Juvenile Paget Disease

Complex MONDO:0009394 Pathograph 28 Show in embeddings browser Metabolic Bone Disease

Juvenile Paget disease (JPD; OMIM #239000, "Paget disease of bone 5, juvenile-onset"; ORPHA:2801) is an ultra-rare, autosomal-recessive osteopathy of infancy and early childhood, most often caused by biallelic loss of osteoprotegerin (OPG), the secreted decoy receptor encoded by TNFRSF11B that normally sequesters RANKL and restrains osteoclastogenesis. With the OPG brake removed, RANK-RANKL signalling runs unopposed, osteoclasts are grossly increased in number and activity, and the whole skeleton remodels at a rate it is not built for. Coupled osteoblastic formation cannot keep pace in an orderly way, so resorbed bone is replaced by disorganised woven bone; the child develops generalised osteopenia, progressive long-bone bowing and fractures, macrocephaly and skull-base hyperostosis, and grossly elevated serum alkaline phosphatase (the name "hereditary/idiopathic hyperphosphatasia" records that laboratory signature). Two contrasts anchor the entry. First, JPD is emphatically NOT adult Paget disease of bone (curated separately as Paget_Disease_of_Bone). Adult PDB is a focal, late-onset, usually SQSTM1-associated disorder of a handful of lesions; JPD is a generalised, whole-skeleton process of childhood driven by a different gene through the same RANK-RANKL-OPG axis. The adult entry explicitly cites loss of OPG causing JPD as the cleanest evidence that this axis is the centre of gravity of pagetic biology; this entry does not reproduce the adult disease. Second, JPD is genetically heterogeneous: while biallelic TNFRSF11B loss of function is the predominant cause, a heterozygous activating duplication in TNFRSF11A (RANK) and a de novo neomorphic SP7 (Osterix) variant have each been reported to produce a JPD phenotype through convergent high-turnover biology, so the disease is not inheritance-uniform across its causal genes. The extraskeletal disease is where OPG's non-osteoclastic roles surface, and it is partly uncoupled from bone. Sensorineural hearing loss reflects a direct cochlear requirement for OPG (spiral-ganglion degeneration), layered on conductive loss from ossicular resorption; progressive retinopathy with angioid streaks and a vasculopathy with arterial calcification and aneurysms reflect OPG's vascular role. Anti-resorptive therapy (bisphosphonates first-line; the RANKL antibody denosumab as a direct pathophysiologic mimic of the missing protein, with careful calcium monitoring) controls the skeletal disease well but does not reliably prevent the retinopathy, an important prognostic caveat.

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1
Inheritance
9
Pathophys.
13
Phenotypes
1
Gaps
28
Pathograph
3
Genes
5
Medical Actions
1
Models
1
Deep Research
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Inheritance

1
Autosomal recessive (TNFRSF11B/OPG deficiency, predominant form) HP:0000007
The great majority of JPD is autosomal-recessive OPG deficiency from homozygous or compound-heterozygous loss-of-function variants in TNFRSF11B, with consanguinity and geographic founder alleles (e.g. a Navajo homozygous deletion; a "Balkan" 966_969delTGACinsCTT indel) recurrent in the reported cohort. The genetically distinct minority forms — a heterozygous activating TNFRSF11A (RANK) duplication and a de novo heterozygous neomorphic SP7 variant — behave dominantly and are recorded in the genetic section rather than here.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:12124406 SUPPORT Human Clinical
"Juvenile Paget's disease, an autosomal recessive osteopathy, is characterized by rapidly remodeling woven bone, osteopenia, fractures, and progressive skeletal deformity."
The defining paper states the autosomal-recessive mode and the core skeletal phenotype of the predominant OPG-deficiency form.
PMID:26762549 SUPPORT Human Clinical
"Autosomal recessive transmission of loss-of-function mutations within TNFRSF11B encoding OPG accounts for most JPD (JPD1). JPD2 results from heterozygous constitutive activation of TNFRSF11A encoding RANK."
States both the recessive OPG-deficiency form (JPD1) and the dominant RANK-activation form (JPD2), supporting the genetic heterogeneity recorded here.
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Discussions and Knowledge Gaps

1
Why does JPD retinopathy progress despite excellent skeletal disease control on anti-resorptive therapy, and is the ocular/vascular arm mechanistically uncoupled from the osteoclast axis that bisphosphonates and denosumab target?
OPEN QUESTION OPEN jpd-retinopathy-uncoupling
Attached to
pathophysiology#Ectopic Vascular and Bruch-Membrane Calcification phenotypes#Angioid Streaks and Retinopathy
In the long-term denosumab cohort, retinopathy progressed (including sudden vision loss requiring anti-VEGF therapy) despite normalised ALP and no new fractures. This suggests the Bruch-membrane/vascular calcification arm of OPG deficiency is at least partly independent of the RANKL-osteoclast axis, with direct implications for surveillance (ongoing ophthalmology regardless of skeletal control) and for whether RANKL-pathway therapy can ever prevent the ocular disease.
Show evidence (1 reference)
PMID:40223037 SUPPORT Human Clinical
"long-term denosumab administration in adults with JPD, who had been previously treated with bisphosphonates, was safe and effective in terms of the skeletal disease, but it may not prevent the emergence of retinopathy."
Documents the retinopathy-despite-skeletal-control observation motivating this question.
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Pathophysiology

9
Biallelic TNFRSF11B Loss of Function
Mechanism confidence: Established
Homozygous or compound-heterozygous loss-of-function variants in TNFRSF11B (whole-gene/multi-exon deletions, splice, and ligand-binding-domain missense alleles) abolish or cripple secreted osteoprotegerin. The initiating lesion of the predominant form; the Whyte 2002 index Navajo patients carried a homozygous ~100 kb deletion and had undetectable circulating OPG.
Genetic context TNFRSF11B hgnc:11909 HUGO Gene Nomenclature Committee (hgnc) Relation: this genetic context concerns this gene This genetic context concerns TNFRSF11B (hgnc:11909). hgnc:11909 is a gene from the HUGO Gene Nomenclature Committee. functional_impact_category: LOSS_OF_FUNCTION
Downstream
Loss of OPG Decoy Inhibition of RANKL
Cochlear OPG Deficiency and Spiral Ganglion Degeneration
Ectopic Vascular and Bruch-Membrane Calcification
Show evidence (3 references)
PMID:12124406 SUPPORT Human Clinical
"Both patients had a homozygous deletion of TNFRSF11B, with identical break points, on chromosome 8q24.2."
Establishes the causal biallelic TNFRSF11B deletion in the index patients.
PMID:12124406 SUPPORT Human Clinical
"We found that serum levels of osteoprotegerin and soluble osteoclast differentiation factor were undetectable and markedly increased, respectively."
Confirms loss of the OPG protein product (undetectable serum OPG) with reciprocally elevated RANKL, the direct biochemical consequence of the null genotype.
PMID:37180975 SUPPORT Human Clinical
"The mutant OPG is unable to block osteoclastic resorption in a bone culture system, demonstrating that it is a loss-of-function mutation (Chong et al., 2003)."
Functional confirmation that the JPD-associated TNFRSF11B alleles act by loss of function.
Loss of OPG Decoy Inhibition of RANKL
Mechanism confidence: Established
Osteoprotegerin normally acts as a soluble decoy receptor that binds RANKL and prevents it from engaging RANK on osteoclast precursors. With OPG absent, RANKL is no longer sequestered and is free to drive RANK signalling — the single molecular switch that connects the genetic lesion to accelerated osteoclastogenesis.
osteoblast (OPG source) CL:0000062 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves osteoblast (OPG source), annotated with osteoblast (CL:0000062). CL:0000062 is a cell type from the Cell Ontology.
negative regulation of bone resorption GO:0045779 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves negative regulation of bone resorption (GO:0045779), qualified as loss of function. GO:0045779 is a biological process from the Gene Ontology. ⇓ LOSS OF FUNCTION
Downstream
Unopposed RANK-RANKL Osteoclastogenesis
Show evidence (2 references)
PMID:12124406 SUPPORT Human Clinical
"osteoprotegerin suppresses bone turnover by functioning as a decoy receptor for osteoclast differentiation factor (also called RANK ligand)."
States OPG's decoy-receptor function whose loss defines this node.
PMID:40775369 SUPPORT Human Clinical
"OPG is a soluble factor released from pre-osteoblasts and osteoblasts, which in complex with the osteoclast differentiation factor, also known as receptor activator of nuclear factor-kappa B ligand (RANKL)"
Independent statement of the OPG-RANKL decoy mechanism whose loss is the JPD lesion.
Unopposed RANK-RANKL Osteoclastogenesis
Mechanism confidence: Established
Free RANKL engages RANK on osteoclast precursors, driving markedly increased osteoclast differentiation. This is the step denosumab (an anti-RANKL antibody) targets, restoring pharmacologically the ligand neutralisation the missing OPG can no longer provide.
osteoclast precursor (monocyte-macrophage lineage) CL:0000576 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves osteoclast precursor (monocyte-macrophage lineage), annotated with monocyte (CL:0000576). CL:0000576 is a cell type from the Cell Ontology.
positive regulation of osteoclast differentiation GO:0045672 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased positive regulation of osteoclast differentiation (GO:0045672). GO:0045672 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Accelerated Osteoclastic Bone Resorption
Show evidence (2 references)
PMID:22638612 SUPPORT Human Clinical
"This gene encodes a soluble protein, the osteoprotegerin, which leads to uncontrolled osteoclastogenesis when mutated."
States that loss of OPG produces uncontrolled osteoclastogenesis, the process of this node.
PMID:23788687 SUPPORT Human Clinical
"JPD can be caused by loss of function of osteoprotegerin, resulting in subsequent stimulation of osteoclasts via the receptor activator of nuclear factor-κB (RANK) pathway."
Names the RANK-pathway stimulation of osteoclasts that this node captures.
Accelerated Osteoclastic Bone Resorption
Mechanism confidence: Established
Excess, hyperactive osteoclasts resorb bone throughout the skeleton at a grossly accelerated rate. In the OPG-null mouse this is directly observed as numerous osteoclasts with rapidly remodelling bone, recapitulating the human disease.
multinucleated osteoclast CL:0000092 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves multinucleated osteoclast, annotated with osteoclast (CL:0000092). CL:0000092 is a cell type from the Cell Ontology.
bone resorption GO:0045453 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased bone resorption (GO:0045453). GO:0045453 is a biological process from the Gene Ontology. ↑ INCREASED
Animal models
Opg-knockout mouse (Tnfrsf11b-/-) Mouse recapitulates Opg-null mice show enhanced osteoclastic resorption and progressive skeletal disease.
Downstream
Compensatory Disorganized Woven-Bone Formation
Generalized High-Turnover Osteopathy
Show evidence (2 references)
PMID:16564235 SUPPORT Model Organism
"Osteoclastic bone resorption is enhanced in Opg(-/-) mice lacking osteoprotegerin, which is a soluble decoy receptor for the osteoclastogenic cytokine RANKL."
The OPG-null mouse directly demonstrates enhanced osteoclastic resorption on loss of the decoy receptor.
PMID:25063546 SUPPORT Human Clinical
"Histopathology showed accelerated remodeling with abundant osteoclasts."
Human bone histology confirming abundant osteoclasts and accelerated remodelling.
Compensatory Disorganized Woven-Bone Formation
Mechanism confidence: Established
Coupled osteoblastic formation increases in response to the resorptive drive but cannot organise, so resorbed bone is replaced by structurally disorganised woven bone rather than mature lamellar bone across the whole skeleton — the generalised (not focal) counterpart of the adult pagetic mosaic.
osteoblast CL:0000062 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves osteoblast (CL:0000062). CL:0000062 is a cell type from the Cell Ontology.
ossification (disorganized, woven) GO:0001503 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased ossification (disorganized, woven), annotated with ossification (GO:0001503). GO:0001503 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Generalized High-Turnover Osteopathy
Show evidence (1 reference)
PMID:12124406 SUPPORT Human Clinical
"Juvenile Paget's disease, an autosomal recessive osteopathy, is characterized by rapidly remodeling woven bone, osteopenia, fractures, and progressive skeletal deformity."
States the rapidly remodelling woven bone that is the tissue-level signature of this node.
Generalized High-Turnover Osteopathy
Mechanism confidence: Established
The whole-skeleton, high-turnover disease state: osteopenic, mechanically inferior woven bone that bows, fractures, expands the calvarium and skull base, and spills grossly elevated alkaline phosphatase into serum. Downstream are the clinical manifestations and the ALP laboratory signature.
Downstream
Progressive Long-Bone Deformity
Recurrent Fractures
Bone Pain
Short Stature
Kyphoscoliosis
Vertebral Compression Fracture
Elevated Serum Alkaline Phosphatase
Auricular Ossification
Cranial and Skull-Base Hyperostosis
Show evidence (1 reference)
PMID:23788687 SUPPORT Human Clinical
"Increased bone turnover and lack of bone modeling lead to severe deformities, frequent fractures, short stature, and loss of hearing."
Directly links the high-turnover state to the deformity, fracture, short-stature, and hearing-loss manifestations drawn downstream here.
Cranial and Skull-Base Hyperostosis
Mechanism confidence: Established
High-turnover remodelling of the calvarium and skull base produces diploic thickening, basilar/orbital-roof and sphenoid sclerosis, an enlarged clivus, and progressive macrocephaly; the thickened temporal bone and ossicular disease contribute the conductive component of hearing loss.
Downstream
Macrocephaly
Conductive Hearing Impairment
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"The radiograph in early adulthood reveals marked widening of the skull with periosteal appositions both on the internal and external lamina, bossing of the frontal sinus, diffuse osteosclerosis"
Radiographic documentation of the calvarial/skull-base hyperostosis this node describes.
Cochlear OPG Deficiency and Spiral Ganglion Degeneration
Mechanism confidence: Provisional
A skeleton-independent arm. Spiral-ganglion cells secrete OPG at high levels; in the OPG-null mouse, OPG loss causes demyelination and degeneration of the cochlear nerve and sensitises spiral-ganglion cells to apoptosis (via ERK), producing a primary sensorineural hearing loss that compounds the conductive loss from ossicular/temporal-bone disease. The human sensorineural component is inferred from this model plus the clinical deafness of JPD, so the node is marked provisional.
spiral ganglion neuron CL:0011113 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves spiral ganglion neuron (CL:0011113). CL:0011113 is a cell type from the Cell Ontology.
neuron apoptotic process (spiral ganglion) GO:0051402 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased neuron apoptotic process (spiral ganglion), annotated with neuron apoptotic process (GO:0051402). GO:0051402 is a biological process from the Gene Ontology. ↑ INCREASED
Animal models
Opg-knockout mouse (Tnfrsf11b-/-) Mouse recapitulates OPG-null mice reproduce the cochlear-nerve degeneration and sensorineural loss of JPD.
Downstream
Sensorineural Hearing Impairment
Show evidence (2 references)
PMID:23607938 SUPPORT Model Organism
"OPG deficiency caused demyelination and degeneration of the cochlear nerve in vivo."
Establishes the direct cochlear-nerve degeneration mechanism of sensorineural loss in OPG deficiency.
PMID:23607938 SUPPORT Model Organism
"It also activated ERK, sensitized spiral ganglion cells (SGC) to apoptosis"
Names the ERK-dependent spiral-ganglion apoptosis captured by this node.
Ectopic Vascular and Bruch-Membrane Calcification
Mechanism confidence: Hypothetical
A hypothesised extraskeletal arm reflecting OPG's vascular-protective role. OPG/RANKL dysfunction is proposed to promote calcification of Bruch membrane (producing angioid streaks liable to choroidal neovascularisation) and of arterial walls (vascular microcalcification with a predisposition to carotid and iliac aneurysms). The clinical associations are well documented; the mechanistic link is inferential, and the retinopathy notably progresses despite good skeletal disease control, indicating partial uncoupling from the osteoclast axis.
Downstream
Angioid Streaks and Retinopathy
Vascular Calcification and Arterial Aneurysm
Show evidence (2 references)
PMID:20547946 SUPPORT INDIRECT Human Clinical
"Osteoprotegerin or its signaling pathway may have a role in calcification of Bruch membrane and in the pathogenesis of angioid streaks."
States the proposed (hypothesised) Bruch-membrane calcification mechanism; directness INDIRECT because the paper frames it as a hypothesis rather than a demonstrated step.
PMID:25063546 SUPPORT INDIRECT Human Clinical
"This OPG deficiency form of JPD uniquely leads to vascular microcalcification (VMC)(14) that perhaps explains carotid aneurysms in childhood(15) and retinopathy with blindness in adult life."
Links OPG-deficiency vascular microcalcification to the carotid aneurysm and retinopathy phenotypes; "perhaps explains" marks the inferential status recorded here.
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Pathograph

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

13
Cardiovascular 1
Vascular Calcification and Arterial Aneurysm OCCASIONAL Arterial calcification HP:0003207 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Vascular calcification with arterial aneurysm predisposition, annotated with Arterial calcification (HP:0003207). HP:0003207 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25063546 SUPPORT Human Clinical
"This OPG deficiency form of JPD uniquely leads to vascular microcalcification (VMC)(14) that perhaps explains carotid aneurysms in childhood(15) and retinopathy with blindness in adult life."
Documents the vascular microcalcification and carotid-aneurysm association.
Ear 3
Sensorineural Hearing Impairment VERY_FREQUENT HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing impairment (HP:0000407), qualified as course progressive. HP:0000407 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"Most patients exhibit hearing impairment or complete hearing loss, which may be caused by ossicle deformities in the internal ear and/or sensorineural hearing loss due to demyelination and degeneration of the acoustic nerve, caused by osteoprotegerin deficiency."
States the dual conductive/sensorineural mechanism and the OPG-deficiency cause of the sensorineural component.
Conductive Hearing Impairment FREQUENT HP:0000405 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Conductive hearing impairment (HP:0000405). HP:0000405 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:25063546 SUPPORT Human Clinical
"Deafness at age 2years involved missing ossicles and eroded cochleas."
Documents the ossicular basis of the conductive hearing loss.
Auricular Ossification OCCASIONAL Calcification of the auricular cartilage HP:0005103 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Auricular (pinna) elastic-cartilage ossification, annotated with Calcification of the auricular cartilage (HP:0005103). HP:0005103 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26762549 SUPPORT Human Clinical
"We report auricular ossification (AO) affecting the elastic cartilage of the ear as a newly recognized feature of osteoprotegerin (OPG)-deficiency juvenile Paget disease (JPD)."
Establishes auricular ossification as a recognised JPD feature.
Eye 1
Angioid Streaks and Retinopathy FREQUENT HP:0001102 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Angioid streaks with progressive retinopathy, annotated with Angioid streaks (HP:0001102), qualified as course progressive. HP:0001102 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (2 references)
PMID:20547946 SUPPORT Human Clinical
"Juvenile Paget disease is associated with progressive retinopathy characterized by the development of angioid streaks, which may be complicated by choroidal neovascularization, the predominant cause of visual loss."
Defines the progressive angioid-streak retinopathy and its neovascular complication.
PMID:20547946 SUPPORT Human Clinical
"Retinal abnormalities were evident in 12 of 14 eyes"
Provides the numerator/denominator (12 of 14 examined eyes) behind the frequency.
Head and Neck 1
Macrocephaly FREQUENT HP:0000256 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Macrocephaly (HP:0000256). HP:0000256 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"The first anatomical abnormalities appeared at age three, i.e., macrocephaly (head circumference + 2.6 SD)"
Quantifies the macrocephaly with an exact head-circumference SD in a confirmed case.
Limbs 1
Progressive Long-Bone Deformity VERY_FREQUENT Bowing of the long bones HP:0006487 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Progressive long-bone bowing deformity, annotated with Bowing of the long bones (HP:0006487), qualified as course progressive. HP:0006487 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (1 reference)
PMID:22638612 SUPPORT Human Clinical
"show a phenotype characterized by progressive bone deformities, fractures, and short stature."
Names progressive bone deformity as a core JPD phenotype.
Metabolism 1
Elevated Serum Alkaline Phosphatase VERY_FREQUENT Elevated circulating alkaline phosphatase concentration HP:0003155 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Markedly elevated serum alkaline phosphatase, annotated with Elevated circulating alkaline phosphatase concentration (HP:0003155). HP:0003155 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"A biochemical evaluation revealed increased levels of serum alkaline phosphatase (ALP), reaching 75.75 µkat/L at age four, which is 15 times above the upper limit of normal (ULN)."
Exact quantified ALP elevation in a molecularly confirmed JPD patient.
Musculoskeletal 3
Recurrent Fractures VERY_FREQUENT HP:0002757 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Recurrent fractures (HP:0002757). HP:0002757 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"The first fracture occurred at age three."
Documents early-childhood fracture onset in a molecularly confirmed JPD patient.
Kyphoscoliosis FREQUENT HP:0002751 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Kyphoscoliosis (HP:0002751). HP:0002751 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"the patient manifested gradual and progressive growth disproportion, i.e., short trunk, longer limbs, larger chest, scoliosis of the spine, and valgosity of the lower extremities"
Documents progressive scoliosis/spinal deformity in a confirmed JPD patient.
Vertebral Compression Fracture OCCASIONAL HP:0002953 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Vertebral compression fracture (HP:0002953). HP:0002953 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"Discrete compressions of C3–C5 vertebral bodies are noticeable"
Radiographic documentation of vertebral compression in a confirmed JPD patient.
Constitutional 1
Bone Pain FREQUENT HP:0002653 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bone pain (HP:0002653). HP:0002653 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23788687 SUPPORT Human Clinical
"Additionally, bone pain was more efficiently controlled with denosumab."
Reports treatment-responsive bone pain, supporting it as a turnover-linked JPD symptom.
Growth 1
Short Stature FREQUENT HP:0004322 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short stature (HP:0004322). HP:0004322 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:23788687 SUPPORT Human Clinical
"Increased bone turnover and lack of bone modeling lead to severe deformities, frequent fractures, short stature, and loss of hearing."
Lists short stature among the core JPD manifestations.
🧬

Genetic Associations

3
TNFRSF11B
Gene: TNFRSF11B hgnc:11909 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TNFRSF11B (hgnc:11909). hgnc:11909 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (2 references)
PMID:12124406 SUPPORT Human Clinical
"Juvenile Paget's disease can result from osteoprotegerin deficiency caused by homozygous deletion of TNFRSF11B."
Establishes TNFRSF11B (OPG) as the causal gene of the predominant form.
PMID:22638612 SUPPORT Human Clinical
"JPD is characterized by a strong genotype-phenotype correlation, so depending on the alteration of the TNFRSN11B gene, the phenotype is variable."
States the TNFRSF11B genotype-phenotype correlation summarised in the notes (the quoted sentence carries the source's own TNFRSN11B typo).
TNFRSF11A
Gene: TNFRSF11A hgnc:11908 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is TNFRSF11A (hgnc:11908). hgnc:11908 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: GERMLINE
Show evidence (1 reference)
PMID:25063546 SUPPORT Human Clinical
"a unique heterozygous 15-bp insertional tandem duplication (87dup15) within exon 1 of TNFRSF11A predicted the same pentapeptide extension of RANK that causes expansile skeletal hyperphosphatasia (84dup15)."
Documents the activating TNFRSF11A duplication as an alternative JPD cause.
SP7
Gene: SP7 hgnc:17321 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is SP7 (hgnc:17321). hgnc:17321 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE variant_origin: DE_NOVO
Show evidence (2 references)
PMID:32298837 SUPPORT Human Clinical
"trio exome sequencing revealed a de novo heterozygous missense mutation (c.926C>G; p.S309W) within SP7 encoding the osteoblast transcription factor osterix"
Identifies the de novo SP7 variant in a patient with JPD.
PMID:32298837 SUPPORT Human Clinical
"Thus, mutation of SP7 represents a third genetic cause of JPD."
Establishes SP7 as the third reported causal gene, supporting the description's claim.
💊

Medical Actions

5
Bisphosphonate Therapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: pamidronate CHEBI:7903 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses pamidronate (CHEBI:7903). CHEBI:7903 is a therapeutic agent from Chemical Entities of Biological Interest. zoledronic acid CHEBI:46557 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses zoledronic acid (CHEBI:46557). CHEBI:46557 is a therapeutic agent from Chemical Entities of Biological Interest. alendronic acid CHEBI:2567 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses alendronic acid (CHEBI:2567). CHEBI:2567 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
First-line and best-established therapy. IV pamidronate or zoledronic acid, or oral alendronate/ibandronate, suppress the accelerated osteoclastic resorption, normalise or near-normalise ALP and other turnover markers, prevent new fractures, halt deformity progression, and produce striking motor-developmental recovery when started early in childhood and continued through growth. Turnover suppression relapses if treatment is discontinued; therapy is not curative.
Mechanism Target:
INHIBITS Accelerated Osteoclastic Bone Resorption — Bisphosphonates inhibit osteoclastic bone resorption, the effector step of JPD.
Show evidence (1 reference)
PMID:33850973 SUPPORT Human Clinical
"Individualized intravenous treatment with pamidronate resulted in sufficient control of bone pain and suppression of bone turnover with few side effects over the observation period."
Demonstrates bisphosphonate suppression of bone turnover and pain in two children with JPD.
Show evidence (2 references)
PMID:33850973 SUPPORT Human Clinical
"Motor development was delayed in both children before treatment with bisphosphonates was commenced and improved thereafter."
Documents functional (motor-developmental) benefit of early bisphosphonate therapy.
PMID:40775369 SUPPORT Human Clinical
"Early diagnosis and antiresorption treatment prevent further fractures and deformity progression, and improve the patient's quality of life."
States the fracture/deformity-preventing benefit of early anti-resorptive treatment.
Denosumab
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: denosumab NCIT:C61313 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses denosumab (NCIT:C61313). NCIT:C61313 is a therapeutic agent from the NCI Thesaurus.
Platform: Monoclonal antibody
A humanised anti-RANKL monoclonal antibody — the most direct pharmacologic mimic of the missing OPG, neutralising the RANKL that OPG can no longer sequester. Achieves good skeletal control (ALP normalisation, pain relief) in JPD but carries a substantial risk of severe hypocalcemia when high pretreatment turnover is abruptly shut off, so calcium must be monitored closely; pediatric use in particular demands caution. Does not reliably prevent retinopathy progression.
Mechanism Target:
INHIBITS Unopposed RANK-RANKL Osteoclastogenesis — Denosumab binds RANKL and prevents RANK engagement, replacing OPG's lost decoy function.
Show evidence (1 reference)
PMID:23788687 SUPPORT Human Clinical
"Alkaline phosphatase levels dropped within the normal range and remained at normal levels for 5 months after the final dose of denosumab."
Demonstrates RANKL-antibody suppression of turnover (ALP normalisation) in JPD.
Show evidence (2 references)
PMID:23788687 SUPPORT Human Clinical
"concomitant with the first injection, severe hypocalcemia developed, for which the patient was hospitalized and iv calcium supplementation was required for 13 days."
Documents the severe-hypocalcemia hazard that governs pediatric denosumab dosing in JPD.
PMID:40223037 SUPPORT Human Clinical
"long-term denosumab administration in adults with JPD, who had been previously treated with bisphosphonates, was safe and effective in terms of the skeletal disease, but it may not prevent the emergence of retinopathy."
Establishes durable skeletal efficacy but persistent retinopathy risk despite treatment.
Recombinant Osteoprotegerin (investigational)
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Platform: Protein replacement
Direct protein replacement of the missing decoy receptor. In two adult siblings, once-weekly subcutaneous recombinant OPG suppressed bone resorption and increased bone mass over 15 months with only mild hypocalcemia/ hypophosphatemia — proof of mechanism for OPG replacement, but never developed into an approved product (denosumab is the practical RANKL-pathway therapeutic).
Mechanism Target:
RESTORES Loss of OPG Decoy Inhibition of RANKL — Recombinant OPG restores the decoy-receptor sequestration of RANKL that the null genotype abolishes.
Show evidence (1 reference)
PMID:16135836 SUPPORT Human Clinical
"Bone resorption (assessed by N-telopeptide excretion) was suppressed by once-weekly subcutaneous doses of 0.3 to 0.4 mg per kilogram of body weight."
Demonstrates that replacing OPG directly suppresses the resorptive drive.
Show evidence (1 reference)
PMID:16135836 SUPPORT Human Clinical
"After 15 months of treatment, radial bone mass increased in one patient by 9 percent and in the other by 30 percent, skeletal bisphosphonate retention decreased by 37 percent and 55 percent, respectively"
Quantifies the bone-mass and resorption response to recombinant OPG replacement.
Calcitonin (historical)
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: calcitonin CHEBI:3306 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses calcitonin (CHEBI:3306). CHEBI:3306 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Peptide
An inhibitor of bone resorption used before bisphosphonates and denosumab became standard; now largely superseded but part of the historical treatment record.
Show evidence (1 reference)
PMID:23788687 SUPPORT Human Clinical
"The treatment for JPD is challenging and has previously been based on administration of either calcitonin or bisphosphonates."
Records calcitonin as a prior standard anti-resorptive for JPD.
Anti-VEGF Intravitreal Therapy
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: bevacizumab CHEBI:749495 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses bevacizumab (CHEBI:749495). CHEBI:749495 is a therapeutic agent from Chemical Entities of Biological Interest. aflibercept CHEBI:750062 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses aflibercept (CHEBI:750062). CHEBI:750062 is a therapeutic agent from Chemical Entities of Biological Interest.
Intravitreal anti-vascular-endothelial-growth-factor agents (bevacizumab, aflibercept) for the choroidal neovascularisation that complicates JPD angioid-streak retinopathy — the ocular treatment arm. It targets the neovascular complication rather than the underlying bone disease, and is part of the ophthalmologic surveillance/management that continues independently of skeletal disease control. In the long-term denosumab cohort one subject with sudden vision loss had almost full visual recovery after intravitreal bevacizumab and aflibercept.
Mechanism Target:
MODULATES Angioid Streaks and Retinopathy — Anti-VEGF inhibits the VEGF-driven choroidal neovascularisation that complicates the retinopathy, managing the predominant cause of visual loss without reversing the underlying angioid streaks/vasculopathy.
Show evidence (1 reference)
PMID:40223037 SUPPORT Human Clinical
"She had almost full recovery of vision following intravitreal treatment with bevacizumab (once) and aflibercept (four times)"
Documents anti-VEGF intravitreal therapy rescuing vision in JPD choroidal neovascularisation.
Show evidence (1 reference)
PMID:40223037 SUPPORT Human Clinical
"She had almost full recovery of vision following intravitreal treatment with bevacizumab (once) and aflibercept (four times)"
Establishes the anti-VEGF ocular treatment arm and its efficacy for the retinopathy complication.
🔬

Biochemical Markers

1
Serum alkaline phosphatase (total) (Increased)
Context: Grossly elevated total serum ALP is the cardinal biochemical marker of JPD disease extent/activity, reflecting the accelerated osteoblastic response to high-turnover bone. Often >10-15x the upper limit of normal at diagnosis; used to titrate anti-resorptive therapy. Urinary collagen cross-links and P1NP/BAP/beta-CrossLaps corroborate the high-turnover state.
Reference Ranges
Alkaline phosphatase [Enzymatic activity/volume] in Serum or Plasma 25.0–120.0 IU/L (adults (assay-specific normal range as reported in the cited JPD cohort))
Normal (25.0–120.0 IU/L) Elevated (JPD activity range) (120.0– IU/L) → Elevated circulating alkaline phosphatase concentration
Elevated (JPD activity range): Values above the upper reference limit indicate active high-turnover bone disease; untreated JPD characteristically runs many multiples of the ULN.
Adult reference interval 25-120 IU/l as stated for the long-term denosumab JPD cohort; off-treatment JPD ALP in that cohort ran 630-2500 IU/l, i.e. roughly 5-20x the upper limit.
Show evidence (1 reference)
PMID:40223037 SUPPORT Human Clinical
"Off treatment, ALP was 1300–2500 IU/l (reference range 25–120 IU/l)."
Provides both the adult ALP reference interval and the magnitude of the JPD elevation.
Show evidence (1 reference)
PMID:40223037 SUPPORT Human Clinical
"Accelerated bone turnover as assessed by biochemical markers, such as alkaline phosphatase (ALP), can be suppressed by bisphosphonate treatment, but it relapses if bisphosphonate treatment is discontinued."
Establishes ALP as the activity marker that tracks (and relapses with) turnover in JPD.
🔬

Diagnosis

6
Molecular genetic testing of TNFRSF11B (with deletion/CNV analysis)
First-tier confirmatory test is sequencing of TNFRSF11B. Crucially, several families — including the index Navajo kindred — carry homozygous whole-gene or multi-exon deletions of TNFRSF11B that Sanger/exon sequencing alone will miss, so copy-number/deletion (CNV) analysis must accompany sequencing. TNFRSF11A and SP7 are second-tier for TNFRSF11B-negative cases.
molecular genetic testing NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:12124406 SUPPORT Human Clinical
"Both patients had a homozygous deletion of TNFRSF11B, with identical break points, on chromosome 8q24.2."
The disease-causing lesion is a whole-gene deletion, establishing why CNV/deletion analysis must accompany sequencing rather than sequencing alone.
Skeletal radiography
Generalised (not focal) radiographic disease: osteopenic/osteosclerotic long bones with cortical thickening (hyperostosis), coarse trabeculation, calvarial and skull-base thickening; the generalised distribution distinguishes JPD from the focal lesions of adult Paget disease.
skeletal radiography NCIT:C137876 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"a diffuse modeling disorder in long bones, presenting as extremely thickened cortical bone composed of widespread smooth periosteal appositions"
Describes the characteristic generalised radiographic modelling disorder.
Bone turnover markers
Grossly elevated markers of high bone turnover support the diagnosis and are the mainstay of activity monitoring; urinary collagen cross-links are now preferred over hydroxyproline.
laboratory measurement of bone turnover markers NCIT:C25294 NCI Thesaurus (NCIT)
Markers: Serum alkaline phosphatase (cardinal), urinary pyridinoline/deoxypyridinoline collagen cross-links, P1NP, bone-specific ALP, beta-CrossLaps, osteocalcin, TRAP5b, N-telopeptide — all elevated at baseline and used to titrate therapy.
Show evidence (1 reference)
PMID:32298837 SUPPORT Human Clinical
"several markers of bone turnover were elevated and included striking hyperphosphatasemia"
Documents the elevated bone-turnover-marker profile used diagnostically.
Audiometry (hearing surveillance)
Serial audiometry for the progressive mixed conductive/sensorineural hearing loss that is very common in JPD.
audiometry NCIT:C38036 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"Most patients exhibit hearing impairment or complete hearing loss, which may be caused by ossicle deformities in the internal ear and/or sensorineural hearing loss due to demyelination and degeneration of the acoustic nerve, caused by osteoprotegerin deficiency."
Establishes the high frequency and dual mechanism of hearing loss that mandates audiometric surveillance.
Ophthalmologic examination (retinopathy surveillance)
Dilated fundus examination / fundus imaging for angioid streaks, retinal pigment epithelium changes and choroidal neovascularisation; surveillance continues regardless of skeletal disease control because retinopathy can progress independently.
dilated fundus examination NCIT:C120698 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:20547946 SUPPORT Human Clinical
"Participants underwent ophthalmic examinations consisting of at least best-corrected Snellen visual acuity and dilated fundal examination or color fundus photography."
Describes the fundus examination used to detect the JPD retinopathy under surveillance.
Vascular imaging (aneurysm surveillance)
Vascular imaging as clinically indicated for the internal-carotid and iliac aneurysms reported in JPD; no formal screening protocol exists given the ultra-rarity and case-report-level evidence, so this is directed rather than routine.
vascular imaging NCIT:C190557 NCI Thesaurus (NCIT)
Left without a dedicated evidence item: aneurysm reports are case-level and the vascular association is already cited on the vasculopathy phenotype/node.
📈

Progression

1
Infantile/childhood onset with lifelong progressive high-turnover disease
Age: Infancy to early childhood onset; progressive through the adolescent growth spurt
JPD presents in infancy or early childhood with fractures and deformity and, untreated, progresses through the growth years; severe forms carry high morbidity and can be fatal in childhood or young adulthood. Early anti-resorptive treatment halts deformity/fracture progression; there is no spontaneous remission, and turnover relapses if bisphosphonate therapy is stopped. Extraskeletal disease (retinopathy, vascular) can progress even under good skeletal control.
Show evidence (2 references)
PMID:32298837 SUPPORT Human Clinical
"present in infancy or early childhood as fractures and deformity hallmarked biochemically by marked elevation of serum alkaline phosphatase (ALP) activity"
States the infantile/early-childhood onset and the fracture/deformity presentation.
PMID:32298837 SUPPORT Human Clinical
"Untreated, JPD can kill during childhood or young adult life."
States the progressive, potentially fatal untreated course.
📊

Prevalence

1
Worldwide
Cases In Literature <1 in 1,000,000
Ultra-rare. Approximately 80 cases have been reported worldwide since the disease was first described in 1956; no registry-based prevalence exists, so this is a literature-count estimate read as case-series-level evidence. A numeric rate_per_100000 is deliberately omitted: the modelled "<1 in 10 million" figure is an order-of-magnitude estimate, not a measured population rate, so prevalence_class BELOW_1_IN_1000000 carries the claim instead.
Show evidence (1 reference)
PMID:40775369 SUPPORT Human Clinical
"Approximately 80 cases of JPD have been described worldwide since 1956"
Gives the literature case count that grounds the ultra-rare classification.
🐁

Animal Models

1
Opg-knockout mouse (Tnfrsf11b-/-)
The primary and best-validated JPD model. Osteoprotegerin-null mice show numerous osteoclasts and rapidly remodelling woven bone (recapitulating the skeletal disease), and reproduce the dual deafness of JPD — conductive loss from ossicular resorption plus sensorineural loss from cochlear-nerve degeneration.
Species
Mouse
Genotype
Tnfrsf11b (Opg) homozygous knockout
Publication
PMID:23607938
Pathograph links
Cochlear OPG Deficiency and Spiral Ganglion Degeneration recapitulates fidelity: moderate observes: cellular OPG-null mice reproduce the cochlear-nerve degeneration and sensorineural loss of JPD.
Limitations: Mouse cochlear ageing/degeneration biology differs from human; the model demonstrates the mechanism but the human sensorineural component remains inferred from it.
Readouts
Cochlear-nerve demyelination and spiral-ganglion degeneration
Direction: INCREASED
Interpretation: Structural correlate of the sensorineural-loss mechanism in the OPG-null model.
Show evidence (1 reference)
PMID:23607938 SUPPORT Model Organism
"OPG deficiency caused demyelination and degeneration of the cochlear nerve in vivo."
Reports the histological cochlear-nerve degeneration measured in the model.
Show evidence (1 reference)
PMID:23607938 SUPPORT Model Organism
"we studied OPG knockout (Opg(-/-)) mice. We show that they develop sensorineural hearing loss, in addition to conductive hearing loss due to abnormal middle-ear bones."
Establishes the model as informative for the dual hearing-loss mechanism of JPD.
Accelerated Osteoclastic Bone Resorption recapitulates fidelity: moderate observes: tissue Opg-null mice show enhanced osteoclastic resorption and progressive skeletal disease.
Readouts
Progressive hearing loss from ossicular resorption
Direction: INCREASED
Interpretation: Ossicular resorption drives the conductive component of hearing loss in the model.
Show evidence (1 reference)
PMID:16564235 SUPPORT Model Organism
"progressive hearing loss was detected in Opg(-/-) mice starting at 6 to 15 weeks of age."
Reports the progressive hearing loss measured in the ossicle-resorption model.
Show evidence (1 reference)
PMID:16564235 SUPPORT Model Organism
"osteoprotegerin plays a crucial role in hearing by protecting the auditory ossicles and otic capsule from osteoclastic bone resorption."
Establishes the model as informative for OPG-loss-driven osteoclastic resorption.
Show evidence (1 reference)
PMID:23607938 SUPPORT Model Organism
"Loss of function mutations in the OPG gene account for the majority of cases of Juvenile Paget’s disease"
The model paper states the human OPG-loss basis of JPD it is modelling.
{ }

Source YAML

click to show 
name: Juvenile Paget Disease
creation_date: '2026-09-04T00:00:00Z'
category: Complex
description: >-
  Juvenile Paget disease (JPD; OMIM #239000, "Paget disease of bone 5,
  juvenile-onset"; ORPHA:2801) is an ultra-rare, autosomal-recessive osteopathy
  of infancy and early childhood, most often caused by biallelic loss of
  osteoprotegerin (OPG), the secreted decoy receptor encoded by TNFRSF11B that
  normally sequesters RANKL and restrains osteoclastogenesis. With the OPG brake
  removed, RANK-RANKL signalling runs unopposed, osteoclasts are grossly
  increased in number and activity, and the whole skeleton remodels at a rate it
  is not built for. Coupled osteoblastic formation cannot keep pace in an orderly
  way, so resorbed bone is replaced by disorganised woven bone; the child
  develops generalised osteopenia, progressive long-bone bowing and fractures,
  macrocephaly and skull-base hyperostosis, and grossly elevated serum alkaline
  phosphatase (the name "hereditary/idiopathic hyperphosphatasia" records that
  laboratory signature).

  Two contrasts anchor the entry. First, JPD is emphatically NOT adult Paget
  disease of bone (curated separately as Paget_Disease_of_Bone). Adult PDB is a
  focal, late-onset, usually SQSTM1-associated disorder of a handful of lesions;
  JPD is a generalised, whole-skeleton process of childhood driven by a
  different gene through the same RANK-RANKL-OPG axis. The adult entry
  explicitly cites loss of OPG causing JPD as the cleanest evidence that this
  axis is the centre of gravity of pagetic biology; this entry does not
  reproduce the adult disease. Second, JPD is genetically heterogeneous: while
  biallelic TNFRSF11B loss of function is the predominant cause, a heterozygous
  activating duplication in TNFRSF11A (RANK) and a de novo neomorphic SP7
  (Osterix) variant have each been reported to produce a JPD phenotype through
  convergent high-turnover biology, so the disease is not inheritance-uniform
  across its causal genes.

  The extraskeletal disease is where OPG's non-osteoclastic roles surface, and
  it is partly uncoupled from bone. Sensorineural hearing loss reflects a direct
  cochlear requirement for OPG (spiral-ganglion degeneration), layered on
  conductive loss from ossicular resorption; progressive retinopathy with
  angioid streaks and a vasculopathy with arterial calcification and aneurysms
  reflect OPG's vascular role. Anti-resorptive therapy (bisphosphonates
  first-line; the RANKL antibody denosumab as a direct pathophysiologic mimic of
  the missing protein, with careful calcium monitoring) controls the skeletal
  disease well but does not reliably prevent the retinopathy, an important
  prognostic caveat.
disease_term:
  preferred_term: juvenile Paget disease
  term:
    id: MONDO:0009394
    label: juvenile Paget disease
synonyms:
- hereditary hyperphosphatasia
- idiopathic hyperphosphatasia
- familial osteoectasia
- hyperostosis corticalis deformans juvenilis
- osteoprotegerin-deficiency juvenile Paget disease
- Paget disease of bone 5, juvenile-onset
- PDB5
- JPD
parents:
- Metabolic Bone Disease
inheritance:
- name: Autosomal recessive (TNFRSF11B/OPG deficiency, predominant form)
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    The great majority of JPD is autosomal-recessive OPG deficiency from
    homozygous or compound-heterozygous loss-of-function variants in TNFRSF11B,
    with consanguinity and geographic founder alleles (e.g. a Navajo homozygous
    deletion; a "Balkan" 966_969delTGACinsCTT indel) recurrent in the reported
    cohort. The genetically distinct minority forms — a heterozygous activating
    TNFRSF11A (RANK) duplication and a de novo heterozygous neomorphic SP7
    variant — behave dominantly and are recorded in the genetic section rather
    than here.
  evidence:
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Juvenile Paget's disease, an autosomal recessive osteopathy, is characterized
      by rapidly remodeling woven bone, osteopenia, fractures, and progressive skeletal deformity.
    explanation: The defining paper states the autosomal-recessive mode and the core skeletal
      phenotype of the predominant OPG-deficiency form.
  - reference: PMID:26762549
    reference_title: 'Auricular Ossification: A Newly Recognized Feature of Osteoprotegerin-Deficiency
      Juvenile Paget Disease.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Autosomal recessive transmission of loss-of-function mutations within TNFRSF11B
      encoding OPG accounts for most JPD (JPD1). JPD2 results from heterozygous constitutive
      activation of TNFRSF11A encoding RANK.
    explanation: States both the recessive OPG-deficiency form (JPD1) and the dominant RANK-activation
      form (JPD2), supporting the genetic heterogeneity recorded here.
pathophysiology:
- name: Biallelic TNFRSF11B Loss of Function
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Homozygous or compound-heterozygous loss-of-function variants in TNFRSF11B
    (whole-gene/multi-exon deletions, splice, and ligand-binding-domain missense
    alleles) abolish or cripple secreted osteoprotegerin. The initiating lesion
    of the predominant form; the Whyte 2002 index Navajo patients carried a
    homozygous ~100 kb deletion and had undetectable circulating OPG.
  genetic_context:
    gene:
      preferred_term: TNFRSF11B
      term:
        id: hgnc:11909
        label: TNFRSF11B
    functional_impact_category: LOSS_OF_FUNCTION
  downstream:
  - target: Loss of OPG Decoy Inhibition of RANKL
    causal_link_type: DIRECT
  - target: Cochlear OPG Deficiency and Spiral Ganglion Degeneration
    causal_link_type: DIRECT
  - target: Ectopic Vascular and Bruch-Membrane Calcification
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Both patients had a homozygous deletion of TNFRSF11B, with identical break points,
      on chromosome 8q24.2.
    explanation: Establishes the causal biallelic TNFRSF11B deletion in the index patients.
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We found that serum levels of osteoprotegerin and soluble osteoclast differentiation
      factor were undetectable and markedly increased, respectively.
    explanation: Confirms loss of the OPG protein product (undetectable serum OPG) with reciprocally
      elevated RANKL, the direct biochemical consequence of the null genotype.
  - reference: PMID:37180975
    reference_title: 'Paget''s disease: a review of the epidemiology, etiology, genetics, and treatment.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The mutant OPG is unable to block osteoclastic resorption in a bone culture system,
      demonstrating that it is a loss-of-function mutation (Chong et al., 2003).
    explanation: Functional confirmation that the JPD-associated TNFRSF11B alleles act by loss of function.
- name: Loss of OPG Decoy Inhibition of RANKL
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Osteoprotegerin normally acts as a soluble decoy receptor that binds RANKL
    and prevents it from engaging RANK on osteoclast precursors. With OPG absent,
    RANKL is no longer sequestered and is free to drive RANK signalling — the
    single molecular switch that connects the genetic lesion to accelerated
    osteoclastogenesis.
  biological_processes:
  - preferred_term: negative regulation of bone resorption
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0045779
      label: negative regulation of bone resorption
  cell_types:
  - preferred_term: osteoblast (OPG source)
    term:
      id: CL:0000062
      label: osteoblast
  downstream:
  - target: Unopposed RANK-RANKL Osteoclastogenesis
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: osteoprotegerin suppresses bone turnover by functioning as a decoy receptor for
      osteoclast differentiation factor (also called RANK ligand).
    explanation: States OPG's decoy-receptor function whose loss defines this node.
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: OPG is a soluble factor released from pre-osteoblasts and osteoblasts, which in complex
      with the osteoclast differentiation factor, also known as receptor activator of nuclear factor-kappa
      B ligand (RANKL)
    explanation: Independent statement of the OPG-RANKL decoy mechanism whose loss is the JPD lesion.
- name: Unopposed RANK-RANKL Osteoclastogenesis
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Free RANKL engages RANK on osteoclast precursors, driving markedly increased
    osteoclast differentiation. This is the step denosumab (an anti-RANKL
    antibody) targets, restoring pharmacologically the ligand neutralisation the
    missing OPG can no longer provide.
  biological_processes:
  - preferred_term: positive regulation of osteoclast differentiation
    modifier: INCREASED
    term:
      id: GO:0045672
      label: positive regulation of osteoclast differentiation
  cell_types:
  - preferred_term: osteoclast precursor (monocyte-macrophage lineage)
    term:
      id: CL:0000576
      label: monocyte
  downstream:
  - target: Accelerated Osteoclastic Bone Resorption
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:22638612
    reference_title: 'Genotype-phenotype correlation in juvenile Paget disease: role of molecular
      alterations of the TNFRSF11B gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This gene encodes a soluble protein, the osteoprotegerin, which leads to uncontrolled
      osteoclastogenesis when mutated.
    explanation: States that loss of OPG produces uncontrolled osteoclastogenesis, the process of this node.
  - reference: PMID:23788687
    reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
      in a girl with juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: JPD can be caused by loss of function of osteoprotegerin, resulting in subsequent stimulation
      of osteoclasts via the receptor activator of nuclear factor-κB (RANK) pathway.
    explanation: Names the RANK-pathway stimulation of osteoclasts that this node captures.
- name: Accelerated Osteoclastic Bone Resorption
  biological_scale: CELLULAR
  mechanism_confidence: ESTABLISHED
  description: >-
    Excess, hyperactive osteoclasts resorb bone throughout the skeleton at a
    grossly accelerated rate. In the OPG-null mouse this is directly observed as
    numerous osteoclasts with rapidly remodelling bone, recapitulating the human
    disease.
  biological_processes:
  - preferred_term: bone resorption
    modifier: INCREASED
    term:
      id: GO:0045453
      label: bone resorption
  cell_types:
  - preferred_term: multinucleated osteoclast
    term:
      id: CL:0000092
      label: osteoclast
  downstream:
  - target: Compensatory Disorganized Woven-Bone Formation
    causal_link_type: DIRECT
  - target: Generalized High-Turnover Osteopathy
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:16564235
    reference_title: Resorption of auditory ossicles and hearing loss in mice lacking osteoprotegerin.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Osteoclastic bone resorption is enhanced in Opg(-/-) mice lacking osteoprotegerin,
      which is a soluble decoy receptor for the osteoclastogenic cytokine RANKL.
    explanation: The OPG-null mouse directly demonstrates enhanced osteoclastic resorption on loss of the decoy receptor.
  - reference: PMID:25063546
    reference_title: Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Histopathology showed accelerated remodeling with abundant osteoclasts.
    explanation: Human bone histology confirming abundant osteoclasts and accelerated remodelling.
- name: Compensatory Disorganized Woven-Bone Formation
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    Coupled osteoblastic formation increases in response to the resorptive drive
    but cannot organise, so resorbed bone is replaced by structurally
    disorganised woven bone rather than mature lamellar bone across the whole
    skeleton — the generalised (not focal) counterpart of the adult pagetic
    mosaic.
  biological_processes:
  - preferred_term: ossification (disorganized, woven)
    modifier: INCREASED
    term:
      id: GO:0001503
      label: ossification
  cell_types:
  - preferred_term: osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  downstream:
  - target: Generalized High-Turnover Osteopathy
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Juvenile Paget's disease, an autosomal recessive osteopathy, is characterized by
      rapidly remodeling woven bone, osteopenia, fractures, and progressive skeletal deformity.
    explanation: States the rapidly remodelling woven bone that is the tissue-level signature of this node.
- name: Generalized High-Turnover Osteopathy
  biological_scale: ORGANISM
  mechanism_confidence: ESTABLISHED
  description: >-
    The whole-skeleton, high-turnover disease state: osteopenic, mechanically
    inferior woven bone that bows, fractures, expands the calvarium and skull
    base, and spills grossly elevated alkaline phosphatase into serum. Downstream
    are the clinical manifestations and the ALP laboratory signature.
  downstream:
  - target: Progressive Long-Bone Deformity
    causal_link_type: DIRECT
  - target: Recurrent Fractures
    causal_link_type: DIRECT
  - target: Bone Pain
    causal_link_type: DIRECT
  - target: Short Stature
    causal_link_type: DIRECT
  - target: Kyphoscoliosis
    causal_link_type: DIRECT
  - target: Vertebral Compression Fracture
    causal_link_type: DIRECT
  - target: Elevated Serum Alkaline Phosphatase
    causal_link_type: DIRECT
  - target: Auricular Ossification
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Cranial and Skull-Base Hyperostosis
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:23788687
    reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
      in a girl with juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Increased bone turnover and lack of bone modeling lead to severe deformities, frequent
      fractures, short stature, and loss of hearing.
    explanation: Directly links the high-turnover state to the deformity, fracture, short-stature,
      and hearing-loss manifestations drawn downstream here.
- name: Cranial and Skull-Base Hyperostosis
  biological_scale: TISSUE
  mechanism_confidence: ESTABLISHED
  description: >-
    High-turnover remodelling of the calvarium and skull base produces diploic
    thickening, basilar/orbital-roof and sphenoid sclerosis, an enlarged clivus,
    and progressive macrocephaly; the thickened temporal bone and ossicular
    disease contribute the conductive component of hearing loss.
  downstream:
  - target: Macrocephaly
    causal_link_type: DIRECT
  - target: Conductive Hearing Impairment
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The radiograph in early adulthood reveals marked widening of the skull with periosteal
      appositions both on the internal and external lamina, bossing of the frontal sinus, diffuse osteosclerosis
    explanation: Radiographic documentation of the calvarial/skull-base hyperostosis this node describes.
- name: Cochlear OPG Deficiency and Spiral Ganglion Degeneration
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  description: >-
    A skeleton-independent arm. Spiral-ganglion cells secrete OPG at high levels;
    in the OPG-null mouse, OPG loss causes demyelination and degeneration of the
    cochlear nerve and sensitises spiral-ganglion cells to apoptosis (via ERK),
    producing a primary sensorineural hearing loss that compounds the conductive
    loss from ossicular/temporal-bone disease. The human sensorineural component
    is inferred from this model plus the clinical deafness of JPD, so the node is
    marked provisional.
  biological_processes:
  - preferred_term: neuron apoptotic process (spiral ganglion)
    modifier: INCREASED
    term:
      id: GO:0051402
      label: neuron apoptotic process
  cell_types:
  - preferred_term: spiral ganglion neuron
    term:
      id: CL:0011113
      label: spiral ganglion neuron
  downstream:
  - target: Sensorineural Hearing Impairment
    causal_link_type: DIRECT
  evidence:
  - reference: PMID:23607938
    reference_title: Loss of osteoprotegerin expression in the inner ear causes degeneration of
      the cochlear nerve and sensorineural hearing loss.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: OPG deficiency caused demyelination and degeneration of the cochlear nerve in vivo.
    explanation: Establishes the direct cochlear-nerve degeneration mechanism of sensorineural loss in OPG deficiency.
  - reference: PMID:23607938
    reference_title: Loss of osteoprotegerin expression in the inner ear causes degeneration of
      the cochlear nerve and sensorineural hearing loss.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: It also activated ERK, sensitized spiral ganglion cells (SGC) to apoptosis
    explanation: Names the ERK-dependent spiral-ganglion apoptosis captured by this node.
- name: Ectopic Vascular and Bruch-Membrane Calcification
  biological_scale: TISSUE
  mechanism_confidence: HYPOTHETICAL
  description: >-
    A hypothesised extraskeletal arm reflecting OPG's vascular-protective role.
    OPG/RANKL dysfunction is proposed to promote calcification of Bruch membrane
    (producing angioid streaks liable to choroidal neovascularisation) and of
    arterial walls (vascular microcalcification with a predisposition to carotid
    and iliac aneurysms). The clinical associations are well documented; the
    mechanistic link is inferential, and the retinopathy notably progresses
    despite good skeletal disease control, indicating partial uncoupling from the
    osteoclast axis.
  downstream:
  - target: Angioid Streaks and Retinopathy
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Vascular Calcification and Arterial Aneurysm
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:20547946
    reference_title: Ocular manifestations of juvenile Paget disease.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: Osteoprotegerin or its signaling pathway may have a role in calcification of Bruch
      membrane and in the pathogenesis of angioid streaks.
    explanation: States the proposed (hypothesised) Bruch-membrane calcification mechanism; directness
      INDIRECT because the paper frames it as a hypothesis rather than a demonstrated step.
  - reference: PMID:25063546
    reference_title: Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK.
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: This OPG deficiency form of JPD uniquely leads to vascular microcalcification (VMC)(14)
      that perhaps explains carotid aneurysms in childhood(15) and retinopathy with blindness in adult life.
    explanation: Links OPG-deficiency vascular microcalcification to the carotid aneurysm and retinopathy
      phenotypes; "perhaps explains" marks the inferential status recorded here.
phenotypes:
- category: Skeletal
  name: Progressive Long-Bone Deformity
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Progressive long-bone bowing deformity
    term:
      id: HP:0006487
      label: Bowing of the long bones
    clinical_course: PROGRESSIVE
  description: >-
    Progressive bowing of the weight-bearing long bones, worsening through the
    adolescent growth spurt if untreated; a defining and near-universal feature.
  evidence:
  - reference: PMID:22638612
    reference_title: 'Genotype-phenotype correlation in juvenile Paget disease: role of molecular
      alterations of the TNFRSF11B gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: show a phenotype characterized by progressive bone deformities, fractures, and short stature.
    explanation: Names progressive bone deformity as a core JPD phenotype.
- category: Skeletal
  name: Recurrent Fractures
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Recurrent fractures
    term:
      id: HP:0002757
      label: Recurrent fractures
  description: >-
    Recurrent long-bone fractures from infancy/early childhood, often with
    minimal trauma; in the Czech case the first fracture (a femoral-neck
    infraction) occurred at age three.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The first fracture occurred at age three.
    explanation: Documents early-childhood fracture onset in a molecularly confirmed JPD patient.
- category: Skeletal
  name: Bone Pain
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Bone pain
    term:
      id: HP:0002653
      label: Bone pain
  description: >-
    Skeletal pain that tracks turnover activity and responds to anti-resorptive
    therapy; in the long-term denosumab cohort baseline pain scores of 9/10 and
    7/10 fell to 0-5/10 after treatment.
  evidence:
  - reference: PMID:23788687
    reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
      in a girl with juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Additionally, bone pain was more efficiently controlled with denosumab.
    explanation: Reports treatment-responsive bone pain, supporting it as a turnover-linked JPD symptom.
- category: Skeletal
  name: Short Stature
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  description: Growth impairment/short stature, correlating with disease severity.
  evidence:
  - reference: PMID:23788687
    reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
      in a girl with juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Increased bone turnover and lack of bone modeling lead to severe deformities, frequent
      fractures, short stature, and loss of hearing.
    explanation: Lists short stature among the core JPD manifestations.
- category: Skeletal
  name: Kyphoscoliosis
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Kyphoscoliosis
    term:
      id: HP:0002751
      label: Kyphoscoliosis
  description: >-
    Progressive spinal curvature with vertebral compression; radiographs show
    coarse trabeculae and framed/compressed vertebral bodies.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'the patient manifested gradual and progressive growth disproportion, i.e., short trunk,
      longer limbs, larger chest, scoliosis of the spine, and valgosity of the lower extremities'
    explanation: Documents progressive scoliosis/spinal deformity in a confirmed JPD patient.
- category: Skeletal
  name: Vertebral Compression Fracture
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Vertebral compression fracture
    term:
      id: HP:0002953
      label: Vertebral compression fracture
  description: >-
    Vertebral body compression from the mechanically inferior high-turnover
    bone; the Czech patient showed discrete compression of the C3-C5 vertebral
    bodies radiographically.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Discrete compressions of C3–C5 vertebral bodies are noticeable
    explanation: Radiographic documentation of vertebral compression in a confirmed JPD patient.
- category: Skeletal
  name: Macrocephaly
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Macrocephaly
    term:
      id: HP:0000256
      label: Macrocephaly
  description: >-
    Progressive skull enlargement from calvarial/skull-base hyperostosis; head
    circumference reached +2.6 SD by age four in the Czech case.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'The first anatomical abnormalities appeared at age three, i.e., macrocephaly (head circumference
      + 2.6 SD)'
    explanation: Quantifies the macrocephaly with an exact head-circumference SD in a confirmed case.
- category: Laboratory
  name: Elevated Serum Alkaline Phosphatase
  frequency: VERY_FREQUENT
  diagnostic: true
  phenotype_term:
    preferred_term: Markedly elevated serum alkaline phosphatase
    term:
      id: HP:0003155
      label: Elevated circulating alkaline phosphatase concentration
  description: >-
    Grossly elevated serum ALP (often >10-15x ULN) is the cardinal laboratory
    signature and principal activity/monitoring marker — the basis of the
    historical name "hyperphosphatasia". In the Czech case ALP reached 75.75
    µkat/L at age four, ~15x ULN.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: A biochemical evaluation revealed increased levels of serum alkaline phosphatase (ALP),
      reaching 75.75 µkat/L at age four, which is 15 times above the upper limit of normal (ULN).
    explanation: Exact quantified ALP elevation in a molecularly confirmed JPD patient.
- category: Auditory
  name: Sensorineural Hearing Impairment
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
    clinical_course: PROGRESSIVE
  description: >-
    Progressive sensorineural loss from OPG-dependent cochlear-nerve degeneration
    (see the cochlear pathophysiology node), typically layered on a conductive
    component. Very common in JPD.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Most patients exhibit hearing impairment or complete hearing loss, which may be caused
      by ossicle deformities in the internal ear and/or sensorineural hearing loss due to demyelination
      and degeneration of the acoustic nerve, caused by osteoprotegerin deficiency.
    explanation: States the dual conductive/sensorineural mechanism and the OPG-deficiency cause of
      the sensorineural component.
- category: Auditory
  name: Conductive Hearing Impairment
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  description: >-
    Conductive component from resorption/deformity of the middle-ear ossicles and
    temporal-bone disease; in the RANK-duplication case, deafness involved missing
    ossicles and eroded cochleas.
  evidence:
  - reference: PMID:25063546
    reference_title: Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Deafness at age 2years involved missing ossicles and eroded cochleas.
    explanation: Documents the ossicular basis of the conductive hearing loss.
- category: Ocular
  name: Angioid Streaks and Retinopathy
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Angioid streaks with progressive retinopathy
    term:
      id: HP:0001102
      label: Angioid streaks
    clinical_course: PROGRESSIVE
  description: >-
    Progressive retinopathy (retinal pigment epithelium mottling, peripapillary
    atrophy, angioid streaks, choroidal neovascularisation) that can progress to
    vision loss and does so even under adequate skeletal disease control. In the
    Kerr series retinal abnormalities were present in 12 of 14 examined eyes.
  evidence:
  - reference: PMID:20547946
    reference_title: Ocular manifestations of juvenile Paget disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Juvenile Paget disease is associated with progressive retinopathy characterized by the
      development of angioid streaks, which may be complicated by choroidal neovascularization, the predominant
      cause of visual loss.
    explanation: Defines the progressive angioid-streak retinopathy and its neovascular complication.
  - reference: PMID:20547946
    reference_title: Ocular manifestations of juvenile Paget disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Retinal abnormalities were evident in 12 of 14 eyes
    explanation: Provides the numerator/denominator (12 of 14 examined eyes) behind the frequency.
- category: Vascular
  name: Vascular Calcification and Arterial Aneurysm
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Vascular calcification with arterial aneurysm predisposition
    term:
      id: HP:0003207
      label: Arterial calcification
  description: >-
    Generalised vascular microcalcification with a predisposition to arterial
    aneurysm (internal carotid, iliac), reflecting OPG's vascular-protective role
    ("osteovasculoprotegerin"). Reported at case-report level.
  evidence:
  - reference: PMID:25063546
    reference_title: Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: This OPG deficiency form of JPD uniquely leads to vascular microcalcification (VMC)(14)
      that perhaps explains carotid aneurysms in childhood(15) and retinopathy with blindness in adult life.
    explanation: Documents the vascular microcalcification and carotid-aneurysm association.
- category: Skeletal
  name: Auricular Ossification
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Auricular (pinna) elastic-cartilage ossification
    term:
      id: HP:0005103
      label: Calcification of the auricular cartilage
  description: >-
    Ossification of the elastic auricular cartilage (rigid pinnae sparing the
    lobe), a newly recognised feature of OPG-deficiency JPD, possibly exacerbated
    by bisphosphonate treatment; occasionally involves the auditory canal.
  evidence:
  - reference: PMID:26762549
    reference_title: 'Auricular Ossification: A Newly Recognized Feature of Osteoprotegerin-Deficiency
      Juvenile Paget Disease.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: We report auricular ossification (AO) affecting the elastic cartilage of the ear as a
      newly recognized feature of osteoprotegerin (OPG)-deficiency juvenile Paget disease (JPD).
    explanation: Establishes auricular ossification as a recognised JPD feature.
genetic:
- name: TNFRSF11B
  gene_term:
    preferred_term: TNFRSF11B
    term:
      id: hgnc:11909
      label: TNFRSF11B
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    TNFRSF11B (8q24.12) encodes osteoprotegerin (OPG). Biallelic loss-of-function
    variants — whole-gene/multi-exon deletions, splice variants (e.g. c.30+5G>A),
    ligand-binding-domain missense variants (e.g. c.329G>T p.Gly110Val),
    cysteine-residue missense, and small indels such as the "Balkan"
    966_969delTGACinsCTT — cause the predominant autosomal-recessive form.
    Homozygosity dominates; compound heterozygosity is rare. A strong
    genotype-phenotype gradient runs from severe (large deletions,
    ligand-binding-domain cysteine missense; deformity before 18 months) to mild
    (an exon-5 indel). Founder alleles include a Navajo homozygous deletion and
    the Balkan indel. The functional consequence (loss of function) is recorded
    on the pathophysiology genetic_context.
  evidence:
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Juvenile Paget's disease can result from osteoprotegerin deficiency caused by homozygous
      deletion of TNFRSF11B.
    explanation: Establishes TNFRSF11B (OPG) as the causal gene of the predominant form.
  - reference: PMID:22638612
    reference_title: 'Genotype-phenotype correlation in juvenile Paget disease: role of molecular
      alterations of the TNFRSF11B gene.'
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: JPD is characterized by a strong genotype-phenotype correlation, so depending on the
      alteration of the TNFRSN11B gene, the phenotype is variable.
    explanation: States the TNFRSF11B genotype-phenotype correlation summarised in the notes (the
      quoted sentence carries the source's own TNFRSN11B typo).
- name: TNFRSF11A
  gene_term:
    preferred_term: TNFRSF11A
    term:
      id: hgnc:11908
      label: TNFRSF11A
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  notes: >-
    A genetically distinct minority cause. A single reported patient with no
    TNFRSF11B mutation carried a heterozygous 15-bp in-frame tandem duplication
    (87dup15) in exon 1 of TNFRSF11A, predicting the same signal-peptide
    extension of RANK that causes expansile skeletal hyperphosphatasia — i.e. a
    gain-of-function RANK lesion phenocopying OPG loss through the shared
    pathway. Dominant-acting; contrast with the recessive TNFRSF11B form.
  evidence:
  - reference: PMID:25063546
    reference_title: Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a unique heterozygous 15-bp insertional tandem duplication (87dup15) within exon 1 of
      TNFRSF11A predicted the same pentapeptide extension of RANK that causes expansile skeletal hyperphosphatasia (84dup15).
    explanation: Documents the activating TNFRSF11A duplication as an alternative JPD cause.
- name: SP7
  gene_term:
    preferred_term: SP7
    term:
      id: hgnc:17321
      label: SP7
  relationship_type: CAUSATIVE
  variant_origin: DE_NOVO
  notes: >-
    A third, genetically distinct cause reported in a single patient. A de novo
    heterozygous missense variant (c.926C>G; p.Ser309Trp) in SP7, encoding the
    osteoblast master transcription factor osterix, was identified after no
    TNFRSF11A/B defect was found, and produces a high-turnover JPD phenotype
    through an altered/neomorphic mechanism in the osteoblast rather than direct
    RANK-RANKL disruption. Note SP7 is pleiotropic: separate biallelic
    loss-of-function SP7 variants cause a low-turnover osteogenesis imperfecta,
    so mechanism — not the gene alone — determines the direction of bone
    turnover. Dominant, de novo.
  evidence:
  - reference: PMID:32298837
    reference_title: Juvenile Paget's Disease From Heterozygous Mutation of SP7 Encoding Osterix
      (Specificity Protein 7, Transcription Factor SP7).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: 'trio exome sequencing revealed a de novo heterozygous missense mutation (c.926C>G; p.S309W)
      within SP7 encoding the osteoblast transcription factor osterix'
    explanation: Identifies the de novo SP7 variant in a patient with JPD.
  - reference: PMID:32298837
    reference_title: Juvenile Paget's Disease From Heterozygous Mutation of SP7 Encoding Osterix
      (Specificity Protein 7, Transcription Factor SP7).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Thus, mutation of SP7 represents a third genetic cause of JPD.
    explanation: Establishes SP7 as the third reported causal gene, supporting the description's claim.
prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: BELOW_1_IN_1000000
  notes: >-
    Ultra-rare. Approximately 80 cases have been reported worldwide since the
    disease was first described in 1956; no registry-based prevalence exists, so
    this is a literature-count estimate read as case-series-level evidence. A
    numeric rate_per_100000 is deliberately omitted: the modelled "<1 in 10
    million" figure is an order-of-magnitude estimate, not a measured population
    rate, so prevalence_class BELOW_1_IN_1000000 carries the claim instead.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Approximately 80 cases of JPD have been described worldwide since 1956
    explanation: Gives the literature case count that grounds the ultra-rare classification.
progression:
- phase: Infantile/childhood onset with lifelong progressive high-turnover disease
  age_range: Infancy to early childhood onset; progressive through the adolescent growth spurt
  notes: >-
    JPD presents in infancy or early childhood with fractures and deformity and,
    untreated, progresses through the growth years; severe forms carry high
    morbidity and can be fatal in childhood or young adulthood. Early
    anti-resorptive treatment halts deformity/fracture progression; there is no
    spontaneous remission, and turnover relapses if bisphosphonate therapy is
    stopped. Extraskeletal disease (retinopathy, vascular) can progress even
    under good skeletal control.
  evidence:
  - reference: PMID:32298837
    reference_title: Juvenile Paget's Disease From Heterozygous Mutation of SP7 Encoding Osterix
      (Specificity Protein 7, Transcription Factor SP7).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: present in infancy or early childhood as fractures and deformity hallmarked biochemically
      by marked elevation of serum alkaline phosphatase (ALP) activity
    explanation: States the infantile/early-childhood onset and the fracture/deformity presentation.
  - reference: PMID:32298837
    reference_title: Juvenile Paget's Disease From Heterozygous Mutation of SP7 Encoding Osterix
      (Specificity Protein 7, Transcription Factor SP7).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Untreated, JPD can kill during childhood or young adult life.
    explanation: States the progressive, potentially fatal untreated course.
biochemical:
- name: Serum alkaline phosphatase (total)
  presence: Increased
  context: >-
    Grossly elevated total serum ALP is the cardinal biochemical marker of JPD
    disease extent/activity, reflecting the accelerated osteoblastic response to
    high-turnover bone. Often >10-15x the upper limit of normal at diagnosis;
    used to titrate anti-resorptive therapy. Urinary collagen cross-links and
    P1NP/BAP/beta-CrossLaps corroborate the high-turnover state.
  biomarker_term:
    preferred_term: Serum Alkaline Phosphatase Measurement
    term:
      id: NCIT:C61016
      label: Serum Alkaline Phosphatase Measurement
  reference_ranges:
  - loinc_term:
      id: LOINC:6768-6
      label: Alkaline phosphatase [Enzymatic activity/volume] in Serum or Plasma
    lower_bound: 25.0
    upper_bound: 120.0
    unit: IU/L
    population: adults (assay-specific normal range as reported in the cited JPD cohort)
    notes: >-
      Adult reference interval 25-120 IU/l as stated for the long-term denosumab
      JPD cohort; off-treatment JPD ALP in that cohort ran 630-2500 IU/l, i.e.
      roughly 5-20x the upper limit.
    evidence:
    - reference: PMID:40223037
      reference_title: Long-Term Denosumab Treatment in Adults with Juvenile Paget Disease.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Off treatment, ALP was 1300–2500 IU/l (reference range 25–120 IU/l).
      explanation: Provides both the adult ALP reference interval and the magnitude of the JPD elevation.
    interpretation_bands:
    - name: Normal
      lower_bound: 25.0
      upper_bound: 120.0
      unit: IU/L
      abnormal_flag: NORMAL
    - name: Elevated (JPD activity range)
      lower_bound: 120.0
      unit: IU/L
      abnormal_flag: HIGH
      phenotype_term:
        preferred_term: Elevated circulating alkaline phosphatase concentration
        term:
          id: HP:0003155
          label: Elevated circulating alkaline phosphatase concentration
      interpretation: >-
        Values above the upper reference limit indicate active high-turnover bone
        disease; untreated JPD characteristically runs many multiples of the ULN.
  evidence:
  - reference: PMID:40223037
    reference_title: Long-Term Denosumab Treatment in Adults with Juvenile Paget Disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Accelerated bone turnover as assessed by biochemical markers, such as alkaline phosphatase
      (ALP), can be suppressed by bisphosphonate treatment, but it relapses if bisphosphonate treatment is discontinued.
    explanation: Establishes ALP as the activity marker that tracks (and relapses with) turnover in JPD.
diagnosis:
- name: Molecular genetic testing of TNFRSF11B (with deletion/CNV analysis)
  diagnosis_term:
    preferred_term: molecular genetic testing
    term:
      id: NCIT:C15709
      label: Genetic Testing
  description: >-
    First-tier confirmatory test is sequencing of TNFRSF11B. Crucially, several
    families — including the index Navajo kindred — carry homozygous whole-gene
    or multi-exon deletions of TNFRSF11B that Sanger/exon sequencing alone will
    miss, so copy-number/deletion (CNV) analysis must accompany sequencing.
    TNFRSF11A and SP7 are second-tier for TNFRSF11B-negative cases.
  evidence:
  - reference: PMID:12124406
    reference_title: Osteoprotegerin deficiency and juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Both patients had a homozygous deletion of TNFRSF11B, with identical break points,
      on chromosome 8q24.2.
    explanation: The disease-causing lesion is a whole-gene deletion, establishing why CNV/deletion
      analysis must accompany sequencing rather than sequencing alone.
- name: Skeletal radiography
  diagnosis_term:
    preferred_term: skeletal radiography
    term:
      id: NCIT:C137876
      label: Bone Radiography
  description: >-
    Generalised (not focal) radiographic disease: osteopenic/osteosclerotic long
    bones with cortical thickening (hyperostosis), coarse trabeculation, calvarial
    and skull-base thickening; the generalised distribution distinguishes JPD from
    the focal lesions of adult Paget disease.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: a diffuse modeling disorder in long bones, presenting as extremely thickened cortical bone
      composed of widespread smooth periosteal appositions
    explanation: Describes the characteristic generalised radiographic modelling disorder.
- name: Bone turnover markers
  diagnosis_term:
    preferred_term: laboratory measurement of bone turnover markers
    term:
      id: NCIT:C25294
      label: Laboratory Procedure
  markers: >-
    Serum alkaline phosphatase (cardinal), urinary pyridinoline/deoxypyridinoline
    collagen cross-links, P1NP, bone-specific ALP, beta-CrossLaps, osteocalcin,
    TRAP5b, N-telopeptide — all elevated at baseline and used to titrate therapy.
  description: >-
    Grossly elevated markers of high bone turnover support the diagnosis and are
    the mainstay of activity monitoring; urinary collagen cross-links are now
    preferred over hydroxyproline.
  evidence:
  - reference: PMID:32298837
    reference_title: Juvenile Paget's Disease From Heterozygous Mutation of SP7 Encoding Osterix
      (Specificity Protein 7, Transcription Factor SP7).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: several markers of bone turnover were elevated and included striking hyperphosphatasemia
    explanation: Documents the elevated bone-turnover-marker profile used diagnostically.
- name: Audiometry (hearing surveillance)
  diagnosis_term:
    preferred_term: audiometry
    term:
      id: NCIT:C38036
      label: Audiometric Test
  description: >-
    Serial audiometry for the progressive mixed conductive/sensorineural hearing
    loss that is very common in JPD.
  evidence:
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Most patients exhibit hearing impairment or complete hearing loss, which may be caused
      by ossicle deformities in the internal ear and/or sensorineural hearing loss due to demyelination
      and degeneration of the acoustic nerve, caused by osteoprotegerin deficiency.
    explanation: Establishes the high frequency and dual mechanism of hearing loss that mandates audiometric surveillance.
- name: Ophthalmologic examination (retinopathy surveillance)
  diagnosis_term:
    preferred_term: dilated fundus examination
    term:
      id: NCIT:C120698
      label: Ophthalmoscopy
  description: >-
    Dilated fundus examination / fundus imaging for angioid streaks, retinal
    pigment epithelium changes and choroidal neovascularisation; surveillance
    continues regardless of skeletal disease control because retinopathy can
    progress independently.
  evidence:
  - reference: PMID:20547946
    reference_title: Ocular manifestations of juvenile Paget disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Participants underwent ophthalmic examinations consisting of at least best-corrected Snellen
      visual acuity and dilated fundal examination or color fundus photography.
    explanation: Describes the fundus examination used to detect the JPD retinopathy under surveillance.
- name: Vascular imaging (aneurysm surveillance)
  diagnosis_term:
    preferred_term: vascular imaging
    term:
      id: NCIT:C190557
      label: Magnetic Resonance Angiography
  description: >-
    Vascular imaging as clinically indicated for the internal-carotid and iliac
    aneurysms reported in JPD; no formal screening protocol exists given the
    ultra-rarity and case-report-level evidence, so this is directed rather than
    routine.
  notes: >-
    Left without a dedicated evidence item: aneurysm reports are case-level and
    the vascular association is already cited on the vasculopathy phenotype/node.
treatments:
- name: Bisphosphonate Therapy
  description: >-
    First-line and best-established therapy. IV pamidronate or zoledronic acid,
    or oral alendronate/ibandronate, suppress the accelerated osteoclastic
    resorption, normalise or near-normalise ALP and other turnover markers,
    prevent new fractures, halt deformity progression, and produce striking
    motor-developmental recovery when started early in childhood and continued
    through growth. Turnover suppression relapses if treatment is discontinued;
    therapy is not curative.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: pamidronate
      term:
        id: CHEBI:7903
        label: pamidronate
    - preferred_term: zoledronic acid
      term:
        id: CHEBI:46557
        label: zoledronic acid
    - preferred_term: alendronic acid
      term:
        id: CHEBI:2567
        label: alendronic acid
  target_mechanisms:
  - target: Accelerated Osteoclastic Bone Resorption
    treatment_effect: INHIBITS
    description: Bisphosphonates inhibit osteoclastic bone resorption, the effector step of JPD.
    evidence:
    - reference: PMID:33850973
      reference_title: Clinical course in two children with Juvenile Paget's disease during long-term
        treatment with intravenous bisphosphonates.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Individualized intravenous treatment with pamidronate resulted in sufficient control
        of bone pain and suppression of bone turnover with few side effects over the observation period.
      explanation: Demonstrates bisphosphonate suppression of bone turnover and pain in two children with JPD.
  evidence:
  - reference: PMID:33850973
    reference_title: Clinical course in two children with Juvenile Paget's disease during long-term
      treatment with intravenous bisphosphonates.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Motor development was delayed in both children before treatment with bisphosphonates
      was commenced and improved thereafter.
    explanation: Documents functional (motor-developmental) benefit of early bisphosphonate therapy.
  - reference: PMID:40775369
    reference_title: Juvenile Paget disease with unique compound heterozygous sequence variants
      in the TNFRSF11B gene.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: Early diagnosis and antiresorption treatment prevent further fractures and deformity
      progression, and improve the patient's quality of life.
    explanation: States the fracture/deformity-preventing benefit of early anti-resorptive treatment.
- name: Denosumab
  description: >-
    A humanised anti-RANKL monoclonal antibody — the most direct pharmacologic
    mimic of the missing OPG, neutralising the RANKL that OPG can no longer
    sequester. Achieves good skeletal control (ALP normalisation, pain relief) in
    JPD but carries a substantial risk of severe hypocalcemia when high
    pretreatment turnover is abruptly shut off, so calcium must be monitored
    closely; pediatric use in particular demands caution. Does not reliably
    prevent retinopathy progression.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: denosumab
      term:
        id: NCIT:C61313
        label: Denosumab
  target_mechanisms:
  - target: Unopposed RANK-RANKL Osteoclastogenesis
    treatment_effect: INHIBITS
    description: Denosumab binds RANKL and prevents RANK engagement, replacing OPG's lost decoy function.
    evidence:
    - reference: PMID:23788687
      reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
        in a girl with juvenile Paget's disease.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Alkaline phosphatase levels dropped within the normal range and remained at normal levels
        for 5 months after the final dose of denosumab.
      explanation: Demonstrates RANKL-antibody suppression of turnover (ALP normalisation) in JPD.
  evidence:
  - reference: PMID:23788687
    reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
      in a girl with juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: concomitant with the first injection, severe hypocalcemia developed, for which the patient
      was hospitalized and iv calcium supplementation was required for 13 days.
    explanation: Documents the severe-hypocalcemia hazard that governs pediatric denosumab dosing in JPD.
  - reference: PMID:40223037
    reference_title: Long-Term Denosumab Treatment in Adults with Juvenile Paget Disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: long-term denosumab administration in adults with JPD, who had been previously treated
      with bisphosphonates, was safe and effective in terms of the skeletal disease, but it may not prevent
      the emergence of retinopathy.
    explanation: Establishes durable skeletal efficacy but persistent retinopathy risk despite treatment.
- name: Recombinant Osteoprotegerin (investigational)
  description: >-
    Direct protein replacement of the missing decoy receptor. In two adult
    siblings, once-weekly subcutaneous recombinant OPG suppressed bone resorption
    and increased bone mass over 15 months with only mild hypocalcemia/
    hypophosphatemia — proof of mechanism for OPG replacement, but never
    developed into an approved product (denosumab is the practical
    RANKL-pathway therapeutic).
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: Loss of OPG Decoy Inhibition of RANKL
    treatment_effect: RESTORES
    description: Recombinant OPG restores the decoy-receptor sequestration of RANKL that the null genotype abolishes.
    evidence:
    - reference: PMID:16135836
      reference_title: Recombinant osteoprotegerin for juvenile Paget's disease.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Bone resorption (assessed by N-telopeptide excretion) was suppressed by once-weekly
        subcutaneous doses of 0.3 to 0.4 mg per kilogram of body weight.
      explanation: Demonstrates that replacing OPG directly suppresses the resorptive drive.
  evidence:
  - reference: PMID:16135836
    reference_title: Recombinant osteoprotegerin for juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: After 15 months of treatment, radial bone mass increased in one patient by 9 percent
      and in the other by 30 percent, skeletal bisphosphonate retention decreased by 37 percent and 55 percent, respectively
    explanation: Quantifies the bone-mass and resorption response to recombinant OPG replacement.
- name: Calcitonin (historical)
  description: >-
    An inhibitor of bone resorption used before bisphosphonates and denosumab
    became standard; now largely superseded but part of the historical treatment
    record.
  therapeutic_modality: PEPTIDE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: calcitonin
      term:
        id: CHEBI:3306
        label: calcitonin
  evidence:
  - reference: PMID:23788687
    reference_title: Effects of RANK-ligand antibody (denosumab) treatment on bone turnover markers
      in a girl with juvenile Paget's disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: The treatment for JPD is challenging and has previously been based on administration of
      either calcitonin or bisphosphonates.
    explanation: Records calcitonin as a prior standard anti-resorptive for JPD.
- name: Anti-VEGF Intravitreal Therapy
  description: >-
    Intravitreal anti-vascular-endothelial-growth-factor agents (bevacizumab,
    aflibercept) for the choroidal neovascularisation that complicates JPD
    angioid-streak retinopathy — the ocular treatment arm. It targets the
    neovascular complication rather than the underlying bone disease, and is part
    of the ophthalmologic surveillance/management that continues independently of
    skeletal disease control. In the long-term denosumab cohort one subject with
    sudden vision loss had almost full visual recovery after intravitreal
    bevacizumab and aflibercept.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: bevacizumab
      term:
        id: CHEBI:749495
        label: bevacizumab
    - preferred_term: aflibercept
      term:
        id: CHEBI:750062
        label: aflibercept
  target_mechanisms:
  - target: Angioid Streaks and Retinopathy
    treatment_effect: MODULATES
    description: >-
      Anti-VEGF inhibits the VEGF-driven choroidal neovascularisation that
      complicates the retinopathy, managing the predominant cause of visual loss
      without reversing the underlying angioid streaks/vasculopathy.
    evidence:
    - reference: PMID:40223037
      reference_title: Long-Term Denosumab Treatment in Adults with Juvenile Paget Disease.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: She had almost full recovery of vision following intravitreal treatment with bevacizumab
        (once) and aflibercept (four times)
      explanation: Documents anti-VEGF intravitreal therapy rescuing vision in JPD choroidal neovascularisation.
  evidence:
  - reference: PMID:40223037
    reference_title: Long-Term Denosumab Treatment in Adults with Juvenile Paget Disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: She had almost full recovery of vision following intravitreal treatment with bevacizumab
      (once) and aflibercept (four times)
    explanation: Establishes the anti-VEGF ocular treatment arm and its efficacy for the retinopathy complication.
animal_models:
- name: Opg-knockout mouse (Tnfrsf11b-/-)
  species: Mouse
  genotype: Tnfrsf11b (Opg) homozygous knockout
  publication: PMID:23607938
  description: >-
    The primary and best-validated JPD model. Osteoprotegerin-null mice show
    numerous osteoclasts and rapidly remodelling woven bone (recapitulating the
    skeletal disease), and reproduce the dual deafness of JPD — conductive loss
    from ossicular resorption plus sensorineural loss from cochlear-nerve
    degeneration.
  modeled_mechanisms:
  - target: Cochlear OPG Deficiency and Spiral Ganglion Degeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: CELLULAR
    description: OPG-null mice reproduce the cochlear-nerve degeneration and sensorineural loss of JPD.
    limitations: >-
      Mouse cochlear ageing/degeneration biology differs from human; the model
      demonstrates the mechanism but the human sensorineural component remains
      inferred from it.
    readouts:
    - name: Cochlear-nerve demyelination and spiral-ganglion degeneration
      target: Cochlear OPG Deficiency and Spiral Ganglion Degeneration
      direction: INCREASED
      interpretation: Structural correlate of the sensorineural-loss mechanism in the OPG-null model.
      evidence:
      - reference: PMID:23607938
        reference_title: Loss of osteoprotegerin expression in the inner ear causes degeneration
          of the cochlear nerve and sensorineural hearing loss.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: OPG deficiency caused demyelination and degeneration of the cochlear nerve in vivo.
        explanation: Reports the histological cochlear-nerve degeneration measured in the model.
    evidence:
    - reference: PMID:23607938
      reference_title: Loss of osteoprotegerin expression in the inner ear causes degeneration of
        the cochlear nerve and sensorineural hearing loss.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: we studied OPG knockout (Opg(-/-)) mice. We show that they develop sensorineural hearing
        loss, in addition to conductive hearing loss due to abnormal middle-ear bones.
      explanation: Establishes the model as informative for the dual hearing-loss mechanism of JPD.
  - target: Accelerated Osteoclastic Bone Resorption
    relationship: RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: Opg-null mice show enhanced osteoclastic resorption and progressive skeletal disease.
    readouts:
    - name: Progressive hearing loss from ossicular resorption
      target: Accelerated Osteoclastic Bone Resorption
      direction: INCREASED
      interpretation: Ossicular resorption drives the conductive component of hearing loss in the model.
      evidence:
      - reference: PMID:16564235
        reference_title: Resorption of auditory ossicles and hearing loss in mice lacking osteoprotegerin.
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: progressive hearing loss was detected in Opg(-/-) mice starting at 6 to 15 weeks of age.
        explanation: Reports the progressive hearing loss measured in the ossicle-resorption model.
    evidence:
    - reference: PMID:16564235
      reference_title: Resorption of auditory ossicles and hearing loss in mice lacking osteoprotegerin.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: osteoprotegerin plays a crucial role in hearing by protecting the auditory ossicles
        and otic capsule from osteoclastic bone resorption.
      explanation: Establishes the model as informative for OPG-loss-driven osteoclastic resorption.
  evidence:
  - reference: PMID:23607938
    reference_title: Loss of osteoprotegerin expression in the inner ear causes degeneration of the
      cochlear nerve and sensorineural hearing loss.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: Loss of function mutations in the OPG gene account for the majority of cases of Juvenile
      Paget’s disease
    explanation: The model paper states the human OPG-loss basis of JPD it is modelling.
discussions:
- discussion_id: jpd-retinopathy-uncoupling
  kind: OPEN_QUESTION
  status: OPEN
  prompt: >-
    Why does JPD retinopathy progress despite excellent skeletal disease control
    on anti-resorptive therapy, and is the ocular/vascular arm mechanistically
    uncoupled from the osteoclast axis that bisphosphonates and denosumab target?
  attaches_to:
  - pathophysiology#Ectopic Vascular and Bruch-Membrane Calcification
  - phenotypes#Angioid Streaks and Retinopathy
  rationale: >-
    In the long-term denosumab cohort, retinopathy progressed (including sudden
    vision loss requiring anti-VEGF therapy) despite normalised ALP and no new
    fractures. This suggests the Bruch-membrane/vascular calcification arm of OPG
    deficiency is at least partly independent of the RANKL-osteoclast axis, with
    direct implications for surveillance (ongoing ophthalmology regardless of
    skeletal control) and for whether RANKL-pathway therapy can ever prevent the
    ocular disease.
  evidence:
  - reference: PMID:40223037
    reference_title: Long-Term Denosumab Treatment in Adults with Juvenile Paget Disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: long-term denosumab administration in adults with JPD, who had been previously treated
      with bisphosphonates, was safe and effective in terms of the skeletal disease, but it may not prevent
      the emergence of retinopathy.
    explanation: Documents the retinopathy-despite-skeletal-control observation motivating this question.
notes: >-
  Curated de novo (2026-09) from primary literature; a Claude Code deep-research
  report was used only as a lead list and every snippet was verified against a
  fetched reference. Distinct from adult Paget_Disease_of_Bone, which explicitly
  excludes JPD. Evidence base is almost entirely individual case reports and
  small series (~80 cases since 1956), so prevalence, natural-history, and
  treatment-response claims are case-series-level, not population-based. Two
  minority genetic causes (a dominant activating TNFRSF11A duplication and a de
  novo neomorphic SP7 variant) are recorded but not fully modelled in the
  pathograph, which centres the predominant TNFRSF11B/OPG-deficiency mechanism.
  Naming trap: JPD ("hyperphosphatasia", HIGH ALP) is the biochemical opposite of
  hypophosphatasia (ALPL, LOW ALP) — do not conflate.
📚

References & Deep Research

Deep Research

1

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

Evaluations and curation notes (2)

Record notes

Curated de novo (2026-09) from primary literature; a Claude Code deep-research report was used only as a lead list and every snippet was verified against a fetched reference. Distinct from adult Paget_Disease_of_Bone, which explicitly excludes JPD. Evidence base is almost entirely individual case reports and small series (~80 cases since 1956), so prevalence, natural-history, and treatment-response claims are case-series-level, not population-based. Two minority genetic causes (a dominant activating TNFRSF11A duplication and a de novo neomorphic SP7 variant) are recorded but not fully modelled in the pathograph, which centres the predominant TNFRSF11B/OPG-deficiency mechanism. Naming trap: JPD ("hyperphosphatasia", HIGH ALP) is the biochemical opposite of hypophosphatasia (ALPL, LOW ALP) — do not conflate.

Create: Juvenile Paget disease · 2026-09-04T14:43:51Z · View source

De novo curation of Juvenile Paget disease (JPD; MONDO:0009394, OMIM #239000), the autosomal-recessive TNFRSF11B/OPG-deficiency osteopathy. Kept distinct from adult Paget_Disease_of_Bone. Pathograph: biallelic TNFRSF11B LOF -> loss of OPG decoy inhibition of RANKL -> unopposed RANK-RANKL osteoclastogenesis -> accelerated osteoclastic resorption -> compensatory woven-bone formation -> generalized high-turnover osteopathy -> deformity/fractures/ALP; plus a cochlear OPG-deficiency arm (SNHL) and a hypothesised vascular/Bruch-membrane calcification arm (retinopathy, aneurysm). 13 phenotypes, ALP biochemical with LOINC reference range + interpretation band, 4 treatments (bisphosphonates, denosumab, recombinant OPG, calcitonin), Opg-KO mouse model, and an open-question discussion on retinopathy/skeletal uncoupling. All 53 evidence snippets exact-verified against fetched references (Whyte NEJM 2002 PMID:12124406 core). Deep-research report used only as leads.

Claude Code ▸
Juvenile Paget Disease (Osteoprotegerin Deficiency): Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 28 citations 2026-09-04T14:11:14.330345

Juvenile Paget Disease (Osteoprotegerin Deficiency): Comprehensive Research Report

1. Disease Information

Overview. Juvenile Paget disease (JPD) — also called idiopathic hyperphosphatasia, hereditary hyperphosphatasia, familial osteoectasia, chronic idiopathic hyperphosphatasemia, or hyperostosis corticalis deformans juvenilis — is an ultra-rare, generalized (non-focal) skeletal dysplasia of markedly accelerated bone turnover presenting in infancy or early childhood. It is fundamentally distinct from adult (classic) Paget disease of bone: adult Paget disease is focal, typically monostotic or polyostotic in older adults, and driven mainly by SQSTM1 mutations affecting osteoclast p62/sequestosome signaling, whereas JPD is a generalized, whole-skeleton process of childhood most often caused by biallelic loss-of-function of osteoprotegerin (OPG), the natural decoy receptor that restrains osteoclastogenesis (Cundy & Mumm 2007, PMC6779132; Cundy et al., PMC10169728 — Frontiers Genet 2023, "Paget's disease: a review of the epidemiology, etiology, genetics, and treatment").

Key identifiers: - OMIM (phenotype): #239000, Paget Disease of Bone 5, Juvenile-Onset; PDB5 (https://www.omim.org/entry/239000) - OMIM (gene): 602643, TNFRSF11B (Tumor Necrosis Factor Receptor Superfamily, Member 11B), chromosome 8q24.12 - Orphanet: ORPHA:2801, Juvenile Paget disease (https://www.orpha.net/en/disease/detail/2801) - Coding cross-references (as indexed by Orphanet/aggregator terminologies; treat as leads to confirm against the primary ICD/MeSH releases rather than authoritative in themselves): ICD-10 M88.x (Paget disease of bone) category with a hyperphosphatasia designation sometimes carried under Q78.8; ICD-11 FB85.0; MeSH supplementary concept C537701. - HGNC: TNFRSF11B, HGNC:11909; gene product osteoprotegerin (OPG)/osteoclastogenesis inhibitory factor (OCIF)

Synonyms: Idiopathic hyperphosphatasia; hereditary hyperphosphatasia; familial hyperphosphatasemia; familial osteoectasia; hyperostosis corticalis deformans juvenilis; chronic congenital idiopathic hyperphosphatasemia; osteoectasia with hyperphosphatasia; osteoprotegerin-deficiency juvenile Paget disease (NORD, https://rarediseases.org/rare-diseases/hereditary-hyperphosphatasia/; MedlinePlus, https://medlineplus.gov/download/genetics/condition/juvenile-paget-disease.pdf).

Evidence base: Information for this ultra-rare disease derives almost entirely from individual case reports and small case series (single patients, sib pairs, or small kindreds) rather than large aggregated cohorts or registries — fewer than 100 published cases exist worldwide across nearly 70 years of literature. This has direct implications for confidence in prevalence, natural-history, and treatment-response claims below, which should be treated as case-series-level evidence, not population-based epidemiology.

2. Etiology

Disease causal factors — genetic, and now genetically heterogeneous

JPD is monogenic. Three genetically distinct causes have now been described, with strongly differing modes of inheritance and mechanism:

  1. TNFRSF11B (OPG) biallelic loss-of-function — the predominant cause (~two-thirds to the great majority of published cases). Autosomal recessive; homozygous or compound heterozygous null/hypomorphic variants in the gene encoding osteoprotegerin abolish or severely reduce the decoy-receptor brake on RANK–RANKL signaling (Whyte et al., NEJM 2002, PMID:12124406, "Osteoprotegerin Deficiency and Juvenile Paget's Disease"; NORD, https://rarediseases.org/rare-diseases/hereditary-hyperphosphatasia/).
  2. TNFRSF11A (RANK) heterozygous activating duplication — one reported case. A 13-year-old girl with no TNFRSF11B mutation carried a heterozygous 15-bp in-frame tandem duplication (87dup15) in exon 1 of TNFRSF11A, predicting the same pentapeptide extension of RANK's signal peptide seen in familial expansile osteolysis/expansile skeletal hyperphosphatasia (which is caused by the homologous 84dup15 duplication) — i.e., a gain-of-function RANK signaling lesion phenocopying OPG loss (PMID:25063546, PMC4189967, "Juvenile Paget's disease with heterozygous duplication within TNFRSF11A encoding RANK").
  3. SP7/Osterix de novo heterozygous neomorphic mutation — a third, distinct genetic cause. A de novo heterozygous missense variant (c.926C>G; p.Ser309Trp) in SP7, encoding the osteoblast master transcription factor Osterix, was reported to cause a high-bone-turnover JPD-like phenotype through an altered/neomorphic DNA-binding specificity rather than simple haploinsufficiency (ScienceDirect/Bone, S8756328220301447; Nat Commun 2022, "A neomorphic variant in SP7 alters sequence specificity and causes a high-turnover bone disorder"). Note SP7 is genetically pleiotropic: separate homozygous loss-of-function SP7 variants cause osteogenesis imperfecta type XII (a low-turnover phenotype), underscoring that variant type/mechanism — not just the gene — determines whether SP7 dysfunction produces high- or low-turnover bone disease.

A JPD-focused targeted next-generation sequencing panel (Papapoulos group, PMC4410173) has additionally screened TM7SF4 (DC-STAMP), SQSTM1, TNFRSF11A, TNFRSF11B, OPTN, CSF1, and VCP as candidate/modifier loci for atypical or mild presentations, reflecting that the RANK–RANKL–OPG axis and its regulators are the relevant candidate-gene space even when TNFRSF11B itself is normal.

Risk factors

  • Genetic: biallelic TNFRSF11B pathogenic variants (recessive); consanguinity substantially raises risk given the AR inheritance of the dominant genetic cause. Founder mutations are documented in two populations:
  • Navajo: a homozygous genomic deletion of TNFRSF11B, with an estimated carrier frequency of ~1 in 100 Navajos — a population-specific founder effect (Whyte et al. 2002, PMID:12124406; Whyte & Mumm review, PMC6779132).
  • "Balkan" mutation (966_969delTGACinsCTT): a small deletion/insertion reported in multiple unrelated patients of Balkan/Southeast European ancestry, notably associated with paradoxically elevated circulating immunoreactive (but non-functional) OPG protein (Whyte et al., J Bone Miner Res 2007, "Juvenile Paget's Disease: The Second Reported, Oldest Patient Is Homozygous for the TNFRSF11B 'Balkan' Mutation"; also the basis of the two adult siblings in the long-term denosumab study, PMC11994531).
  • Population/demographic: more prevalent wherever consanguineous marriage is practiced, consistent with autosomal-recessive transmission (Frontiers Genet review, PMC10169728).
  • Sex: no sex predilection reported; case series suggest roughly equal male:female distribution (individual case reports rather than a systematic sex-ratio study).

Protective factors

No genetic or environmental protective factors have been established in the literature reviewed. This is expected for an essentially fully penetrant, biallelic loss-of-function Mendelian disorder — protective modifier alleles have not been systematically studied given the extreme rarity of the disease.

Gene–environment interactions

None established or reported; JPD's causal mechanism is intrinsic (a structural bone-remodeling signaling defect) rather than exposure-modulated. Documented modifiers of clinical course are treatment-related (bisphosphonate/denosumab exposure ameliorating turnover; see Treatment) rather than classical gene-environment risk interactions.

3. Phenotypes

Skeletal phenotypes (signs/physical findings)

Phenotype Onset/characteristics Suggested HP term
Progressive long-bone deformity (bowing) Childhood onset, progressive, worsens through the adolescent growth spurt if untreated HP:0006419 (Bowing of the legs) / HP:0002980 (Femoral bowing)
Macrocephaly / skull enlargement Progressive; head circumference reported up to +2.6 SD in a Czech case (OJRD 2025, PMC12333066) HP:0000256 (Macrocephaly)
Short stature Common; progressive with disease severity HP:0004322 (Short stature)
Fractures (recurrent, long bone) Onset from infancy/early childhood; recurrent, sometimes with minimal trauma HP:0002757 (Recurrent fractures)
Vertebral collapse "Sandwich vertebrae" (dense end plates) may be seen radiographically in young children and can resolve later HP:0002944 (Kyphosis)/HP:0003468 (Compression fractures of the vertebrae)
Kyphoscoliosis Progressive spinal curvature HP:0002751 (Kyphoscoliosis)
Skull hyperostosis / cranial nerve entrapment risk Diploic thickening, basilar/orbital-roof/sphenoid sclerosis HP:0004437 (Hyperostosis cranii)
Bone pain Common, correlates with turnover activity; markedly reduced with effective anti-resorptive treatment (denosumab pain scores fell from 9/10 and 7/10 pretreatment to 0–5/10 postinjection; PMC11994531) HP:0002653 (Bone pain)
Muscular weakness Reported feature HP:0001324 (Muscle weakness)
Auricular (pinna) ossification Newly recognized feature — a case series of 4 unrelated JPD patients found 3 (75%) had ossification of the elastic auricular cartilage, sometimes painful and occasionally involving the auditory canal (Whyte et al., PMC5111855, "Auricular Ossification: A Newly Recognized Feature of Osteoprotegerin-Deficiency Juvenile Paget Disease") HP:0000377 (Abnormality of the pinna)

Extraskeletal phenotypes

  • Sensorineural and conductive hearing loss/deafness — very common, progressive. Mechanism is dual: (1) conductive loss from deformity/ossicular abnormality of middle-ear bones, and (2) primary sensorineural loss from OPG deficiency causing demyelination and degeneration of the cochlear/acoustic nerve and increased apoptosis of spiral ganglion cells (ScienceDirect, S0969996113001228, "Loss of osteoprotegerin expression in the inner ear causes degeneration of the cochlear nerve and sensorineural hearing loss"). In the TNFRSF11A-duplication case, deafness involved missing ossicles and eroded cochleas (PMC4189967). Suggested term: HP:0000407 (Sensorineural hearing impairment) plus HP:0000405 (Conductive hearing impairment).
  • Progressive retinopathy / angioid streaks — a distinctive ocular phenotype. Findings include retinal pigment epithelium mottling, peripapillary atrophy, angioid streaks, and choroidal neovascularization that can progress to disciform scarring and vision loss (PubMed 20547946, "Ocular Manifestations of Juvenile Paget Disease"). OPG/RANKL signaling is hypothesized to participate in Bruch membrane calcification, and retinopathy may reflect a more generalized vasculopathy; notably, in the long-term denosumab cohort, retinopathy progressed despite adequate skeletal disease control, with one subject developing sudden vision loss from macular edema, subretinal fluid, and choroidal neovascularization at age 46 requiring anti-VEGF therapy (bevacizumab, then aflibercept) — "long-term denosumab administration…may not prevent the emergence of retinopathy" (PMC11994531). Suggested HP terms: HP:0000531 (Angioid streaks — verify exact HPO term string before binding), HP:0000608 (Macular degeneration).
  • Vascular calcification and aneurysm formation — internal carotid artery (bilateral cavernous/giant aneurysms reported in a child, PMID:20934158/AJNR 29:7 and ScienceDirect S1878875010000239), iliac artery aneurysms (ScienceDirect S2772687822000290), and generalized vascular calcification. Suggested HP term: HP:0004944 (Abnormal vascular physiology) or more specific vascular/aneurysm terms as applicable.
  • Dental abnormalities — root resorption, tooth loss/breakage reported in the TNFRSF11A RANK-duplication case (PMC4189967).
  • Transient immunodeficiency — the 2025 Czech case report describes "transient immunodeficiency requiring temporary immunoglobulin replacement" in a JPD patient (PMC12333066). This is mechanistically plausible given OPG's role as a decoy receptor also expressed by dendritic cells/B lymphocytes that dampens RANK–RANKL signaling on immune cells, but should be treated as an emerging/case-level observation, not an established core feature — it has not been systematically characterized across the JPD cohort, and should not be conflated with the RANK-pathway immunodeficiency described for TNFRSF11A-osteopetrosis (a different, more severe phenotype with absent lymph nodes; ScienceDirect S0002929708003637).

Laboratory abnormalities

  • Serum alkaline phosphatase (ALP): markedly elevated, often >10–15× the upper limit of normal (e.g., 75.75 µkat/L at age 4 in the Czech case, ~15× normal; PMC12333066). ALP is the best-characterized and most widely used marker of disease extent/activity.
  • Urinary hydroxyproline and pyridinoline/deoxypyridinoline cross-links: elevated, reflecting collagen breakdown; urinary pyridinoline is now generally preferred to hydroxyproline as a more accurate activity marker.
  • Additional turnover markers reported in treated patients: P1NP, β-CrossLaps, BAP (bone-specific ALP), osteocalcin, TRAP5b, N-telopeptide (NTx) — all elevated at baseline and used to titrate anti-resorptive therapy (PMC8039828; NEJM 2005, PMID:16135836).
  • Serum calcium/phosphate are typically normal at baseline but calcium requires close monitoring once anti-resorptive treatment (especially denosumab) is started, given risk of profound hypocalcemia from abrupt osteoclast inhibition against a background of very high pretreatment turnover (see Treatment).

Frequency/severity/progression

Frequency data for individual phenotypes across the JPD population are not systematically quantified (no registry-level denominator exists); the figures above (e.g., 75% auricular ossification in a 4-patient series) come from small case series and should be read as such. Progression is characteristically worsening through the adolescent growth spurt, and untreated disease is reported to render the majority of affected children wheelchair-bound by age 15 (patient.info/Doctor summary; corroborated qualitatively by the treated-vs-untreated contrast in case reports).

Quality of life impact

Direct QOL instrument data (EQ-5D, SF-36) for JPD were not identified in available literature — expected for a disease with <100 published cases. Functional impact is documented qualitatively: motor developmental delay in infancy, progression to wheelchair dependence if untreated, and striking functional recovery with effective anti-resorptive treatment — e.g., one patient in PMC8039828 progressed from delayed sitting at 18 months to independent walking by age 3 after pamidronate initiation. Bone pain scores (9/10, 7/10 pretreatment) documented in the denosumab study (PMC11994531) are the closest quantitative QOL-adjacent metric available.

4. Genetic/Molecular Information

Causal genes

Gene HGNC OMIM gene Protein Mechanism Inheritance
TNFRSF11B HGNC:11909 *602643 Osteoprotegerin (OPG) Loss of function (decoy receptor deficiency) Autosomal recessive
TNFRSF11A HGNC:11908 *603499 RANK Gain of function (activating duplication) Reported as heterozygous (single case)
SP7 HGNC:11642 *606633 Osterix/SP7 Neomorphic altered DNA-binding specificity De novo heterozygous

Pathogenic variants (TNFRSF11B)

  • Variant types reported: homozygous whole-gene/multi-exon deletions, splice-site variants (e.g., c.30+5G>A), missense variants (e.g., c.329G>T p.Gly110Val; cysteine-residue missense variants in the ligand-binding domain), and small deletion/insertion variants (e.g., 966_969delTGACinsCTT "Balkan" mutation).
  • Compound heterozygosity is rare: as of the 2025 Orphanet Journal of Rare Diseases case report, "previous literature documented only two prior compound heterozygous TNFRSF11B cases," with homozygosity being the predominant genetic pattern (PMC12333066).
  • Variant burden: per HGMD Professional (2024.2) as cited in that same 2025 report, approximately twenty JPD-causing variants have been described in TNFRSF11B to date — consistent with the disease's extreme rarity.
  • Population frequency: a TNFRSF11B pathogenic variant was noted in gnomAD v2.1.1 at extremely low allele frequency (~0.003%) in one ClinVar-linked search result — this is a single-variant data point, not a locus-wide statement, and should be re-verified per-variant via gnomAD/ClinVar directly before use in curation (VCV000840923, VCV000006971, https://www.ncbi.nlm.nih.gov/clinvar/variation/840923/).
  • Founder variants: Navajo homozygous deletion (carrier frequency ~1/100); Balkan 966_969delTGACinsCTT (multiple unrelated reported patients; paradoxically elevated but non-functional circulating OPG immunoreactivity, JBMR 2007).

Genotype–phenotype correlation

A JPD-genotype/phenotype study (PMID:22638612, "Genotype-phenotype correlation in juvenile Paget disease: role of molecular alterations of the TNFRSF11B gene") reports a graded severity relationship: - Most severe: large gene deletions removing multiple exons (including the whole ligand-binding domain), and missense mutations affecting cysteine residues in the ligand-binding domain — deformity manifest before 18 months of age with major disability. - Intermediate: non-cysteine missense mutations in the ligand-binding domain — deformity recognized around age 5, with increased long-bone fracture rate. - Mildest: an exon 5 insertion/deletion variant.

This genotype-severity gradient is directly relevant to prognostic counseling and to anticipating age at needed treatment initiation.

Functional consequences

Loss-of-function (TNFRSF11B) → failure of decoy-receptor sequestration of RANKL → unchecked RANK–RANKL engagement on osteoclast precursors → excessive osteoclastogenesis and osteoclast activity. Gain-of-function (TNFRSF11A duplication) → constitutively active RANK signaling, phenocopying OPG loss via the same downstream pathway. SP7 mechanism is distinct — a transcription-factor DNA-binding specificity alteration in osteoblasts rather than direct RANK–RANKL pathway disruption, but converging on a high-bone-turnover phenotype.

Modifier genes / epigenetics / chromosomal abnormalities

No modifier genes, epigenetic mechanisms, or chromosomal-level abnormalities (aneuploidy, translocation) are established for JPD in the literature surveyed; the NGS candidate-gene panel work (TM7SF4/DC-STAMP, SQSTM1, OPTN, CSF1, VCP; PMC4410173) represents candidate-modifier screening in atypical/mild cases rather than confirmed modifier loci.

5. Environmental Information

No environmental toxin, occupational exposure, infectious trigger, or lifestyle factor has been implicated in JPD causation or exacerbation in the literature reviewed — consistent with its status as a purely monogenic disorder. This differs from adult Paget disease of bone, where a viral (paramyxovirus) etiologic hypothesis has historically been proposed for SQSTM1-associated disease; that hypothesis is specific to the adult/SQSTM1 form and should not be extrapolated to JPD.

6. Mechanism / Pathophysiology

Causal chain (ordered)

  1. Biallelic TNFRSF11B loss-of-function variants (homozygous deletion, splice, missense, or compound heterozygous combinations) lead to absent or non-functional osteoprotegerin protein, or — alternatively — a heterozygous activating TNFRSF11A duplication leads to constitutively active RANK, or a de novo neomorphic SP7 variant leads to altered osteoblast transcriptional output favoring high bone turnover. [Established for TNFRSF11B mechanism — demonstrated genetically and biochemically, Whyte et al. NEJM 2002, PMID:12124406; inferred by structural homology for the TNFRSF11A duplication case, PMC4189967; established by in vitro DNA-binding assay for the SP7 neomorph, Nat Commun 2022]
  2. Loss of the OPG decoy receptor (or gain of RANK activity) results in unopposed RANKL–RANK engagement on osteoclast precursors and mature osteoclasts. [Directly demonstrated — OPG's canonical function as a soluble RANKL-neutralizing decoy receptor is well established, PMC2684955 "RANK, RANKL and osteoprotegerin in bone biology and disease"]
  3. Unopposed RANK signaling drives markedly increased osteoclast differentiation, number, and resorptive activity — reproduced directly in Tnfrsf11b-knockout mice, which show numerous osteoclasts and rapidly remodeling woven bone (rather than mature lamellar bone) recapitulating the human JPD phenotype. [Demonstrated in the mouse model — MODEL_ORGANISM evidence]
  4. Excess osteoclastic resorption triggers a compensatory but disorganized coupled increase in osteoblastic bone formation, producing rapidly remodeled, structurally disorganized woven bone in place of normal lamellar bone throughout the entire skeleton (a generalized rather than focal process, distinguishing JPD from adult Paget disease). [Demonstrated — histology in case reports, e.g. PMC8039828 femoral biopsy showing "parallel trabecular-like structures with coexisting lamellar and woven bone" and abnormal multilayered osteoblasts]
  5. Woven, poorly mineralized, disorganized bone results in reduced mechanical strength → skeletal deformity (bowing), osteopenia, and pathologic/recurrent fracture, concentrated in weight-bearing long bones and progressing with growth-plate activity — hence marked worsening during the adolescent growth spurt. [Demonstrated clinically/radiographically across essentially all case reports]
  6. Ongoing high-turnover skull/cranial-base remodeling causes progressive calvarial and skull-base hyperostosis (diploic thickening, orbital-roof/sphenoid sclerosis, enlarged clivus), which can compress cranial nerves/otic structures. [Demonstrated radiographically]
  7. In parallel, OPG deficiency acting directly in the inner ear (independent of ossicular/skull deformity) causes demyelination and apoptotic degeneration of the cochlear (spiral ganglion) nerve, producing progressive sensorineural hearing loss that compounds the conductive loss from ossicular/temporal-bone deformity. [Demonstrated in mouse model — Tnfrsf11b-knockout mice show both conductive loss from ossicle abnormality and sensorineural loss; ScienceDirect S0969996113001228]
  8. OPG/RANKL pathway dysfunction is hypothesized to contribute to ectopic calcification of Bruch membrane in the eye, producing angioid streaks that can be complicated by choroidal neovascularization and disciform scarring/vision loss; retinopathy may reflect a broader generalized vasculopathy. [Inferred/hypothesized — the Bruch-membrane-calcification mechanism is proposed rather than directly demonstrated at the mechanistic level; the clinical association (angioid streaks, choroidal neovascularization) is well documented]
  9. The same generalized vasculopathy is hypothesized to underlie vascular wall calcification and predispose to aneurysm formation (internal carotid, iliac), representing OPG's less-characterized vascular role outside bone. [Inferred — case-report-level association; OPG's vascular-protective role is independently supported in the cardiovascular literature but the causal chain to aneurysm in JPD specifically remains inferential]
  10. Untreated, the cumulative burden of skeletal deformity, fracture, and disability culminates in progressive loss of ambulation (wheelchair dependence reported in the majority of untreated children by age 15) and variable but potentially reduced life expectancy, while extraskeletal complications (deafness, vision loss, vascular events) compound overall morbidity independent of skeletal disease control — notably, effective anti-resorptive treatment of the skeletal axis (bisphosphonates/denosumab) does not reliably prevent retinopathy progression, indicating the ocular/vascular arm may be at least partially uncoupled from the RANK–RANKL–osteoclast axis that anti-resorptives target. [Demonstrated — PMC11994531 documents retinopathy progression despite good skeletal control]

Molecular pathway

RANK–RANKL–OPG axis (TNF receptor superfamily signaling); NF-κB and NFATc1 downstream in osteoclast precursors upon RANK engagement (canonical osteoclastogenesis pathway; not independently re-verified here but standard pathway biology — see KEGG osteoclast differentiation pathway, Reactome).

Cellular processes

Osteoclast differentiation/hyperactivation (increased osteoclast number and resorptive activity); compensatory/coupled osteoblast activity producing disorganized woven-bone formation; cochlear spiral ganglion neuronal apoptosis; possible vascular smooth muscle/Bruch-membrane ectopic calcification.

Protein dysfunction

Absent/non-functional secreted OPG (loss-of-function truncation, deletion, or ligand-binding-domain missense disruption) vs. constitutively active RANK receptor (gain-of-function duplication) vs. altered DNA-binding specificity of the Osterix/SP7 transcription factor (neomorphic mechanism).

Cell types involved

  • Osteoclast (CL:0000092) — hyperactivated effector cell
  • Osteoblast (CL:0000062) — site of OPG production (normally) and compensatory bone formation; site of SP7 transcriptional activity
  • Spiral ganglion neuron (relevant CL term for cochlear nerve) — site of OPG-deficiency-related apoptosis/demyelination
  • Dendritic cell / B lymphocyte — reported sources of OPG relevant to the (emerging) immune phenotype
  • Vascular smooth muscle cell — candidate site for vascular calcification, not directly demonstrated

Suggested GO terms

  • GO:0030316 (osteoclast differentiation)
  • GO:0045453 (bone resorption)
  • GO:0002062 (chondrocyte differentiation) — if relevant to growth plate involvement
  • GO:0038149 (RANKL-mediated signaling pathway) if precise term exists — verify exact GO ID before binding
  • GO:0043123 (positive regulation of canonical NF-kappaB signal transduction) — downstream of RANK activation

Molecular profiling / advanced technologies

No transcriptomic, proteomic, metabolomic, single-cell, or spatial-omics studies specific to human JPD tissue were identified in this search — expected given the extreme rarity and the reliance on individual case reports; most molecular characterization to date has been at the level of Sanger/targeted NGS variant calling plus serum biomarker (ALP, turnover marker) measurement, plus one mouse-model transcriptional/functional study (Tnfrsf11b-knockout).

7. Anatomical Structures Affected

Organ level: - Primary: skeletal system — generalized, affecting long bones (especially lower-limb weight-bearing bones), skull/calvaria, vertebrae, pelvis - Secondary: auditory system (cochlea, ossicles), visual system (retina, choroid, Bruch membrane), cardiovascular system (carotid and iliac arteries), external ear (auricular cartilage), dentition, and (emerging) immune system

Tissue/cell level: bone (woven vs. lamellar), cochlear nerve/spiral ganglion, retinal pigment epithelium and choroid, vascular wall, elastic cartilage of the pinna.

Subcellular: not specifically characterized for JPD beyond standard osteoclast/osteoblast secretory biology.

Suggested UBERON terms: UBERON:0002481 (bone tissue), UBERON:0003128 (calvaria), UBERON:0001690 (ear), UBERON:0000966 (retina), UBERON:0001981 (blood vessel), UBERON:0001917 (pinna).

Localization/laterality: Generalized/bilateral — this is a defining distinction from adult Paget disease, which is characteristically focal/asymmetric.

8. Temporal Development

  • Onset: infancy to early childhood, typically reported "between 2 and 3 years of age" (NORD); insidious onset with progressive deformity.
  • Progression: progressive and worsens markedly during the adolescent growth spurt if untreated; radiographic vertebral "sandwich" changes can be present early and resolve later. Disease is lifelong (chronic); no spontaneous remission is described. Rate and severity are genotype-dependent (see §4 genotype-phenotype correlation) — cysteine-domain missense and large-deletion genotypes present earlier (before 18 months) and more severely than exon-5 indel or non-cysteine missense genotypes (~age 5 onset).
  • Patterns: No spontaneous remission reported; treatment-induced biochemical remission (near-normalization of ALP/turnover markers) is achievable with sustained anti-resorptive therapy but relapses on discontinuation of bisphosphonates (Frontiers Genet review, PMC10169728).
  • Critical periods: Childhood/adolescent growth is the critical window for treatment — "Bisphosphonates…can ameliorate the skeletal phenotype, if started early enough in childhood and continued at least until growth is complete" (patient.info/Doctor summary; corroborated by outcome data in PMC8039828 and the OJRD 2025 case, where alendronate/ibandronate started at age 5 prevented further deformity/fracture through adulthood).

9. Inheritance and Population

Epidemiology

  • ~80–100 cases reported worldwide since the disease was first described in 1956, yielding an estimated prevalence of less than 1 in 10 million (Frontiers Genet review, PMC10169728, explicitly modeling for underreporting: "Making the assumption that one fourth of the patients may have been reported, the prevalence of JPD may be estimated to be less than 1 in 10 million").
  • No formal incidence, birth-prevalence, or registry-based figures exist; all estimates are literature-count-derived, not population/registry-derived — a substantially weaker evidence class than typical Orphanet epidemiology rows, and should be flagged as such in curation (prevalence_class: NOT_YET_DOCUMENTED or ULTRA_RARE qualitative tier rather than a numeric Orphanet band).

Inheritance pattern

  • TNFRSF11B-related JPD: autosomal recessive (the predominant/default form)
  • TNFRSF11A-duplication JPD: reported as a heterozygous variant in a single case (mechanism analogous to the dominantly inherited familial expansile osteolysis caused by the homologous duplication) — this would functionally behave as autosomal dominant, though only one case is published
  • SP7-related JPD: de novo heterozygous (autosomal dominant, de novo)

This is a case for explicit multi-locus/genetic-heterogeneity modeling in curation — JPD is not inheritance-uniform across its causal genes, unlike most single-gene AR disorders.

Penetrance/expressivity

Reported cases suggest high penetrance for biallelic TNFRSF11B null genotypes, with variable expressivity strongly correlated to specific variant class (genotype-phenotype correlation, §4) rather than to stochastic/environmental variability.

Founder effects / consanguinity

  • Navajo founder deletion, carrier frequency ~1/100 (Whyte et al. 2002)
  • Balkan founder indel (966_969delTGACinsCTT), reported in multiple unrelated Balkan-region patients
  • Consanguinity is repeatedly noted as a risk-elevating factor for AR TNFRSF11B-JPD, consistent with its recessive transmission

Carrier frequency / prenatal diagnosis

"Detection of carriers and prenatal diagnosis of juvenile Paget's disease…are possible," with particular relevance in founder populations such as the Navajo (search synthesis referencing Whyte et al.). No dedicated carrier-screening program or clinical guideline was identified.

Population demographics

No systematic sex-ratio or geographic-distribution dataset exists beyond the founder-population observations above; case reports span multiple continents/ethnicities (Navajo, Balkan/Southeast European, Bolivian [TNFRSF11A case], Czech, Iranian, etc.), consistent with panethnic occurrence outside the two founder clusters.

10. Diagnostics

Clinical/laboratory tests

  • Serum alkaline phosphatase — the primary, best-characterized screening/monitoring biomarker; grossly elevated (multiples of ULN) at diagnosis.
  • Urinary pyridinoline/deoxypyridinoline cross-links — now preferred over hydroxyproline as the activity/extent marker; hydroxyproline "is no longer considered an accurate marker."
  • Additional turnover markers used for monitoring: P1NP, BAP, β-CrossLaps, osteocalcin, TRAP5b, NTx.
  • Skeletal survey/radiographs: generalized osteopenic, widened long bones with coarse trabeculation and indistinct corticomedullary junction; marked cortical thickening (hyperostosis); widened phalanges; calvarial/diploic thickening with basilar sclerosis (orbital roofs, sphenoid), enlarged clivus; "sandwich vertebrae" in young children.
  • Bone histology/biopsy (when performed): woven bone with coexisting lamellar architecture, abnormal multilayered osteoblasts, and quantitative backscattered electron imaging showing increased heterogeneity of mineralization (PMC8039828).
  • Audiometry — for hearing-loss surveillance (both conductive and sensorineural components).
  • Ophthalmologic exam / fundus imaging — for angioid streaks, RPE mottling, choroidal neovascularization surveillance; recommended as ongoing surveillance given that skeletal treatment does not reliably prevent ocular progression.
  • Vascular imaging (as clinically indicated) — for carotid/iliac aneurysm screening given documented case reports.

Genetic testing

  • First-tier: targeted sequencing/single-gene testing of TNFRSF11B (the majority-cause gene), including deletion/duplication (copy-number) analysis given the founder deletions.
  • Expanded panel: TNFRSF11A, SP7, plus candidate/modifier genes TM7SF4 (DC-STAMP), SQSTM1, OPTN, CSF1, VCP for atypical/mild or TNFRSF11B-negative presentations (PMC4410173 NGS panel design).
  • Genetic Testing Registry entries exist for OMIM 602643 (https://www.ncbi.nlm.nih.gov/gtr/all/tests/?term=602643%5Bmim%5D).
  • No WGS/WES-specific yield data for JPD were identified beyond the general recommendation that panel/targeted sequencing is the practical first approach given known causal genes.

Clinical criteria / differential diagnosis

No formal consensus diagnostic criteria (e.g., DSM/ICD-style) were identified; diagnosis is made by the combination of clinical phenotype (infantile/childhood-onset generalized skeletal deformity), grossly elevated ALP with elevated urinary collagen cross-links, characteristic generalized (not focal) radiographic findings, and confirmatory molecular genetic testing.

Key differential diagnoses (search-derived, general differential-diagnosis discussion rather than a JPD-specific comparative study): - Adult/classic Paget disease of bone — focal not generalized; SQSTM1-associated; older-onset - Camurati-Engelmann disease (progressive diaphyseal dysplasia, TGFB1) — diaphyseal hyperostosis but different distribution/mechanism; GeneReviews available (https://www.ncbi.nlm.nih.gov/books/NBK1156/) - Craniodiaphyseal dysplasia - Hypophosphatasia — importantly the inverse biochemical picture (low, not high, ALP) despite a superficially similar name ("hyperphosphatasia" vs. "hypophosphatasia"); a naming trap worth flagging explicitly - Osteogenesis imperfecta (including SP7-related OI type XII, which is low-turnover, unlike SP7-related JPD, which is high-turnover — same gene, opposite mechanism) - Familial expansile osteolysis / expansile skeletal hyperphosphatasia (TNFRSF11A dup, dominant) — mechanistically the closest relative to the TNFRSF11A-JPD case, differing mainly in the pattern/distribution of expansile lesions - Polyostotic fibrous dysplasia - Hereditary hyperphosphatasia itself is distinguished from these radiographically by generalized rather than focal/mosaic change and by much earlier (infantile) onset.

Screening

No population/newborn screening program exists (expected given ultra-rarity); cascade/carrier testing in founder populations (Navajo, Balkan) is the relevant targeted-screening context.

11. Outcome/Prognosis

  • Untreated natural history: progressive skeletal deformity and disability; per patient.info's clinical summary, the majority of untreated affected children become wheelchair-bound by age 15.
  • Variable severity/mortality: "Without curative treatment options, severe forms of juvenile Paget disease are a debilitating disease with high morbidity and increased mortality. However, the severity of disease is variable…and some patients will survive beyond the age of 50 years" (search synthesis of multiple sources; consistent with the genotype-phenotype gradient in §4). No formal survival curves or life-expectancy statistics were identified — again reflecting the case-report evidence base.
  • Treated outcomes: substantial and durable improvement in bone turnover markers, prevention of new fractures, and preserved/restored mobility with early, sustained anti-resorptive therapy (bisphosphonates or denosumab); e.g., the Czech patient treated from age 5 remained fracture-free and "physically active throughout adulthood without significant quality-of-life limitations" by age 19 (PMC12333066); the two-adult denosumab cohort saw ALP "steadily normalized" and pain scores fall from 7–9/10 to 0–5/10 with no new fractures over 12–13.5 years (PMC11994531).
  • Persistent extraskeletal risk despite skeletal control: retinopathy can still progress (including a case of sudden severe vision loss at age 46 despite 11+ years of denosumab) — an important prognostic caveat that skeletal disease control is not equivalent to complete disease control.
  • Complications driving morbidity: fractures, progressive deafness, vision loss from retinopathy/choroidal neovascularization, vascular aneurysm (carotid, iliac) with attendant rupture/bleeding risk, and (rarely) death from unrelated intercurrent illness in a JPD patient (one child in PMC8039828 died of pneumococcal meningitis, unrelated to JPD itself, at age 5.6 after 4.5 years of treatment).
  • Prognostic factors: TNFRSF11B genotype class (cysteine-domain/large-deletion vs. milder variant classes) is the clearest prognostic biomarker identified; age at treatment initiation is a major modifiable prognostic factor.

12. Treatment

Pharmacotherapy — anti-resorptive therapy is the mainstay

Bisphosphonates (first-line, most experience): - Suppress the pathologically accelerated bone turnover; demonstrated to normalize/near-normalize ALP and other turnover markers, prevent new fractures, halt deformity progression, and produce striking motor-developmental recovery when started early in childhood and continued through growth completion. - Agents used: pamidronate (IV, individually titrated dosing — e.g., 9 mg/kg/year in 3 cycles, later adjusted to 0.75 mg/kg every 4–5 weeks for pain control, or up to 5.6–9.2 mg/kg/year; PMC8039828), zoledronic acid (IV, e.g., 0.025 mg/kg with extended dosing intervals), alendronate and ibandronate (oral, in the Czech case achieving 73–80% reductions in P1NP/ALP/BAP and 41% reduction in β-CrossLaps by age 19; PMC12333066). - Caveat: turnover-marker suppression relapses if bisphosphonate treatment is discontinued — treatment is not curative and requires long-term/indefinite administration through growth. - Suggested NCIT term: NCIT:C15986 (Pharmacotherapy), or more specifically bisphosphonate class terms; therapeutic_agent candidates include CHEBI terms for pamidronate, zoledronic acid, alendronate, ibandronate.

Denosumab (RANKL-neutralizing monoclonal antibody — mechanistically the most direct pharmacologic mimic of the missing OPG protein): - In a girl with JPD, denosumab produced better disease control than bisphosphonate — ALP normalized and bone pain was more effectively controlled — but severe hypocalcemia occurred with the first injection, requiring hospitalization and IV calcium (PMID:23788687). - In the long-term adult cohort (two Balkan-mutation homozygous siblings, treated 12–13.5 years), individualized low, frequent dosing (30 mg every 2.5–3 months, i.e., 0.35–0.58 mg/kg — lower than standard osteoporosis dosing but more frequent) achieved sustained ALP normalization and pain control with no new fractures; asymptomatic hypocalcemia occurred after each injection in one subject during the first 2 years, then resolved (PMC11994531). - Explicit pediatric caution: "caution is needed if denosumab is given to children with JPD who have very high rates of bone turnover" — a cautionary pediatric case in the literature describes severe hungry bone syndrome with rebound hypercalcemia after denosumab initiation in a child (PMC11994531). - Denosumab does not reliably prevent retinopathy progression even with excellent skeletal control (see §11). - Suggested treatment_term: NCIT:C15986 (Pharmacotherapy); therapeutic_agent NCIT:C2477 (Denosumab, if this is the correct current NCIT code — verify).

Calcitonin: historically used before bisphosphonates became standard; "treatment with inhibitors of bone resorption (calcitonin or bisphosphonates) showed remarkable clinical and radiographic improvement" (early literature synthesis) — now largely superseded by bisphosphonates/denosumab.

Recombinant osteoprotegerin (investigational, proof-of-concept): Cundy et al., NEJM 2005 (PMID:16135836, "Recombinant Osteoprotegerin for Juvenile Paget's Disease") treated two adult siblings with once-weekly subcutaneous recombinant OPG (0.3–0.4 mg/kg); after 15 months, radial bone mass increased 9% and 30% respectively, skeletal bisphosphonate retention (a resorption surrogate) fell 37% and 55%, with radiographic improvement and only mild hypocalcemia/hypophosphatemia as adverse effects. This is proof-of-mechanism for direct OPG replacement but was never developed into an approved product; denosumab has since become the practical RANKL-pathway-targeted therapeutic.

Advanced/targeted therapeutics

No gene therapy, cell therapy, RNA-based therapy, or approved targeted biologic beyond denosumab was identified for JPD specifically.

Surgical/interventional

Not systematically detailed in the sources reviewed beyond fracture management; orthopedic correction of deformity may be considered per general pediatric orthopedic principles (not JPD-specific evidence identified). Vascular aneurysms have required neurointerventional/surgical management in individual case reports (carotid, iliac aneurysm cases).

Supportive/rehabilitative

  • Hearing aids/cochlear management for progressive hearing loss
  • Ophthalmologic surveillance and anti-VEGF intravitreal therapy (bevacizumab, aflibercept) for choroidal neovascularization complicating retinopathy — demonstrated effective ("almost full recovery of vision" in PMC11994531)
  • Physical therapy/motor rehabilitation, particularly around treatment initiation in infants with motor delay

Experimental

An investigational angiotensin-II type 1 receptor blockade approach was studied in the mouse model of JPD, improving bone mineral density and left ventricular contractility (ScienceDirect S0014299919304716) — a MODEL_ORGANISM-level finding relevant to the cardiovascular arm of the disease, not yet translated to human JPD treatment. No registered human clinical trials specific to JPD were identified in this search (contrast with the unrelated hypophosphatasia trial NCT00894075 that surfaced due to name similarity — a naming-confusion trap to avoid).

Treatment strategy

The practical algorithm emerging from the case literature: early diagnosis → early initiation of anti-resorptive therapy (bisphosphonate first-line; denosumab as an alternative/escalation with careful calcium monitoring) → continue through completion of growth → lifelong surveillance for extraskeletal complications (audiometry, ophthalmologic exam, vascular imaging) that may progress independent of skeletal control.

13. Prevention

  • Primary prevention: none possible for the genetic lesion itself; the only primary-prevention-adjacent measure is genetic counseling and carrier testing in founder populations (Navajo, Balkan) to inform reproductive decision-making, plus stated feasibility of prenatal diagnosis where a familial variant is known.
  • Secondary prevention: early biochemical/clinical recognition (elevated ALP in an infant/toddler with skeletal deformity) followed by prompt anti-resorptive treatment is repeatedly framed in the literature as the single most important prognosis-modifying intervention — "Early diagnosis and antiresorption treatment prevent further fractures and deformity progression, and improve the patient's quality of life" (search synthesis referencing PMC12333066 and related sources).
  • Tertiary prevention: ongoing multidisciplinary surveillance (audiology, ophthalmology, vascular imaging as indicated) to catch and treat extraskeletal complications (hearing loss interventions, anti-VEGF therapy for choroidal neovascularization, vascular aneurysm monitoring/intervention) that may progress independent of skeletal disease control.
  • Genetic counseling: recommended for families of affected individuals given autosomal recessive inheritance (TNFRSF11B form) and documented founder effects; carrier frequency data exist for the Navajo population specifically (~1/100).
  • Screening programs: no population-based newborn or carrier screening program for JPD was identified; targeted carrier screening in known founder populations is the closest analog described in the literature.

14. Other Species / Natural Disease

No naturally occurring veterinary/companion-animal JPD analog (OMIA entry) was identified in this search. The relevant cross-species biology is the engineered mouse knockout model (below) rather than a spontaneously occurring animal disease.

Orthologous gene: Tnfrsf11b (mouse ortholog of human TNFRSF11B); NCBI Gene ID for mouse Tnfrsf11b not independently verified here — confirm before curation.

15. Model Organisms

Tnfrsf11b (OPG) knockout mouse — the primary and best-validated model

  • Phenotype recapitulation: "Mice that lack osteoprotegerin owing to the knockout of Tnfrsf11b have numerous osteoclasts and rapidly remodeling woven bone rather than…lamellar bone. These mice manifest juvenile Paget's disease" — i.e., a high-fidelity recapitulation of the core skeletal phenotype (osteoclast excess, woven-bone remodeling), directly analogous to loss-of-function human TNFRSF11B disease.
  • Extraskeletal recapitulation: Tnfrsf11b-knockout mice also develop both conductive hearing loss (from abnormal middle-ear ossicles) and sensorineural hearing loss (from cochlear nerve demyelination/degeneration and spiral ganglion apoptosis) — closely mirroring the dual-mechanism deafness seen in human JPD (ScienceDirect S0969996113001228).
  • Cardiovascular extension: the same/related OPG-deficient mouse model has been used to study cardiovascular consequences, where angiotensin II type 1 receptor blockade improved bone mineral density and left ventricular contractility — extending the model beyond skeletal phenotyping into the vascular/cardiac domain relevant to JPD's aneurysm/vasculopathy phenotype (ScienceDirect S0014299919304716).
  • Limitations: specific reported limitations of the mouse model versus human JPD (e.g., whether retinopathy/angioid streaks are reproduced) were not identified in this search and should be checked directly in the primary Tnfrsf11b-knockout characterization papers (Bucay et al. 1998, Genes Dev, and Simonet et al. 1997, Cell — foundational OPG-knockout papers; PMIDs not independently re-verified in this pass and should be confirmed before citation).

No other model organism (zebrafish, Drosophila, C. elegans, iPSC/organoid) system for JPD was identified in this search.

Summary of Notable Gaps and Curation Flags

  • Evidence tier: virtually the entire evidence base is individual case reports/small series (<100 total published patients); prevalence and natural-history statistics are literature-count estimates, not registry data — grade accordingly.
  • Genetic heterogeneity: JPD is not TNFRSF11B-exclusive. TNFRSF11A (RANK, gain-of-function duplication, single case) and SP7 (Osterix, de novo neomorphic, distinct mechanism) are documented alternate causal genes with different inheritance patterns — this needs explicit multi-gene/multi-inheritance modeling if curated, not a single AR TNFRSF11B block.
  • A same-gene, opposite-mechanism trap: SP7 loss-of-function causes low-turnover osteogenesis imperfecta type XII, while a distinct SP7 neomorphic gain-of-function variant causes high-turnover JPD — do not conflate.
  • A name trap: "hyperphosphatasia" (JPD) vs. "hypophosphatasia" (a biochemically opposite, ALPL-related disorder) — verify no cross-contamination in any automated/AI-assisted literature search given the near-identical names.
  • Retinopathy is not fully treatment-coupled: skeletal disease control (bisphosphonate or denosumab) does not guarantee prevention of progressive retinopathy — an important point for any treatment-target-mechanism modeling.
  • Several claims above were drawn from AI-generated search-result syntheses rather than directly fetched primary-source text (multiple PMC/NEJM/Wiley full-text fetches were blocked by CAPTCHA/paywall/403 during this research pass, including OMIM 239000 direct fetch, the PMC6779132 review, the NEJM Whyte 2002 full text, and Orphanet's page). Where a claim is load-bearing for curation (exact quotes, specific numeric values, PMID linkage), the primary source should be independently re-fetched and the snippet verified against it before it is entered into any evidence-graded knowledge base record, per this repository's zero-tolerance policy on unverified snippets.

Sources