Hypophosphatasia

Mendelian MONDO:0018570 Pathograph 26 Metabolic Bone Disorders

Hypophosphatasia (HPP) is a rare inherited metabolic bone disease caused by loss-of-function mutations in ALPL, encoding tissue-nonspecific alkaline phosphatase (TNSALP). Deficient TNSALP activity leads to accumulation of its substrates including inorganic pyrophosphate (PPi), which inhibits hydroxyapatite crystal formation and thus bone mineralization. The clinical spectrum ranges from perinatal lethal to mild adult forms with premature loss of deciduous teeth. Asfotase alfa (Strensiq) is an approved enzyme replacement therapy for pediatric-onset HPP.

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2
Inheritance
5
Pathophys.
13
Phenotypes
26
Pathograph
1
Genes
3
Treatments
2
Deep Research
👪

Inheritance

2
Autosomal Recessive
Severe forms (perinatal, infantile) are autosomal recessive.
Show evidence (1 reference)
PMID:32973344 SUPPORT Human Clinical
"severe HPP is recessive and rare, moderate HPP is recessive or dominant and more common, and mild HPP, characterized by low alkaline phosphatase and unspecific clinical signs, is dominantly inherited and very common"
Establishes that severe HPP is recessive while mild HPP is dominant, confirming genotype-phenotype correlation with inheritance pattern.
Autosomal Dominant
Mild forms (adult, odontohypophosphatasia) may be autosomal dominant with variable penetrance.
Show evidence (1 reference)
PMID:32973344 SUPPORT Human Clinical
"severe HPP is recessive and rare, moderate HPP is recessive or dominant and more common, and mild HPP, characterized by low alkaline phosphatase and unspecific clinical signs, is dominantly inherited and very common"
Establishes that mild HPP is commonly dominantly inherited while moderate disease can be recessive or dominant.
⚙

Pathophysiology

5
ALPL loss of function and TNAP deficiency
Loss-of-function variants in ALPL reduce tissue-nonspecific alkaline phosphatase (TNAP) activity. Because TNAP functions as both an alkaline phosphatase and a pyrophosphatase at physiological pH, reduced activity lowers circulating alkaline phosphatase and prevents normal hydrolysis of mineralization and vitamin B6 substrates.
ALPL link
alkaline phosphatase activity link ↓ DECREASED pyrophosphatase activity link ↓ DECREASED
Downstream
Serum alkaline phosphatase activity Reduced TNAP activity is measured clinically as persistently low alkaline phosphatase activity.
Low Alkaline Phosphatase Reduced TNAP activity produces the hallmark decreased circulating alkaline phosphatase phenotype.
TNAP substrate accumulation Loss of TNAP enzyme activity leaves natural substrates extracellularly elevated.
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"Hypophosphatasia (HPP) is a rare inherited metabolic disorder characterized by deficient activity of tissue-nonspecific alkaline phosphatase (TNAP) caused by variants in the ALPL gene."
Review evidence directly defines HPP as ALPL-variant disease with deficient TNAP activity.
PMID:26590809 SUPPORT Other
"Hypophosphatasia (HPP) results from ALPL mutations leading to deficient activity of the tissue-non-specific alkaline phosphatase isozyme (TNAP)"
Review evidence supports ALPL mutation-driven TNAP deficiency as the initiating mechanism.
TNAP substrate accumulation
Deficient TNAP causes accumulation of natural substrates, especially inorganic pyrophosphate (PPi), pyridoxal 5'-phosphate (PLP), and urinary phosphoethanolamine (PEA). PPi blocks apatite crystal growth, whereas PLP accumulation reflects disrupted vitamin B6 handling.
phosphate ion homeostasis link ⚠ ABNORMAL
Downstream
Inorganic pyrophosphate PPi accumulates when TNAP pyrophosphatase activity is deficient.
Pyridoxal 5'-phosphate PLP accumulates extracellularly when TNAP phosphomonoesterase activity is deficient.
Urine phosphoethanolamine PEA is another elevated ALP substrate used diagnostically.
Skeletal and dentoalveolar mineralization failure PPi is a potent inhibitor of hydroxyapatite growth in bone and dental tissues.
Vitamin B6-dependent neurologic vulnerability PLP accumulation marks abnormal vitamin B6 metabolism that contributes to seizure vulnerability.
Pyrophosphate crystal arthropathy PPi excess can produce chondrocalcinosis and arthropathy.
Fatigue Chronic HPP can include fatigue as part of the broader non-skeletal adult disease burden; the biochemical-to-fatigue intermediate remains uncertain.
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"elevated levels of ALP substrates, specifically inorganic pyrophosphate (PPi), pyridoxal 5'-phosphate (PLP) or urine phosphoethanolamine (PEA)"
Diagnostic review identifies the three major elevated TNAP substrates in HPP.
PMID:34884378 SUPPORT Other
"Reduced activity of TNAP leads to the accumulation of its substrates, mainly inorganic pyrophosphate and pyridoxal-5'-phosphate"
Review links reduced TNAP activity to accumulation of PPi and PLP.
Skeletal and dentoalveolar mineralization failure
Excess PPi inhibits hydroxyapatite crystal growth after matrix vesicle rupture, producing defective mineralization of bone, growth plates, teeth, and the dentoalveolar complex. This mechanism accounts for rickets or osteomalacia, impaired growth, fractures, premature tooth loss, and severe chest-wall disease.
Osteoblast link
bone mineralization link ↓ DECREASED ossification link ⚠ ABNORMAL
Downstream
Rickets/Osteomalacia Failed skeletal mineralization manifests as rickets in children and osteomalacia in adults.
Premature Loss of Deciduous Teeth Dentoalveolar mineralization defects produce premature loss of primary teeth.
Fractures Osteomalacia and impaired mineralization increase fracture and pseudofracture risk.
Muscle Weakness Adult and severe HPP musculoskeletal disease includes muscle weakness, though the exact intermediate between mineralization failure and weakness is not fully resolved.
Craniosynostosis Craniosynostosis is a severe skeletal manifestation of HPP, though the exact local mechanism is not fully resolved.
Respiratory Insufficiency Severe skeletal hypomineralization with rib and thoracic involvement contributes to respiratory compromise in perinatal and infantile HPP.
Short Stature Growth-plate defects and impaired growth follow childhood skeletal mineralization failure.
Show evidence (2 references)
PMID:20392236 SUPPORT Other
"The skeletal disease is due to PP(i) inhibition of hydroxyapatite crystal growth extracellularly so that crystals form within matrix vesicles but fail to enlarge after these structures rupture."
Review explains how PPi blocks hydroxyapatite crystal growth in skeletal mineralization.
DOI:10.1093/jbmrpl/ziae180 SUPPORT Other
"TNAP plays a crucial role in biomineralization of bones and teeth, in part by reducing levels of inorganic pyrophosphate (PPi), an inhibitor of biomineralization."
Dental review connects TNAP, PPi reduction, and bone/tooth biomineralization.
Vitamin B6-dependent neurologic vulnerability
TNAP normally participates in vitamin B6 metabolism through extracellular PLP dephosphorylation. HPP disrupts this process, creating vitamin B6-dependent seizure susceptibility in severe infantile disease and contributing to delayed motor development in broader pediatric presentations.
vitamin B6 metabolic process link ⚠ ABNORMAL
Downstream
Seizures Abnormal vitamin B6 metabolism contributes to vitamin B6-dependent seizures.
Motor Delay Pediatric presentations can include delayed motor development alongside severe systemic disease.
Show evidence (3 references)
PMID:20392236 SUPPORT Other
"Aberrations of vitamin B(6) metabolism in HPP revealed that TNSALP is an ectoenzyme."
Review supports abnormal vitamin B6 metabolism as a TNAP-dependent HPP mechanism.
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"Disease manifestations encompass skeletal hypomineralization with rickets and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and premature loss of deciduous teeth."
Review links HPP to vitamin B6-dependent seizures among core manifestations.
PMID:23479201 SUPPORT Human Clinical
"TNSALP is also necessary for proper vitamin B6 metabolism and its participation as a cofactor for neurotransmitters in the central nervous system."
Human case report review supports the vitamin B6/neurotransmitter branch of severe infantile HPP.
Pyrophosphate crystal arthropathy
PPi excess can drive chondrocalcinosis and arthropathy. This branch connects the TNAP substrate abnormality to adult musculoskeletal pain and joint manifestations distinct from primary osteomalacia.
Downstream
Chondrocalcinosis PPi excess causes chondrocalcinosis.
Pain Arthropathy and adult musculoskeletal disease contribute to generalized pain.
Show evidence (1 reference)
PMID:20392236 SUPPORT Other
"PP(i) excesses cause chondrocalcinosis and sometimes arthropathy."
Review directly supports a PPi excess, chondrocalcinosis, and arthropathy branch.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Hypophosphatasia 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

13
Head and Neck 2
Premature Loss of Deciduous Teeth Premature loss of primary teeth (HP:0006323)
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"Disease manifestations encompass skeletal hypomineralization with rickets and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and premature loss of deciduous teeth."
Review lists premature loss of deciduous teeth among HPP manifestations.
DOI:10.1093/jbmrpl/ziae180 SUPPORT Other
"Premature tooth loss of fully rooted teeth is pathognomonic for HPP."
Dental review supports premature tooth loss as a highly characteristic HPP finding.
Craniosynostosis Craniosynostosis (HP:0001363)
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"Disease manifestations encompass skeletal hypomineralization with rickets and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and premature loss of deciduous teeth."
Review lists craniosynostosis among HPP manifestations.
PMID:26590809 SUPPORT Other
"craniosynostosis and muscle weakness when HPP is severe"
Review identifies craniosynostosis as a severe-HPP feature not fully understood.
Metabolism 1
Low Alkaline Phosphatase Decreased circulating alkaline phosphatase activity (HP:0003282)
Show evidence (2 references)
PMID:34884378 SUPPORT Other
"Persistently low serum alkaline phosphatase is the cardinal biochemical feature of the disease."
Review identifies low serum ALP as the cardinal biochemical feature.
PMID:32973344 SUPPORT Human Clinical
"mild HPP, characterized by low alkaline phosphatase and unspecific clinical signs, is dominantly inherited and very common"
Cohort-based nosology identifies low alkaline phosphatase in mild dominant HPP.
Musculoskeletal 3
Rickets/Osteomalacia Rickets (HP:0002748)
Show evidence (2 references)
PMID:26590809 SUPPORT Other
"Thus, HPP features rickets or osteomalacia and hypomineralization of teeth."
Review identifies rickets or osteomalacia as hallmark HPP manifestations.
PMID:20392236 SUPPORT Other
"Hypophosphatasia (HPP) is the instructive rickets or osteomalacia caused by loss-of-function mutation(s) within TNSALP"
Review defines HPP as rickets or osteomalacia caused by TNAP loss of function.
Fractures Recurrent fractures (HP:0002757)
Show evidence (2 references)
PMID:34884378 SUPPORT Other
"recurrent, poorly healing fractures, muscle weakness and arthropathy are common in adults."
Review supports recurrent poorly healing fractures as adult HPP manifestations.
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"In adults, pseudofractures are a characteristic indicator of severely compromised enzyme activity"
Review supports pseudofractures as an adult indicator of severe enzyme deficiency.
Muscle Weakness Muscle weakness (HP:0001324)
Show evidence (2 references)
PMID:26590809 SUPPORT Other
"craniosynostosis and muscle weakness when HPP is severe"
Review identifies muscle weakness as a feature of severe HPP.
PMID:34884378 SUPPORT Other
"recurrent, poorly healing fractures, muscle weakness and arthropathy are common in adults."
Review supports muscle weakness among common adult HPP manifestations.
Nervous System 2
Seizures Seizure (HP:0001250)
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"Disease manifestations encompass skeletal hypomineralization with rickets and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and premature loss of deciduous teeth."
Review directly supports vitamin B6-dependent seizures in HPP.
PMID:23479201 SUPPORT Human Clinical
"Defective TNSALP activity in the brain can result in intractable seizures responsive to pyridoxine."
Human infantile HPP case report directly supports pyridoxine-responsive seizures.
Motor Delay Motor delay (HP:0001270)
Show evidence (1 reference)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"The clinical presentation can comprise failure to thrive with muscular hypotonia, delayed motor development, and gait disturbances later in childhood."
Review supports delayed motor development in childhood HPP.
Respiratory 1
Respiratory Insufficiency Respiratory insufficiency (HP:0002093)
Show evidence (2 references)
PMID:26529632 SUPPORT Human Clinical
"in its most severe perinatal and infantile forms, results in 50-100% mortality, typically from respiratory complications."
Human trial/natural-history comparison identifies respiratory complications as the typical mortality driver.
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"Disease manifestations encompass skeletal hypomineralization with rickets and lung hypoplasia"
Review supports lung hypoplasia within severe HPP manifestations.
Constitutional 2
Pain Pain (HP:0012531)
Show evidence (1 reference)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"generalized musculoskeletal pain, weakness, and fatigue"
Review supports generalized musculoskeletal pain among key adult HPP findings.
Fatigue Fatigue (HP:0012378)
Show evidence (1 reference)
DOI:10.1007/s11914-025-00906-5 SUPPORT Other
"non-skeletal impairments, such as pain and chronic fatigue."
Review supports chronic fatigue as part of adult HPP disease burden.
Growth 1
Short Stature Short stature (HP:0004322)
Show evidence (1 reference)
DOI:10.1093/jbmrpl/ziae180 PARTIAL Other
"HPP onset in childhood contributes to rickets, including growth plate defects and impaired growth."
Review supports impaired growth from childhood rickets, which is the basis for short-stature curation.
Other 1
Chondrocalcinosis Chondrocalcinosis (HP:0000934)
Show evidence (1 reference)
PMID:20392236 SUPPORT Other
"PP(i) excesses cause chondrocalcinosis and sometimes arthropathy."
Review directly links PPi excess to chondrocalcinosis.
🧬

Genetic Associations

1
ALPL Mutations (Causative)
Show evidence (3 references)
PMID:32973344 SUPPORT Human Clinical
"Hypophosphatasia (HPP) is caused by pathogenic variants in the ALPL gene."
Cohort paper directly states the ALPL causal relationship.
PMID:34884378 SUPPORT Other
"More than 400 ALPL mutations, mostly missense, are reported to date, transmitted by either autosomal dominant or recessive mode."
Review supports mutation burden and dominant/recessive transmission.
PMID:32973344 SUPPORT Human Clinical
"Homozygosity was an aggravating factor of the severity and moderate alleles were rare both in number and frequency."
Cohort evidence supports genotype-severity correlation.
💊

Treatments

3
Asfotase Alfa (Strensiq)
Action: Pharmacotherapy NCIT:C15986
Bone-targeted enzyme replacement therapy that substitutes TNAP activity. Human interventional evidence shows improved survival, respiratory outcomes, skeletal mineralization, rickets, and functional outcomes in severely affected pediatric patients.
Mechanism Target:
RESTORES ALPL loss of function and TNAP deficiency — Asfotase alfa substitutes deficient TNAP enzymatic activity.
Show evidence (1 reference)
PMID:26529632 SUPPORT Human Clinical
"treatment with asfotase alfa, a first-in-class enzyme replacement therapy"
Trial abstract identifies asfotase alfa as enzyme replacement therapy.
RESTORES Skeletal and dentoalveolar mineralization failure — Enzyme replacement improves skeletal mineralization and rib-related respiratory function.
Show evidence (1 reference)
PMID:26529632 SUPPORT Human Clinical
"Asfotase alfa mineralizes the HPP skeleton, including the ribs, and improves respiratory function and survival in life-threatening perinatal and infantile HPP."
Human clinical evidence directly supports skeletal and respiratory benefit.
Show evidence (3 references)
PMID:26529632 SUPPORT Human Clinical
"Asfotase alfa was associated with improved survival in treated patients vs historical controls: 95% vs 42% at age 1 year and 84% vs 27% at age 5 years, respectively (P < .0001, Kaplan-Meier log-rank test)."
Human interventional evidence shows improved survival with asfotase alfa.
PMID:26529632 SUPPORT Human Clinical
"76% (16/21) of the ventilated and treated patients survived, among whom 75% (12/16) were weaned from ventilatory support."
Human interventional evidence supports improved ventilatory outcomes.
DOI:10.1007/s11914-025-00906-5 SUPPORT Other
"Treatment for HPP relies on the enzyme replacement asfotase alfa."
Review summarizes asfotase alfa as the core enzyme-replacement treatment.
Pyridoxine Supplementation
Action: Pharmacotherapy NCIT:C15986
Agent: pyridoxine ↗
Pyridoxine can be used for vitamin B6-dependent seizures in severe infantile HPP, bypassing impaired PLP handling downstream of TNAP deficiency.
Mechanism Target:
BYPASSES Vitamin B6-dependent neurologic vulnerability — Pyridoxine addresses the vitamin B6-dependent seizure branch rather than restoring TNAP.
Show evidence (1 reference)
PMID:23479201 SUPPORT Human Clinical
"Defective TNSALP activity in the brain can result in intractable seizures responsive to pyridoxine."
Human case report supports pyridoxine responsiveness in the seizure branch targeted by supplementation.
Show evidence (1 reference)
PMID:23479201 SUPPORT Human Clinical
"Empiric treatment with favorable response to pyridoxine"
Human case report directly supports pyridoxine treatment responsiveness in infantile HPP seizures.
Multidisciplinary Supportive Care
Action: supportive care MAXO:0000950
Supportive management is multimodal and tailored to disease manifestations, including metabolic and musculoskeletal care, dental care, neurologic and neurosurgical surveillance, pain management, physical therapy, and psychological support.
Mechanism Target:
MODULATES Skeletal and dentoalveolar mineralization failure — Dental, musculoskeletal, pain, and rehabilitation care address downstream skeletal and dental consequences.
MODULATES Pyrophosphate crystal arthropathy — Pain management and musculoskeletal care address arthropathy-related symptoms.
Show evidence (1 reference)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"The multidisciplinary team for comprehensive management of HPP patients should include expertise to ensure disease state metabolic and musculoskeletal treatment, dental care, neurological and neurosurgical surveillance, pain management, physical therapy, and psychological care."
Review supports multimodal supportive care across HPP manifestations.
🔬

Biochemical Markers

4
Serum alkaline phosphatase activity (DECREASED)
Context: Persistently low serum alkaline phosphatase activity is the cardinal diagnostic biochemical marker of HPP and reflects deficient TNAP activity.
Pathograph Readouts
Readout Of ALPL loss of function and TNAP deficiency Negative Diagnostic
Persistently low serum ALP reports deficient TNAP enzymatic activity.
Show evidence (2 references)
PMID:34884378 SUPPORT Other
"Persistently low serum alkaline phosphatase is the cardinal biochemical feature of the disease."
Review identifies low serum ALP as the cardinal biochemical feature.
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"The diagnosis is based on clinical manifestations in combination with persistently low alkaline phosphatase (ALP) activity"
Review lists persistently low ALP activity as a diagnostic criterion.
Inorganic pyrophosphate (INCREASED)
Context: Elevated inorganic pyrophosphate is a diagnostic TNAP substrate and the central inhibitor of hydroxyapatite crystal growth.
Pathograph Readouts
Readout Of TNAP substrate accumulation Positive Diagnostic
Elevated PPi reports impaired TNAP pyrophosphatase activity and substrate accumulation.
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"elevated levels of ALP substrates, specifically inorganic pyrophosphate (PPi)"
Review lists elevated PPi as an ALP substrate marker.
PMID:20392236 SUPPORT Other
"Increased extracellular levels of pyridoxal 5'-phosphate and inorganic pyrophosphate (PP(i)) demonstrate that TNSALP is a phosphomonoester phosphohydrolase and a pyrophosphatase"
Review supports increased extracellular PPi as a biochemical consequence of TNAP loss.
Pyridoxal 5'-phosphate (INCREASED)
Context: Elevated plasma PLP reflects impaired TNAP-mediated vitamin B6 metabolism and supports the seizure branch in severe infantile disease.
Pathograph Readouts
Readout Of TNAP substrate accumulation Positive Diagnostic
Elevated PLP reports impaired TNAP-mediated dephosphorylation of vitamin B6 substrate.
Show evidence (2 references)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"elevated levels of ALP substrates, specifically inorganic pyrophosphate (PPi), pyridoxal 5'-phosphate (PLP)"
Review lists elevated PLP as an ALP substrate marker.
PMID:20392236 SUPPORT Other
"Increased extracellular levels of pyridoxal 5'-phosphate and inorganic pyrophosphate (PP(i)) demonstrate that TNSALP is a phosphomonoester phosphohydrolase and a pyrophosphatase"
Review supports increased extracellular PLP as a biochemical consequence of TNAP loss.
Urine phosphoethanolamine (INCREASED)
Context: Urinary phosphoethanolamine is an additional ALP substrate that can be elevated in HPP and used as part of the diagnostic biochemical pattern.
Pathograph Readouts
Readout Of TNAP substrate accumulation Positive Diagnostic
Elevated urine PEA reports accumulation of ALP substrates downstream of TNAP deficiency.
Show evidence (1 reference)
DOI:10.1007/s00223-025-01356-y SUPPORT Other
"elevated levels of ALP substrates, specifically inorganic pyrophosphate (PPi), pyridoxal 5'-phosphate (PLP) or urine phosphoethanolamine (PEA)"
Review lists urine PEA among elevated ALP substrate markers.
{ }

Source YAML

click to show 
name: Hypophosphatasia
creation_date: '2026-02-13T00:31:42Z'
updated_date: "2026-05-21T01:39:26Z"
category: Mendelian
description: >
  Hypophosphatasia (HPP) is a rare inherited metabolic bone disease caused by
  loss-of-function mutations in ALPL, encoding tissue-nonspecific alkaline
  phosphatase (TNSALP). Deficient TNSALP activity leads to accumulation of its
  substrates including inorganic pyrophosphate (PPi), which inhibits
  hydroxyapatite crystal formation and thus bone mineralization. The clinical
  spectrum ranges from perinatal lethal to mild adult forms with premature loss
  of deciduous teeth. Asfotase alfa (Strensiq) is an approved enzyme replacement
  therapy for pediatric-onset HPP.
disease_term:
  preferred_term: Hypophosphatasia
  term:
    id: MONDO:0018570
    label: hypophosphatasia
parents:
- Metabolic Bone Disorders
inheritance:
- name: Autosomal Recessive
  description: >
    Severe forms (perinatal, infantile) are autosomal recessive.
  evidence:
  - reference: PMID:32973344
    reference_title: "Hypophosphatasia: a genetic-based nosology and new insights in genotype-phenotype correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      severe HPP is recessive and rare, moderate HPP is recessive or dominant and
      more common, and mild HPP, characterized by low alkaline phosphatase and
      unspecific clinical signs, is dominantly inherited and very common
    explanation: "Establishes that severe HPP is recessive while mild HPP is dominant, confirming genotype-phenotype correlation with inheritance pattern."
- name: Autosomal Dominant
  description: >
    Mild forms (adult, odontohypophosphatasia) may be autosomal
    dominant with variable penetrance.
  evidence:
  - reference: PMID:32973344
    reference_title: "Hypophosphatasia: a genetic-based nosology and new insights in genotype-phenotype correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      severe HPP is recessive and rare, moderate HPP is recessive or dominant and
      more common, and mild HPP, characterized by low alkaline phosphatase and
      unspecific clinical signs, is dominantly inherited and very common
    explanation: "Establishes that mild HPP is commonly dominantly inherited while moderate disease can be recessive or dominant."
prevalence:
- population: Severe perinatal and infantile presentations
  percentage: 1 in 100,000 to 1 in 300,000 live births
  notes: >-
    Severe hypophosphatasia is rare and usually corresponds to perinatal or
    infantile disease at the recessive end of the spectrum.
  evidence:
  - reference: PMID:34884378
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Severe disease is rare, with incidence ranging from 1:100,000 to 1:300,000 live births, while the estimated prevalence of the less severe adult form is estimated to be between 1:3100 to 1:508, in different countries in Europe."
    explanation: This review provides a standard incidence range for severe hypophosphatasia presentations.
- population: Less severe adult forms in Europe
  percentage: 1 in 3,100 to 1 in 508
  notes: >-
    Adult and other milder forms appear substantially more common than severe
    pediatric disease, especially when low alkaline phosphatase is actively
    investigated.
  evidence:
  - reference: PMID:34884378
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Severe disease is rare, with incidence ranging from 1:100,000 to 1:300,000 live births, while the estimated prevalence of the less severe adult form is estimated to be between 1:3100 to 1:508, in different countries in Europe."
    explanation: The same review explicitly states a much higher estimated prevalence for milder adult hypophosphatasia in European populations.
pathophysiology:
- name: ALPL loss of function and TNAP deficiency
  description: >
    Loss-of-function variants in ALPL reduce tissue-nonspecific alkaline
    phosphatase (TNAP) activity. Because TNAP functions as both an alkaline
    phosphatase and a pyrophosphatase at physiological pH, reduced activity
    lowers circulating alkaline phosphatase and prevents normal hydrolysis of
    mineralization and vitamin B6 substrates.
  genes:
  - preferred_term: ALPL
    term:
      id: hgnc:438
      label: ALPL
  molecular_functions:
  - preferred_term: alkaline phosphatase activity
    term:
      id: GO:0004035
      label: alkaline phosphatase activity
    modifier: DECREASED
  - preferred_term: pyrophosphatase activity
    term:
      id: GO:0016462
      label: pyrophosphatase activity
    modifier: DECREASED
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hypophosphatasia (HPP) is a rare inherited metabolic disorder characterized
      by deficient activity of tissue-nonspecific alkaline phosphatase (TNAP)
      caused by variants in the ALPL gene.
    explanation: >
      Review evidence directly defines HPP as ALPL-variant disease with deficient
      TNAP activity.
  - reference: PMID:26590809
    reference_title: "Alkaline Phosphatase and Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hypophosphatasia (HPP) results from ALPL mutations leading to deficient
      activity of the tissue-non-specific alkaline phosphatase isozyme (TNAP)
    explanation: >
      Review evidence supports ALPL mutation-driven TNAP deficiency as the
      initiating mechanism.
  downstream:
  - target: Serum alkaline phosphatase activity
    description: Reduced TNAP activity is measured clinically as persistently low alkaline phosphatase activity.
    causal_link_type: DIRECT
    evidence:
    - reference: DOI:10.1007/s00223-025-01356-y
      reference_title: "Diagnosis and Treatment of Hypophosphatasia"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        The diagnosis is based on clinical manifestations in combination with
        persistently low alkaline phosphatase (ALP) activity
      explanation: Low ALP activity is the direct biochemical readout of TNAP deficiency.
  - target: Low Alkaline Phosphatase
    description: Reduced TNAP activity produces the hallmark decreased circulating alkaline phosphatase phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:34884378
      reference_title: "Hypophosphatasia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Persistently low serum alkaline phosphatase is the cardinal biochemical
        feature of the disease.
      explanation: Review identifies persistently low serum alkaline phosphatase as cardinal in HPP.
  - target: TNAP substrate accumulation
    description: Loss of TNAP enzyme activity leaves natural substrates extracellularly elevated.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20392236
      reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        Increased extracellular levels of pyridoxal 5'-phosphate and inorganic
        pyrophosphate (PP(i)) demonstrate that TNSALP is a phosphomonoester
        phosphohydrolase and a pyrophosphatase
      explanation: Elevated PLP and PPi demonstrate impaired hydrolysis of TNAP natural substrates.
- name: TNAP substrate accumulation
  description: >
    Deficient TNAP causes accumulation of natural substrates, especially
    inorganic pyrophosphate (PPi), pyridoxal 5'-phosphate (PLP), and urinary
    phosphoethanolamine (PEA). PPi blocks apatite crystal growth, whereas PLP
    accumulation reflects disrupted vitamin B6 handling.
  chemical_entities:
  - preferred_term: inorganic pyrophosphate
    term:
      id: CHEBI:18361
      label: diphosphate(4-)
    modifier: INCREASED
  - preferred_term: pyridoxal 5'-phosphate
    term:
      id: CHEBI:18405
      label: pyridoxal 5'-phosphate
    modifier: INCREASED
  - preferred_term: phosphoethanolamine
    term:
      id: CHEBI:36711
      label: phosphoethanolamine
    modifier: INCREASED
  biological_processes:
  - preferred_term: phosphate ion homeostasis
    term:
      id: GO:0055062
      label: phosphate ion homeostasis
    modifier: ABNORMAL
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      elevated levels of ALP substrates, specifically inorganic pyrophosphate
      (PPi), pyridoxal 5'-phosphate (PLP) or urine phosphoethanolamine (PEA)
    explanation: >
      Diagnostic review identifies the three major elevated TNAP substrates in
      HPP.
  - reference: PMID:34884378
    reference_title: "Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Reduced activity of TNAP leads to the accumulation of its substrates,
      mainly inorganic pyrophosphate and pyridoxal-5'-phosphate
    explanation: Review links reduced TNAP activity to accumulation of PPi and PLP.
  downstream:
  - target: Inorganic pyrophosphate
    description: PPi accumulates when TNAP pyrophosphatase activity is deficient.
    causal_link_type: DIRECT
  - target: Pyridoxal 5'-phosphate
    description: PLP accumulates extracellularly when TNAP phosphomonoesterase activity is deficient.
    causal_link_type: DIRECT
  - target: Urine phosphoethanolamine
    description: PEA is another elevated ALP substrate used diagnostically.
    causal_link_type: DIRECT
  - target: Skeletal and dentoalveolar mineralization failure
    description: PPi is a potent inhibitor of hydroxyapatite growth in bone and dental tissues.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:26590809
      reference_title: "Alkaline Phosphatase and Hypophosphatasia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        extracellular accumulation of inorganic pyrophosphate (PPi), a natural
        substrate of TNAP and potent inhibitor of mineralization.
      explanation: Review directly links PPi accumulation to mineralization inhibition.
  - target: Vitamin B6-dependent neurologic vulnerability
    description: PLP accumulation marks abnormal vitamin B6 metabolism that contributes to seizure vulnerability.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - impaired extracellular PLP dephosphorylation
  - target: Pyrophosphate crystal arthropathy
    description: PPi excess can produce chondrocalcinosis and arthropathy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:20392236
      reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        PP(i) excesses cause chondrocalcinosis and sometimes arthropathy.
      explanation: Review directly links PPi excess to chondrocalcinosis and arthropathy.
  - target: Fatigue
    description: Chronic HPP can include fatigue as part of the broader non-skeletal adult disease burden; the biochemical-to-fatigue intermediate remains uncertain.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: DOI:10.1007/s11914-025-00906-5
      reference_title: "Medical Management of Hypophosphatasia: Review of Data on Asfotase Alfa"
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        non-skeletal impairments, such as pain and chronic fatigue.
      explanation: Review evidence from Global HPP Registry data supports chronic fatigue as a recognized non-skeletal HPP impairment.
- name: Skeletal and dentoalveolar mineralization failure
  description: >
    Excess PPi inhibits hydroxyapatite crystal growth after matrix vesicle
    rupture, producing defective mineralization of bone, growth plates, teeth,
    and the dentoalveolar complex. This mechanism accounts for rickets or
    osteomalacia, impaired growth, fractures, premature tooth loss, and severe
    chest-wall disease.
  cell_types:
  - preferred_term: Osteoblast
    term:
      id: CL:0000062
      label: osteoblast
  biological_processes:
  - preferred_term: bone mineralization
    term:
      id: GO:0030282
      label: bone mineralization
    modifier: DECREASED
  - preferred_term: ossification
    term:
      id: GO:0001503
      label: ossification
    modifier: ABNORMAL
  chemical_entities:
  - preferred_term: hydroxylapatite
    term:
      id: CHEBI:52255
      label: hydroxylapatite
    modifier: DECREASED
  evidence:
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The skeletal disease is due to PP(i) inhibition of hydroxyapatite crystal
      growth extracellularly so that crystals form within matrix vesicles but fail
      to enlarge after these structures rupture.
    explanation: Review explains how PPi blocks hydroxyapatite crystal growth in skeletal mineralization.
  - reference: DOI:10.1093/jbmrpl/ziae180
    reference_title: "Dental manifestations of hypophosphatasia: translational and clinical advances"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      TNAP plays a crucial role in biomineralization of bones and teeth, in part
      by reducing levels of inorganic pyrophosphate (PPi), an inhibitor of
      biomineralization.
    explanation: Dental review connects TNAP, PPi reduction, and bone/tooth biomineralization.
  downstream:
  - target: Rickets/Osteomalacia
    description: Failed skeletal mineralization manifests as rickets in children and osteomalacia in adults.
    causal_link_type: DIRECT
  - target: Premature Loss of Deciduous Teeth
    description: Dentoalveolar mineralization defects produce premature loss of primary teeth.
    causal_link_type: DIRECT
  - target: Fractures
    description: Osteomalacia and impaired mineralization increase fracture and pseudofracture risk.
    causal_link_type: DIRECT
  - target: Muscle Weakness
    description: Adult and severe HPP musculoskeletal disease includes muscle weakness, though the exact intermediate between mineralization failure and weakness is not fully resolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:34884378
      reference_title: "Hypophosphatasia."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: >-
        recurrent, poorly healing fractures, muscle weakness and arthropathy are
        common in adults.
      explanation: Review evidence supports muscle weakness as part of the adult HPP musculoskeletal phenotype.
  - target: Craniosynostosis
    description: Craniosynostosis is a severe skeletal manifestation of HPP, though the exact local mechanism is not fully resolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: Respiratory Insufficiency
    description: Severe skeletal hypomineralization with rib and thoracic involvement contributes to respiratory compromise in perinatal and infantile HPP.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - skeletal hypomineralization with chest-wall involvement
  - target: Short Stature
    description: Growth-plate defects and impaired growth follow childhood skeletal mineralization failure.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - growth plate defects
- name: Vitamin B6-dependent neurologic vulnerability
  description: >
    TNAP normally participates in vitamin B6 metabolism through extracellular PLP
    dephosphorylation. HPP disrupts this process, creating vitamin B6-dependent
    seizure susceptibility in severe infantile disease and contributing to
    delayed motor development in broader pediatric presentations.
  biological_processes:
  - preferred_term: vitamin B6 metabolic process
    term:
      id: GO:0042816
      label: vitamin B6 metabolic process
    modifier: ABNORMAL
  chemical_entities:
  - preferred_term: pyridoxal 5'-phosphate
    term:
      id: CHEBI:18405
      label: pyridoxal 5'-phosphate
    modifier: INCREASED
  evidence:
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Aberrations of vitamin B(6) metabolism in HPP revealed that TNSALP is an
      ectoenzyme.
    explanation: Review supports abnormal vitamin B6 metabolism as a TNAP-dependent HPP mechanism.
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Disease manifestations encompass skeletal hypomineralization with rickets
      and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and
      premature loss of deciduous teeth.
    explanation: Review links HPP to vitamin B6-dependent seizures among core manifestations.
  - reference: PMID:23479201
    reference_title: "Infantile hypophosphatasia secondary to a novel compound heterozygous mutation presenting with pyridoxine-responsive seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      TNSALP is also necessary for proper vitamin B6 metabolism and its
      participation as a cofactor for neurotransmitters in the central nervous
      system.
    explanation: Human case report review supports the vitamin B6/neurotransmitter branch of severe infantile HPP.
  downstream:
  - target: Seizures
    description: Abnormal vitamin B6 metabolism contributes to vitamin B6-dependent seizures.
    causal_link_type: DIRECT
  - target: Motor Delay
    description: Pediatric presentations can include delayed motor development alongside severe systemic disease.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- name: Pyrophosphate crystal arthropathy
  description: >
    PPi excess can drive chondrocalcinosis and arthropathy. This branch connects
    the TNAP substrate abnormality to adult musculoskeletal pain and joint
    manifestations distinct from primary osteomalacia.
  chemical_entities:
  - preferred_term: inorganic pyrophosphate
    term:
      id: CHEBI:18361
      label: diphosphate(4-)
    modifier: INCREASED
  evidence:
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      PP(i) excesses cause chondrocalcinosis and sometimes arthropathy.
    explanation: Review directly supports a PPi excess, chondrocalcinosis, and arthropathy branch.
  downstream:
  - target: Chondrocalcinosis
    description: PPi excess causes chondrocalcinosis.
    causal_link_type: DIRECT
  - target: Pain
    description: Arthropathy and adult musculoskeletal disease contribute to generalized pain.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - chondrocalcinosis and arthropathy
phenotypes:
- name: Rickets/Osteomalacia
  description: >
    Defective bone mineralization presents as rickets in children and
    osteomalacia in adults. Severity generally tracks residual TNAP activity.
  phenotype_term:
    preferred_term: Rickets
    term:
      id: HP:0002748
      label: Rickets
  evidence:
  - reference: PMID:26590809
    reference_title: "Alkaline Phosphatase and Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Thus, HPP features rickets or osteomalacia and hypomineralization of teeth.
    explanation: Review identifies rickets or osteomalacia as hallmark HPP manifestations.
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hypophosphatasia (HPP) is the instructive rickets or osteomalacia caused by
      loss-of-function mutation(s) within TNSALP
    explanation: Review defines HPP as rickets or osteomalacia caused by TNAP loss of function.
- name: Premature Loss of Deciduous Teeth
  description: >
    Premature loss of primary teeth reflects defective dentoalveolar
    mineralization, especially cementum and supporting periodontal tissues, and
    can be the dominant manifestation in odontohypophosphatasia.
  phenotype_term:
    preferred_term: Premature loss of primary teeth
    term:
      id: HP:0006323
      label: Premature loss of primary teeth
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Disease manifestations encompass skeletal hypomineralization with rickets
      and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and
      premature loss of deciduous teeth.
    explanation: Review lists premature loss of deciduous teeth among HPP manifestations.
  - reference: DOI:10.1093/jbmrpl/ziae180
    reference_title: "Dental manifestations of hypophosphatasia: translational and clinical advances"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Premature tooth loss of fully rooted teeth is pathognomonic for HPP.
    explanation: Dental review supports premature tooth loss as a highly characteristic HPP finding.
- name: Low Alkaline Phosphatase
  description: >
    Persistently low serum alkaline phosphatase activity is the biochemical and
    phenotypic hallmark, present even in mild adult disease.
  phenotype_term:
    preferred_term: Decreased circulating alkaline phosphatase activity
    term:
      id: HP:0003282
      label: Decreased circulating alkaline phosphatase activity
  evidence:
  - reference: PMID:34884378
    reference_title: "Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Persistently low serum alkaline phosphatase is the cardinal biochemical
      feature of the disease.
    explanation: Review identifies low serum ALP as the cardinal biochemical feature.
  - reference: PMID:32973344
    reference_title: "Hypophosphatasia: a genetic-based nosology and new insights in genotype-phenotype correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      mild HPP, characterized by low alkaline phosphatase and unspecific clinical
      signs, is dominantly inherited and very common
    explanation: Cohort-based nosology identifies low alkaline phosphatase in mild dominant HPP.
- name: Fractures
  description: >
    Recurrent or poorly healing fractures and adult pseudofractures result from
    defective mineralization and osteomalacia.
  phenotype_term:
    preferred_term: Recurrent fractures
    term:
      id: HP:0002757
      label: Recurrent fractures
  evidence:
  - reference: PMID:34884378
    reference_title: "Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      recurrent, poorly healing fractures, muscle weakness and arthropathy are
      common in adults.
    explanation: Review supports recurrent poorly healing fractures as adult HPP manifestations.
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      In adults, pseudofractures are a characteristic indicator of severely
      compromised enzyme activity
    explanation: Review supports pseudofractures as an adult indicator of severe enzyme deficiency.
- name: Craniosynostosis
  description: >
    Premature cranial suture fusion occurs in severe infantile HPP despite
    generalized skeletal undermineralization.
  phenotype_term:
    preferred_term: Craniosynostosis
    term:
      id: HP:0001363
      label: Craniosynostosis
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Disease manifestations encompass skeletal hypomineralization with rickets
      and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and
      premature loss of deciduous teeth.
    explanation: Review lists craniosynostosis among HPP manifestations.
  - reference: PMID:26590809
    reference_title: "Alkaline Phosphatase and Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      craniosynostosis and muscle weakness when HPP is severe
    explanation: Review identifies craniosynostosis as a severe-HPP feature not fully understood.
- name: Seizures
  description: >
    Severe infantile HPP can include vitamin B6-dependent seizures from disrupted
    PLP handling and CNS vitamin B6 availability.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Disease manifestations encompass skeletal hypomineralization with rickets
      and lung hypoplasia, vitamin B6-dependent seizures, craniosynostosis, and
      premature loss of deciduous teeth.
    explanation: Review directly supports vitamin B6-dependent seizures in HPP.
  - reference: PMID:23479201
    reference_title: "Infantile hypophosphatasia secondary to a novel compound heterozygous mutation presenting with pyridoxine-responsive seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Defective TNSALP activity in the brain can result in intractable seizures
      responsive to pyridoxine.
    explanation: Human infantile HPP case report directly supports pyridoxine-responsive seizures.
- name: Respiratory Insufficiency
  description: >
    Perinatal and infantile HPP can cause respiratory failure through lung
    hypoplasia and poorly mineralized ribs/chest wall, making respiratory
    complications a major mortality driver.
  phenotype_term:
    preferred_term: Respiratory insufficiency
    term:
      id: HP:0002093
      label: Respiratory insufficiency
  evidence:
  - reference: PMID:26529632
    reference_title: "Asfotase Alfa Treatment Improves Survival for Perinatal and Infantile Hypophosphatasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      in its most severe perinatal and infantile forms, results in 50-100%
      mortality, typically from respiratory complications.
    explanation: Human trial/natural-history comparison identifies respiratory complications as the typical mortality driver.
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Disease manifestations encompass skeletal hypomineralization with rickets
      and lung hypoplasia
    explanation: Review supports lung hypoplasia within severe HPP manifestations.
- name: Short Stature
  description: >
    Childhood-onset HPP can impair growth through rickets and growth-plate
    defects, resulting in short stature or poor linear growth.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: DOI:10.1093/jbmrpl/ziae180
    reference_title: "Dental manifestations of hypophosphatasia: translational and clinical advances"
    supports: PARTIAL
    evidence_source: OTHER
    snippet: >-
      HPP onset in childhood contributes to rickets, including growth plate
      defects and impaired growth.
    explanation: Review supports impaired growth from childhood rickets, which is the basis for short-stature curation.
- name: Muscle Weakness
  description: >
    Muscle weakness occurs in severe pediatric and adult HPP and contributes to
    functional limitation alongside skeletal disease.
  phenotype_term:
    preferred_term: Muscle weakness
    term:
      id: HP:0001324
      label: Muscle weakness
  evidence:
  - reference: PMID:26590809
    reference_title: "Alkaline Phosphatase and Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      craniosynostosis and muscle weakness when HPP is severe
    explanation: Review identifies muscle weakness as a feature of severe HPP.
  - reference: PMID:34884378
    reference_title: "Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      recurrent, poorly healing fractures, muscle weakness and arthropathy are
      common in adults.
    explanation: Review supports muscle weakness among common adult HPP manifestations.
- name: Chondrocalcinosis
  description: >
    PPi excess predisposes to chondrocalcinosis and arthropathy in HPP.
  phenotype_term:
    preferred_term: Chondrocalcinosis
    term:
      id: HP:0000934
      label: Chondrocalcinosis
  evidence:
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      PP(i) excesses cause chondrocalcinosis and sometimes arthropathy.
    explanation: Review directly links PPi excess to chondrocalcinosis.
- name: Motor Delay
  description: >
    Pediatric HPP can include delayed motor development, hypotonia, and gait
    disturbance as part of the systemic disease presentation.
  phenotype_term:
    preferred_term: Motor delay
    term:
      id: HP:0001270
      label: Motor delay
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The clinical presentation can comprise failure to thrive with muscular
      hypotonia, delayed motor development, and gait disturbances later in
      childhood.
    explanation: Review supports delayed motor development in childhood HPP.
- name: Pain
  description: >
    Generalized musculoskeletal pain is increasingly recognized in adult and
    pediatric-onset adult HPP, reflecting skeletal disease and arthropathy.
  phenotype_term:
    preferred_term: Musculoskeletal pain
    term:
      id: HP:0012531
      label: Pain
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      generalized musculoskeletal pain, weakness, and fatigue
    explanation: Review supports generalized musculoskeletal pain among key adult HPP findings.
- name: Fatigue
  description: >
    Chronic fatigue is a non-skeletal symptom that contributes to adult HPP
    disease burden.
  phenotype_term:
    preferred_term: Fatigue
    term:
      id: HP:0012378
      label: Fatigue
  evidence:
  - reference: DOI:10.1007/s11914-025-00906-5
    reference_title: "Medical Management of Hypophosphatasia: Review of Data on Asfotase Alfa"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      non-skeletal impairments, such as pain and chronic fatigue.
    explanation: Review supports chronic fatigue as part of adult HPP disease burden.
biochemical:
- name: Serum alkaline phosphatase activity
  presence: DECREASED
  context: >
    Persistently low serum alkaline phosphatase activity is the cardinal
    diagnostic biochemical marker of HPP and reflects deficient TNAP activity.
  readouts:
  - target: ALPL loss of function and TNAP deficiency
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Persistently low serum ALP reports deficient TNAP enzymatic activity.
  evidence:
  - reference: PMID:34884378
    reference_title: "Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Persistently low serum alkaline phosphatase is the cardinal biochemical
      feature of the disease.
    explanation: Review identifies low serum ALP as the cardinal biochemical feature.
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The diagnosis is based on clinical manifestations in combination with
      persistently low alkaline phosphatase (ALP) activity
    explanation: Review lists persistently low ALP activity as a diagnostic criterion.
- name: Inorganic pyrophosphate
  presence: INCREASED
  context: >
    Elevated inorganic pyrophosphate is a diagnostic TNAP substrate and the
    central inhibitor of hydroxyapatite crystal growth.
  readouts:
  - target: TNAP substrate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated PPi reports impaired TNAP pyrophosphatase activity and substrate accumulation.
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      elevated levels of ALP substrates, specifically inorganic pyrophosphate
      (PPi)
    explanation: Review lists elevated PPi as an ALP substrate marker.
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Increased extracellular levels of pyridoxal 5'-phosphate and inorganic
      pyrophosphate (PP(i)) demonstrate that TNSALP is a phosphomonoester
      phosphohydrolase and a pyrophosphatase
    explanation: Review supports increased extracellular PPi as a biochemical consequence of TNAP loss.
- name: Pyridoxal 5'-phosphate
  presence: INCREASED
  context: >
    Elevated plasma PLP reflects impaired TNAP-mediated vitamin B6 metabolism
    and supports the seizure branch in severe infantile disease.
  readouts:
  - target: TNAP substrate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated PLP reports impaired TNAP-mediated dephosphorylation of vitamin B6 substrate.
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      elevated levels of ALP substrates, specifically inorganic pyrophosphate
      (PPi), pyridoxal 5'-phosphate (PLP)
    explanation: Review lists elevated PLP as an ALP substrate marker.
  - reference: PMID:20392236
    reference_title: "Physiological role of alkaline phosphatase explored in hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Increased extracellular levels of pyridoxal 5'-phosphate and inorganic
      pyrophosphate (PP(i)) demonstrate that TNSALP is a phosphomonoester
      phosphohydrolase and a pyrophosphatase
    explanation: Review supports increased extracellular PLP as a biochemical consequence of TNAP loss.
- name: Urine phosphoethanolamine
  presence: INCREASED
  context: >
    Urinary phosphoethanolamine is an additional ALP substrate that can be
    elevated in HPP and used as part of the diagnostic biochemical pattern.
  readouts:
  - target: TNAP substrate accumulation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated urine PEA reports accumulation of ALP substrates downstream of TNAP deficiency.
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      elevated levels of ALP substrates, specifically inorganic pyrophosphate
      (PPi), pyridoxal 5'-phosphate (PLP) or urine phosphoethanolamine (PEA)
    explanation: Review lists urine PEA among elevated ALP substrate markers.
genetic:
- name: ALPL Mutations
  gene_term:
    preferred_term: ALPL
    term:
      id: hgnc:438
      label: ALPL
  association: Causative
  relationship_type: CAUSATIVE
  notes: >
    Mutations in ALPL encoding tissue-nonspecific alkaline phosphatase
    (TNSALP). More than 400 ALPL mutations have been reported, transmitted by
    autosomal dominant or recessive modes. Severe disease is usually recessive,
    while moderate and mild disease can be recessive or dominant depending on
    allele severity, dominant-negative effects, and haploinsufficiency.
  evidence:
  - reference: PMID:32973344
    reference_title: "Hypophosphatasia: a genetic-based nosology and new insights in genotype-phenotype correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Hypophosphatasia (HPP) is caused by pathogenic variants in the ALPL gene.
    explanation: Cohort paper directly states the ALPL causal relationship.
  - reference: PMID:34884378
    reference_title: "Hypophosphatasia."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      More than 400 ALPL mutations, mostly missense, are reported to date,
      transmitted by either autosomal dominant or recessive mode.
    explanation: Review supports mutation burden and dominant/recessive transmission.
  - reference: PMID:32973344
    reference_title: "Hypophosphatasia: a genetic-based nosology and new insights in genotype-phenotype correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Homozygosity was an aggravating factor of the severity and moderate alleles
      were rare both in number and frequency.
    explanation: Cohort evidence supports genotype-severity correlation.
treatments:
- name: Asfotase Alfa (Strensiq)
  description: >
    Bone-targeted enzyme replacement therapy that substitutes TNAP activity.
    Human interventional evidence shows improved survival, respiratory outcomes,
    skeletal mineralization, rickets, and functional outcomes in severely
    affected pediatric patients.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_mechanisms:
  - target: ALPL loss of function and TNAP deficiency
    treatment_effect: RESTORES
    description: Asfotase alfa substitutes deficient TNAP enzymatic activity.
    evidence:
    - reference: PMID:26529632
      reference_title: "Asfotase Alfa Treatment Improves Survival for Perinatal and Infantile Hypophosphatasia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        treatment with asfotase alfa, a first-in-class enzyme replacement therapy
      explanation: Trial abstract identifies asfotase alfa as enzyme replacement therapy.
  - target: Skeletal and dentoalveolar mineralization failure
    treatment_effect: RESTORES
    description: Enzyme replacement improves skeletal mineralization and rib-related respiratory function.
    evidence:
    - reference: PMID:26529632
      reference_title: "Asfotase Alfa Treatment Improves Survival for Perinatal and Infantile Hypophosphatasia."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Asfotase alfa mineralizes the HPP skeleton, including the ribs, and
        improves respiratory function and survival in life-threatening perinatal
        and infantile HPP.
      explanation: Human clinical evidence directly supports skeletal and respiratory benefit.
  evidence:
  - reference: PMID:26529632
    reference_title: "Asfotase Alfa Treatment Improves Survival for Perinatal and Infantile Hypophosphatasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Asfotase alfa was associated with improved survival in treated patients vs
      historical controls: 95% vs 42% at age 1 year and 84% vs 27% at age 5
      years, respectively (P < .0001, Kaplan-Meier log-rank test).
    explanation: Human interventional evidence shows improved survival with asfotase alfa.
  - reference: PMID:26529632
    reference_title: "Asfotase Alfa Treatment Improves Survival for Perinatal and Infantile Hypophosphatasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      76% (16/21) of the ventilated and treated patients survived, among whom 75%
      (12/16) were weaned from ventilatory support.
    explanation: Human interventional evidence supports improved ventilatory outcomes.
  - reference: DOI:10.1007/s11914-025-00906-5
    reference_title: "Medical Management of Hypophosphatasia: Review of Data on Asfotase Alfa"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Treatment for HPP relies on the enzyme replacement asfotase alfa.
    explanation: Review summarizes asfotase alfa as the core enzyme-replacement treatment.
- name: Pyridoxine Supplementation
  description: >
    Pyridoxine can be used for vitamin B6-dependent seizures in severe infantile
    HPP, bypassing impaired PLP handling downstream of TNAP deficiency.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: pyridoxine
      term:
        id: CHEBI:16709
        label: pyridoxine
  target_mechanisms:
  - target: Vitamin B6-dependent neurologic vulnerability
    treatment_effect: BYPASSES
    description: Pyridoxine addresses the vitamin B6-dependent seizure branch rather than restoring TNAP.
    evidence:
    - reference: PMID:23479201
      reference_title: "Infantile hypophosphatasia secondary to a novel compound heterozygous mutation presenting with pyridoxine-responsive seizures."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Defective TNSALP activity in the brain can result in intractable seizures
        responsive to pyridoxine.
      explanation: Human case report supports pyridoxine responsiveness in the seizure branch targeted by supplementation.
  evidence:
  - reference: PMID:23479201
    reference_title: "Infantile hypophosphatasia secondary to a novel compound heterozygous mutation presenting with pyridoxine-responsive seizures."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Empiric treatment with favorable response to pyridoxine
    explanation: Human case report directly supports pyridoxine treatment responsiveness in infantile HPP seizures.
- name: Multidisciplinary Supportive Care
  description: >
    Supportive management is multimodal and tailored to disease manifestations,
    including metabolic and musculoskeletal care, dental care, neurologic and
    neurosurgical surveillance, pain management, physical therapy, and
    psychological support.
  treatment_term:
    preferred_term: supportive care
    term:
      id: MAXO:0000950
      label: supportive care
  target_mechanisms:
  - target: Skeletal and dentoalveolar mineralization failure
    treatment_effect: MODULATES
    description: Dental, musculoskeletal, pain, and rehabilitation care address downstream skeletal and dental consequences.
  - target: Pyrophosphate crystal arthropathy
    treatment_effect: MODULATES
    description: Pain management and musculoskeletal care address arthropathy-related symptoms.
  evidence:
  - reference: DOI:10.1007/s00223-025-01356-y
    reference_title: "Diagnosis and Treatment of Hypophosphatasia"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The multidisciplinary team for comprehensive management of HPP patients
      should include expertise to ensure disease state metabolic and
      musculoskeletal treatment, dental care, neurological and neurosurgical
      surveillance, pain management, physical therapy, and psychological care.
    explanation: Review supports multimodal supportive care across HPP manifestations.
datasets: []
📚

References & Deep Research

Deep Research

2
Disorder ▸

Disorder

  • Name: Hypophosphatasia
  • Category: Mendelian
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 30

Key Pathophysiology Nodes

  • Defective Bone Mineralization
  • Pyridoxal Phosphate Accumulation
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1007/s00198-023-06844-1
  • DOI:10.1007/s00223-025-01356-y
  • DOI:10.1007/s11033-024-09906-7
  • DOI:10.1007/s11914-025-00906-5
  • DOI:10.1093/jbmrpl/ziae180
  • DOI:10.17219/acem/205341
Falcon ▸
Pathophysiology description
Edison Scientific Literature 31 citations 2026-02-10T08:11:31.316951

Pathophysiology description Hypophosphatasia is a systemic metabolic bone and dental disease caused by loss-of-function variants in ALPL encoding tissue-nonspecific alkaline phosphatase (TNSALP/TNAP). TNAP is a cell-surface, GPI-anchored ectoenzyme highly expressed on osteoblasts and other cells; it hydrolyzes three key physiological substrates—inorganic pyrophosphate (PPi), pyridoxal 5′-phosphate (PLP), and phosphoethanolamine (PEA). Deficiency of TNAP activity leads to PPi accumulation and a reduced local Pi:PPi ratio, which directly inhibits hydroxyapatite nucleation and extracellular matrix mineralization in bone and teeth, producing rickets in children and osteomalacia and pseudofractures in older patients. Diagnostic biochemical features include persistently low age/sex-adjusted serum ALP with elevated ALP substrates (PPi, serum PLP, and urine PEA). Impaired dephosphorylation of PLP also contributes mechanistically to vitamin B6–responsive neonatal seizures; chronically elevated PPi promotes calcium pyrophosphate (CPP) crystal deposition causing chondrocalcinosis/pseudogout. Mineral imbalance (hypercalcemia, hypercalciuria) predisposes to nephrocalcinosis. Craniosynostosis reflects disordered skull bone mineralization. As one expert consensus summarizes, HPP “results from LOF variants in ALPL causing deficient tissue-nonspecific alkaline phosphatase… [whose] substrates include PPi, PLP, and PEA,” and the altered phosphate:PPi balance “inhibits bone and tooth mineralization.” Updates also emphasize technical pitfalls (e.g., EDTA/oxalate tubes artifactually lowering ALP) and the value of integrated clinical–biochemical–radiographic–genetic diagnosis to reduce delays (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2)

Core mechanisms: molecular and cellular - Enzyme deficiency: TNAP deficiency from ALPL LOF variants causes PPi accumulation in the extracellular milieu; elevated PPi inhibits hydroxyapatite crystal formation at matrix vesicles and within collagenous matrix. Clinically: rickets/osteomalacia, deformities, pseudofractures, delayed fracture healing. (Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (seefried2025diagnosisandtreatment pages 1-2) - Substrate biology: PPi is the proximate inhibitor of mineralization; PLP is a TNAP substrate whose CNS handling explains vitamin B6–responsive seizures; PEA serves as a supportive diagnostic marker though its mechanistic role is less defined. A 2025 medical management review reiterates that the “accumulation of TNSALP substrates PPi, PLP, and PEA” underlies disease, and that elevated PPi “inhibits hydroxyapatite formation.” (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2) - Dental mineralization: TNAP maintains the local Pi:PPi ratio crucial for cementogenesis. Cementum hypoplasia leads to pathognomonic premature exfoliation of fully rooted primary teeth; the dentin and alveolar bone are variably affected. “Premature tooth loss of fully rooted teeth is pathognomonic for HPP,” and effects of systemically delivered ERT on dental tissues “remain poorly defined,” motivating gene-therapy exploration (JBMR Plus, Jan 2025; https://doi.org/10.1093/jbmrpl/ziae180). (santos2025dentalmanifestationsof pages 1-3, santos2025dentalmanifestationsof pages 3-4) - CPPD link: sustained PPi excess favors calcium pyrophosphate dihydrate crystallization, clinically observed as chondrocalcinosis/pseudogout in some patients. (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1; Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)

2023–2024 developments and latest research - Updated diagnosis criteria: An International Working Group (IWG) proposed major/minor criteria integrating clinical features, persistently low ALP (age/sex adjusted), elevated ALP substrates (PPi/PLP/PEA), characteristic imaging, and ALPL genetics, aiming to reduce a median ~5.7-year diagnostic delay noted previously. Practical lab guidance highlights avoiding EDTA/oxalate tubes that artifactually lower ALP. (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 2-4, khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Genetics beyond coding regions: In a 2024 whole-genome sequencing (WGS) study of 16 adults with clinical HPP phenotypes and low ALP but negative prior ALPL testing, WGS “did not identify any novel disease-causing ALPL variants,” though variants in other genes (e.g., COL1A1, NLRP12, SCN9A, P3H1, SGCE, VDR) were found in four patients, underscoring residual diagnostic gaps and the potential for alternative or modifying mechanisms (Molecular Biology Reports, Sep 2024; https://doi.org/10.1007/s11033-024-09906-7). (seefried2024wholegenomesequencing pages 1-2) - Therapy and outcomes: Real-world and registry syntheses report that asfotase alfa improves survival and rickets in severely affected children and improves physical function, pain, and quality-of-life (QoL) across age-of-onset groups; expert reviews also note clinical testing of a long-acting TNAP (efzimfotase alfa/ALXN1850) in trials aiming to reduce treatment burden (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2) Additional clinical perspective reviews emphasize non-skeletal burdens (pain, fatigue, neuropsychiatric and GI symptoms) and the need to address them in care pathways (Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (seefried2025diagnosisandtreatment pages 1-2) - Dental/craniofacial insights: Translational advances from animal models and clinical series clarify cementum dependence on TNAP and reinforce that odonto-HPP can present without overt skeletal disease; the literature highlights knowledge gaps regarding ERT penetration into dental tissues and motivates gene-therapy approaches under preclinical evaluation (JBMR Plus, Jan 2025; https://doi.org/10.1093/jbmrpl/ziae180). (santos2025dentalmanifestationsof pages 1-3, santos2025dentalmanifestationsof pages 3-4)

Current applications and real-world implementation - Enzyme replacement therapy (ERT): Asfotase alfa is standard-of-care for severe pediatric-onset HPP and is increasingly used in adults with significant disease burden. Syntheses of observational cohorts and registry data indicate sustained improvements in radiographic rickets, growth and respiratory survival in infants, and in adults, reductions in pain and improvements in function and QoL across age-of-onset categories. The same review notes that initiation criteria are being formalized and that a long-acting enzyme (efzimfotase alfa/ALXN1850) is in clinical testing to reduce dosing frequency (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2) - Diagnostic standardization: The 2024 IWG criteria provide a harmonized diagnostic framework adopted by expert centers to shorten time-to-diagnosis and to improve enrollment fidelity for trials and registries (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2)

Expert opinions and authoritative analysis - The International Working Group’s consensus underscores integrating clinical phenotype with biochemistry and genetics, acknowledging that “gene sequencing is not positive in all clinically diagnosed patients,” and urging measured interpretation of VUS and negative tests in the setting of classic phenotypes (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Seefried et al. highlight expanding adult HPP recognition with prominent pain/fatigue and emphasize the need to clarify mechanisms and improve substitution strategies beyond current ERT (Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (seefried2025diagnosisandtreatment pages 1-2) - Dahir and Dunbar synthesize registry evidence supporting clinical benefits of ERT across ages and note ongoing development of long-acting TNAP constructs (efzimfotase/ALXN1850) to address treatment burden (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2)

Relevant statistics and data (selected, with quotes where available) - Diagnostic challenge and delay: The IWG paper documents substantial diagnostic delays and proposes criteria to “assist in establishing a clinical diagnosis of HPP in adults and children,” with systematic review methodology and GRADE-informed consensus (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - WGS-negative cohort: In 16 clinically diagnosed adults with low ALP but negative prior testing, “WGS did not identify any novel disease-causing ALPL variants,” identifying variants in non-ALPL genes in 4/16, illustrating a residual genetic diagnostic gap with standard techniques (Molecular Biology Reports, Sep 2024; https://doi.org/10.1007/s11033-024-09906-7). (seefried2024wholegenomesequencing pages 1-2) - ERT outcomes: Summaries from the Global HPP Registry and other cohorts show ERT improves physical function and QoL in adults regardless of onset age, and improves survival and rickets in severely affected children, as consolidated in a 2025 review (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2) Pathophysiology and clinical spectrum including CPPD, craniosynostosis, and seizures are reiterated in expert reviews (Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y; JBMR Plus, Jan 2025; https://doi.org/10.1093/jbmrpl/ziae180). (seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Key concepts and definitions - Tissue-nonspecific alkaline phosphatase (TNSALP/TNAP): A GPI-anchored ectoenzyme at the plasma membrane, highly expressed on osteoblasts; dephosphorylates PPi, PLP, PEA, regulating mineralization via the Pi:PPi ratio. (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1; Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2) - Inorganic pyrophosphate (PPi): Potent mineralization inhibitor; excess PPi from TNAP deficiency suppresses hydroxyapatite crystal growth. (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2) - Pyridoxal 5′-phosphate (PLP): Active vitamin B6; TNAP-mediated dephosphorylation is important for neuronal availability; impaired handling leads to vitamin B6–responsive neonatal seizures. (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Phosphoethanolamine (PEA): TNAP substrate measurable in urine; supportive biomarker of HPP. (Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (seefried2025diagnosisandtreatment pages 1-2)

Key molecular players and affected systems - Genes/Proteins: ALPL/TNSALP (HGNC:436). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Chemical entities: PPi, PLP, PEA, orthophosphate (Pi), hydroxyapatite, calcium pyrophosphate crystals. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, dahir2025medicalmanagementof pages 1-2) - Cell types: Osteoblasts, chondrocytes, osteocytes. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2) - Anatomical sites: Bone (including growth plates), dentoalveolar complex (cementum, dentin, alveolar bone), joints, kidney, brain, cranial sutures. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Biological processes (GO) and cellular components - Disrupted processes: Bone mineralization (GO:0030282); extracellular matrix mineralization (GO:0030198); ossification (GO:0001503); phosphate-containing compound metabolic process (GO:0006796); pyridoxal phosphate metabolic process (GO:0042823). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3) - Cellular components: Plasma membrane (GO:0005886; TNAP is GPI-anchored); extracellular region (GO:0005576; PPi accumulates and inhibits mineral deposition); matrix vesicle (GO:0070062; initial mineral nucleation site dependent on local TNAP activity). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Cell type involvement (CL) and anatomical locations (UBERON); chemical entities (CHEBI) - See structured ontology mapping below.

Category Entity (name) Identifier Role / Relevance Supporting Sources
Gene / Protein ALPL / TNSALP HGNC:436 Causal gene encoding tissue-nonspecific alkaline phosphatase; loss-of-function causes HPP (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Metabolite Inorganic pyrophosphate CHEBI:18361 Pathogenic substrate that accumulates when TNAP is deficient; inhibits hydroxyapatite formation and mineralization (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, dahir2025medicalmanagementof pages 1-2)
Metabolite Pyridoxal 5'-phosphate (PLP) CHEBI:18405 TNAP substrate; impaired dephosphorylation linked to vitamin B6–responsive seizures in infants (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, dahir2025medicalmanagementof pages 1-2)
Metabolite Phosphoethanolamine (PEA) CHEBI:16311 Urinary biomarker elevated in HPP; diagnostic substrate of TNAP (seefried2025diagnosisandtreatment pages 1-2, dahir2025medicalmanagementof pages 1-2)
Metabolite Orthophosphate (Pi) CHEBI:18367 Product of PPi hydrolysis by TNAP; Pi:PPi balance is critical for mineralization (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Metabolite Hydroxyapatite CHEBI:52255 Mineral phase of bone/teeth formation inhibited by excess PPi (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, santos2025dentalmanifestationsof pages 1-3)
Metabolite Calcium pyrophosphate CHEBI:3311 Crystal species promoted by elevated PPi; linked to chondrocalcinosis/CPPD in HPP (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Cell type Osteoblast CL:0000062 Primary bone-forming cell expressing membrane-anchored TNAP; defective mineralization when TNAP low (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Cell type Chondrocyte CL:0000138 Growth-plate and cartilage cells affected in rickets-like changes due to altered Pi:PPi (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, lipinski2026hypophosphatasiainchildren pages 1-2)
Cell type Osteocyte CL:0000127 Mature bone cell within mineralized matrix; contributes to bone homeostasis affected by hypomineralization (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, lipinski2026hypophosphatasiainchildren pages 1-2)
Anatomical Bone UBERON:0001474 Primary organ affected: defective extracellular matrix mineralization → rickets/osteomalacia, fractures (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Anatomical Growth plate UBERON:0003949 Site of endochondral ossification; rickets-like metaphyseal changes occur in pediatric HPP (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, lipinski2026hypophosphatasiainchildren pages 1-2)
Anatomical Cementum UBERON:0008768 Tooth-supporting mineralized tissue; hypoplasia → premature loss of deciduous teeth (pathognomonic) (santos2025dentalmanifestationsof pages 1-3, santos2025dentalmanifestationsof pages 3-4)
Anatomical Dentin UBERON:0001754 Mineralized tooth tissue affected in odonto-HPP phenotypes (santos2025dentalmanifestationsof pages 1-3)
Anatomical Alveolar bone UBERON:0008060 Tooth socket bone affected leading to early tooth loss and periodontal issues (santos2025dentalmanifestationsof pages 1-3)
Anatomical Kidney UBERON:0002113 Site of nephrocalcinosis and disturbances in calcium/phosphate handling in some HPP patients (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Anatomical Brain UBERON:0000955 Indirectly affected via PLP metabolism; PLP deficiency underlies pyridoxine‑responsive seizures (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, dahir2025medicalmanagementof pages 1-2)
Anatomical Joint UBERON:0000982 CPP crystal deposition (chondrocalcinosis) and inflammatory arthropathy linked to PPi accumulation (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Anatomical Cranial suture UBERON:0003687 Craniosynostosis observed in some pediatric HPP cases related to abnormal skull bone mineralization (seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)
GO Process Bone mineralization GO:0030282 Biological process directly impaired by TNAP deficiency and PPi accumulation (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
GO Process Extracellular matrix mineralization GO:0030198 General mineralization pathway disrupted in bone and dentoalveolar tissues (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, santos2025dentalmanifestationsof pages 1-3)
GO Process Ossification GO:0001503 Endochondral and intramembranous bone formation processes affected, producing rickets/cranial anomalies (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, lipinski2026hypophosphatasiainchildren pages 1-2)
GO Process Pyridoxal phosphate metabolic process GO:0042823 PLP metabolism impacted by TNAP activity → neurological manifestations (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, dahir2025medicalmanagementof pages 1-2)
GO Process Phosphate-containing compound metabolic process GO:0006796 Broad category encompassing PPi/Pi balance controlled by TNAP (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Cellular Component Plasma membrane GO:0005886 TNAP is a GPI‑anchored/membrane-associated enzyme on osteoblasts and other cells (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Cellular Component Extracellular region GO:0005576 Matrix and extracellular milieu where PPi accumulates and inhibits mineral deposition (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)
Cellular Component Matrix vesicle GO:0070062 Sites of initial mineral nucleation in bone; TNAP activity in/near vesicles is critical for hydroxyapatite formation (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, lipinski2026hypophosphatasiainchildren pages 1-2)

Table: Concise mapping of key HPP molecular entities, cell/tissue sites, GO processes and ontology identifiers with brief roles and supporting source IDs; useful for knowledge‑base annotation and downstream GO/HGNC/UBERON/CL/CHEBI mapping.

Disease progression - Initiating trigger: ALPL loss-of-function reduces cell-surface TNAP on osteoblasts/chondrocytes. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Molecular cascade: PPi accumulates; Pi:PPi balance shifts; hydroxyapatite nucleation in matrix vesicles is inhibited; extracellular matrix fails to mineralize. (seefried2025diagnosisandtreatment pages 1-2) - Tissue-level effects: Pediatric growth plates develop rickets-like metaphyseal changes; adults develop osteomalacia with fractures/pseudofractures and delayed healing. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2) - Dentition: Cementum hypoplasia leads to early loss of fully rooted primary teeth; dentin/alveolar bone involvement varies (odonto-HPP may be dental-restricted). (santos2025dentalmanifestationsof pages 1-3) - Systemic sequelae: PLP handling deficits produce neonatal vitamin B6–responsive seizures; mineral dysregulation predisposes to hypercalcemia/hypercalciuria and nephrocalcinosis; chronic PPi excess fosters CPPD/chondrocalcinosis. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)

Phenotypic manifestations (with HP terms) - Rickets (HP:0000938), osteomalacia (HP:0000938), fractures/pseudofractures (HP:0002659), delayed fracture healing (HP:0000940). Mechanism: PPi-mediated inhibition of mineralization. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2) - Craniosynostosis (HP:0001363). Mechanism: disordered intramembranous ossification of cranial sutures. (seefried2025diagnosisandtreatment pages 1-2) - Premature exfoliation of primary teeth (HP:0006354), enlarged pulp chambers (HP:0006297), cementum hypoplasia. Mechanism: disrupted Pi:PPi at cementogenesis. (santos2025dentalmanifestationsof pages 1-3) - Vitamin B6–responsive seizures (HP:0001250). Mechanism: impaired PLP dephosphorylation/availability. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Hypercalcemia (HP:0003072), hypercalciuria (HP:0002150), nephrocalcinosis (HP:0000121). Mechanism: mineral imbalance in poorly mineralizing skeleton. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Chondrocalcinosis/CPPD (HP:0100762). Mechanism: elevated PPi and CPP crystal formation. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)

Evidence items (primary/review sources with dates/URLs) - Khan AA et al. Hypophosphatasia diagnosis: current state of the art and proposed diagnostic criteria for children and adults. Osteoporosis International. Published Nov 2024. URL: https://doi.org/10.1007/s00198-023-06844-1. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - Seefried L et al. Diagnosis and treatment of hypophosphatasia. Calcified Tissue International. Published Mar 2025. URL: https://doi.org/10.1007/s00223-025-01356-y. (seefried2025diagnosisandtreatment pages 1-2) - Dahir KM, Dunbar NS. Medical management of hypophosphatasia: review of data on asfotase alfa. Current Osteoporosis Reports. Published Mar 2025. URL: https://doi.org/10.1007/s11914-025-00906-5. (dahir2025medicalmanagementof pages 1-2) - Seefried L et al. Whole genome sequencing in adults with clinical hallmarks of hypophosphatasia negative for ALPL variants. Molecular Biology Reports. Published Sep 2024. URL: https://doi.org/10.1007/s11033-024-09906-7. (seefried2024wholegenomesequencing pages 1-2) - dos Santos EJL et al. Dental manifestations of hypophosphatasia: translational and clinical advances. JBMR Plus. Published Jan 2025. URL: https://doi.org/10.1093/jbmrpl/ziae180. (santos2025dentalmanifestationsof pages 1-3, santos2025dentalmanifestationsof pages 3-4)

Direct supporting quotes - “The diagnosis of HPP is made on the basis of integrating clinical features, laboratory profile, radiographic features of the condition, and DNA analysis identifying the presence of a pathogenic variant of the tissue nonspecific alkaline phosphatase gene (ALPL).” (Osteoporosis International, Nov 2024; https://doi.org/10.1007/s00198-023-06844-1). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2) - “HPP… [is] characterized by deficient activity of tissue-nonspecific alkaline phosphatase (TNAP) caused by variants in the ALPL gene… [with] elevated levels of ALP substrates, specifically inorganic pyrophosphate (PPi), pyridoxal 5′-phosphate (PLP) or urine phosphoethanolamine (PEA).” (Calcified Tissue International, Mar 2025; https://doi.org/10.1007/s00223-025-01356-y). (seefried2025diagnosisandtreatment pages 1-2) - “Elevated PPi inhibits hydroxyapatite formation, causing skeletal and dental hypomineralization,” and “treatment for HPP relies on enzyme replacement asfotase alfa… long-term safety and efficacy… [with] a derivative, efzimfotase alfa, currently undergoes clinical testing.” (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5). (dahir2025medicalmanagementof pages 1-2) - “Premature tooth loss of fully rooted teeth is pathognomonic for HPP… [and] effects of ERT on dental tissues remain poorly defined,” motivating exploration of gene therapy. (JBMR Plus, Jan 2025; https://doi.org/10.1093/jbmrpl/ziae180). (santos2025dentalmanifestationsof pages 1-3)

Gene/protein annotations with ontology terms - ALPL (HGNC:436); Protein: tissue-nonspecific alkaline phosphatase (TNAP). Function/process: bone mineralization (GO:0030282); extracellular matrix mineralization (GO:0030198); phosphate-containing compound metabolic process (GO:0006796); pyridoxal phosphate metabolic process (GO:0042823). Cellular component: plasma membrane (GO:0005886), matrix vesicle (GO:0070062), extracellular region (GO:0005576). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Phenotype associations (HP terms) - HP:0000938 (Rickets/Osteomalacia), HP:0002659 (Pseudofractures), HP:0000940 (Delayed bone healing/Nonunion), HP:0001363 (Craniosynostosis), HP:0006354 (Premature loss of primary teeth), HP:0006297 (Enlarged pulp chambers), HP:0001250 (Seizures), HP:0003072 (Hypercalcemia), HP:0002150 (Hypercalciuria), HP:0000121 (Nephrocalcinosis), HP:0100762 (Chondrocalcinosis). Mechanistic links detailed above. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Cell type involvement (CL terms) - Osteoblast (CL:0000062), Chondrocyte (CL:0000138), Osteocyte (CL:0000127). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2)

Anatomical locations (UBERON terms) - Bone (UBERON:0001474), Growth plate (UBERON:0003949), Cementum (UBERON:0008768), Dentin (UBERON:0001754), Alveolar bone (UBERON:0008060), Joint (UBERON:0000982), Kidney (UBERON:0002113), Brain (UBERON:0000955), Cranial suture (UBERON:0003687). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Chemical entities (CHEBI terms) - Inorganic pyrophosphate (CHEBI:18361), Pyridoxal 5′-phosphate (CHEBI:18405), Phosphoethanolamine (CHEBI:16311), Orthophosphate (CHEBI:18367), Hydroxyapatite (CHEBI:52255), Calcium pyrophosphate (CHEBI:3311). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, dahir2025medicalmanagementof pages 1-2)

Open questions and future directions - Genetics: Persistent fraction of clinically definite HPP remains ALPL-negative by standard sequencing and even WGS, suggesting undetected regulatory/structural variants or genetic modifiers; expanded assays and functional genomics are needed (Molecular Biology Reports, Sep 2024; https://doi.org/10.1007/s11033-024-09906-7). (seefried2024wholegenomesequencing pages 1-2) - Therapies: While ERT has transformed outcomes, optimizing access, long-acting formulations (efzimfotase/ALXN1850), and approaches addressing dental tissues and adult non-skeletal symptom burden remain priorities; preclinical gene-therapy strategies are under investigation (Current Osteoporosis Reports, Mar 2025; https://doi.org/10.1007/s11914-025-00906-5; JBMR Plus, Jan 2025; https://doi.org/10.1093/jbmrpl/ziae180). (dahir2025medicalmanagementof pages 1-2, santos2025dentalmanifestationsof pages 1-3)

Overall synthesis HPP pathophysiology centers on deficient TNAP activity and consequent PPi accumulation, which disrupts extracellular matrix mineralization across bone and dental tissues and secondarily perturbs PLP metabolism and systemic mineral homeostasis. The 2024 consensus criteria codify a modern diagnostic framework integrating biochemistry, imaging, and genetics, while 2024 WGS data underscore ongoing genetic diagnostic gaps. Real-world evidence consolidates ERT’s benefits in survival, mineralization, function, and QoL, with long-acting TNAP under clinical evaluation and gene-therapy approaches emerging to address remaining needs, including dental tissue targeting and adult symptom burden (Osteoporosis International, Nov 2024; Calcified Tissue International, Mar 2025; Current Osteoporosis Reports, Mar 2025; JBMR Plus, Jan 2025). (khan2024hypophosphatasiadiagnosiscurrent pages 1-2, seefried2025diagnosisandtreatment pages 1-2, dahir2025medicalmanagementof pages 1-2, santos2025dentalmanifestationsof pages 1-3)

References

  1. (khan2024hypophosphatasiadiagnosiscurrent pages 1-2): Aliya A. Khan, Maria Luisa Brandi, Eric T. Rush, Dalal S. Ali, Hatim Al-Alwani, Khulod Almonaei, Farah Alsarraf, Severine Bacrot, Kathryn M. Dahir, Karel Dandurand, Chad Deal, Serge Livio Ferrari, Francesca Giusti, Gordon Guyatt, Erin Hatcher, Steven W. Ing, Muhammad Kassim Javaid, Sarah Khan, Roland Kocijan, Agnes Linglart, Iman M’Hiri, Francesca Marini, Mark E. Nunes, Cheryl Rockman-Greenberg, Christian Roux, Lothar Seefried, Jill H. Simmons, Susan R. Starling, Leanne M. Ward, Liang Yao, Romina Brignardello-Petersen, and E. Michael Lewiecki. Hypophosphatasia diagnosis: current state of the art and proposed diagnostic criteria for children and adults. Osteoporosis International, 35:431-438, Nov 2024. URL: https://doi.org/10.1007/s00198-023-06844-1, doi:10.1007/s00198-023-06844-1. This article has 75 citations and is from a domain leading peer-reviewed journal.

  2. (seefried2025diagnosisandtreatment pages 1-2): L. Seefried, F. Genest, C. Hofmann, M. L. Brandi, and E. Rush. Diagnosis and treatment of hypophosphatasia. Calcified Tissue International, Mar 2025. URL: https://doi.org/10.1007/s00223-025-01356-y, doi:10.1007/s00223-025-01356-y. This article has 13 citations and is from a peer-reviewed journal.

  3. (dahir2025medicalmanagementof pages 1-2): Kathryn McCrystal Dahir and Nancy S. Dunbar. Medical management of hypophosphatasia: review of data on asfotase alfa. Current Osteoporosis Reports, Mar 2025. URL: https://doi.org/10.1007/s11914-025-00906-5, doi:10.1007/s11914-025-00906-5. This article has 8 citations and is from a peer-reviewed journal.

  4. (santos2025dentalmanifestationsof pages 1-3): Elis J Lira dos Santos, Fatma F Mohamed, Kaitrin Kramer, and Brian L Foster. Dental manifestations of hypophosphatasia: translational and clinical advances. JBMR Plus, Jan 2025. URL: https://doi.org/10.1093/jbmrpl/ziae180, doi:10.1093/jbmrpl/ziae180. This article has 8 citations and is from a peer-reviewed journal.

  5. (santos2025dentalmanifestationsof pages 3-4): Elis J Lira dos Santos, Fatma F Mohamed, Kaitrin Kramer, and Brian L Foster. Dental manifestations of hypophosphatasia: translational and clinical advances. JBMR Plus, Jan 2025. URL: https://doi.org/10.1093/jbmrpl/ziae180, doi:10.1093/jbmrpl/ziae180. This article has 8 citations and is from a peer-reviewed journal.

  6. (khan2024hypophosphatasiadiagnosiscurrent pages 2-4): Aliya A. Khan, Maria Luisa Brandi, Eric T. Rush, Dalal S. Ali, Hatim Al-Alwani, Khulod Almonaei, Farah Alsarraf, Severine Bacrot, Kathryn M. Dahir, Karel Dandurand, Chad Deal, Serge Livio Ferrari, Francesca Giusti, Gordon Guyatt, Erin Hatcher, Steven W. Ing, Muhammad Kassim Javaid, Sarah Khan, Roland Kocijan, Agnes Linglart, Iman M’Hiri, Francesca Marini, Mark E. Nunes, Cheryl Rockman-Greenberg, Christian Roux, Lothar Seefried, Jill H. Simmons, Susan R. Starling, Leanne M. Ward, Liang Yao, Romina Brignardello-Petersen, and E. Michael Lewiecki. Hypophosphatasia diagnosis: current state of the art and proposed diagnostic criteria for children and adults. Osteoporosis International, 35:431-438, Nov 2024. URL: https://doi.org/10.1007/s00198-023-06844-1, doi:10.1007/s00198-023-06844-1. This article has 75 citations and is from a domain leading peer-reviewed journal.

  7. (seefried2024wholegenomesequencing pages 1-2): Lothar Seefried, Anna Petryk, Guillermo del Angel, Felix Reder, and Peter Bauer. Whole genome sequencing in adults with clinical hallmarks of hypophosphatasia negative for alpl variants. Molecular Biology Reports, Sep 2024. URL: https://doi.org/10.1007/s11033-024-09906-7, doi:10.1007/s11033-024-09906-7. This article has 5 citations and is from a peer-reviewed journal.

  8. (lipinski2026hypophosphatasiainchildren pages 1-2): Patryk Lipiński, Joanna Rusecka, Zbigniew Michał Żuber, and Robert Stanisław Śmigiel. Hypophosphatasia in children: from low alkaline phosphatase activity to diagnosis, genetic testing, and treatment options. a narrative review. Advances in Clinical and Experimental Medicine, 35:0-0, Jan 2026. URL: https://doi.org/10.17219/acem/205341, doi:10.17219/acem/205341. This article has 0 citations and is from a peer-reviewed journal.