Pycnodysostosis

Mendelian MONDO:0009940 Pathograph 26 Sclerosing Bone Dysplasias

Pycnodysostosis is an autosomal recessive osteochondrodysplasia caused by loss-of-function mutations in the CTSK gene encoding cathepsin K, a lysosomal cysteine protease highly expressed in osteoclasts. Cathepsin K is the major protease responsible for degradation of type I collagen in the bone matrix. In pycnodysostosis, osteoclasts can acidify the resorption lacuna normally but cannot degrade the organic bone matrix, leading to osteosclerosis and short stature. Characteristic features include increased bone density with pathologic fractures, open fontanelles and sutures, and short stature. The French painter Henri de Toulouse-Lautrec is believed to have had this condition.

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1
Inheritance
5
Pathophys.
21
Phenotypes
26
Pathograph
2
Genes
2
Treatments
1
Deep Research
👪

Inheritance

1
Autosomal Recessive
Autosomal recessive inheritance. 33 different CTSK mutations have been identified in 59 unrelated families worldwide, with 37% from Europe and 31% from Asia.
Show evidence (1 reference)
PMID:8703060 SUPPORT
"Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21"
Establishes autosomal recessive inheritance and chromosomal localization.
⚙

Pathophysiology

5
Cathepsin K Deficiency in Osteoclasts
Cathepsin K is a lysosomal cysteine protease with highest expression in osteoclasts. Loss-of-function mutations cause total loss or inactivity of cathepsin K protein. Hot mutation spots are found in exons 6 and 7, with 70% of mutations in the mature domain.
Osteoclast link
lysosomal protein catabolic process link ↓ DECREASED collagen catabolic process link ↓ DECREASED proteolysis link ↓ DECREASED
lysosome link
Downstream
Impaired Organic Bone Matrix Degradation Loss or inactivity of CTSK/cathepsin K in osteoclasts impairs degradation of type I collagen and other organic bone matrix proteins during bone resorption.
Show evidence (3 references)
PMID:8703060 SUPPORT
"pycnodysostosis results from gene defects in a lysosomal protease with highest expression in osteoclasts"
Identifies cathepsin K as an osteoclast-specific lysosomal protease causing pycnodysostosis.
PMID:21569238 SUPPORT
"CTSK mutations result in total loss or inactivity of the CTSK protein, which causes abnormal degradation of bone matrix proteins such as type I collagen"
Confirms that CTSK mutations abolish collagen degradation capacity.
PMID:21569238 SUPPORT
"The hot mutation spots are found in exons 6 and 7"
Identifies mutational hotspots in the CTSK gene.
Impaired Organic Bone Matrix Degradation
Cathepsin K is the major protease responsible for degradation of type I collagen in the bone matrix during bone resorption. Unlike osteopetrosis, osteoclasts in pycnodysostosis can acidify the resorption lacuna normally but cannot degrade the demineralized organic matrix. This leads to accumulation of undigested collagen matrix and osteosclerosis.
bone resorption link ↓ DECREASED bone remodeling link ⚠ ABNORMAL
Downstream
Osteosclerotic brittle-bone phenotype Failure to digest demineralized type I collagen matrix produces osteosclerosis, abnormal bone architecture, and fracture susceptibility.
Craniofacial and suture remodeling defect Impaired osteoclast collagen degradation alters skull, clavicle, facial, and mandibular remodeling, producing delayed closure of sutures and characteristic craniofacial morphology.
Dentodigital and upper-airway skeletal consequences Abnormal jaw, digit, nail, and dental development follows the same impaired skeletal matrix remodeling process and contributes to dental crowding, malocclusion, and obstructive sleep apnea.
Show evidence (1 reference)
PMID:8703060 SUPPORT
"cathepsin K is a major protease in bone resorption"
Establishes cathepsin K as the primary bone matrix-degrading enzyme.
Osteosclerotic brittle-bone phenotype
Matrix retention and defective osteoclast-mediated remodeling cause dense but brittle bone, producing generalized osteosclerosis, pathologic fractures, short stature, and distal phalangeal osteolysis.
osteoclast link
bone remodeling link ⚠ ABNORMAL bone resorption link ↓ DECREASED
Downstream
Generalized osteosclerosis Increased bone density is the skeletal readout of impaired organic matrix turnover.
Short stature Defective skeletal remodeling and osteosclerotic bone dysplasia contribute to short stature.
Recurrent fractures Dense but structurally abnormal bone predisposes to pathologic and recurrent fractures.
Acroosteolysis of the distal phalanges Distal phalangeal bone remodeling abnormalities produce terminal phalangeal osteolysis.
Show evidence (1 reference)
PMID:21569238 SUPPORT Human Clinical
"including short stature, an increase in bone density with pathologic fractures"
Review of reported patients supports short stature, increased bone density, and pathologic fractures as the core brittle-bone phenotype.
Craniofacial and suture remodeling defect
Osteoclast collagen-degradation failure disrupts cranial vault, mandibular, maxillary, clavicular, and orbital skeletal modeling, producing delayed fontanelle and suture closure, frontal bossing, midface retrusion, micrognathia, obtuse mandibular angle, clavicular dysplasia, blue sclerae, and proptosis.
bone remodeling link ⚠ ABNORMAL
Downstream
Delayed closure of the anterior fontanelle Skull remodeling defects delay anterior fontanelle closure.
Delayed cranial suture closure Impaired skull remodeling leaves cranial sutures persistently open.
Frontal bossing Altered craniofacial modeling produces frontal bossing.
Midface retrusion Maxillary and midfacial hypoplasia reflect abnormal craniofacial remodeling.
Micrognathia Mandibular remodeling defects produce a small mandible.
Obtuse angle of mandible Mandibular modeling abnormalities produce an obtuse mandibular angle.
Clavicular dysplasia Skeletal remodeling abnormalities involve the clavicles.
Blue sclerae Blue sclerae accompany the craniofacial phenotype in pycnodysostosis.
Proptosis Orbital craniofacial morphology contributes to ocular proptosis.
Show evidence (1 reference)
PMID:28576543 SUPPORT Human Clinical
"characteristic facial appearance (delayed closure of fontanelles and cranial sutures, mandibular hypoplasia and angle disorder, blue sclera)"
ENT case-series evidence supports the craniofacial and suture-remodeling phenotype cluster.
Dentodigital and upper-airway skeletal consequences
The same collagen-rich skeletal matrix turnover defect affects distal phalanges, nails, teeth, maxillomandibular alignment, and the upper airway, producing brachydactyly, nail dysplasia, delayed tooth eruption, enamel hypoplasia, dental crowding, malocclusion, and obstructive sleep apnea.
bone remodeling link ⚠ ABNORMAL
Downstream
Brachydactyly Distal appendicular skeletal involvement produces short digits.
Nail dysplasia Distal digit involvement includes dysplastic nails.
Delayed eruption of teeth Abnormal craniofacial and dental development delays tooth eruption.
Enamel hypoplasia Dental developmental abnormalities include enamel hypoplasia.
Dental crowding Maxillomandibular skeletal constraints contribute to dental crowding.
Dental malocclusion Jaw remodeling abnormalities produce malocclusion.
Obstructive sleep apnea Craniofacial and upper-airway anatomy predispose to obstructive sleep apnea.
Narrow palate Maxillary and oral skeletal remodeling abnormalities produce a narrow or grooved palate.
Show evidence (1 reference)
PMID:28576543 SUPPORT Human Clinical
"All patients had facial dysmorphism with frontal bossing and the hands and feet had short digits with overlying cutaneous wrinkles that tapered off with large overriding nails."
ENT case-series evidence supports digital and nail involvement alongside craniofacial dysmorphism.
⬡

Pathograph

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

Phenotypes

21
Eye 2
Blue sclerae Blue sclerae (HP:0000592)
Show evidence (1 reference)
PMID:28576543 SUPPORT Human Clinical
"characteristic facial appearance (delayed closure of fontanelles and cranial sutures, mandibular hypoplasia and angle disorder, blue sclera)"
ENT case series abstract lists blue sclera as part of the characteristic facial phenotype.
Proptosis Proptosis (HP:0000520)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"ocular proptosis (8 of 8)"
Pediatric cohort documents proptosis in all eight evaluated children.
Head and Neck 5
Frontal bossing Frontal bossing (HP:0002007)
Show evidence (1 reference)
PMID:40523612 SUPPORT Human Clinical
"frontal bossing (92 %)"
Systematic review identifies frontal bossing as a common craniofacial feature in published cases.
Midface retrusion Midface retrusion (HP:0011800)
Show evidence (1 reference)
PMID:40523612 SUPPORT Human Clinical
"midfacial hypoplasia (100 %)"
Systematic review of reported patients supports midface retrusion through universal midfacial hypoplasia in the reviewed maxillofacial cohort.
Micrognathia Micrognathia (HP:0000347)
Show evidence (1 reference)
PMID:40523612 SUPPORT Human Clinical
"micrognathia (92 %)"
Systematic review identifies micrognathia as a recurrent craniofacial finding in published cases.
Delayed eruption of teeth Delayed eruption of teeth (HP:0000684)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"delayed teeth eruption (8 of 8)"
Pediatric cohort documents delayed eruption in all eight evaluated children.
Enamel hypoplasia Enamel hypoplasia (HP:0006297)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"enamel hypoplasia (7 of 8)"
Pediatric cohort documents enamel hypoplasia in most evaluated children.
Integument 1
Nail dysplasia Nail dysplasia (HP:0002164)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"dysplastic nails (8 of 8)"
Pediatric cohort documents nail dysplasia in all eight evaluated children.
Limbs 1
Brachydactyly Brachydactyly (HP:0001156)
Show evidence (1 reference)
PMID:28576543 SUPPORT Human Clinical
"All patients had facial dysmorphism with frontal bossing and the hands and feet had short digits with overlying cutaneous wrinkles that tapered off with large overriding nails."
Pediatric ENT case series documents short digits of the hands and feet, supporting brachydactyly.
Musculoskeletal 1
Recurrent fractures Recurrent fractures (HP:0002757)
Show evidence (1 reference)
PMID:21569238 SUPPORT Human Clinical
"an increase in bone density with pathologic fractures"
Review of 159 reported patients identifies pathologic fractures as a typical skeletal phenotype.
Nervous System 1
Obstructive sleep apnea Obstructive sleep apnea (HP:0002870)
Show evidence (1 reference)
PMID:28576543 SUPPORT Human Clinical
"Video recordings showed that six of the eight patients (75%) had respiratory distress and four (50%) had sleep apnea."
Pediatric ENT case series documents obstructive sleep apnea in half of the evaluated patients.
Growth 1
Short stature Short stature (HP:0004322)
Show evidence (1 reference)
PMID:21569238 SUPPORT Human Clinical
"including short stature, an increase in bone density with pathologic fractures"
Review of 159 reported patients lists short stature as a typical phenotype.
Other 9
Generalized osteosclerosis Generalized osteosclerosis (HP:0005789)
Show evidence (1 reference)
PMID:8703060 SUPPORT Human Clinical
"Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21."
Foundational clinical description of generalized osteosclerosis in pycnodysostosis.
Acroosteolysis of the distal phalanges Osteolytic defects of the distal phalanges of the hand (HP:0009839)
Show evidence (1 reference)
PMID:28576543 SUPPORT Human Clinical
"acroosteolysis of the distal phalanges."
ENT case series abstract names acroosteolysis of the distal phalanges as a cardinal diagnostic feature; HPO grounds this to the exact-synonym hand distal-phalange osteolysis term.
Clavicular dysplasia Abnormal clavicle morphology (HP:0000889)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"dysplastic acromial ends of the clavicles (6 of 8)"
Pediatric cohort documents abnormal clavicular morphology affecting the acromial ends.
Delayed closure of the anterior fontanelle Delayed closure of the anterior fontanelle (HP:0001476)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"large fontanel with delayed closure (8 of 8)"
Cohort data directly support delayed closure of the anterior fontanelle.
Delayed cranial suture closure Delayed cranial suture closure (HP:0000270)
Show evidence (1 reference)
PMID:40523612 SUPPORT Human Clinical
"unclosed cranial sutures (97 %)"
Systematic review of 69 reported patients identifies unclosed cranial sutures as a near-constant maxillofacial feature.
Obtuse angle of mandible Obtuse angle of mandible (HP:0005446)
Show evidence (1 reference)
PMID:11474477 SUPPORT Human Clinical
"obtuse mandibular angle (8 of 8)"
Pediatric cohort documents obtuse mandibular angle in all eight evaluated patients.
Dental crowding Dental crowding (HP:0000678)
Show evidence (1 reference)
PMID:38532649 SUPPORT Human Clinical
"dental crowding, malocclusion (anterior crossbite, posterior open bite)"
Dedicated oro-dental cohort study identifies dental crowding as a characteristic dental manifestation.
Dental malocclusion Dental malocclusion (HP:0000689)
Show evidence (1 reference)
PMID:38532649 SUPPORT Human Clinical
"malocclusion (anterior crossbite, posterior open bite)"
Dedicated oro-dental cohort study identifies malocclusion as a characteristic dental manifestation.
Narrow palate Narrow palate (HP:0000189)
Show evidence (1 reference)
PMID:40523612 SUPPORT Human Clinical
"narrow and grooved palate (100-73 %)"
Systematic review identifies narrow or grooved palate as a high-frequency oral/maxillofacial feature.
🧬

Genetic Associations

2
CTSK Mutations (Causative)
Show evidence (2 references)
PMID:8703060 SUPPORT
"Nonsense, missense, and stop codon mutations in the gene encoding cathepsin K were identified in patients"
Identifies the range of CTSK mutation types in pycnodysostosis.
PMID:21569238 SUPPORT
"Thirty three different CTSK mutations have been found in 59 unrelated pycnodysostosis families"
Comprehensive catalog of 33 mutations in 59 families.
CTSK (Pathogenic Variants)
Show evidence (1 reference)
CGGV:assertion_8135617e-f334-4c22-aa9e-b1efd50e9326-2022-11-11T180000.000Z SUPPORT Other
"CTSK | HGNC:2536 | pycnodysostosis | MONDO:0009940 | AR | Definitive"
ClinGen classifies the CTSK-pycnodysostosis gene-disease relationship as definitive with autosomal recessive inheritance.
💊

Treatments

2
Supportive Care
Action: supportive care MAXO:0000950
Fracture management and orthopedic surveillance. No targeted therapy available, though cathepsin K represents a potential therapeutic target.
Genetic Counseling
Action: genetic counseling MAXO:0000079
Genetic counseling for affected families given autosomal recessive inheritance.
{ }

Source YAML

click to show 
name: Pycnodysostosis
creation_date: '2026-02-13T00:31:42Z'
updated_date: '2026-05-21T12:10:54Z'
category: Mendelian
description: >
  Pycnodysostosis is an autosomal recessive osteochondrodysplasia caused by
  loss-of-function mutations in the CTSK gene encoding cathepsin K, a lysosomal
  cysteine protease highly expressed in osteoclasts. Cathepsin K is the major
  protease responsible for degradation of type I collagen in the bone matrix.
  In pycnodysostosis, osteoclasts can acidify the resorption lacuna normally
  but cannot degrade the organic bone matrix, leading to osteosclerosis and
  short stature. Characteristic features include increased bone density with
  pathologic fractures, open fontanelles and sutures, and short stature.
  The French painter Henri de Toulouse-Lautrec is believed to have had
  this condition.
disease_term:
  preferred_term: pycnodysostosis
  term:
    id: MONDO:0009940
    label: pycnodysostosis
parents:
- Sclerosing Bone Dysplasias
inheritance:
- name: Autosomal Recessive
  description: >
    Autosomal recessive inheritance. 33 different CTSK mutations have been
    identified in 59 unrelated families worldwide, with 37% from Europe
    and 31% from Asia.
  evidence:
  - reference: PMID:8703060
    reference_title: "Pycnodysostosis, a lysosomal disease caused by cathepsin K deficiency."
    supports: SUPPORT
    snippet: "Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21"
    explanation: "Establishes autosomal recessive inheritance and chromosomal localization."
prevalence:
- population: Global population
  percentage: Approximately 1 per million
  notes: >-
    A 2016 molecular cohort study states that pycnodysostosis prevalence is
    estimated at about 1 per million overall, with a founder-enriched local
    prevalence of 3 per million reported in Ceara State in northeastern Brazil.
  evidence:
  - reference: PMID:27558267
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pycnodysostosis is an autosomal recessive skeletal dysplasia, the prevalence of which is estimated to be low (1 per million). Nevertheless, in recent years we have found 27 affected individuals from 22 families in Ceará State, a region of the Brazilian Northeast, giving a local prevalence of 3 per million."
    explanation: This molecular epidemiology study provides both a commonly cited global prevalence estimate and a higher founder-population prevalence from northeastern Brazil.
  - reference: PMID:21569238
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we performed a literature retrospective study of 159 pycnodysostosis patients reported since 1996 and focused on the genetic characteristics of CTSK mutations and/or the clinical phenotypes of pycnodysostosis. Thirty three different CTSK mutations have been found in 59 unrelated pycnodysostosis families."
    explanation: This earlier review corroborates the disorder's rarity by showing the limited number of reported patients and families in the indexed literature.
pathophysiology:
- name: Cathepsin K Deficiency in Osteoclasts
  description: >
    Cathepsin K is a lysosomal cysteine protease with highest expression in
    osteoclasts. Loss-of-function mutations cause total loss or inactivity
    of cathepsin K protein. Hot mutation spots are found in exons 6 and 7,
    with 70% of mutations in the mature domain.
  cell_types:
  - preferred_term: Osteoclast
    term:
      id: CL:0000092
      label: osteoclast
  locations:
  - preferred_term: lysosome
    term:
      id: GO:0005764
      label: lysosome
  biological_processes:
  - preferred_term: lysosomal protein catabolic process
    term:
      id: GO:1905146
      label: lysosomal protein catabolic process
    modifier: DECREASED
  - preferred_term: collagen catabolic process
    term:
      id: GO:0030574
      label: collagen catabolic process
    modifier: DECREASED
  - preferred_term: proteolysis
    term:
      id: GO:0006508
      label: proteolysis
    modifier: DECREASED
  evidence:
  - reference: PMID:8703060
    reference_title: "Pycnodysostosis, a lysosomal disease caused by cathepsin K deficiency."
    supports: SUPPORT
    snippet: "pycnodysostosis results from gene defects in a lysosomal protease with highest expression in osteoclasts"
    explanation: "Identifies cathepsin K as an osteoclast-specific lysosomal protease causing pycnodysostosis."
  - reference: PMID:21569238
    reference_title: "Clinical and animal research findings in pycnodysostosis and gene mutations of cathepsin K from 1996 to 2011."
    supports: SUPPORT
    snippet: "CTSK mutations result in total loss or inactivity of the CTSK protein, which causes abnormal degradation of bone matrix proteins such as type I collagen"
    explanation: "Confirms that CTSK mutations abolish collagen degradation capacity."
  - reference: PMID:21569238
    reference_title: "Clinical and animal research findings in pycnodysostosis and gene mutations of cathepsin K from 1996 to 2011."
    supports: SUPPORT
    snippet: "The hot mutation spots are found in exons 6 and 7"
    explanation: "Identifies mutational hotspots in the CTSK gene."
  downstream:
  - target: Impaired Organic Bone Matrix Degradation
    description: >
      Loss or inactivity of CTSK/cathepsin K in osteoclasts impairs degradation
      of type I collagen and other organic bone matrix proteins during bone
      resorption.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:21569238
      reference_title: "Clinical and animal research findings in pycnodysostosis and gene mutations of cathepsin K from 1996 to 2011."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >
        CTSK mutations result in total loss or inactivity of the CTSK protein,
        which causes abnormal degradation of bone matrix proteins such as type I
        collagen.
      explanation: >
        This review links CTSK loss or inactivity directly to abnormal
        degradation of type I collagen and other bone matrix proteins.
- name: Impaired Organic Bone Matrix Degradation
  description: >
    Cathepsin K is the major protease responsible for degradation of type I
    collagen in the bone matrix during bone resorption. Unlike osteopetrosis,
    osteoclasts in pycnodysostosis can acidify the resorption lacuna normally
    but cannot degrade the demineralized organic matrix. This leads to
    accumulation of undigested collagen matrix and osteosclerosis.
  biological_processes:
  - preferred_term: bone resorption
    term:
      id: GO:0045453
      label: bone resorption
    modifier: DECREASED
  - preferred_term: bone remodeling
    term:
      id: GO:0046849
      label: bone remodeling
    modifier: ABNORMAL
  evidence:
  - reference: PMID:8703060
    reference_title: "Pycnodysostosis, a lysosomal disease caused by cathepsin K deficiency."
    supports: SUPPORT
    snippet: "cathepsin K is a major protease in bone resorption"
    explanation: "Establishes cathepsin K as the primary bone matrix-degrading enzyme."
  downstream:
  - target: Osteosclerotic brittle-bone phenotype
    description: >
      Failure to digest demineralized type I collagen matrix produces
      osteosclerosis, abnormal bone architecture, and fracture susceptibility.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - collagen-rich organic matrix retention
    - impaired osteoclast-mediated bone remodeling
    evidence:
    - reference: PMID:21569238
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "including short stature, an increase in bone density with pathologic fractures"
      explanation: The clinical review connects pycnodysostosis to increased bone density, pathologic fractures, and short stature.
  - target: Craniofacial and suture remodeling defect
    description: >
      Impaired osteoclast collagen degradation alters skull, clavicle, facial,
      and mandibular remodeling, producing delayed closure of sutures and
      characteristic craniofacial morphology.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - impaired cranial and mandibular bone remodeling
    evidence:
    - reference: PMID:28576543
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "characteristic facial appearance (delayed closure of fontanelles and cranial sutures, mandibular hypoplasia and angle disorder, blue sclera)"
      explanation: ENT case-series evidence links the skeletal disorder to delayed cranial closure, mandibular abnormalities, and blue sclera.
  - target: Dentodigital and upper-airway skeletal consequences
    description: >
      Abnormal jaw, digit, nail, and dental development follows the same
      impaired skeletal matrix remodeling process and contributes to dental
      crowding, malocclusion, and obstructive sleep apnea.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - mandibular and maxillary remodeling defect
    - distal phalangeal skeletal involvement
    evidence:
    - reference: PMID:28576543
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "All patients had facial dysmorphism with frontal bossing and the hands and feet had short digits with overlying cutaneous wrinkles that tapered off with large overriding nails."
      explanation: ENT case-series evidence supports combined craniofacial and digital involvement.
- name: Osteosclerotic brittle-bone phenotype
  description: >
    Matrix retention and defective osteoclast-mediated remodeling cause dense
    but brittle bone, producing generalized osteosclerosis, pathologic fractures,
    short stature, and distal phalangeal osteolysis.
  biological_processes:
  - preferred_term: bone remodeling
    term:
      id: GO:0046849
      label: bone remodeling
    modifier: ABNORMAL
  - preferred_term: bone resorption
    term:
      id: GO:0045453
      label: bone resorption
    modifier: DECREASED
  cell_types:
  - preferred_term: osteoclast
    term:
      id: CL:0000092
      label: osteoclast
  evidence:
  - reference: PMID:21569238
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "including short stature, an increase in bone density with pathologic fractures"
    explanation: Review of reported patients supports short stature, increased bone density, and pathologic fractures as the core brittle-bone phenotype.
  downstream:
  - target: Generalized osteosclerosis
    description: Increased bone density is the skeletal readout of impaired organic matrix turnover.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:8703060
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21."
      explanation: Foundational clinical description supports osteosclerosis as a defining phenotype.
  - target: Short stature
    description: Defective skeletal remodeling and osteosclerotic bone dysplasia contribute to short stature.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - osteochondrodysplasia
    evidence:
    - reference: PMID:21569238
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "including short stature, an increase in bone density with pathologic fractures"
      explanation: Review of 159 patients lists short stature with increased bone density and fractures.
  - target: Recurrent fractures
    description: Dense but structurally abnormal bone predisposes to pathologic and recurrent fractures.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - brittle osteosclerotic bone
    evidence:
    - reference: PMID:21569238
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "an increase in bone density with pathologic fractures"
      explanation: Review evidence supports pathologic fractures as a typical consequence of increased bone density.
  - target: Acroosteolysis of the distal phalanges
    description: Distal phalangeal bone remodeling abnormalities produce terminal phalangeal osteolysis.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - distal phalangeal skeletal involvement
    evidence:
    - reference: PMID:28576543
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "acroosteolysis of the distal phalanges."
      explanation: ENT case series identifies distal phalangeal acroosteolysis as a cardinal feature.
- name: Craniofacial and suture remodeling defect
  description: >
    Osteoclast collagen-degradation failure disrupts cranial vault, mandibular,
    maxillary, clavicular, and orbital skeletal modeling, producing delayed
    fontanelle and suture closure, frontal bossing, midface retrusion,
    micrognathia, obtuse mandibular angle, clavicular dysplasia, blue sclerae,
    and proptosis.
  biological_processes:
  - preferred_term: bone remodeling
    term:
      id: GO:0046849
      label: bone remodeling
    modifier: ABNORMAL
  evidence:
  - reference: PMID:28576543
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facial appearance (delayed closure of fontanelles and cranial sutures, mandibular hypoplasia and angle disorder, blue sclera)"
    explanation: ENT case-series evidence supports the craniofacial and suture-remodeling phenotype cluster.
  downstream:
  - target: Delayed closure of the anterior fontanelle
    description: Skull remodeling defects delay anterior fontanelle closure.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - cranial vault remodeling defect
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "large fontanel with delayed closure (8 of 8)"
      explanation: Pediatric cohort documents delayed fontanel closure in all eight evaluated patients.
  - target: Delayed cranial suture closure
    description: Impaired skull remodeling leaves cranial sutures persistently open.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - cranial suture remodeling defect
    evidence:
    - reference: PMID:40523612
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "unclosed cranial sutures (97 %)"
      explanation: Systematic review identifies unclosed cranial sutures as a near-constant feature.
  - target: Frontal bossing
    description: Altered craniofacial modeling produces frontal bossing.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - craniofacial skeletal remodeling defect
    evidence:
    - reference: PMID:40523612
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "frontal bossing (92 %)"
      explanation: Systematic review supports frontal bossing as a common craniofacial feature.
  - target: Midface retrusion
    description: Maxillary and midfacial hypoplasia reflect abnormal craniofacial remodeling.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - maxillofacial skeletal remodeling defect
    evidence:
    - reference: PMID:40523612
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "midfacial hypoplasia (100 %)"
      explanation: Systematic review supports midfacial hypoplasia as universal in the reviewed maxillofacial cohort.
  - target: Micrognathia
    description: Mandibular remodeling defects produce a small mandible.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - mandibular remodeling defect
    evidence:
    - reference: PMID:40523612
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "micrognathia (92 %)"
      explanation: Systematic review supports micrognathia as a recurrent craniofacial finding.
  - target: Obtuse angle of mandible
    description: Mandibular modeling abnormalities produce an obtuse mandibular angle.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - mandibular remodeling defect
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "obtuse mandibular angle (8 of 8)"
      explanation: Pediatric cohort documents obtuse mandibular angle in all evaluated children.
  - target: Clavicular dysplasia
    description: Skeletal remodeling abnormalities involve the clavicles.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - clavicular skeletal remodeling defect
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "dysplastic acromial ends of the clavicles (6 of 8)"
      explanation: Pediatric cohort documents abnormal clavicular morphology.
  - target: Blue sclerae
    description: Blue sclerae accompany the craniofacial phenotype in pycnodysostosis.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28576543
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "characteristic facial appearance (delayed closure of fontanelles and cranial sutures, mandibular hypoplasia and angle disorder, blue sclera)"
      explanation: ENT case series lists blue sclera as part of the characteristic facial appearance.
  - target: Proptosis
    description: Orbital craniofacial morphology contributes to ocular proptosis.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - orbital craniofacial remodeling defect
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "ocular proptosis (8 of 8)"
      explanation: Pediatric cohort documents ocular proptosis in all eight evaluated children.
- name: Dentodigital and upper-airway skeletal consequences
  description: >
    The same collagen-rich skeletal matrix turnover defect affects distal
    phalanges, nails, teeth, maxillomandibular alignment, and the upper airway,
    producing brachydactyly, nail dysplasia, delayed tooth eruption, enamel
    hypoplasia, dental crowding, malocclusion, and obstructive sleep apnea.
  biological_processes:
  - preferred_term: bone remodeling
    term:
      id: GO:0046849
      label: bone remodeling
    modifier: ABNORMAL
  evidence:
  - reference: PMID:28576543
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had facial dysmorphism with frontal bossing and the hands and feet had short digits with overlying cutaneous wrinkles that tapered off with large overriding nails."
    explanation: ENT case-series evidence supports digital and nail involvement alongside craniofacial dysmorphism.
  downstream:
  - target: Brachydactyly
    description: Distal appendicular skeletal involvement produces short digits.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - distal phalangeal skeletal remodeling defect
    evidence:
    - reference: PMID:28576543
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "All patients had facial dysmorphism with frontal bossing and the hands and feet had short digits with overlying cutaneous wrinkles that tapered off with large overriding nails."
      explanation: Case-series evidence documents short digits of the hands and feet.
  - target: Nail dysplasia
    description: Distal digit involvement includes dysplastic nails.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - distal digit skeletal and appendageal involvement
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "dysplastic nails (8 of 8)"
      explanation: Pediatric cohort documents nail dysplasia in all evaluated children.
  - target: Delayed eruption of teeth
    description: Abnormal craniofacial and dental development delays tooth eruption.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - dentoalveolar remodeling defect
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "delayed teeth eruption (8 of 8)"
      explanation: Pediatric cohort documents delayed tooth eruption in all evaluated children.
  - target: Enamel hypoplasia
    description: Dental developmental abnormalities include enamel hypoplasia.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:11474477
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "enamel hypoplasia (7 of 8)"
      explanation: Pediatric cohort documents enamel hypoplasia in most evaluated children.
  - target: Dental crowding
    description: Maxillomandibular skeletal constraints contribute to dental crowding.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - jaw remodeling defect
    evidence:
    - reference: PMID:38532649
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "dental crowding, malocclusion (anterior crossbite, posterior open bite)"
      explanation: Oro-dental cohort evidence identifies dental crowding as a characteristic manifestation.
  - target: Dental malocclusion
    description: Jaw remodeling abnormalities produce malocclusion.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - maxillomandibular remodeling defect
    evidence:
    - reference: PMID:38532649
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "malocclusion (anterior crossbite, posterior open bite)"
      explanation: Oro-dental cohort evidence identifies malocclusion as a characteristic manifestation.
  - target: Obstructive sleep apnea
    description: Craniofacial and upper-airway anatomy predispose to obstructive sleep apnea.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - upper-airway narrowing from craniofacial skeletal morphology
    evidence:
    - reference: PMID:28576543
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Video recordings showed that six of the eight patients (75%) had respiratory distress and four (50%) had sleep apnea."
      explanation: ENT case series documents sleep apnea in affected children.
  - target: Narrow palate
    description: Maxillary and oral skeletal remodeling abnormalities produce a narrow or grooved palate.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - maxillofacial skeletal remodeling defect
    evidence:
    - reference: PMID:40523612
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "narrow and grooved palate (100-73 %)"
      explanation: Systematic review supports narrow or grooved palate as a high-frequency oral/maxillofacial feature.
phenotypes:
- category: Skeletal
  name: Generalized osteosclerosis
  description: >
    Diffuse increased bone density is a core radiographic feature of
    pycnodysostosis.
  phenotype_term:
    preferred_term: generalized osteosclerosis
    term:
      id: HP:0005789
      label: Generalized osteosclerosis
  evidence:
  - reference: PMID:8703060
    reference_title: "Pycnodysostosis, a lysosomal disease caused by cathepsin K deficiency."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pycnodysostosis, an autosomal recessive osteochondrodysplasia characterized by osteosclerosis and short stature, maps to chromosome 1q21."
    explanation: Foundational clinical description of generalized osteosclerosis in pycnodysostosis.
- category: Skeletal
  name: Short stature
  description: >
    Short stature is a characteristic growth phenotype in affected individuals.
  phenotype_term:
    preferred_term: short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:21569238
    reference_title: "Clinical and animal research findings in pycnodysostosis and gene mutations of cathepsin K from 1996 to 2011."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "including short stature, an increase in bone density with pathologic fractures"
    explanation: Review of 159 reported patients lists short stature as a typical phenotype.
- category: Skeletal
  name: Recurrent fractures
  description: >
    Fragile sclerotic bone predisposes affected individuals to pathologic or
    recurrent fractures.
  phenotype_term:
    preferred_term: recurrent fractures
    term:
      id: HP:0002757
      label: Recurrent fractures
  evidence:
  - reference: PMID:21569238
    reference_title: "Clinical and animal research findings in pycnodysostosis and gene mutations of cathepsin K from 1996 to 2011."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an increase in bone density with pathologic fractures"
    explanation: Review of 159 reported patients identifies pathologic fractures as a typical skeletal phenotype.
- category: Skeletal
  name: Brachydactyly
  description: >
    Short digits of the hands and feet are recurrent appendicular findings in
    pycnodysostosis.
  phenotype_term:
    preferred_term: brachydactyly
    term:
      id: HP:0001156
      label: Brachydactyly
  evidence:
  - reference: PMID:28576543
    reference_title: "Pycnodysostosis at otorhinolaryngology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "All patients had facial dysmorphism with frontal bossing and the hands and feet had short digits with overlying cutaneous wrinkles that tapered off with large overriding nails."
    explanation: Pediatric ENT case series documents short digits of the hands and feet, supporting brachydactyly.
- category: Skeletal
  name: Acroosteolysis of the distal phalanges
  description: >
    Resorption of the terminal phalanges is a cardinal distinguishing feature of
    pycnodysostosis.
  phenotype_term:
    preferred_term: acroosteolysis of the distal phalanges
    term:
      id: HP:0009839
      label: Osteolytic defects of the distal phalanges of the hand
  evidence:
  - reference: PMID:28576543
    reference_title: "Pycnodysostosis at otorhinolaryngology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "acroosteolysis of the distal phalanges."
    explanation: ENT case series abstract names acroosteolysis of the distal phalanges as a cardinal diagnostic feature; HPO grounds this to the exact-synonym hand distal-phalange osteolysis term.
- category: Skeletal
  name: Clavicular dysplasia
  description: >
    Abnormal clavicular morphology, particularly involving the acromial ends, is
    reported in affected children.
  phenotype_term:
    preferred_term: clavicular dysplasia
    term:
      id: HP:0000889
      label: Abnormal clavicle morphology
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dysplastic acromial ends of the clavicles (6 of 8)"
    explanation: Pediatric cohort documents abnormal clavicular morphology affecting the acromial ends.
- category: Craniofacial
  name: Delayed closure of the anterior fontanelle
  description: >
    Persistence of a large anterior fontanelle beyond the expected age is a
    common cranial finding.
  phenotype_term:
    preferred_term: delayed closure of the anterior fontanelle
    term:
      id: HP:0001476
      label: Delayed closure of the anterior fontanelle
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "large fontanel with delayed closure (8 of 8)"
    explanation: Cohort data directly support delayed closure of the anterior fontanelle.
- category: Craniofacial
  name: Delayed cranial suture closure
  description: >
    Persistently open or delayed-closing cranial sutures are a hallmark skull
    abnormality in pycnodysostosis.
  phenotype_term:
    preferred_term: delayed cranial suture closure
    term:
      id: HP:0000270
      label: Delayed cranial suture closure
  evidence:
  - reference: PMID:40523612
    reference_title: "Oral and maxillofacial manifestations of Pycnodysostosis: a summary of clinical, radiological and cephalometric diagnostic criteria. A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "unclosed cranial sutures (97 %)"
    explanation: Systematic review of 69 reported patients identifies unclosed cranial sutures as a near-constant maxillofacial feature.
- category: Craniofacial
  name: Frontal bossing
  description: >
    Frontal bossing is a recurrent component of the characteristic craniofacial
    appearance.
  phenotype_term:
    preferred_term: frontal bossing
    term:
      id: HP:0002007
      label: Frontal bossing
  evidence:
  - reference: PMID:40523612
    reference_title: "Oral and maxillofacial manifestations of Pycnodysostosis: a summary of clinical, radiological and cephalometric diagnostic criteria. A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "frontal bossing (92 %)"
    explanation: Systematic review identifies frontal bossing as a common craniofacial feature in published cases.
- category: Craniofacial
  name: Midface retrusion
  description: >
    Maxillary and midfacial hypoplasia produce a retrusive middle third of the
    face.
  phenotype_term:
    preferred_term: midface retrusion
    term:
      id: HP:0011800
      label: Midface retrusion
  evidence:
  - reference: PMID:40523612
    reference_title: "Oral and maxillofacial manifestations of Pycnodysostosis: a summary of clinical, radiological and cephalometric diagnostic criteria. A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "midfacial hypoplasia (100 %)"
    explanation: Systematic review of reported patients supports midface retrusion through universal midfacial hypoplasia in the reviewed maxillofacial cohort.
- category: Craniofacial
  name: Micrognathia
  description: >
    A small mandible is a frequent feature of the pycnodysostosis facial
    phenotype.
  phenotype_term:
    preferred_term: micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: PMID:40523612
    reference_title: "Oral and maxillofacial manifestations of Pycnodysostosis: a summary of clinical, radiological and cephalometric diagnostic criteria. A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "micrognathia (92 %)"
    explanation: Systematic review identifies micrognathia as a recurrent craniofacial finding in published cases.
- category: Craniofacial
  name: Obtuse angle of mandible
  description: >
    Loss of the normal gonial angle is a diagnostically important mandibular
    abnormality.
  phenotype_term:
    preferred_term: obtuse angle of mandible
    term:
      id: HP:0005446
      label: Obtuse angle of mandible
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "obtuse mandibular angle (8 of 8)"
    explanation: Pediatric cohort documents obtuse mandibular angle in all eight evaluated patients.
- category: Ophthalmologic
  name: Blue sclerae
  description: >
    Blue sclerae are part of the characteristic craniofacial and ocular
    appearance described in pycnodysostosis.
  phenotype_term:
    preferred_term: blue sclerae
    term:
      id: HP:0000592
      label: Blue sclerae
  evidence:
  - reference: PMID:28576543
    reference_title: "Pycnodysostosis at otorhinolaryngology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characteristic facial appearance (delayed closure of fontanelles and cranial sutures, mandibular hypoplasia and angle disorder, blue sclera)"
    explanation: ENT case series abstract lists blue sclera as part of the characteristic facial phenotype.
- category: Ophthalmologic
  name: Proptosis
  description: >
    Prominent eyes or proptosis occur as part of the characteristic
    craniofacial phenotype.
  phenotype_term:
    preferred_term: proptosis
    term:
      id: HP:0000520
      label: Proptosis
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "ocular proptosis (8 of 8)"
    explanation: Pediatric cohort documents proptosis in all eight evaluated children.
- category: Dermatologic
  name: Nail dysplasia
  description: >
    Dysplastic nails are a recurrent appendageal feature in affected children.
  phenotype_term:
    preferred_term: nail dysplasia
    term:
      id: HP:0002164
      label: Nail dysplasia
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dysplastic nails (8 of 8)"
    explanation: Pediatric cohort documents nail dysplasia in all eight evaluated children.
- category: Dental
  name: Delayed eruption of teeth
  description: >
    Delayed eruption affects the dentition and contributes to the characteristic
    oral phenotype.
  phenotype_term:
    preferred_term: delayed eruption of teeth
    term:
      id: HP:0000684
      label: Delayed eruption of teeth
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "delayed teeth eruption (8 of 8)"
    explanation: Pediatric cohort documents delayed eruption in all eight evaluated children.
- category: Dental
  name: Enamel hypoplasia
  description: >
    Enamel hypoplasia is part of the recurrent dental phenotype.
  phenotype_term:
    preferred_term: enamel hypoplasia
    term:
      id: HP:0006297
      label: Enamel hypoplasia
  evidence:
  - reference: PMID:11474477
    reference_title: "Pycnodysostosis: clinical, radiologic, and endocrine evaluation and linear growth after growth hormone therapy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "enamel hypoplasia (7 of 8)"
    explanation: Pediatric cohort documents enamel hypoplasia in most evaluated children.
- category: Dental
  name: Dental crowding
  description: >
    Marked crowding is a recurrent orthodontic problem in pycnodysostosis.
  phenotype_term:
    preferred_term: dental crowding
    term:
      id: HP:0000678
      label: Dental crowding
  evidence:
  - reference: PMID:38532649
    reference_title: "Pycnodysostosis: Characteristics of teeth, mouth and jaws."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "dental crowding, malocclusion (anterior crossbite, posterior open bite)"
    explanation: Dedicated oro-dental cohort study identifies dental crowding as a characteristic dental manifestation.
- category: Dental
  name: Dental malocclusion
  description: >
    Malocclusion, including anterior crossbite and posterior open bite, is a
    recurrent dentofacial manifestation.
  phenotype_term:
    preferred_term: dental malocclusion
    term:
      id: HP:0000689
      label: Dental malocclusion
  evidence:
  - reference: PMID:38532649
    reference_title: "Pycnodysostosis: Characteristics of teeth, mouth and jaws."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "malocclusion (anterior crossbite, posterior open bite)"
    explanation: Dedicated oro-dental cohort study identifies malocclusion as a characteristic dental manifestation.
- category: Craniofacial
  name: Narrow palate
  description: >
    A narrow or grooved palate is a frequent oral/maxillofacial finding in
    pycnodysostosis and reflects abnormal maxillofacial skeletal remodeling.
  phenotype_term:
    preferred_term: narrow palate
    term:
      id: HP:0000189
      label: Narrow palate
  evidence:
  - reference: PMID:40523612
    reference_title: "Oral and maxillofacial manifestations of Pycnodysostosis: a summary of clinical, radiological and cephalometric diagnostic criteria. A systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "narrow and grooved palate (100-73 %)"
    explanation: Systematic review identifies narrow or grooved palate as a high-frequency oral/maxillofacial feature.
- category: Respiratory
  name: Obstructive sleep apnea
  description: >
    Upper-airway narrowing can lead to clinically significant obstructive sleep
    apnea.
  phenotype_term:
    preferred_term: obstructive sleep apnea
    term:
      id: HP:0002870
      label: Obstructive sleep apnea
  evidence:
  - reference: PMID:28576543
    reference_title: "Pycnodysostosis at otorhinolaryngology."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Video recordings showed that six of the eight patients (75%) had respiratory distress and four (50%) had sleep apnea."
    explanation: Pediatric ENT case series documents obstructive sleep apnea in half of the evaluated patients.
genetic:
- name: CTSK Mutations
  association: Causative
  notes: >
    Homozygous or compound heterozygous loss-of-function mutations in
    CTSK on chromosome 1q21. Thirty-three different mutations identified
    in 59 unrelated families. Mutation types include nonsense, missense,
    and stop codon mutations. 70% in the mature domain, 24% in the
    proregion, 6% in the preregion.
  evidence:
  - reference: PMID:8703060
    reference_title: "Pycnodysostosis, a lysosomal disease caused by cathepsin K deficiency."
    supports: SUPPORT
    snippet: "Nonsense, missense, and stop codon mutations in the gene encoding cathepsin K were identified in patients"
    explanation: "Identifies the range of CTSK mutation types in pycnodysostosis."
  - reference: PMID:21569238
    reference_title: "Clinical and animal research findings in pycnodysostosis and gene mutations of cathepsin K from 1996 to 2011."
    supports: SUPPORT
    snippet: "Thirty three different CTSK mutations have been found in 59 unrelated pycnodysostosis families"
    explanation: "Comprehensive catalog of 33 mutations in 59 families."
- name: CTSK
  gene_term:
    preferred_term: CTSK
    term:
      id: hgnc:2536
      label: CTSK
  association: Pathogenic Variants
  evidence:
  - reference: CGGV:assertion_8135617e-f334-4c22-aa9e-b1efd50e9326-2022-11-11T180000.000Z
    reference_title: "CTSK / pycnodysostosis (Definitive)"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "CTSK | HGNC:2536 | pycnodysostosis | MONDO:0009940 | AR | Definitive"
    explanation: ClinGen classifies the CTSK-pycnodysostosis gene-disease relationship as definitive with autosomal recessive inheritance.
treatments:
- name: Supportive Care
  description: >
    Fracture management and orthopedic surveillance. No targeted
    therapy available, though cathepsin K represents a potential
    therapeutic target.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
- name: Genetic Counseling
  description: >
    Genetic counseling for affected families given autosomal
    recessive inheritance.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: MAXO:0000079
      label: genetic counseling
📚

References & Deep Research

Deep Research

1
Codex ▸
Question
gpt-5

Question

Make the phenotype section of kb/disorders/Pycnodysostosis.yaml as complete and evidence-backed as possible using exact PMID-supported phenotype evidence, while avoiding an unrelated broad rewrite.

Selected PMID-backed phenotype evidence

  • PMID:8703060 Foundational clinical description supporting generalized osteosclerosis and short stature.
  • PMID:21569238 Review of 159 reported patients supporting the typical core phenotype set of short stature, increased bone density with pathologic fractures, and open fontanels/sutures.
  • PMID:11474477 Eight-child cohort supporting delayed fontanel closure, obtuse mandibular angle, delayed tooth eruption, enamel hypoplasia, clavicular dysplasia, proptosis, and nail dysplasia.
  • PMID:28576543 Eight-patient ENT series supporting brachydactyly/short digits, blue sclerae, midfacial hypoplasia, micrognathia, proptosis, malocclusion, and sleep apnea.
  • PMID:38532649 Dedicated oro-dental cohort supporting dental crowding and dental malocclusion.
  • PMID:40523612 Systematic review of 69 reported patients supporting frontal bossing, unclosed cranial sutures, midfacial hypoplasia, micrognathia, obtuse gonial angle, and severe dental crowding.

Curation decisions

  • Replaced the overly broad HP:0011002 Osteopetrosis mapping with HP:0005789 Generalized osteosclerosis.
  • Split the prior broad open-fontanelle claim into Delayed closure of the anterior fontanelle and Delayed cranial suture closure.
  • Added only phenotypes directly named in abstracts or abstract result lines.
  • Kept phenotype ontology terms specific but avoided terms that were more specific than the abstract wording could safely support.
  • Omitted frequency: and structured onset: annotations because the available quantitative signals were cohort- or review-specific and not clean whole-disease estimates.