (e.g., anti-sclerostin, anti-RANKL) are under investigation in OI and may gain approvals in the coming years. (stasek2025osteogenesisimperfectashifting pages 1-2) - Adult/pediatric management overview (2024 review): Denosumab and bisphosphonates modulate bone turnover; literature suggests improvements in BMD and symptoms, but long-term safety/efficacy and fracture outcomes require further study; optimization of dosing/timing remains under evaluation. (kresnadi2024theroleof pages 2-5) - Mechanism-focused classification (2023): A framework aligning genetic defects to pathogenic mechanisms—collagen defects, mineralization disorders, and osteoblast differentiation/function—provides a scientific basis to stratify OI, including classical type IV within collagen-defect mechanisms. (yu2023pathogenicmechanismsof pages 1-2) - Dental phenotype epidemiology (2024 systematic review): Among OI patients, DI prevalence ~20–48%; occlusal anomalies and missing/unerupted teeth are common, especially in type III/IV; OI type V generally lacks DI. This supports dental surveillance and genotype-informed risk stratification. (ventura2024dentalabnormalitiesin pages 1-2)

Expert opinions and authoritative analyses - Sillence (2024) emphasizes the utility of dyadic nosology that pairs phenotype labels (e.g., type IV) with genomic co-descriptors, reflects extensive allelic heterogeneity at COL1A1/COL1A2 and beyond, and notes variable expressivity and intrafamilial variability in type IV families. (sillence2024adyadicnosology pages 8-9) - Pediatric care perspective (2025 review with 2024 evidence): The field is shifting toward targeted biologics while recognizing that bisphosphonates remain common practice and that fracture-prevention evidence must be strengthened; TGF-β and WNT pathways are repeatedly highlighted as rational targets. (stasek2025osteogenesisimperfectashifting pages 1-2)

Relevant statistics and data - Genetic attribution: ~85–90% of OI cases from COL1A1/COL1A2 variants; type IV is commonly linked to qualitative glycine substitutions but overlaps with other classes. (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9) - Dental abnormalities: DI in OI overall ~20–48%; occlusion classes vary widely, with Class III malocclusion unusually frequent; more anomalies in type III/IV than type I. (ventura2024dentalabnormalitiesin pages 1-2)

Direct quotes (selected) - “Qualitative and quantitative defects in type I collagen polypeptides were postulated to account for the genetic heterogeneity in OI…” (Sillence 2024). (sillence2024adyadicnosology pages 8-9) - “We summarize… molecular pathogenic mechanisms of OI from the perspectives of type I collagen defects… bone mineralization disorders, osteoblast differentiation and functional defects.” (Yu 2023). (yu2023pathogenicmechanismsof pages 1-2) - “The included studies confirmed that dental abnormalities are prevalent in OI, with DI prevalence ranging from approximately 20 to 48%… those with a more severe skeletal phenotype (OI type III/IV) exhibited more dental abnormalities…” (Ventura 2024). (ventura2024dentalabnormalitiesin pages 1-2) - “There are no licensed treatments for children with osteogenesis imperfecta… Meta-analyses suggest that anti-fracture efficacy… is equivocal. New therapies are undergoing clinical trials…” (Arundel & Bishop 2024). (stasek2025osteogenesisimperfectashifting pages 1-2)

Applications and real-world implementations - Off-label antiresorptives (pamidronate, zoledronic acid) widely used in pediatric OI care; systematic expert reviews call for harmonized dosing and robust long-term outcomes data. (stasek2025osteogenesisimperfectashifting pages 1-2, hasegawa2025osteogenesisimperfectapathogenesis pages 1-2) - Adult programs increasingly evaluate anabolic/antiresorptive sequences (e.g., teriparatide followed by antiresorptives in broader OI literature), though fracture-reduction evidence remains limited and is an active trial focus (outside the specific sources cited here). (kresnadi2024theroleof pages 2-5) - Multidisciplinary monitoring for dental abnormalities is warranted given high prevalence of DI and malocclusion, particularly in type III/IV cohorts. (ventura2024dentalabnormalitiesin pages 1-2)

Gene/protein annotations with ontology terms - COL1A1 (HGNC:2197); COL1A2 (HGNC:2198). Processes: extracellular matrix organization (GO:0030198); collagen fibril organization (GO:0030199); bone mineralization (GO:0030282); TGF-β signaling pathway (GO:0007179); WNT signaling pathway (GO:0016055). Components: endoplasmic reticulum (GO:0005783); Golgi apparatus (GO:0005794); extracellular matrix (GO:0031012). (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9)

Phenotype associations (HPO terms, descriptive) - Recurrent fractures; skeletal deformities including scoliosis/kyphosis; short stature; dentinogenesis imperfecta type I; variable hearing loss; normal/gray sclerae in many type IV patients. (sillence2024adyadicnosology pages 8-9, khan2024beyondbrittlebones pages 2-3, ventura2024dentalabnormalitiesin pages 1-2)

Cell type involvement (CL terms) - Osteoblasts (CL:0000062), osteocytes (CL:0000138), osteoclasts (CL:0000092), odontoblasts (CL:0000067). (claeys2021collagentransportand pages 1-2, yu2023pathogenicmechanismsof pages 1-2, ventura2024dentalabnormalitiesin pages 1-2)

Anatomical locations (UBERON terms) - Bone element (UBERON:0001474); dentin (UBERON:0001752); sclera (UBERON:0001772); cochlea (UBERON:0002247). (claeys2021collagentransportand pages 1-2, khan2024beyondbrittlebones pages 2-3, ventura2024dentalabnormalitiesin pages 1-2)

Chemical entities (CHEBI terms) - Zoledronic acid (CHEBI:101277); Pamidronate (CHEBI:8069); Teriparatide (CHEBI:38763). (kresnadi2024theroleof pages 2-5, hasegawa2025osteogenesisimperfectapathogenesis pages 1-2)

Limitations of the current evidence set - While multiple 2023–2024 sources were integrated (nosology, dental epidemiology, management reviews, mechanism classification), some highly relevant 2024 bench/clinical studies on TGF-β modulation (e.g., losartan models) and WNT modulators (e.g., sclerostin/DKK1-targeted agents) were identified in searches but not retrievable as citable evidence items in this session; claims regarding these specific agents are therefore framed at the pathway level using authoritative reviews. (yu2023pathogenicmechanismsof pages 1-2, sillence2024adyadicnosology pages 8-9)

Evidence items with PMIDs/DOIs, URLs, publication dates - Sillence DO. A dyadic nosology for Osteogenesis Imperfecta and Bone Fragility Syndromes 2024. Calcif Tissue Int. 2024 Jun;115:873–890. doi:10.1007/s00223-024-01248-7. URL: https://doi.org/10.1007/s00223-024-01248-7 (sillence2024adyadicnosology pages 8-9) - Yu H, et al. Pathogenic mechanisms of osteogenesis imperfecta, evidence for classification. Orphanet J Rare Dis. 2023 Aug. doi:10.1186/s13023-023-02849-5. URL: https://doi.org/10.1186/s13023-023-02849-5 (yu2023pathogenicmechanismsof pages 1-2) - Claeys L, et al. Collagen transport and related pathways in Osteogenesis Imperfecta. Hum Genet. 2021 Jun;140:1121–1141. doi:10.1007/s00439-021-02302-2. URL: https://doi.org/10.1007/s00439-021-02302-2 (claeys2021collagentransportand pages 1-2) - Ventura L, et al. Dental Abnormalities in Osteogenesis Imperfecta: A Systematic Review. Calcif Tissue Int. 2024 Sep;115:461–479. doi:10.1007/s00223-024-01293-2. URL: https://doi.org/10.1007/s00223-024-01293-2 (ventura2024dentalabnormalitiesin pages 1-2) - Arundel P, Bishop N. Medical Management for Fracture Prevention in Children with OI. Calcif Tissue Int. 2024 Mar;115:812–827. doi:10.1007/s00223-024-01202-7. URL: https://doi.org/10.1007/s00223-024-01202-7 (stasek2025osteogenesisimperfectashifting pages 1-2) - Kresnadi A, et al. The Role of Denosumab and Bisphosphonate in OI: A Literature Review. Salud, Ciencia y Tecnología. 2024 Apr;4:894. doi:10.56294/saludcyt2024894. URL: https://doi.org/10.56294/saludcyt2024894 (kresnadi2024theroleof pages 2-5) - Hasegawa K. Osteogenesis imperfecta: pathogenesis, classification, and treatment. Clin Pediatr Endocrinol. 2025 Jan;34:152–161. doi:10.1297/cpe.2025-0009. URL: https://doi.org/10.1297/cpe.2025-0009 (hasegawa2025osteogenesisimperfectapathogenesis pages 1-2) - Khan H, et al. Beyond brittle bones: Genetic mechanisms underlying OI. World Acad Sci J. 2024 Oct. doi:10.3892/wasj.2024.284. URL: https://doi.org/10.3892/wasj.2024.284 (khan2024beyondbrittlebones pages 2-3) - Dinulescu A, et al. New Perspectives of Therapies in OI—A Literature Review. J Clin Med. 2024 Feb;13:1065. doi:10.3390/jcm13041065. URL: https://doi.org/10.3390/jcm13041065 (dinulescu2024newperspectivesof pages 1-2)

Overall synthesis - OI type IV reflects a moderate-severity collagen I matrix disorder centered on COL1A1/COL1A2 variants that disrupt collagen biosynthesis and extracellular assembly, with secondary dysregulation of TGF-β and WNT pathways affecting bone remodeling. Clinically, it features recurrent fractures, deformity, short stature, and variable DI/hearing/scleral involvement, with substantial overlap across classical Sillence types. 2023–2024 updates emphasize nosology integration of genotype and phenotype, caution about equivocal anti-fracture evidence for pediatric bisphosphonates, and growing interest in targeted pathway therapies; robust long-term fracture outcomes and standardized approaches remain priorities. (sillence2024adyadicnosology pages 8-9, yu2023pathogenicmechanismsof pages 1-2, stasek2025osteogenesisimperfectashifting pages 1-2, kresnadi2024theroleof pages 2-5, ventura2024dentalabnormalitiesin pages 1-2)

References

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  2. (claeys2021collagentransportand pages 1-2): Lauria Claeys, Silvia Storoni, Marelise Eekhoff, Mariet Elting, Lisanne Wisse, Gerard Pals, Nathalie Bravenboer, Alessandra Maugeri, and Dimitra Micha. Collagen transport and related pathways in osteogenesis imperfecta. Human Genetics, 140:1121-1141, Jun 2021. URL: https://doi.org/10.1007/s00439-021-02302-2, doi:10.1007/s00439-021-02302-2. This article has 108 citations and is from a peer-reviewed journal.

  3. (yu2023pathogenicmechanismsof pages 1-2): Hongjie Yu, Changrong Li, Huixiao Wu, Weibo Xia, Yanzhou Wang, Jiajun Zhao, and Chao Xu. Pathogenic mechanisms of osteogenesis imperfecta, evidence for classification. Orphanet Journal of Rare Diseases, Aug 2023. URL: https://doi.org/10.1186/s13023-023-02849-5, doi:10.1186/s13023-023-02849-5. This article has 31 citations and is from a peer-reviewed journal.

  4. (kresnadi2024theroleof pages 2-5): Agus Kresnadi, Tri Wahyu Martanto, Arif Zulkarnain, and Hizbillah Yazid. The role of denosumab and bisphosphonate in osteogenesis imperfecta: a literature review. Salud, Ciencia y Tecnología, 4:894, Apr 2024. URL: https://doi.org/10.56294/saludcyt2024894, doi:10.56294/saludcyt2024894. This article has 1 citations.

  5. (khan2024beyondbrittlebones pages 2-3): Hammal Khan, Zaheer Ahmed, and Muhammad Umair. Beyond brittle bones: genetic mechanisms underlying osteogenesis imperfecta (review). World Academy of Sciences Journal, Oct 2024. URL: https://doi.org/10.3892/wasj.2024.284, doi:10.3892/wasj.2024.284. This article has 1 citations.

  6. (ventura2024dentalabnormalitiesin pages 1-2): Laura Ventura, Sara J. E. Verdonk, Lidiia Zhytnik, Angela Ridwan-Pramana, Marjolijn Gilijamse, Willem H. Schreuder, Kirsten A. van Gelderen-Ziesemer, Ton Schoenmaker, Dimitra Micha, and Elisabeth M. W. Eekhoff. Dental abnormalities in osteogenesis imperfecta: a systematic review. Calcified Tissue International, 115:461-479, Sep 2024. URL: https://doi.org/10.1007/s00223-024-01293-2, doi:10.1007/s00223-024-01293-2. This article has 14 citations and is from a peer-reviewed journal.

  7. (hasegawa2025osteogenesisimperfectapathogenesis pages 1-2): Kosei Hasegawa. Osteogenesis imperfecta: pathogenesis, classification, and treatment. Clinical Pediatric Endocrinology, 34:152-161, Jan 2025. URL: https://doi.org/10.1297/cpe.2025-0009, doi:10.1297/cpe.2025-0009. This article has 1 citations and is from a peer-reviewed journal.

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