Fibrodysplasia Ossificans Progressiva

Genetic MONDO:0007606 Pathograph 10 Musculoskeletal Disease Genetic Disease

A rare, severely disabling genetic disorder characterized by progressive heterotopic ossification of skeletal muscles, fascia, tendons, and ligaments, with congenital malformation of the great toes. The condition is caused by gain-of-function mutations in the ACVR1 gene encoding a BMP type I receptor, leading to aberrant bone formation in soft tissues.

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Pathophysiology

Constitutive BMP Signaling Activation

The ACVR1 R206H mutation creates a pH-sensitive switch in the receptor's activation domain, leading to ligand-independent activation of BMP signaling and inappropriate osteogenic differentiation of connective tissue progenitors.

BMP signaling pathway link ossification link

Downstream

Heterotopic Ossification Aberrant BMP signaling drives differentiation of muscle and connective tissue progenitor cells into chondrocytes and osteoblasts, leading to formation of qualitatively normal bone at ectopic sites.

Congenital Great Toe Malformation Aberrant ACVR1 signaling during embryonic patterning disrupts first digit development.

Activin A Neomorphic Signaling Mutant receptor acquires abnormal signaling response to Activin A.

Show evidence (1 reference)

PMID:17572636 SUPPORT

"Protein modeling predicts that substitution with histidine, and only histidine, creates a pH-sensitive switch within the activation domain of the receptor that leads to ligand-independent activation of ACVR1 in fibrodysplasia ossificans progressiva."

This study explains the unique molecular mechanism of the R206H mutation creating pH-dependent receptor dysregulation.

Impaired FKBP1A Regulatory Binding

The R206H mutation reduces binding affinity for FKBP1A/FKBP12, a safeguard protein that normally prevents inappropriate BMP signaling, resulting in leaky activation of the pathway.

Osteoblast link

Downstream

Constitutive BMP Signaling Activation Loss of FKBP1A inhibition lowers the activation threshold for mutant ACVR1 signaling.

Show evidence (1 reference)

PMID:20463014 SUPPORT

"The R206H mutant showed a decreased binding affinity for FKBP1A/FKBP12, a known safeguard molecule against the leakage of transforming growth factor (TGF)-beta or BMP signaling"

Loss of FKBP1A binding is a key mechanism allowing leaky BMP signaling.

Activin A Neomorphic Signaling

The R206H mutation renders ACVR1 responsive to Activin A ligands, which normally antagonize BMP signaling. This neomorphic gain-of-function allows Activin A to aberrantly activate osteogenic signaling, driving heterotopic ossification. Anti-Activin A antibodies can block HO. Activin A is an obligate factor for the initiation of HO in FOP.

BMP signaling pathway link

Downstream

Inflammatory Triggering of Flare-ups Injury-related Activin A release aberrantly activates mutant ACVR1 in local tissues.

Heterotopic Ossification Activin A-driven mutant receptor signaling initiates ectopic chondrogenic and osteogenic programs.

Show evidence (1 reference)

PMID:26896819 PARTIAL

"Most FOP patients carry an activating mutation in a bone morphogenetic protein (BMP) type I receptor gene, ACVR1(R206H), that promotes ectopic chondrogenesis and osteogenesis and, in turn, HO"

Supports mutant ACVR1-driven ectopic osteochondrogenesis, but does not directly establish Activin A neomorphic signaling.

Heterotopic Ossification

Progressive formation of qualitatively normal bone in extraskeletal tissues including muscles, tendons, ligaments, and fascia, typically following episodic inflammatory flare-ups. The process occurs through endochondral ossification with distinct histological stages: inflammatory/catabolic phase, fibroproliferative phase, chondrogenic phase, and osteogenic phase.

Osteoblast link Chondrocyte link

Endochondral ossification link Cartilage development link

Downstream

Progressive Joint Immobility Bridging ectopic bone progressively ankyloses major joints.

Joint Stiffness Early periarticular ossification reduces range of motion.

Scoliosis Asymmetric axial heterotopic bone and contractures distort spinal alignment.

Restrictive Ventilatory Defect Thoracic cage ossification limits chest wall expansion and lung mechanics.

Show evidence (1 reference)

PMID:26896819 SUPPORT

"Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable genetic disorder of progressive extraskeletal ossification, is the most disabling form of heterotopic ossification (HO) in humans"

Establishes FOP as the most severe form of heterotopic ossification.

Inflammatory Triggering of Flare-ups

Macrophages, mast cells, and lymphocytes infiltrate affected tissues during the catabolic phase, releasing inflammatory cytokines that create a permissive microenvironment for heterotopic ossification. Mast cell depletion reduces HO by approximately 50%, and combined mast cell/macrophage depletion reduces HO by approximately 75%.

Macrophage link Mast cell link

Inflammatory response link

Downstream

Heterotopic Ossification Cytokine-rich flare environments recruit progenitors and promote endochondral ectopic bone formation.

Show evidence (1 reference)

PMID:26896819 NO_EVIDENCE

Snippet establishes severe progressive HO in FOP but does not directly provide evidence for immune-cell inflammatory triggering mechanisms.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

Referential integrity issues (2):

Target 'Progressive Joint Immobility' (from 'Heterotopic Ossification') not found in named elements
Target 'Joint Stiffness' (from 'Heterotopic Ossification') not found in named elements

●

Phenotypes

Ear 1

Conductive Hearing Impairment Conductive hearing impairment (HP:0000405)

Hearing loss in FOP is typically conductive rather than sensorineural.

Show evidence (1 reference)

PMID:10499116 SUPPORT Human Clinical

"The findings of both studies indicate that individuals with FOP are at risk for hearing loss and that the type of loss is predominantly conductive in nature"

Supports conductive hearing impairment as a recognized non-skeletal manifestation of FOP.

Head and Neck 1

Restricted Mouth Opening Trismus (HP:0000211)

Maxillofacial heterotopic ossification can severely restrict jaw opening and complicate eating, oral care, and airway management.

Show evidence (1 reference)

PMID:28390760 SUPPORT Human Clinical

"As the condition progresses, HO leads to joint ankylosis, breathing difficulties, and mouth-opening restriction, and it can shorten the patient's lifespan."

Supports restricted mouth opening as a clinically important manifestation of maxillofacial heterotopic ossification.

Limbs 2

Congenital Great Toe Malformation Abnormal hallux morphology (HP:0001844)

Classic hallux abnormalities include shortening of the great toe with hallux valgus and first-ray malformation. This is the most important early diagnostic clue in classic FOP.

Show evidence (1 reference)

PMID:21116899 SUPPORT Human Clinical

"A shortened great toe and hallux valgus were frequently found in patients with FOP."

Supports the characteristic hallux shortening and hallux valgus of FOP.

Context-specific annotations (1)

Onset: CONGENITAL

The great-toe malformation is a congenital skeletal anomaly.

Show evidence (1 reference)

PMID:21116899 SUPPORT Human Clinical

"These findings were thought to exist from birth and may be a key to an early diagnosis."

Supports congenital onset of the great-toe abnormality.

Short Thumb Short thumb (HP:0009778)

Thumb shortening is an additional skeletal clue that can help identify FOP, including patients whose great toes appear less obviously abnormal.

Show evidence (1 reference)

PMID:25343126 SUPPORT Human Clinical

"The thumb shortening and cervical spine abnormalities are other skeletal features often observed in FOP."

Supports short thumb as part of the congenital skeletal phenotype.

Metabolism 1

Soft Tissue Swelling During Flare-ups Edema (HP:0000969)

Preosseous flare-ups often present as inflammatory soft-tissue swelling and may occur in the back, neck, jaw, or limbs.

Show evidence (1 reference)

PMID:27025942 SUPPORT Human Clinical

"The most common presenting symptoms of flare-ups were swelling (93%), pain (86%), or decreased mobility (79%)."

Supports inflammatory soft-tissue swelling as a hallmark presenting symptom of FOP flare-ups.

Musculoskeletal 2

Scoliosis FREQUENT Scoliosis (HP:0002650)

Thoracolumbar or lumbar curves are common, may become rigid by early adulthood, and can impair sitting or standing balance.

Show evidence (1 reference)

PMID:7929490 SUPPORT Human Clinical

"Twenty-six (65 per cent) of the patients had scoliosis, which, according to the clinical records and the recollection of the patients, had been present during childhood."

26/40 = 65%, which falls in the FREQUENT band; the same cohort report also indicates childhood onset.

Context-specific annotations (1)

Onset: CHILDHOOD

In the 40-patient series, scoliosis was already present in childhood.

Show evidence (1 reference)

PMID:7929490 SUPPORT Human Clinical

"Twenty-six (65 per cent) of the patients had scoliosis, which, according to the clinical records and the recollection of the patients, had been present during childhood."

Supports childhood onset of scoliosis in the reported cohort.

Cervical Spine Malformations Fused cervical vertebrae (HP:0002949)

Characteristic radiographic abnormalities include enlarged posterior elements, tall narrow vertebral bodies, and fusion of cervical facet joints.

Show evidence (1 reference)

PMID:15959366 SUPPORT Human Clinical

"In the FOP patient group, characteristic anomalies, including large posterior elements, tall narrow vertebral bodies,and fusion of the facet joints between C2 and C7, were observed."

Supports characteristic congenital cervical spine malformations, including fusion involving the cervical vertebrae.

Context-specific annotations (1)

Onset: CONGENITAL

These cervical spine abnormalities are congenital skeletal defects.

Show evidence (1 reference)

PMID:15959366 SUPPORT Human Clinical

"FOP patients exhibit a characteristic set of congenital spine malformations."

Supports congenital onset of the cervical spine abnormalities.

Respiratory 1

Restrictive Ventilatory Defect Restrictive ventilatory defect (HP:0002091)

Thoracic heterotopic ossification causes restrictive respiratory mechanics and underlies much of the cardiorespiratory mortality in FOP.

Show evidence (2 references)

PMID:40597333 SUPPORT Human Clinical

"Spirometry showed a uniform pattern of restrictive physiology in all eight participants with no significant difference amongst the group."

Supports restrictive ventilatory physiology in a modern FOP cohort.

PMID:20194327 SUPPORT Human Clinical

"The most common causes of death in patients with fibrodysplasia ossificans progressiva were cardiorespiratory failure from thoracic insufficiency syndrome (54%; median age, forty-two years) and pneumonia (15%; median age, forty years)."

Supports thoracic insufficiency syndrome as a major life-limiting respiratory complication of FOP.

Constitutional 1

Acute Flare-up Pain Pain (HP:0012531)

Acute pain is a common presenting feature of flare-ups and contributes substantially to physical disability.

Show evidence (1 reference)

PMID:26564023 SUPPORT Human Clinical

"Fibrodysplasia ossificans progressiva (FOP) is a rare disorder characterized by episodes of acute pain and heterotopic ossification of soft tissue, and progressively limited physical function and social participation."

Supports acute pain as a core clinical manifestation during FOP flare-ups.

Other 4

Heterotopic Ossification Ectopic ossification (HP:0011986)

Progressive formation of ectopic bone in soft connective tissues including muscles, fascia, tendons, and ligaments. FOP lesions may accumulate even in the absence of a recognized flare-up.

Show evidence (1 reference)

PMID:36152026 SUPPORT Human Clinical

"FOP is characterized by painful, recurrent flare-ups, and disabling, cumulative heterotopic ossification (HO) in soft tissues."

Supports cumulative soft-tissue heterotopic ossification as the defining phenotype of FOP.

Context-specific annotations (1)

Onset: CHILDHOOD

Classic FOP develops a heterotopic skeleton during childhood.

Show evidence (1 reference)

PMID:17572636 SUPPORT Human Clinical

"Individuals with fibrodysplasia ossificans progressiva are born with malformations of the great toes and develop a heterotopic skeleton during childhood"

Supports childhood onset of classic heterotopic ossification.

Joint Ankylosis Ankylosis (HP:0031013)

Progressive bridging heterotopic bone can ankylize major joints and cause persistent loss of mobility.

Show evidence (1 reference)

PMID:28390760 SUPPORT Human Clinical

"As the condition progresses, HO leads to joint ankylosis, breathing difficulties, and mouth-opening restriction, and it can shorten the patient's lifespan."

Directly supports joint ankylosis as a clinical consequence of progressive heterotopic ossification in FOP.

Limitation of Neck Motion Limitation of neck motion (HP:0005986)

Neck stiffness and reduced cervical range of motion are often early manifestations of cervical involvement in FOP.

Show evidence (1 reference)

PMID:15959366 SUPPORT Human Clinical

"Generalized neck stiffness and decreased range of motion were noted in most children with FOP."

Supports neck stiffness with limited cervical motion as an early musculoskeletal manifestation.

Proximal Tibial Osteochondromas VERY_FREQUENT Osteochondroma (HP:0030431)

These lesions are usually asymptomatic, most commonly bilateral, and typically arise near the pes anserinus.

Show evidence (1 reference)

PMID:18245597 SUPPORT Human Clinical

"Ninety percent of all patients had osteochondroma of the proximal part of the tibia."

90% falls in the VERY_FREQUENT band and directly supports proximal tibial osteochondromas as a common skeletal manifestation of FOP.

🧬

Genetic Associations

ACVR1 (Causative)

Autosomal Dominant

Show evidence (3 references)

PMID:17572636 SUPPORT

"Substitution of adenine for guanine at nucleotide 617 replaces an evolutionarily conserved arginine with histidine at residue 206 of ACVR1 in all classically affected individuals, making this one of the most highly conserved disease-causing mutations in the human genome."

The R206H mutation is identified as the causative mutation in all classic FOP cases and is highly conserved.

PMID:29097342 SUPPORT

"Most patients with fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder of heterotopic ossification, have the same causative mutation in ACVR1, R206H."

Confirms R206H as the predominant mutation while noting variant cases.

CGGV:assertion_0439e75f-fc1b-4841-8c9a-17f3568ce8a4-2023-03-01T170000.000Z SUPPORT Other

ClinGen classifies the ACVR1-fibrodysplasia ossificans progressiva gene-disease relationship as definitive with autosomal dominant inheritance.

💊

Treatments

Palovarotene

Action: Pharmacotherapy NCIT:C15986

Agent: palovarotene ↗

Retinoic acid receptor gamma (RARgamma) agonist that inhibits endochondral ossification, the final mandatory step in heterotopic bone formation. FDA-approved in 2023 for patients 8 years and older (females) and 10 years and older (males).

Show evidence (2 references)

PMID:26896819 PARTIAL

"palovarotene maintained joint, limb, and body motion, providing clear evidence for its encompassing therapeutic potential as a treatment for FOP."

The study demonstrates palovarotene's therapeutic efficacy in preserving mobility in FOP mouse models.

PMID:26896819 PARTIAL

"palovarotene restored long bone growth, maintained growth plate function, and protected growing mutant neonates"

Demonstrates palovarotene's ability to preserve skeletal development while preventing heterotopic ossification.

Corticosteroids

Action: systemic corticosteroid therapy Ontology label: Systemic Corticosteroid Therapy NCIT:C122080

Used during acute flare-ups to reduce inflammation, though efficacy in preventing ossification is limited. Must be administered early in flare-ups for potential benefit.

Show evidence (1 reference)

PMID:26896819 PARTIAL

"Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable genetic disorder of progressive extraskeletal ossification"

The article notes FOP was untreatable, highlighting the limited efficacy of symptomatic treatments like corticosteroids.

Avoidance of Trauma

Primary preventive strategy including avoidance of intramuscular injections, falls, and surgical procedures that may trigger flare-ups. Represents a key component of supportive care.

Show evidence (1 reference)

PMID:26896819 PARTIAL

"palovarotene effectively inhibited HO in injury-induced and genetic mouse models of the disease"

Since injury induces HO in FOP models, avoidance of trauma is a key preventive strategy.

Genetic Counseling

Action: genetic counseling MAXO:0000079

Essential for affected individuals and families given the autosomal dominant inheritance pattern and severe disease burden.

Show evidence (1 reference)

PMID:17572636 PARTIAL

"Individuals with fibrodysplasia ossificans progressiva are born with malformations of the great toes and develop a heterotopic skeleton during childhood because of an identical heterozygous mutation"

Identification of the causative mutation enables genetic counseling and potential prenatal diagnosis.

Garetosmab

Action: Pharmacotherapy NCIT:C15986

Agent: garetosmab ↗

Anti-Activin A monoclonal antibody that blocks the neomorphic signaling caused by the ACVR1 R206H mutation. Phase 3 OPTIMA trial showed over 90% reduction in new heterotopic ossification lesions. Regulatory submission expected 2025-2026.

Show evidence (1 reference)

PMID:26896819 PARTIAL

"Most FOP patients carry an activating mutation in a bone morphogenetic protein (BMP) type I receptor gene, ACVR1(R206H), that promotes ectopic chondrogenesis and osteogenesis and, in turn, HO"

Establishes the molecular rationale for anti-Activin A therapy targeting the aberrant signaling through mutant ACVR1.

🌍

Environmental Factors

Trauma

Physical trauma, including minor injuries, intramuscular injections, and surgical procedures, can trigger flare-ups leading to new heterotopic ossification. Avoidance of trauma is a key management strategy.

Show evidence (1 reference)

PMID:26896819 PARTIAL

"palovarotene effectively inhibited HO in injury-induced and genetic mouse models of the disease"

The use of injury-induced models demonstrates trauma as a key trigger for heterotopic ossification in FOP.

Viral Illness

Viral infections may trigger inflammatory flare-ups and subsequent heterotopic ossification episodes.

Show evidence (1 reference)

PMID:26896819 NO_EVIDENCE

"Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable genetic disorder of progressive extraskeletal ossification"

Snippet does not mention viral illness as a trigger.

{ }

Source YAML

click to show

name: Fibrodysplasia Ossificans Progressiva
creation_date: '2025-12-19T01:18:09Z'
updated_date: '2026-04-19T07:29:40Z'
category: Genetic
parents:
- Musculoskeletal Disease
- Genetic Disease
description: >-
  A rare, severely disabling genetic disorder characterized by progressive
  heterotopic ossification of skeletal muscles, fascia, tendons, and ligaments,
  with congenital malformation of the great toes. The condition is caused by
  gain-of-function mutations in the ACVR1 gene encoding a BMP type I receptor,
  leading to aberrant bone formation in soft tissues.
prevalence:
- population: United States residents
  percentage: 0.88 per million
  notes: >-
    A 2021 U.S. ascertainment study across major treatment centers and a
    patient organization estimated prevalence at 0.88 per million residents.
  evidence:
  - reference: PMID:34353327
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      An adjusted prevalence of 0.88 per million US residents was calculated
      using either an average survival rate estimate of 98.4% or a conservative
      survival rate estimate of 92.3% (based on the Kaplan-Meier survival curve
      from a previous study) and the US Census 2020 estimate of 329,992,681 on
      prevalence day.
    explanation: >-
      This is a direct population-based U.S. prevalence estimate for FOP.
- population: France residents
  percentage: 1.36 per million inhabitants
  notes: >-
    French national database linkage estimated FOP prevalence at 1.36 per
    million inhabitants.
  evidence:
  - reference: PMID:28666455
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Using a capture-recapture methodology to adjust the crude number of
      patients identified in both data sources, 89 FOP patients were
      identified, which results in a prevalence of 1.36 per million
      inhabitants (CI95% = [1.10; 1.68]).
    explanation: >-
      This national French record-linkage study provides an independent
      population prevalence estimate for FOP.
pathophysiology:
- name: Constitutive BMP Signaling Activation
  description: >-
    The ACVR1 R206H mutation creates a pH-sensitive switch in the receptor's
    activation domain, leading to ligand-independent activation of BMP
    signaling and inappropriate osteogenic differentiation of connective
    tissue progenitors.
  biological_processes:
  - preferred_term: BMP signaling pathway
    term:
      id: GO:0030509
      label: BMP signaling pathway
  - preferred_term: ossification
    term:
      id: GO:0001503
      label: ossification
  downstream:
  - target: Heterotopic Ossification
    description: >-
      Aberrant BMP signaling drives differentiation of muscle and connective
      tissue progenitor cells into chondrocytes and osteoblasts, leading to
      formation of qualitatively normal bone at ectopic sites.
    evidence:
    - reference: PMID:20463014
      reference_title: "Molecular consequences of the ACVR1(R206H) mutation of fibrodysplasia ossificans progressiva."
      supports: SUPPORT
      snippet: >-
        mild activation of osteogenic BMP-signaling in extraskeletal sites
        such as muscle, which eventually lead to delayed and progressive
        ectopic bone formation in FOP patients
      explanation: >-
        The study demonstrates that the R206H mutation causes BMP signal
        activation in muscle tissue, leading to ectopic bone formation.
  - target: Congenital Great Toe Malformation
    description: Aberrant ACVR1 signaling during embryonic patterning disrupts first digit development.
  - target: Activin A Neomorphic Signaling
    description: Mutant receptor acquires abnormal signaling response to Activin A.
  evidence:
  - reference: PMID:17572636
    reference_title: "Functional modeling of the ACVR1 (R206H) mutation in FOP."
    supports: SUPPORT
    snippet: >-
      Protein modeling predicts that substitution with histidine, and only
      histidine, creates a pH-sensitive switch within the activation domain
      of the receptor that leads to ligand-independent activation of ACVR1
      in fibrodysplasia ossificans progressiva.
    explanation: >-
      This study explains the unique molecular mechanism of the R206H mutation
      creating pH-dependent receptor dysregulation.
- name: Impaired FKBP1A Regulatory Binding
  description: >-
    The R206H mutation reduces binding affinity for FKBP1A/FKBP12, a safeguard
    protein that normally prevents inappropriate BMP signaling, resulting in
    leaky activation of the pathway.
  cell_types:
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  evidence:
  - reference: PMID:20463014
    reference_title: "Molecular consequences of the ACVR1(R206H) mutation of fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    snippet: >-
      The R206H mutant showed a decreased binding affinity for FKBP1A/FKBP12,
      a known safeguard molecule against the leakage of transforming growth
      factor (TGF)-beta or BMP signaling
    explanation: >-
      Loss of FKBP1A binding is a key mechanism allowing leaky BMP signaling.
  downstream:
  - target: Constitutive BMP Signaling Activation
    description: Loss of FKBP1A inhibition lowers the activation threshold for mutant ACVR1 signaling.
- name: Activin A Neomorphic Signaling
  description: >-
    The R206H mutation renders ACVR1 responsive to Activin A ligands, which
    normally antagonize BMP signaling. This neomorphic gain-of-function
    allows Activin A to aberrantly activate osteogenic signaling, driving
    heterotopic ossification. Anti-Activin A antibodies can block HO.
    Activin A is an obligate factor for the initiation of HO in FOP.
  biological_processes:
  - preferred_term: BMP signaling pathway
    term:
      id: GO:0030509
      label: BMP signaling pathway
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      Most FOP patients carry an activating mutation in a bone morphogenetic
      protein (BMP) type I receptor gene, ACVR1(R206H), that promotes ectopic
      chondrogenesis and osteogenesis and, in turn, HO
    explanation: >-
      Supports mutant ACVR1-driven ectopic osteochondrogenesis, but does not
      directly establish Activin A neomorphic signaling.
  notes: >-
    This discovery led to development of garetosmab (anti-Activin A antibody)
    as a targeted therapy for FOP.
  downstream:
  - target: Inflammatory Triggering of Flare-ups
    description: Injury-related Activin A release aberrantly activates mutant ACVR1 in local tissues.
  - target: Heterotopic Ossification
    description: Activin A-driven mutant receptor signaling initiates ectopic chondrogenic and osteogenic programs.
- name: Heterotopic Ossification
  description: >-
    Progressive formation of qualitatively normal bone in extraskeletal tissues
    including muscles, tendons, ligaments, and fascia, typically following
    episodic inflammatory flare-ups. The process occurs through endochondral
    ossification with distinct histological stages: inflammatory/catabolic phase,
    fibroproliferative phase, chondrogenic phase, and osteogenic phase.
  cell_types:
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  - preferred_term: Chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  biological_processes:
  - preferred_term: Endochondral ossification
    term:
      id: GO:0001958
      label: endochondral ossification
  - preferred_term: Cartilage development
    term:
      id: GO:0051216
      label: cartilage development
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: SUPPORT
    snippet: >-
      Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable
      genetic disorder of progressive extraskeletal ossification, is the most
      disabling form of heterotopic ossification (HO) in humans
    explanation: >-
      Establishes FOP as the most severe form of heterotopic ossification.
  downstream:
  - target: Progressive Joint Immobility
    description: Bridging ectopic bone progressively ankyloses major joints.
  - target: Joint Stiffness
    description: Early periarticular ossification reduces range of motion.
  - target: Scoliosis
    description: Asymmetric axial heterotopic bone and contractures distort spinal alignment.
  - target: Restrictive Ventilatory Defect
    description: Thoracic cage ossification limits chest wall expansion and lung mechanics.
- name: Inflammatory Triggering of Flare-ups
  description: >-
    Macrophages, mast cells, and lymphocytes infiltrate affected tissues during
    the catabolic phase, releasing inflammatory cytokines that create a permissive
    microenvironment for heterotopic ossification. Mast cell depletion reduces HO
    by approximately 50%, and combined mast cell/macrophage depletion reduces HO
    by approximately 75%.
  cell_types:
  - preferred_term: Macrophage
    term:
      id: CL:0000235
      label: macrophage
  - preferred_term: Mast cell
    term:
      id: CL:0000097
      label: mast cell
  biological_processes:
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: NO_EVIDENCE
    snippet: >-
      Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable
      genetic disorder of progressive extraskeletal ossification, is the most
      disabling form of heterotopic ossification (HO) in humans
    explanation: >-
      Snippet establishes severe progressive HO in FOP but does not directly
      provide evidence for immune-cell inflammatory triggering mechanisms.
  notes: >-
    Multiple lines of evidence indicate a key role for the immune system in
    driving FOP pathogenesis. Activin A produced by innate immune cells after
    soft-tissue injury aberrantly signals through mutant ACVR1.
  downstream:
  - target: Heterotopic Ossification
    description: Cytokine-rich flare environments recruit progenitors and promote endochondral ectopic bone formation.
phenotypes:
- category: Skeletal
  name: Congenital Great Toe Malformation
  diagnostic: true
  notes: >-
    Classic hallux abnormalities include shortening of the great toe with
    hallux valgus and first-ray malformation. This is the most important early
    diagnostic clue in classic FOP.
  evidence:
  - reference: PMID:21116899
    reference_title: "Deformity of the great toe in fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A shortened great toe and hallux valgus were frequently found in
      patients with FOP.
    explanation: >-
      Supports the characteristic hallux shortening and hallux valgus of FOP.
  phenotype_contexts:
  - onset:
      onset_category: CONGENITAL
    notes: The great-toe malformation is a congenital skeletal anomaly.
    evidence:
    - reference: PMID:21116899
      reference_title: "Deformity of the great toe in fibrodysplasia ossificans progressiva."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        These findings were thought to exist from birth and may be a key to
        an early diagnosis.
      explanation: Supports congenital onset of the great-toe abnormality.
  phenotype_term:
    preferred_term: Abnormal hallux morphology
    term:
      id: HP:0001844
      label: Abnormal hallux morphology
- category: Skeletal
  name: Heterotopic Ossification
  notes: >-
    Progressive formation of ectopic bone in soft connective tissues including
    muscles, fascia, tendons, and ligaments. FOP lesions may accumulate even
    in the absence of a recognized flare-up.
  evidence:
  - reference: PMID:36152026
    reference_title: "The natural history of fibrodysplasia ossificans progressiva: A prospective, global 36-month study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      FOP is characterized by painful, recurrent flare-ups, and disabling,
      cumulative heterotopic ossification (HO) in soft tissues.
    explanation: >-
      Supports cumulative soft-tissue heterotopic ossification as the defining
      phenotype of FOP.
  phenotype_contexts:
  - onset:
      onset_category: CHILDHOOD
    notes: Classic FOP develops a heterotopic skeleton during childhood.
    evidence:
    - reference: PMID:17572636
      reference_title: "Functional modeling of the ACVR1 (R206H) mutation in FOP."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Individuals with fibrodysplasia ossificans progressiva are born with
        malformations of the great toes and develop a heterotopic skeleton
        during childhood
      explanation: Supports childhood onset of classic heterotopic ossification.
  phenotype_term:
    preferred_term: Progressive heterotopic ossification
    term:
      id: HP:0011986
      label: Ectopic ossification
- category: Musculoskeletal
  name: Acute Flare-up Pain
  notes: >-
    Acute pain is a common presenting feature of flare-ups and contributes
    substantially to physical disability.
  evidence:
  - reference: PMID:26564023
    reference_title: "Quality of life of patients with fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Fibrodysplasia ossificans progressiva (FOP) is a rare disorder
      characterized by episodes of acute pain and heterotopic ossification of
      soft tissue, and progressively limited physical function and social
      participation.
    explanation: >-
      Supports acute pain as a core clinical manifestation during FOP flare-ups.
  phenotype_term:
    preferred_term: Acute flare-up pain
    term:
      id: HP:0012531
      label: Pain
- category: Musculoskeletal
  name: Soft Tissue Swelling During Flare-ups
  notes: >-
    Preosseous flare-ups often present as inflammatory soft-tissue swelling and
    may occur in the back, neck, jaw, or limbs.
  evidence:
  - reference: PMID:27025942
    reference_title: "The Natural History of Flare-Ups in Fibrodysplasia Ossificans Progressiva (FOP): A Comprehensive Global Assessment."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common presenting symptoms of flare-ups were swelling (93%),
      pain (86%), or decreased mobility (79%).
    explanation: >-
      Supports inflammatory soft-tissue swelling as a hallmark presenting
      symptom of FOP flare-ups.
  phenotype_term:
    preferred_term: Soft tissue swelling during flare-ups
    term:
      id: HP:0000969
      label: Edema
- category: Musculoskeletal
  name: Joint Ankylosis
  notes: >-
    Progressive bridging heterotopic bone can ankylize major joints and cause
    persistent loss of mobility.
  evidence:
  - reference: PMID:28390760
    reference_title: "Restricted Mandibular Movement Attributed to Ossification of Mandibular Depressors and Medial Pterygoid Muscles in Patients With Fibrodysplasia Ossificans Progressiva: A Report of 3 Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As the condition progresses, HO leads to joint ankylosis, breathing
      difficulties, and mouth-opening restriction, and it can shorten the
      patient's lifespan.
    explanation: >-
      Directly supports joint ankylosis as a clinical consequence of
      progressive heterotopic ossification in FOP.
  phenotype_term:
    preferred_term: Joint ankylosis
    term:
      id: HP:0031013
      label: Ankylosis
- category: Skeletal
  name: Scoliosis
  frequency: FREQUENT
  notes: >-
    Thoracolumbar or lumbar curves are common, may become rigid by early
    adulthood, and can impair sitting or standing balance.
  evidence:
  - reference: PMID:7929490
    reference_title: "Spinal deformity in patients who have fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Twenty-six (65 per cent) of the patients had scoliosis, which, according
      to the clinical records and the recollection of the patients, had been
      present during childhood.
    explanation: >-
      26/40 = 65%, which falls in the FREQUENT band; the same cohort report
      also indicates childhood onset.
  phenotype_contexts:
  - onset:
      onset_category: CHILDHOOD
    notes: In the 40-patient series, scoliosis was already present in childhood.
    evidence:
    - reference: PMID:7929490
      reference_title: "Spinal deformity in patients who have fibrodysplasia ossificans progressiva."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Twenty-six (65 per cent) of the patients had scoliosis, which,
        according to the clinical records and the recollection of the
        patients, had been present during childhood.
      explanation: Supports childhood onset of scoliosis in the reported cohort.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
- category: Skeletal
  name: Cervical Spine Malformations
  notes: >-
    Characteristic radiographic abnormalities include enlarged posterior
    elements, tall narrow vertebral bodies, and fusion of cervical facet joints.
  evidence:
  - reference: PMID:15959366
    reference_title: "Developmental anomalies of the cervical spine in patients with fibrodysplasia ossificans progressiva are distinctly different from those in patients with Klippel-Feil syndrome: clues from the BMP signaling pathway."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In the FOP patient group, characteristic anomalies, including large
      posterior elements, tall narrow vertebral bodies,and fusion of the facet
      joints between C2 and C7, were observed.
    explanation: >-
      Supports characteristic congenital cervical spine malformations,
      including fusion involving the cervical vertebrae.
  phenotype_contexts:
  - onset:
      onset_category: CONGENITAL
    notes: These cervical spine abnormalities are congenital skeletal defects.
    evidence:
    - reference: PMID:15959366
      reference_title: "Developmental anomalies of the cervical spine in patients with fibrodysplasia ossificans progressiva are distinctly different from those in patients with Klippel-Feil syndrome: clues from the BMP signaling pathway."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        FOP patients exhibit a characteristic set of congenital spine
        malformations.
      explanation: Supports congenital onset of the cervical spine abnormalities.
  phenotype_term:
    preferred_term: Congenital cervical spine malformations
    term:
      id: HP:0002949
      label: Fused cervical vertebrae
- category: Musculoskeletal
  name: Limitation of Neck Motion
  notes: >-
    Neck stiffness and reduced cervical range of motion are often early
    manifestations of cervical involvement in FOP.
  evidence:
  - reference: PMID:15959366
    reference_title: "Developmental anomalies of the cervical spine in patients with fibrodysplasia ossificans progressiva are distinctly different from those in patients with Klippel-Feil syndrome: clues from the BMP signaling pathway."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Generalized neck stiffness and decreased range of motion were noted in
      most children with FOP.
    explanation: >-
      Supports neck stiffness with limited cervical motion as an early
      musculoskeletal manifestation.
  phenotype_term:
    preferred_term: Limitation of neck motion
    term:
      id: HP:0005986
      label: Limitation of neck motion
- category: Skeletal
  name: Short Thumb
  notes: >-
    Thumb shortening is an additional skeletal clue that can help identify FOP,
    including patients whose great toes appear less obviously abnormal.
  evidence:
  - reference: PMID:25343126
    reference_title: "Radiographic characteristics of the hand and cervical spine in fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The thumb shortening and cervical spine abnormalities are other skeletal
      features often observed in FOP.
    explanation: Supports short thumb as part of the congenital skeletal phenotype.
  phenotype_term:
    preferred_term: Short thumb
    term:
      id: HP:0009778
      label: Short thumb
- category: Sensory
  name: Conductive Hearing Impairment
  notes: >-
    Hearing loss in FOP is typically conductive rather than sensorineural.
  evidence:
  - reference: PMID:10499116
    reference_title: "Conductive hearing loss in individuals with fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The findings of both studies indicate that individuals with FOP are at
      risk for hearing loss and that the type of loss is predominantly
      conductive in nature
    explanation: >-
      Supports conductive hearing impairment as a recognized non-skeletal
      manifestation of FOP.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
- category: Musculoskeletal
  name: Restricted Mouth Opening
  notes: >-
    Maxillofacial heterotopic ossification can severely restrict jaw opening and
    complicate eating, oral care, and airway management.
  evidence:
  - reference: PMID:28390760
    reference_title: "Restricted Mandibular Movement Attributed to Ossification of Mandibular Depressors and Medial Pterygoid Muscles in Patients With Fibrodysplasia Ossificans Progressiva: A Report of 3 Cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As the condition progresses, HO leads to joint ankylosis, breathing
      difficulties, and mouth-opening restriction, and it can shorten the
      patient's lifespan.
    explanation: >-
      Supports restricted mouth opening as a clinically important manifestation
      of maxillofacial heterotopic ossification.
  phenotype_term:
    preferred_term: Restricted mouth opening
    term:
      id: HP:0000211
      label: Trismus
- category: Skeletal
  name: Proximal Tibial Osteochondromas
  frequency: VERY_FREQUENT
  notes: >-
    These lesions are usually asymptomatic, most commonly bilateral, and
    typically arise near the pes anserinus.
  evidence:
  - reference: PMID:18245597
    reference_title: "Proximal tibial osteochondromas in patients with fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ninety percent of all patients had osteochondroma of the proximal part
      of the tibia.
    explanation: >-
      90% falls in the VERY_FREQUENT band and directly supports proximal tibial
      osteochondromas as a common skeletal manifestation of FOP.
  phenotype_term:
    preferred_term: Proximal tibial osteochondromas
    term:
      id: HP:0030431
      label: Osteochondroma
- category: Respiratory
  name: Restrictive Ventilatory Defect
  notes: >-
    Thoracic heterotopic ossification causes restrictive respiratory mechanics
    and underlies much of the cardiorespiratory mortality in FOP.
  evidence:
  - reference: PMID:40597333
    reference_title: "Respiratory oscillometry in individuals with fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Spirometry showed a uniform pattern of restrictive physiology in all
      eight participants with no significant difference amongst the group.
    explanation: >-
      Supports restrictive ventilatory physiology in a modern FOP cohort.
  - reference: PMID:20194327
    reference_title: "Early mortality and cardiorespiratory failure in patients with fibrodysplasia ossificans progressiva."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common causes of death in patients with fibrodysplasia
      ossificans progressiva were cardiorespiratory failure from thoracic
      insufficiency syndrome (54%; median age, forty-two years) and pneumonia
      (15%; median age, forty years).
    explanation: >-
      Supports thoracic insufficiency syndrome as a major life-limiting
      respiratory complication of FOP.
  phenotype_term:
    preferred_term: Restrictive ventilatory defect
    term:
      id: HP:0002091
      label: Restrictive ventilatory defect
genetic:
- name: ACVR1
  association: Causative
  inheritance:
  - name: Autosomal Dominant
  notes: >-
    The c.617G>A (p.R206H) mutation is found in approximately 97% of
    classically affected individuals. One of the most highly conserved
    disease-causing mutations in the human genome.
  evidence:
  - reference: PMID:17572636
    reference_title: "Functional modeling of the ACVR1 (R206H) mutation in FOP."
    supports: SUPPORT
    snippet: >-
      Substitution of adenine for guanine at nucleotide 617 replaces an
      evolutionarily conserved arginine with histidine at residue 206 of
      ACVR1 in all classically affected individuals, making this one of the
      most highly conserved disease-causing mutations in the human genome.
    explanation: >-
      The R206H mutation is identified as the causative mutation in all
      classic FOP cases and is highly conserved.
  - reference: PMID:29097342
    reference_title: "Variable signaling activity by FOP ACVR1 mutations."
    supports: SUPPORT
    snippet: >-
      Most patients with fibrodysplasia ossificans progressiva (FOP), a rare
      genetic disorder of heterotopic ossification, have the same causative
      mutation in ACVR1, R206H.
    explanation: >-
      Confirms R206H as the predominant mutation while noting variant cases.
  - reference: CGGV:assertion_0439e75f-fc1b-4841-8c9a-17f3568ce8a4-2023-03-01T170000.000Z
    reference_title: "ACVR1 / fibrodysplasia ossificans progressiva (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "ACVR1 | HGNC:171 | fibrodysplasia ossificans progressiva | MONDO:0007606 | AD | Definitive"
    explanation: ClinGen classifies the ACVR1-fibrodysplasia ossificans progressiva gene-disease relationship as definitive with autosomal dominant inheritance.
environmental:
- name: Trauma
  notes: >-
    Physical trauma, including minor injuries, intramuscular injections, and
    surgical procedures, can trigger flare-ups leading to new heterotopic
    ossification. Avoidance of trauma is a key management strategy.
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      palovarotene effectively inhibited HO in injury-induced and genetic
      mouse models of the disease
    explanation: >-
      The use of injury-induced models demonstrates trauma as a key trigger
      for heterotopic ossification in FOP.
- name: Viral Illness
  notes: >-
    Viral infections may trigger inflammatory flare-ups and subsequent
    heterotopic ossification episodes.
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: NO_EVIDENCE
    snippet: >-
      Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable
      genetic disorder of progressive extraskeletal ossification
    explanation: >-
      Snippet does not mention viral illness as a trigger.
treatments:
- name: Palovarotene
  description: >-
    Retinoic acid receptor gamma (RARgamma) agonist that inhibits
    endochondral ossification, the final mandatory step in heterotopic bone
    formation. FDA-approved in 2023 for patients 8 years and older (females)
    and 10 years and older (males).
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      palovarotene maintained joint, limb, and body motion, providing clear
      evidence for its encompassing therapeutic potential as a treatment for FOP.
    explanation: >-
      The study demonstrates palovarotene's therapeutic efficacy in
      preserving mobility in FOP mouse models.
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      palovarotene restored long bone growth, maintained growth plate function,
      and protected growing mutant neonates
    explanation: >-
      Demonstrates palovarotene's ability to preserve skeletal development
      while preventing heterotopic ossification.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: palovarotene
      term:
        id: CHEBI:188559
        label: palovarotene
- name: Corticosteroids
  description: >-
    Used during acute flare-ups to reduce inflammation, though efficacy
    in preventing ossification is limited. Must be administered early
    in flare-ups for potential benefit.
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      Fibrodysplasia ossificans progressiva (FOP), a rare and as yet untreatable
      genetic disorder of progressive extraskeletal ossification
    explanation: >-
      The article notes FOP was untreatable, highlighting the limited efficacy
      of symptomatic treatments like corticosteroids.
  treatment_term:
    preferred_term: systemic corticosteroid therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
- name: Avoidance of Trauma
  description: >-
    Primary preventive strategy including avoidance of intramuscular
    injections, falls, and surgical procedures that may trigger flare-ups.
    Represents a key component of supportive care.
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      palovarotene effectively inhibited HO in injury-induced and genetic
      mouse models of the disease
    explanation: >-
      Since injury induces HO in FOP models, avoidance of trauma is a key
      preventive strategy.
- name: Genetic Counseling
  description: >-
    Essential for affected individuals and families given the autosomal
    dominant inheritance pattern and severe disease burden.
  evidence:
  - reference: PMID:17572636
    reference_title: "Functional modeling of the ACVR1 (R206H) mutation in FOP."
    supports: PARTIAL
    snippet: >-
      Individuals with fibrodysplasia ossificans progressiva are born with
      malformations of the great toes and develop a heterotopic skeleton during
      childhood because of an identical heterozygous mutation
    explanation: >-
      Identification of the causative mutation enables genetic counseling
      and potential prenatal diagnosis.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: MAXO:0000079
      label: genetic counseling
- name: Garetosmab
  description: >-
    Anti-Activin A monoclonal antibody that blocks the neomorphic signaling
    caused by the ACVR1 R206H mutation. Phase 3 OPTIMA trial showed over 90%
    reduction in new heterotopic ossification lesions. Regulatory submission
    expected 2025-2026.
  evidence:
  - reference: PMID:26896819
    reference_title: "Palovarotene Inhibits Heterotopic Ossification and Maintains Limb Mobility and Growth in Mice With the Human ACVR1(R206H) Fibrodysplasia Ossificans Progressiva (FOP) Mutation."
    supports: PARTIAL
    snippet: >-
      Most FOP patients carry an activating mutation in a bone morphogenetic
      protein (BMP) type I receptor gene, ACVR1(R206H), that promotes ectopic
      chondrogenesis and osteogenesis and, in turn, HO
    explanation: >-
      Establishes the molecular rationale for anti-Activin A therapy targeting
      the aberrant signaling through mutant ACVR1.
  notes: >-
    Targets the specific molecular defect in FOP where mutant ACVR1 aberrantly
    responds to Activin A. Represents a mechanism-based targeted therapy.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: garetosmab
      term:
        id: NCIT:C170022
        label: Garetosmab
disease_term:
  preferred_term: fibrodysplasia ossificans progressiva
  term:
    id: MONDO:0007606
    label: fibrodysplasia ossificans progressiva
references:
- reference: DOI:10.1002/jbm4.10821
  title: Palovarotene Action Against Heterotopic Ossification Includes a Reduction of Local Participating Activin <scp>A‐Expressing</scp> Cell Populations
  findings: []
- reference: DOI:10.1073/pnas.1302703111
  title: Hypertrophic chondrocytes can become osteoblasts and osteocytes in endochondral bone formation
  findings: []
- reference: DOI:10.1073/pnas.2019152118
  title: SOX9 keeps growth plates and articular cartilage healthy by inhibiting chondrocyte dedifferentiation/osteoblastic redifferentiation
  findings: []
- reference: DOI:10.1186/s12874-023-02080-7
  title: Study methodology and insights from the palovarotene clinical development program in fibrodysplasia ossificans progressiva
  findings: []
- reference: DOI:10.1631/jzus.b2300779
  title: Advancements in mechanisms and drug treatments for fibrodysplasia ossificans progressiva
  findings: []
- reference: DOI:10.3389/fcell.2017.00047
  title: A Novel Role for the BMP Antagonist Noggin in Sensitizing Cells to Non-canonical Wnt-5a/Ror2/Disheveled Pathway Activation
  findings: []
- reference: DOI:10.3389/fcell.2021.637011
  title: CCDC154 Mutant Caused Abnormal Remodeling of the Otic Capsule and Hearing Loss in Mice
  findings: []
- reference: DOI:10.3390/biom14020147
  title: The HIF-1α and mTOR Pathways Amplify Heterotopic Ossification
  findings: []
- reference: DOI:10.3390/biom14030349
  title: Intersections of Fibrodysplasia Ossificans Progressiva and Traumatic Heterotopic Ossification
  findings: []
- reference: DOI:10.3390/biom14030357
  title: Immunologic Aspects in Fibrodysplasia Ossificans Progressiva
  findings: []
- reference: DOI:10.3390/biomedicines12040779
  title: Cellular and Molecular Mechanisms of Heterotopic Ossification in Fibrodysplasia Ossificans Progressiva
  findings: []
- reference: PMID:24677724
  title: Chondrocyte hypertrophy in skeletal development, growth, and disease.
  findings: []
- reference: PMID:25122769
  title: Mitogen-activated protein kinase (MAPK)-regulated interactions between Osterix and Runx2 are critical for the transcriptional osteogenic program.
  findings: []
- reference: PMID:28473268
  title: The congenital great toe malformation of fibrodysplasia ossificans progressiva? - A close call.
  findings: []
- reference: PMID:33572801
  title: ALK2 Receptor Kinase Association with FKBP12.6 Is Structurally Conserved with the ALK2-FKBP12 Complex.
  findings: []

📚

References & Deep Research

References

DOI:10.1002/jbm4.10821

Palovarotene Action Against Heterotopic Ossification Includes a Reduction of Local Participating Activin <scp>A‐Expressing</scp> Cell Populations