Johanson-Blizzard syndrome

Mendelian MONDO:0009479 Pathograph 24 Show in embeddings browser hereditary disease

Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive multisystem disorder caused by biallelic loss-of-function variants in UBR1, which encodes one of the E3 ubiquitin ligases of the N-end rule (Arg/N-degron) branch of the ubiquitin-proteasome system. Its clinical hallmark is congenital exocrine pancreatic insufficiency together with hypoplasia or aplasia of the nasal alae, aplasia cutis of the scalp, oligodontia of the permanent teeth, sensorineural hearing loss, short stature and variable intellectual disability; hypothyroidism, other endocrinopathies including later-onset diabetes, and cardiac, genitourinary and anorectal malformations occur in a subset. In affected individuals the pancreas does not express UBR1 and shows an intrauterine-onset destructive pancreatitis with acinar loss and fibro-fatty replacement, so exocrine failure is largely established by birth. The proximate molecular defect is failure of regulated N-degron proteolysis, but the specific disease-relevant substrate(s) stabilized in human pancreas and in the developing craniofacial, cochlear and endocrine tissues remain undefined; missense alleles that retain partial catalytic activity are associated with milder disease.

Ask OpenScientist

Ask a research question about Johanson-Blizzard syndrome. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

1
Inheritance
6
Pathophys.
13
Phenotypes
1
Gaps
24
Pathograph
1
Genes
3
Medical Actions
1
Models
1
Deep Research
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
JBS is caused by biallelic (homozygous or compound heterozygous) loss-of-function variants in UBR1; parental consanguinity is frequently observed given the rarity of the allele.
Autosomal recessive inheritance
Show evidence (2 references)
PMID:16311597 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation."
The gene-discovery paper states the autosomal recessive inheritance and the defining clinical triad.
PMID:34760428 SUPPORT Human Clinical
"The prevalence of JBS is estimated to be 1 in 250,000, with no reported difference in gender while parental consanguinity is frequently observed"
Records the frequent parental consanguinity consistent with recessive inheritance of a rare allele.
?

Discussions and Knowledge Gaps

1
Does the Ubr1(-/-) mouse capture the intrauterine destructive pancreatitis that produces exocrine failure in human JBS, or only a milder functional insufficiency that leaves the destructive prenatal mechanism unmodeled?
HUMAN MODEL MISMATCH jbs_mouse_pancreatic_fidelity
Attached to
pathophysiology#Intrauterine Destructive Pancreatitis
In human JBS the pancreas does not express UBR1 and shows an intrauterine-onset destructive pancreatitis with acinar loss and fibro-fatty replacement. The Ubr1(-/-) mouse reproduces functional exocrine pancreatic insufficiency with impaired stimulus-secretion coupling and increased injury susceptibility, but the reported phenotype is milder and does not recapitulate the destructive prenatal pancreatitis, nor the craniofacial, dental and auditory malformations. Functional redundancy among the overlapping N-end rule ligases (notably UBR2) in the mouse is a candidate explanation. The mismatch matters because the destructive-pancreatitis mechanism, not simple secretory failure, is what makes JBS exocrine insufficiency congenital and near-total, so a model that omits it cannot test interventions aimed at the destructive process itself.
Proposed experiments
Prenatal pancreatic histology in Ubr1/Ubr2 compound-deficient mice
jbs_ubr1_ubr2_pancreas
Compare prenatal and early-postnatal pancreatic histology (acinar apoptosis, inflammation, fibro-fatty replacement) across Ubr1(-/-) and Ubr1/Ubr2 compound-deficient genotypes against controls, to test whether removing the redundant N-end rule ligase unmasks the destructive prenatal pancreatitis seen in human JBS.
Would support
pathophysiology#Intrauterine Destructive Pancreatitis
Would refute
pathophysiology#Intrauterine Destructive Pancreatitis
Supporting outcome
  • Compound-deficient animals develop destructive prenatal pancreatitis with acinar apoptosis and fibro-fatty replacement resembling human JBS, absent in single Ubr1(-/-) animals.
Refuting outcome
  • No genotype reproduces the destructive prenatal pancreatitis, indicating the human mechanism depends on factors not captured by murine N-end rule ligase loss.
⚙

Pathophysiology

6
Biallelic UBR1 Loss of Function
Homozygous or compound heterozygous variants in UBR1 abolish or strongly reduce the activity of the encoded E3 ubiquitin ligase. Most JBS alleles are nonsense, frameshift or splice-site changes that abolish activity; missense changes in the conserved UBR-box and RING-H2 domains reduce it. In patient pancreas UBR1 protein is not expressed.
UBR1 hgnc:16808 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves UBR1 (hgnc:16808). hgnc:16808 is a gene from the HUGO Gene Nomenclature Committee.
Genetic context UBR1 hgnc:16808 HUGO Gene Nomenclature Committee (hgnc) Relation: this genetic context concerns this gene This genetic context concerns UBR1 (hgnc:16808). hgnc:16808 is a gene from the HUGO Gene Nomenclature Committee. allele_type: nonsense, frameshift, splice-site, missense, or whole-exon deletion/duplication variant_origin: GERMLINE functional_impact_category: LOSS_OF_FUNCTION
UBR1 ubiquitin-protein ligase activity GO:0004842 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves UBR1 ubiquitin-protein ligase activity, annotated with ubiquitin-protein transferase activity (GO:0004842), qualified as loss of function. GO:0004842 is a molecular function from the Gene Ontology. ⇓ LOSS OF FUNCTION
Downstream
Impaired N-end Rule Proteolysis Loss of UBR1 catalytic function directly removes the substrate-recognition and ubiquitin-transfer step it performs in the N-end rule pathway.
Show evidence (2 references)
PMID:16311597 SUPPORT Human Clinical
"We mapped the disease-associated locus to chromosome 15q14-21.1 and identified mutations, mostly truncating ones, in the gene UBR1 in 12 unrelated families with Johanson-Blizzard syndrome."
Establishes UBR1 as the disease gene and the predominance of truncating, activity-abolishing mutations.
PMID:21931868 SUPPORT In Vitro
"Most JBS-causing alterations of UBR1 are nonsense, frameshift or splice-site mutations that abolish UBR1 activity."
Classifies the mutational spectrum as loss-of-function that abolishes ligase activity.
Impaired N-end Rule Proteolysis
UBR1 recognizes destabilizing N-terminal residues (N-degrons) and targets those substrates for ubiquitin-dependent degradation. Its loss impairs regulated N-degron proteolysis, with metabolic stabilization of specific N-end rule substrates in affected tissues. The identity of the disease-relevant substrate(s) in human pancreas and developing organs is not established.
N-end rule pathway proteolysis GO:0071596 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased N-end rule pathway proteolysis, annotated with ubiquitin-dependent protein catabolic process via the N-end rule pathway (GO:0071596). GO:0071596 is a biological process from the Gene Ontology. ↓ DECREASED
Downstream
Intrauterine Destructive Pancreatitis In the exocrine pancreas, loss of N-end rule proteolysis is followed by a destructive prenatal pancreatitis; the intervening substrate is unknown, so the edge is annotated with unknown intermediates.
Multisystem Developmental and Organ Dysfunction Beyond the pancreas, UBR1 loss perturbs other organs, converging on the craniofacial, ectodermal, cochlear and endocrine malformations of JBS. The tissue-specific developmental mechanism has not been demonstrated, so the edge carries unknown intermediates.
Show evidence (1 reference)
PMID:21931868 SUPPORT In Vitro
"One class of degradation signals (degrons) recognized by UBR1 are destabilizing N-terminal residues of protein substrates."
Defines the N-degron substrates whose regulated degradation fails when UBR1 is lost.
Intrauterine Destructive Pancreatitis
The pancreas of affected individuals does not express UBR1 and shows an intrauterine-onset destructive pancreatitis, with acinar cell injury and progressive fibro-fatty replacement of the exocrine parenchyma.
pancreatic acinar cell CL:0002064 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves pancreatic acinar cell (CL:0002064). CL:0002064 is a cell type from the Cell Ontology.
dysregulated acinar cell apoptosis GO:0006915 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves dysregulated acinar cell apoptosis, annotated with apoptotic process (GO:0006915). GO:0006915 is a biological process from the Gene Ontology. ↕ DYSREGULATED
Downstream
Exocrine Pancreatic Failure Destruction and fatty replacement of acinar tissue removes the zymogen-secreting capacity of the gland, producing exocrine insufficiency that is largely established by birth.
Show evidence (1 reference)
PMID:16311597 SUPPORT Human Clinical
"Pancreas of individuals with Johanson-Blizzard syndrome did not express UBR1 and had intrauterine-onset destructive pancreatitis."
Direct histopathological description of absent UBR1 and destructive prenatal pancreatitis in patient pancreas. The cited abstracts characterize the lesion as destructive but do not report an apoptosis direction, so the acinar apoptosis node is annotated DYSREGULATED rather than INCREASED.
Exocrine Pancreatic Failure
Near-total loss of exocrine (enzyme-secreting) pancreatic function is the defining functional consequence, presenting in the neonatal or early infantile period with steatorrhea and poor growth. (Named "Exocrine Pancreatic Failure" to keep this mechanism node distinct from the "Exocrine pancreatic insufficiency" clinical phenotype in the flat pathograph namespace.)
Animal models
Ubr1-null mouse exocrine pancreatic phenotype Mouse partially recapitulates Ubr1(-/-) mice develop exocrine pancreatic insufficiency with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury, directionally matching the human exocrine defect.
Downstream
Malabsorption and Failure to Thrive Absent pancreatic enzyme output causes maldigestion and malabsorption of fat, protein and fat-soluble vitamins, driving failure to thrive.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Lists exocrine pancreatic insufficiency as the leading feature of JBS.
Malabsorption and Failure to Thrive
Fat and fat-soluble vitamin malabsorption secondary to exocrine pancreatic insufficiency, the nutritional route to poor growth in infancy.
Downstream
Failure to thrive Malabsorption presents clinically as failure to thrive, often the presenting complaint in infancy.
Short stature Chronic malabsorption contributes to postnatal growth restriction and short stature, through intermediate nutritional deficits.
Show evidence (1 reference)
PMID:10423811 SUPPORT Human Clinical
"Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction."
Names pancreatic insufficiency alongside postnatal growth restriction, the nutritional consequence modeled at this node.
Multisystem Developmental and Organ Dysfunction
A convergence node for the extra-pancreatic manifestations of UBR1 loss: craniofacial and ectodermal maldevelopment (nasal alae, scalp, teeth), cochlear dysfunction, and endocrine gland involvement. Each downstream edge is an association rather than a demonstrated tissue-specific mechanism, so all are annotated with unknown intermediates.
Downstream
Hypoplasia of the nasal alae Hypoplasia or aplasia of the nasal alae is the most constant craniofacial feature and can be detected prenatally.
Aplasia cutis congenita of scalp Midline scalp ectodermal (aplasia cutis) defects are a recurrent feature.
Oligodontia Absence of permanent teeth (oligodontia) with malformed primary teeth is a hallmark dental anomaly.
Sensorineural hearing loss Bilateral severe-to-profound sensorineural hearing loss is one of the most common features; the cochlear mechanism of UBR1 loss is uncharacterized.
Hypothyroidism Hypothyroidism is a recognized endocrine manifestation; other endocrinopathies (growth hormone deficiency, later-onset diabetes) occur in a subset.
Intellectual disability Developmental delay and intellectual disability are recurrent, though variable in severity; the neural substrate of UBR1 loss is uncharacterized.
Microcephaly Microcephaly is a recurrent dysmorphic feature of the craniofacial developmental arm.
Anal atresia Anorectal anomalies including imperforate anus arise as part of the developmental malformation spectrum.
Congenital heart defect Cardiac malformations occur in a subset of patients.
Genitourinary anomaly Genitourinary malformations occur in a subset of patients.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Enumerates the extra-pancreatic malformations and organ involvement grouped at this node.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Johanson-Blizzard syndrome 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
Cardiovascular 1
Congenital heart defect Abnormal heart morphology HP:0001627 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Congenital heart defect, annotated with Abnormal heart morphology (HP:0001627). HP:0001627 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Names anomalies in the cardiac system among the disease features.
Digestive 2
Exocrine pancreatic insufficiency VERY_FREQUENT HP:0001738 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Exocrine pancreatic insufficiency (HP:0001738). HP:0001738 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:16311597 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation."
Names congenital exocrine pancreatic insufficiency as a defining feature.
Anal atresia HP:0002023 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Anal atresia (HP:0002023). HP:0002023 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:10423811 SUPPORT Human Clinical
"Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction."
Names anorectal anomalies among the characterizing features.
Ear 1
Sensorineural hearing loss FREQUENT Sensorineural hearing impairment HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing loss, annotated with Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"One of the most common symptoms in JBS patients is bilateral severe to profound sensorineural hearing loss."
States that bilateral severe-to-profound sensorineural hearing loss is among the commonest features.
Endocrine 1
Hypothyroidism HP:0000821 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypothyroidism (HP:0000821). HP:0000821 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Names hypothyroidism among the disease features.
Genitourinary 1
Genitourinary anomaly Abnormality of the genitourinary system HP:0000119 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Genitourinary anomaly, annotated with Abnormality of the genitourinary system (HP:0000119). HP:0000119 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Names anomalies in the genitourinary system among the disease features.
Head and Neck 3
Hypoplasia of the nasal alae VERY_FREQUENT Underdeveloped nasal alae HP:0000430 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoplasia of the nasal alae, annotated with Underdeveloped nasal alae (HP:0000430). HP:0000430 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:16311597 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation."
Names nasal wing (alae) aplasia as a defining malformation.
PMID:10423811 SUPPORT Human Clinical
"Sonographic findings of aplastic alae nasi (beak-like nose) and dilated sigmoid colon led to the prenatal diagnosis."
Confirms aplastic alae nasi as a prenatally detectable feature.
Oligodontia HP:0000677 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Oligodontia (HP:0000677). HP:0000677 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"It is characterized by developmental delay and several dysmorphic features such as microcephaly, absence of permanent teeth, hypoplasia of the alae nasi, and scalp defects."
Names absence of permanent teeth among the characteristic features.
Microcephaly HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"It is characterized by developmental delay and several dysmorphic features such as microcephaly, absence of permanent teeth, hypoplasia of the alae nasi, and scalp defects."
Lists microcephaly among the dysmorphic features.
Integument 1
Aplasia cutis congenita of scalp HP:0007385 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Aplasia cutis congenita of scalp (HP:0007385). HP:0007385 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Names cutis aplasia on the scalp as a characterizing feature.
Nervous System 1
Intellectual disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Names developmental delay and mental retardation among the disease features.
Growth 2
Short stature HP:0004322 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Short stature (HP:0004322). HP:0004322 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:10423811 SUPPORT Human Clinical
"Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction."
Names postnatal growth restriction as a characterizing feature.
Failure to thrive HP:0001508 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Failure to thrive (HP:0001508). HP:0001508 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Names failure to thrive among the disease features.
🧬

Genetic Associations

1
UBR1 (Causal biallelic variant)
Gene: UBR1 hgnc:16808 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is UBR1 (hgnc:16808). hgnc:16808 is a gene from the HUGO Gene Nomenclature Committee.
Show evidence (2 references)
PMID:16311597 SUPPORT Human Clinical
"We mapped the disease-associated locus to chromosome 15q14-21.1 and identified mutations, mostly truncating ones, in the gene UBR1 in 12 unrelated families with Johanson-Blizzard syndrome."
Original identification of UBR1 as the JBS disease gene across 12 families.
PMID:21931868 SUPPORT In Vitro
"one of them (H160R) was inactive in yeast-based activity assays, the other one (Q1224E) had a detectable but weak activity, and the third one (V146L) exhibited a decreased but significant activity, in agreement with manifestations of JBS in the corresponding JBS patients."
Functional assays establish a genotype-severity correlation with residual catalytic activity.
💊

Medical Actions

3
Pancreatic enzyme replacement and fat-soluble vitamin supplementation
Action: pancreatic enzyme replacement therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is pancreatic enzyme replacement therapy, annotated with Protein Replacement Therapy (NCIT:C16221). NCIT:C16221 is a clinical intervention from the NCI Thesaurus. Ontology label: Protein Replacement Therapy NCIT:C16221
Agent: pancrelipase NCIT:C29345 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses pancrelipase (NCIT:C29345). NCIT:C29345 is a therapeutic agent from the NCI Thesaurus.
Platform: Protein replacement
Oral pancreatic enzyme replacement therapy (pancrelipase) with fat-soluble vitamin (A, D, E, K) supplementation is the mainstay treatment for the exocrine pancreatic component, given lifelong.
Mechanism Target:
BYPASSES Exocrine Pancreatic Failure — Supplies the digestive enzymes the destroyed acinar tissue can no longer secrete; it does not correct the underlying UBR1/N-end rule defect.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Establishes the exocrine pancreatic insufficiency that enzyme replacement is directed at.
Target Phenotypes: Exocrine pancreatic insufficiency HP:0001738 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Exocrine pancreatic insufficiency (HP:0001738). HP:0001738 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Supports the exocrine pancreatic insufficiency indication for this therapy.
Levothyroxine replacement
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: levothyroxine NCIT:C62080 NCI Thesaurus (NCIT) Relation: this treatment uses this therapeutic agent This treatment uses levothyroxine (NCIT:C62080). NCIT:C62080 is a therapeutic agent from the NCI Thesaurus.
Platform: Small molecule
Thyroid hormone (levothyroxine) replacement for hypothyroidism identified on endocrine surveillance.
Mechanism Target:
BYPASSES Hypothyroidism — Replaces deficient thyroid hormone; supportive, not disease-modifying.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Establishes the hypothyroidism this replacement therapy addresses.
Target Phenotypes: Hypothyroidism HP:0000821 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Hypothyroidism (HP:0000821). HP:0000821 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation,..."
Supports hypothyroidism as a treatable feature of JBS.
Cochlear device implantation
Action: cochlear device implantationNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is cochlear device implantation, annotated with Surgical Procedure (NCIT:C15329), qualified as medical device cochlear implant. NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Platform: Device
Cochlear implantation for bilateral severe-to-profound sensorineural hearing loss, followed by aural rehabilitation. It improves hearing thresholds and access to sound, though spoken-language development is not always achieved.
Mechanism Target:
BYPASSES Sensorineural hearing loss — A cochlear implant bypasses the failed cochlear sensory transduction by directly stimulating the auditory nerve; it does not restore native cochlear function.
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"After receiving the cochlear implant, our patient showed substantial improvement in her hearing threshold and communication abilities when compared to the preoperative condition."
Reports the audiological benefit of implantation for the JBS hearing loss.
Target Phenotypes: Sensorineural hearing loss HP:0000407 Human Phenotype Ontology (HP) Relation: this treatment targets this phenotype This treatment targets Sensorineural hearing loss, annotated with Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"although cochlear implantation is considered a good approach for the management of JBS patients, the development of spoken language is not always achieved"
Documents both the value and the limits of cochlear implantation in JBS.
🔬

Diagnosis

3
Molecular genetic testing of UBR1
Confirmatory diagnosis rests on identifying biallelic UBR1 variants; sequencing detects most alleles, with MLPA reserved for exon-level deletions/duplications missed by sequencing.
molecular genetic testing (UBR1 sequencing) NCIT:C15709 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:22072859 SUPPORT Human Clinical
"A molecular study was performed which revealed a novel homozygous UBR1 mutation."
Illustrates molecular confirmation by identifying a biallelic UBR1 variant.
Audiologic evaluation
Auditory brainstem response and audiometry characterize the bilateral sensorineural hearing loss and guide hearing habilitation.
auditory brainstem response evaluation NCIT:C184949 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"her hearing evaluation using auditory brainstem response revealed bilateral severe to profound SNHL."
Shows auditory brainstem response used to characterize the SNHL of JBS.
Prenatal ultrasonography
The characteristic aplastic nasal alae can be recognized on prenatal ultrasound, enabling prenatal diagnosis in at-risk pregnancies.
prenatal (obstetric) ultrasonography NCIT:C17230 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:10423811 SUPPORT Human Clinical
"Sonographic findings of aplastic alae nasi (beak-like nose) and dilated sigmoid colon led to the prenatal diagnosis."
Documents prenatal ultrasound establishing the diagnosis from the nasal alae finding.
📊

Prevalence

1
General population
Birth Prevalence 0.4 per 100,000 1–9 per 1,000,000 (births)
Estimated at 1 in 250,000 (4 per million; 0.4 per 100,000). Fewer than about 100-150 patients have been reported worldwide. The cited source gives the bare rate with no geographic scoping, so no region is asserted here.
Show evidence (1 reference)
PMID:34760428 SUPPORT Human Clinical
"The prevalence of JBS is estimated to be 1 in 250,000, with no reported difference in gender while parental consanguinity is frequently observed"
Direct source for the 1-in-250,000 birth-prevalence estimate converted here.
🐁

Animal Models

1
Ubr1-null mouse exocrine pancreatic phenotype
Species
Mouse
Genotype
Ubr1(-/-)
Publication
PMID:16311597
Pathograph links
Exocrine Pancreatic Failure partially recapitulates fidelity: moderate observes: organism Ubr1(-/-) mice develop exocrine pancreatic insufficiency with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury, directionally matching the human exocrine defect.
Limitations: The murine phenotype is milder than human JBS: the abstract reports functional exocrine insufficiency and injury susceptibility but not the intrauterine-onset destructive pancreatitis seen in patient pancreas, and the mouse does not reproduce the craniofacial, dental or auditory malformations. Functional redundancy with the overlapping N-end rule ligase UBR2 in mice is thought to buffer the single-Ubr1 knockout.
Readouts
Exocrine pancreatic function
Direction: DECREASED
Show evidence (1 reference)
PMID:16311597 SUPPORT Model Organism
"we found that Ubr1(-/-) mice, whose previously reported phenotypes include reduced weight and behavioral abnormalities, had an exocrine pancreatic insufficiency, with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury."
Reports the reduced exocrine pancreatic function measured in the null mouse.
Show evidence (1 reference)
PMID:16311597 SUPPORT Model Organism
"we found that Ubr1(-/-) mice, whose previously reported phenotypes include reduced weight and behavioral abnormalities, had an exocrine pancreatic insufficiency, with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury."
Establishes the null mouse as informative for the exocrine pancreatic insufficiency node, while its milder phenotype grounds the mismatch below.
{ }

Source YAML

click to show 
name: Johanson-Blizzard syndrome
creation_date: "2026-09-04T00:00:00Z"
category: Mendelian
description: >-
  Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive multisystem
  disorder caused by biallelic loss-of-function variants in UBR1, which encodes
  one of the E3 ubiquitin ligases of the N-end rule (Arg/N-degron) branch of the
  ubiquitin-proteasome system. Its clinical hallmark is congenital exocrine
  pancreatic insufficiency together with hypoplasia or aplasia of the nasal alae,
  aplasia cutis of the scalp, oligodontia of the permanent teeth, sensorineural
  hearing loss, short stature and variable intellectual disability; hypothyroidism,
  other endocrinopathies including later-onset diabetes, and cardiac,
  genitourinary and anorectal malformations occur in a subset. In affected
  individuals the pancreas does not express UBR1 and shows an intrauterine-onset
  destructive pancreatitis with acinar loss and fibro-fatty replacement, so
  exocrine failure is largely established by birth. The proximate molecular defect
  is failure of regulated N-degron proteolysis, but the specific disease-relevant
  substrate(s) stabilized in human pancreas and in the developing craniofacial,
  cochlear and endocrine tissues remain undefined; missense alleles that retain
  partial catalytic activity are associated with milder disease.
disease_term:
  preferred_term: Johanson-Blizzard syndrome
  term:
    id: MONDO:0009479
    label: Johanson-Blizzard syndrome
parents:
- hereditary disease
synonyms:
- JBS
- UBR1-related exocrine pancreatic insufficiency with multiple malformations
- nasal alar hypoplasia, hypothyroidism, pancreatic achylia and congenital deafness
- trypsinogen deficiency disease
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    JBS is caused by biallelic (homozygous or compound heterozygous)
    loss-of-function variants in UBR1; parental consanguinity is frequently
    observed given the rarity of the allele.
  evidence:
  - reference: PMID:16311597
    reference_title: >-
      Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation.
    explanation: >-
      The gene-discovery paper states the autosomal recessive inheritance and the
      defining clinical triad.
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The prevalence of JBS is estimated to be 1 in 250,000, with no reported difference in gender while parental consanguinity is frequently observed
    explanation: >-
      Records the frequent parental consanguinity consistent with recessive
      inheritance of a rare allele.
prevalence:
- population: General population
  measure_type: BIRTH_PREVALENCE
  prevalence_class: BAND_1_9_PER_1000000
  rate_per_100000: 0.4
  notes: >-
    Estimated at 1 in 250,000 (4 per million; 0.4 per 100,000). Fewer than about
    100-150 patients have been reported worldwide. The cited source gives the
    bare rate with no geographic scoping, so no region is asserted here.
  evidence:
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The prevalence of JBS is estimated to be 1 in 250,000, with no reported difference in gender while parental consanguinity is frequently observed
    explanation: >-
      Direct source for the 1-in-250,000 birth-prevalence estimate converted here.
pathophysiology:
- name: Biallelic UBR1 Loss of Function
  role: trigger
  biological_scale: MOLECULAR
  description: >-
    Homozygous or compound heterozygous variants in UBR1 abolish or strongly
    reduce the activity of the encoded E3 ubiquitin ligase. Most JBS alleles are
    nonsense, frameshift or splice-site changes that abolish activity; missense
    changes in the conserved UBR-box and RING-H2 domains reduce it. In patient
    pancreas UBR1 protein is not expressed.
  genes:
  - preferred_term: UBR1
    term:
      id: hgnc:16808
      label: UBR1
  genetic_context:
    gene:
      preferred_term: UBR1
      term:
        id: hgnc:16808
        label: UBR1
    allele_type: nonsense, frameshift, splice-site, missense, or whole-exon deletion/duplication
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
  molecular_functions:
  - preferred_term: UBR1 ubiquitin-protein ligase activity
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0004842
      label: ubiquitin-protein transferase activity
  evidence:
  - reference: PMID:16311597
    reference_title: >-
      Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We mapped the disease-associated locus to chromosome 15q14-21.1 and identified mutations, mostly truncating ones, in the gene UBR1 in 12 unrelated families with Johanson-Blizzard syndrome.
    explanation: >-
      Establishes UBR1 as the disease gene and the predominance of truncating,
      activity-abolishing mutations.
  - reference: PMID:21931868
    reference_title: >-
      Ubiquitin ligases of the N-end rule pathway: assessment of mutations in UBR1 that cause the Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Most JBS-causing alterations of UBR1 are nonsense, frameshift or splice-site mutations that abolish UBR1 activity.
    explanation: >-
      Classifies the mutational spectrum as loss-of-function that abolishes ligase
      activity.
  downstream:
  - target: Impaired N-end Rule Proteolysis
    description: >-
      Loss of UBR1 catalytic function directly removes the substrate-recognition
      and ubiquitin-transfer step it performs in the N-end rule pathway.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:16311597
      reference_title: >-
        Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        UBR1 encodes one of at least four functionally overlapping E3 ubiquitin ligases of the N-end rule pathway, a conserved proteolytic system whose substrates include proteins with destabilizing N-terminal residues.
      explanation: >-
        Places UBR1 as a recognin of the N-end rule pathway whose loss impairs that
        proteolytic step.
- name: Impaired N-end Rule Proteolysis
  biological_scale: MOLECULAR
  description: >-
    UBR1 recognizes destabilizing N-terminal residues (N-degrons) and targets
    those substrates for ubiquitin-dependent degradation. Its loss impairs
    regulated N-degron proteolysis, with metabolic stabilization of specific N-end
    rule substrates in affected tissues. The identity of the disease-relevant
    substrate(s) in human pancreas and developing organs is not established.
  biological_processes:
  - preferred_term: N-end rule pathway proteolysis
    modifier: DECREASED
    term:
      id: GO:0071596
      label: ubiquitin-dependent protein catabolic process via the N-end rule pathway
  evidence:
  - reference: PMID:21931868
    reference_title: >-
      Ubiquitin ligases of the N-end rule pathway: assessment of mutations in UBR1 that cause the Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      One class of degradation signals (degrons) recognized by UBR1 are destabilizing N-terminal residues of protein substrates.
    explanation: >-
      Defines the N-degron substrates whose regulated degradation fails when UBR1
      is lost.
  downstream:
  - target: Intrauterine Destructive Pancreatitis
    description: >-
      In the exocrine pancreas, loss of N-end rule proteolysis is followed by a
      destructive prenatal pancreatitis; the intervening substrate is unknown, so
      the edge is annotated with unknown intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:16311597
      reference_title: >-
        Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Our findings indicate that deficiency of UBR1 perturbs the pancreas' acinar cells and other organs, presumably owing to metabolic stabilization of specific substrates of the N-end rule pathway.
      explanation: >-
        Attributes the acinar-cell injury to substrate stabilization downstream of
        UBR1 loss, while the hedged "presumably" marks the intermediate as unknown.
  - target: Multisystem Developmental and Organ Dysfunction
    description: >-
      Beyond the pancreas, UBR1 loss perturbs other organs, converging on the
      craniofacial, ectodermal, cochlear and endocrine malformations of JBS. The
      tissue-specific developmental mechanism has not been demonstrated, so the
      edge carries unknown intermediates.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:16311597
      reference_title: >-
        Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Our findings indicate that deficiency of UBR1 perturbs the pancreas' acinar cells and other organs, presumably owing to metabolic stabilization of specific substrates of the N-end rule pathway.
      explanation: >-
        States that UBR1 deficiency perturbs organs beyond the pancreas, the
        support for a multisystem developmental branch.
- name: Intrauterine Destructive Pancreatitis
  biological_scale: TISSUE
  description: >-
    The pancreas of affected individuals does not express UBR1 and shows an
    intrauterine-onset destructive pancreatitis, with acinar cell injury and
    progressive fibro-fatty replacement of the exocrine parenchyma.
  cell_types:
  - preferred_term: pancreatic acinar cell
    term:
      id: CL:0002064
      label: pancreatic acinar cell
  biological_processes:
  - preferred_term: dysregulated acinar cell apoptosis
    modifier: DYSREGULATED
    term:
      id: GO:0006915
      label: apoptotic process
  evidence:
  - reference: PMID:16311597
    reference_title: >-
      Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pancreas of individuals with Johanson-Blizzard syndrome did not express UBR1 and had intrauterine-onset destructive pancreatitis.
    explanation: >-
      Direct histopathological description of absent UBR1 and destructive prenatal
      pancreatitis in patient pancreas. The cited abstracts characterize the
      lesion as destructive but do not report an apoptosis direction, so the
      acinar apoptosis node is annotated DYSREGULATED rather than INCREASED.
  downstream:
  - target: Exocrine Pancreatic Failure
    description: >-
      Destruction and fatty replacement of acinar tissue removes the
      zymogen-secreting capacity of the gland, producing exocrine insufficiency
      that is largely established by birth.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:16311597
      reference_title: >-
        Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation.
      explanation: >-
        States that congenital exocrine pancreatic insufficiency is the pancreatic
        endpoint of the disease.
- name: Exocrine Pancreatic Failure
  biological_scale: ORGANISM
  description: >-
    Near-total loss of exocrine (enzyme-secreting) pancreatic function is the
    defining functional consequence, presenting in the neonatal or early infantile
    period with steatorrhea and poor growth. (Named "Exocrine Pancreatic Failure"
    to keep this mechanism node distinct from the "Exocrine pancreatic
    insufficiency" clinical phenotype in the flat pathograph namespace.)
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Lists exocrine pancreatic insufficiency as the leading feature of JBS.
  downstream:
  - target: Malabsorption and Failure to Thrive
    description: >-
      Absent pancreatic enzyme output causes maldigestion and malabsorption of
      fat, protein and fat-soluble vitamins, driving failure to thrive.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Names both exocrine pancreatic insufficiency and failure to thrive among
        the disease features linked here.
- name: Malabsorption and Failure to Thrive
  biological_scale: ORGANISM
  description: >-
    Fat and fat-soluble vitamin malabsorption secondary to exocrine pancreatic
    insufficiency, the nutritional route to poor growth in infancy.
  evidence:
  - reference: PMID:10423811
    reference_title: >-
      Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction.
    explanation: >-
      Names pancreatic insufficiency alongside postnatal growth restriction, the
      nutritional consequence modeled at this node.
  downstream:
  - target: Failure to thrive
    description: >-
      Malabsorption presents clinically as failure to thrive, often the presenting
      complaint in infancy.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Lists failure to thrive among the clinical features.
  - target: Short stature
    description: >-
      Chronic malabsorption contributes to postnatal growth restriction and short
      stature, through intermediate nutritional deficits.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Chronic energy and protein malnutrition from fat and protein malabsorption.
    evidence:
    - reference: PMID:10423811
      reference_title: >-
        Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction.
      explanation: >-
        Records postnatal growth restriction as a feature to which malabsorption
        contributes.
- name: Multisystem Developmental and Organ Dysfunction
  biological_scale: TISSUE
  description: >-
    A convergence node for the extra-pancreatic manifestations of UBR1 loss:
    craniofacial and ectodermal maldevelopment (nasal alae, scalp, teeth),
    cochlear dysfunction, and endocrine gland involvement. Each downstream edge is
    an association rather than a demonstrated tissue-specific mechanism, so all are
    annotated with unknown intermediates.
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Enumerates the extra-pancreatic malformations and organ involvement grouped
      at this node.
  downstream:
  - target: Hypoplasia of the nasal alae
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Hypoplasia or aplasia of the nasal alae is the most constant craniofacial
      feature and can be detected prenatally.
    evidence:
    - reference: PMID:16311597
      reference_title: >-
        Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation.
      explanation: >-
        Names nasal wing (alae) aplasia among the malformations of the disease.
  - target: Aplasia cutis congenita of scalp
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Midline scalp ectodermal (aplasia cutis) defects are a recurrent feature.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Lists cutis aplasia on the scalp as a characterizing feature.
  - target: Oligodontia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Absence of permanent teeth (oligodontia) with malformed primary teeth is a
      hallmark dental anomaly.
    evidence:
    - reference: PMID:34760428
      reference_title: >-
        Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        It is characterized by developmental delay and several dysmorphic features such as microcephaly, absence of permanent teeth, hypoplasia of the alae nasi, and scalp defects.
      explanation: >-
        Lists absence of permanent teeth among the characteristic features.
  - target: Sensorineural hearing loss
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Bilateral severe-to-profound sensorineural hearing loss is one of the most
      common features; the cochlear mechanism of UBR1 loss is uncharacterized.
    evidence:
    - reference: PMID:34760428
      reference_title: >-
        Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        One of the most common symptoms in JBS patients is bilateral severe to profound sensorineural hearing loss.
      explanation: >-
        States that sensorineural hearing loss is among the commonest features.
  - target: Hypothyroidism
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Hypothyroidism is a recognized endocrine manifestation; other
      endocrinopathies (growth hormone deficiency, later-onset diabetes) occur in a
      subset.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Names hypothyroidism among the disease features.
  - target: Intellectual disability
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Developmental delay and intellectual disability are recurrent, though
      variable in severity; the neural substrate of UBR1 loss is uncharacterized.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Names developmental delay and mental retardation among the disease
        features.
  - target: Microcephaly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Microcephaly is a recurrent dysmorphic feature of the craniofacial
      developmental arm.
    evidence:
    - reference: PMID:34760428
      reference_title: >-
        Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        It is characterized by developmental delay and several dysmorphic features such as microcephaly, absence of permanent teeth, hypoplasia of the alae nasi, and scalp defects.
      explanation: >-
        Lists microcephaly among the characteristic dysmorphic features.
  - target: Anal atresia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Anorectal anomalies including imperforate anus arise as part of the
      developmental malformation spectrum.
    evidence:
    - reference: PMID:10423811
      reference_title: >-
        Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction.
      explanation: >-
        Names anorectal anomalies among the characterizing features.
  - target: Congenital heart defect
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Cardiac malformations occur in a subset of patients.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Names anomalies in the cardiac system among the disease features.
  - target: Genitourinary anomaly
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Genitourinary malformations occur in a subset of patients.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Names anomalies in the genitourinary system among the disease features.
phenotypes:
- name: Exocrine pancreatic insufficiency
  category: Gastrointestinal
  diagnostic: true
  frequency: VERY_FREQUENT
  description: >-
    Congenital, near-universal exocrine pancreatic insufficiency from
    intrauterine destruction and fatty replacement of the pancreas.
  phenotype_term:
    preferred_term: Exocrine pancreatic insufficiency
    term:
      id: HP:0001738
      label: Exocrine pancreatic insufficiency
  evidence:
  - reference: PMID:16311597
    reference_title: >-
      Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation.
    explanation: >-
      Names congenital exocrine pancreatic insufficiency as a defining feature.
- name: Hypoplasia of the nasal alae
  category: Craniofacial
  diagnostic: true
  frequency: VERY_FREQUENT
  description: >-
    Hypoplasia or aplasia of the nasal alae ("beaked" nose), the most constant
    craniofacial feature; detectable on prenatal ultrasound.
  phenotype_term:
    preferred_term: Hypoplasia of the nasal alae
    term:
      id: HP:0000430
      label: Underdeveloped nasal alae
  evidence:
  - reference: PMID:16311597
    reference_title: >-
      Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (OMIM 243800) is an autosomal recessive disorder that includes congenital exocrine pancreatic insufficiency, multiple malformations such as nasal wing aplasia, and frequent mental retardation.
    explanation: >-
      Names nasal wing (alae) aplasia as a defining malformation.
  - reference: PMID:10423811
    reference_title: >-
      Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Sonographic findings of aplastic alae nasi (beak-like nose) and dilated sigmoid colon led to the prenatal diagnosis.
    explanation: >-
      Confirms aplastic alae nasi as a prenatally detectable feature.
- name: Aplasia cutis congenita of scalp
  category: Integumentary
  description: >-
    Midline scalp aplasia cutis (ectodermal defect), a recurrent feature.
  phenotype_term:
    preferred_term: Aplasia cutis congenita of scalp
    term:
      id: HP:0007385
      label: Aplasia cutis congenita of scalp
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Names cutis aplasia on the scalp as a characterizing feature.
- name: Oligodontia
  category: Dental
  diagnostic: true
  description: >-
    Absence of permanent teeth with malformed, widely spaced primary teeth.
  phenotype_term:
    preferred_term: Oligodontia
    term:
      id: HP:0000677
      label: Oligodontia
  evidence:
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is characterized by developmental delay and several dysmorphic features such as microcephaly, absence of permanent teeth, hypoplasia of the alae nasi, and scalp defects.
    explanation: >-
      Names absence of permanent teeth among the characteristic features.
- name: Sensorineural hearing loss
  category: Auditory
  frequency: FREQUENT
  description: >-
    Bilateral severe-to-profound sensorineural hearing loss, one of the most
    common features; a frequent indication for cochlear implantation.
  phenotype_term:
    preferred_term: Sensorineural hearing loss
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One of the most common symptoms in JBS patients is bilateral severe to profound sensorineural hearing loss.
    explanation: >-
      States that bilateral severe-to-profound sensorineural hearing loss is among
      the commonest features.
- name: Hypothyroidism
  category: Endocrine
  description: >-
    Hypothyroidism is a recognized endocrine manifestation; longitudinal
    endocrine surveillance is recommended. No quotable frequency figure was
    available in the cached sources, so no frequency band is asserted.
  phenotype_term:
    preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Names hypothyroidism among the disease features.
- name: Short stature
  category: Growth
  description: >-
    Short stature/postnatal growth restriction, partly nutritional and often
    persisting despite treatment.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:10423811
    reference_title: >-
      Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction.
    explanation: >-
      Names postnatal growth restriction as a characterizing feature.
- name: Failure to thrive
  category: Growth
  description: >-
    Failure to thrive from malabsorption, often the presenting complaint in
    infancy.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Names failure to thrive among the disease features.
- name: Intellectual disability
  category: Neurologic
  description: >-
    Intellectual disability/developmental delay, variable in severity; some
    patients have normal intelligence.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Names developmental delay and mental retardation among the disease features.
- name: Microcephaly
  category: Craniofacial
  description: >-
    Microcephaly is a recurrent dysmorphic feature.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It is characterized by developmental delay and several dysmorphic features such as microcephaly, absence of permanent teeth, hypoplasia of the alae nasi, and scalp defects.
    explanation: >-
      Lists microcephaly among the dysmorphic features.
- name: Anal atresia
  category: Gastrointestinal
  description: >-
    Anorectal anomalies including imperforate anus/anal atresia occur in a subset.
  phenotype_term:
    preferred_term: Anal atresia
    term:
      id: HP:0002023
      label: Anal atresia
  evidence:
  - reference: PMID:10423811
    reference_title: >-
      Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome is a rare autosomal recessive disorder characterized by aplasia of alae nasi, pancreatic insufficiency, aplasia cutis, anorectal anomalies and postnatal growth restriction.
    explanation: >-
      Names anorectal anomalies among the characterizing features.
- name: Congenital heart defect
  category: Cardiovascular
  description: >-
    Cardiac malformations occur in a subset of patients. The cited source names
    cardiac-system anomalies generically, so the binding is the general
    heart-morphology term rather than a specific defect.
  phenotype_term:
    preferred_term: Congenital heart defect
    term:
      id: HP:0001627
      label: Abnormal heart morphology
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Names anomalies in the cardiac system among the disease features.
- name: Genitourinary anomaly
  category: Genitourinary
  description: >-
    Genitourinary malformations occur in a subset of patients. The cited source
    names genitourinary-system anomalies generically, so the binding is the
    general system-level term.
  phenotype_term:
    preferred_term: Genitourinary anomaly
    term:
      id: HP:0000119
      label: Abnormality of the genitourinary system
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Names anomalies in the genitourinary system among the disease features.
genetic:
- name: UBR1
  association: Causal biallelic variant
  gene_term:
    preferred_term: UBR1
    term:
      id: hgnc:16808
      label: UBR1
  notes: >-
    UBR1 (chromosome 15q15.2) encodes an E3 ubiquitin ligase of the N-end rule
    pathway. Biallelic loss-of-function variants cause JBS; most are truncating
    (nonsense/frameshift/splice), with missense variants in the conserved UBR-box
    and RING-H2 domains producing milder disease when residual catalytic activity
    is retained. No predominant founder allele is known.
  evidence:
  - reference: PMID:16311597
    reference_title: >-
      Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We mapped the disease-associated locus to chromosome 15q14-21.1 and identified mutations, mostly truncating ones, in the gene UBR1 in 12 unrelated families with Johanson-Blizzard syndrome.
    explanation: >-
      Original identification of UBR1 as the JBS disease gene across 12 families.
  - reference: PMID:21931868
    reference_title: >-
      Ubiquitin ligases of the N-end rule pathway: assessment of mutations in UBR1 that cause the Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      one of them (H160R) was inactive in yeast-based activity assays, the other one (Q1224E) had a detectable but weak activity, and the third one (V146L) exhibited a decreased but significant activity, in agreement with manifestations of JBS in the corresponding JBS patients.
    explanation: >-
      Functional assays establish a genotype-severity correlation with residual
      catalytic activity.
diagnosis:
- name: Molecular genetic testing of UBR1
  description: >-
    Confirmatory diagnosis rests on identifying biallelic UBR1 variants;
    sequencing detects most alleles, with MLPA reserved for exon-level
    deletions/duplications missed by sequencing.
  diagnosis_term:
    preferred_term: molecular genetic testing (UBR1 sequencing)
    term:
      id: NCIT:C15709
      label: Genetic Testing
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A molecular study was performed which revealed a novel homozygous UBR1 mutation.
    explanation: >-
      Illustrates molecular confirmation by identifying a biallelic UBR1 variant.
- name: Audiologic evaluation
  description: >-
    Auditory brainstem response and audiometry characterize the bilateral
    sensorineural hearing loss and guide hearing habilitation.
  diagnosis_term:
    preferred_term: auditory brainstem response evaluation
    term:
      id: NCIT:C184949
      label: Auditory Brainstem Response
  evidence:
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      her hearing evaluation using auditory brainstem response revealed bilateral severe to profound SNHL.
    explanation: >-
      Shows auditory brainstem response used to characterize the SNHL of JBS.
- name: Prenatal ultrasonography
  description: >-
    The characteristic aplastic nasal alae can be recognized on prenatal
    ultrasound, enabling prenatal diagnosis in at-risk pregnancies.
  diagnosis_term:
    preferred_term: prenatal (obstetric) ultrasonography
    term:
      id: NCIT:C17230
      label: Ultrasound Imaging
  evidence:
  - reference: PMID:10423811
    reference_title: >-
      Johanson-Blizzard syndrome: a prenatal ultrasonographic diagnosis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Sonographic findings of aplastic alae nasi (beak-like nose) and dilated sigmoid colon led to the prenatal diagnosis.
    explanation: >-
      Documents prenatal ultrasound establishing the diagnosis from the nasal
      alae finding.
environmental: []
treatments:
- name: Pancreatic enzyme replacement and fat-soluble vitamin supplementation
  description: >-
    Oral pancreatic enzyme replacement therapy (pancrelipase) with fat-soluble
    vitamin (A, D, E, K) supplementation is the mainstay treatment for the
    exocrine pancreatic component, given lifelong.
  therapeutic_modality: PROTEIN_REPLACEMENT
  treatment_term:
    preferred_term: pancreatic enzyme replacement therapy
    term:
      id: NCIT:C16221
      label: Protein Replacement Therapy
    therapeutic_agent:
    - preferred_term: pancrelipase
      term:
        id: NCIT:C29345
        label: Pancrelipase
  target_phenotypes:
  - preferred_term: Exocrine pancreatic insufficiency
    term:
      id: HP:0001738
      label: Exocrine pancreatic insufficiency
  target_mechanisms:
  - target: Exocrine Pancreatic Failure
    treatment_effect: BYPASSES
    description: >-
      Supplies the digestive enzymes the destroyed acinar tissue can no longer
      secrete; it does not correct the underlying UBR1/N-end rule defect.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Establishes the exocrine pancreatic insufficiency that enzyme replacement
        is directed at.
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Supports the exocrine pancreatic insufficiency indication for this therapy.
- name: Levothyroxine replacement
  description: >-
    Thyroid hormone (levothyroxine) replacement for hypothyroidism identified on
    endocrine surveillance.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: levothyroxine
      term:
        id: NCIT:C62080
        label: Levothyroxine
  target_phenotypes:
  - preferred_term: Hypothyroidism
    term:
      id: HP:0000821
      label: Hypothyroidism
  target_mechanisms:
  - target: Hypothyroidism
    treatment_effect: BYPASSES
    description: >-
      Replaces deficient thyroid hormone; supportive, not disease-modifying.
    evidence:
    - reference: PMID:22072859
      reference_title: Johanson-Blizzard syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
      explanation: >-
        Establishes the hypothyroidism this replacement therapy addresses.
  evidence:
  - reference: PMID:22072859
    reference_title: Johanson-Blizzard syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Johanson-Blizzard syndrome (JBS) is a rare autosomal recessive disease characterized by exocrine pancreatic insufficiency, hypoplastic or aplastic nasal alae, cutis aplasia on the scalp, and other features including developmental delay, failure to thrive, hearing loss, mental retardation, hypothyroidism, dental abnormalities, and anomalies in cardiac and genitourinary systems.
    explanation: >-
      Supports hypothyroidism as a treatable feature of JBS.
- name: Cochlear device implantation
  description: >-
    Cochlear implantation for bilateral severe-to-profound sensorineural hearing
    loss, followed by aural rehabilitation. It improves hearing thresholds and
    access to sound, though spoken-language development is not always achieved.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: cochlear device implantation
    term:
      id: NCIT:C15329
      label: Surgical Procedure
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: cochlear implant
        term:
          id: NCIT:C157820
          label: Cochlear Implant
  target_phenotypes:
  - preferred_term: Sensorineural hearing loss
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  target_mechanisms:
  - target: Sensorineural hearing loss
    treatment_effect: BYPASSES
    description: >-
      A cochlear implant bypasses the failed cochlear sensory transduction by
      directly stimulating the auditory nerve; it does not restore native cochlear
      function.
    evidence:
    - reference: PMID:34760428
      reference_title: >-
        Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        After receiving the cochlear implant, our patient showed substantial improvement in her hearing threshold and communication abilities when compared to the preoperative condition.
      explanation: >-
        Reports the audiological benefit of implantation for the JBS hearing loss.
  evidence:
  - reference: PMID:34760428
    reference_title: >-
      Performance of Children With Johanson-Blizzard Syndrome After Cochlear Implantation.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      although cochlear implantation is considered a good approach for the management of JBS patients, the development of spoken language is not always achieved
    explanation: >-
      Documents both the value and the limits of cochlear implantation in JBS.
animal_models:
- name: Ubr1-null mouse exocrine pancreatic phenotype
  species: Mouse
  genotype: Ubr1(-/-)
  publication: PMID:16311597
  modeled_mechanisms:
  - target: Exocrine Pancreatic Failure
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: ORGANISM
    description: >-
      Ubr1(-/-) mice develop exocrine pancreatic insufficiency with impaired
      stimulus-secretion coupling and increased susceptibility to pancreatic
      injury, directionally matching the human exocrine defect.
    limitations: >-
      The murine phenotype is milder than human JBS: the abstract reports
      functional exocrine insufficiency and injury susceptibility but not the
      intrauterine-onset destructive pancreatitis seen in patient pancreas, and the
      mouse does not reproduce the craniofacial, dental or auditory malformations.
      Functional redundancy with the overlapping N-end rule ligase UBR2 in mice is
      thought to buffer the single-Ubr1 knockout.
    readouts:
    - name: Exocrine pancreatic function
      target: Exocrine Pancreatic Failure
      direction: DECREASED
      evidence:
      - reference: PMID:16311597
        reference_title: >-
          Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          we found that Ubr1(-/-) mice, whose previously reported phenotypes include reduced weight and behavioral abnormalities, had an exocrine pancreatic insufficiency, with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury.
        explanation: >-
          Reports the reduced exocrine pancreatic function measured in the null
          mouse.
    evidence:
    - reference: PMID:16311597
      reference_title: >-
        Deficiency of UBR1, a ubiquitin ligase of the N-end rule pathway, causes pancreatic dysfunction, malformations and mental retardation (Johanson-Blizzard syndrome).
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        we found that Ubr1(-/-) mice, whose previously reported phenotypes include reduced weight and behavioral abnormalities, had an exocrine pancreatic insufficiency, with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury.
      explanation: >-
        Establishes the null mouse as informative for the exocrine pancreatic
        insufficiency node, while its milder phenotype grounds the mismatch below.
discussions:
- discussion_id: jbs_mouse_pancreatic_fidelity
  kind: HUMAN_MODEL_MISMATCH
  attaches_to:
  - pathophysiology#Intrauterine Destructive Pancreatitis
  prompt: >-
    Does the Ubr1(-/-) mouse capture the intrauterine destructive pancreatitis
    that produces exocrine failure in human JBS, or only a milder functional
    insufficiency that leaves the destructive prenatal mechanism unmodeled?
  rationale: >-
    In human JBS the pancreas does not express UBR1 and shows an
    intrauterine-onset destructive pancreatitis with acinar loss and fibro-fatty
    replacement. The Ubr1(-/-) mouse reproduces functional exocrine pancreatic
    insufficiency with impaired stimulus-secretion coupling and increased injury
    susceptibility, but the reported phenotype is milder and does not recapitulate
    the destructive prenatal pancreatitis, nor the craniofacial, dental and
    auditory malformations. Functional redundancy among the overlapping N-end rule
    ligases (notably UBR2) in the mouse is a candidate explanation. The mismatch
    matters because the destructive-pancreatitis mechanism, not simple secretory
    failure, is what makes JBS exocrine insufficiency congenital and near-total, so
    a model that omits it cannot test interventions aimed at the destructive
    process itself.
  proposed_experiments:
  - experiment_id: jbs_ubr1_ubr2_pancreas
    name: Prenatal pancreatic histology in Ubr1/Ubr2 compound-deficient mice
    description: >-
      Compare prenatal and early-postnatal pancreatic histology (acinar apoptosis,
      inflammation, fibro-fatty replacement) across Ubr1(-/-) and Ubr1/Ubr2
      compound-deficient genotypes against controls, to test whether removing the
      redundant N-end rule ligase unmasks the destructive prenatal pancreatitis
      seen in human JBS.
    would_support:
    - pathophysiology#Intrauterine Destructive Pancreatitis
    supporting_outcome:
    - >-
      Compound-deficient animals develop destructive prenatal pancreatitis with
      acinar apoptosis and fibro-fatty replacement resembling human JBS, absent in
      single Ubr1(-/-) animals.
    would_refute:
    - pathophysiology#Intrauterine Destructive Pancreatitis
    refuting_outcome:
    - >-
      No genotype reproduces the destructive prenatal pancreatitis, indicating the
      human mechanism depends on factors not captured by murine N-end rule ligase
      loss.
clinical_trials: []
datasets: []
notes: >-
  Curated de novo from a Claude Code deep-research report (see
  research/Johanson-Blizzard_Syndrome-deep-research-claude_code.md) with every
  ontology term and evidence snippet independently verified. Two CURIEs suggested
  by the report were rejected during term verification: HP:0001060 (proposed for
  aplasia cutis; it is actually "Axillary pterygium" - the scalp defect is bound
  here to HP:0007385) and CHEBI:6710 (proposed for levothyroxine; it is actually
  meclofenamic acid - levothyroxine is bound here to NCIT:C62080). The specific
  N-end rule substrate(s) stabilized in human pancreas and developing organs
  remain undefined, so the extra-pancreatic developmental edges are annotated
  INDIRECT_UNKNOWN_INTERMEDIATES.
📚

References & Deep Research

Deep Research

1

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

Evaluations and curation notes (3)

Record notes

Curated de novo from a Claude Code deep-research report (see research/Johanson-Blizzard_Syndrome-deep-research-claude_code.md) with every ontology term and evidence snippet independently verified. Two CURIEs suggested by the report were rejected during term verification: HP:0001060 (proposed for aplasia cutis; it is actually "Axillary pterygium" - the scalp defect is bound here to HP:0007385) and CHEBI:6710 (proposed for levothyroxine; it is actually meclofenamic acid - levothyroxine is bound here to NCIT:C62080). The specific N-end rule substrate(s) stabilized in human pancreas and developing organs remain undefined, so the extra-pancreatic developmental edges are annotated INDIRECT_UNKNOWN_INTERMEDIATES.

Review round 1: ai4c-reviewer findings · 2026-09-04T15:03:14Z · View source

Addressed the ai4c-reviewer CHANGES_REQUESTED review on PR #10938 in a single bundled push. Per finding: 1. Apoptosis direction. The "Intrauterine Destructive Pancreatitis" node's acinar-apoptosis process was modifier INCREASED with no supporting snippet; the cited abstracts describe the lesion only as "destructive pancreatitis" and give no apoptosis direction (the "impaired apoptosis / induced necrosis" reading lives in the DR report, not a citable paper). Re-annotated to modifier DYSREGULATED (a real ModifierEnum value and the honest reading), renamed the process preferred_term accordingly, and added an explanation line stating the abstracts do not report a direction. Did not add necrosis/inflammation GO terms: no exact-quote evidence for them exists in the cached references. 2. Added a diagnosis: section with three entries, each with an exact-quote snippet already in the cache: molecular UBR1 testing (NCIT:C15709, PMID:22072859), audiologic evaluation via auditory brainstem response (NCIT:C184949, PMID:34760428), and prenatal ultrasonography (NCIT:C17230, PMID:10423811). Pancreatic exocrine function testing was intentionally omitted - no quotable fecal-elastase/function-test snippet was available and inventing one would violate evidence discipline. 3. Added cardiac (HP:0001627 Abnormal heart morphology) and genitourinary (HP:0000119 Abnormality of the genitourinary system) phenotypes, both citing the generic "...anomalies in cardiac and genitourinary systems" clause of PMID:22072859. Bound the general system-level terms rather than specific defects (ASD/hypospadias) because the snippet is generic - binding a narrower term would over-claim beyond the source. 4. Connected the three orphaned phenotypes (Intellectual disability, Microcephaly, Anal atresia) plus the two new cardiac/GU phenotypes with INDIRECT_UNKNOWN_INTERMEDIATES downstream edges from the "Multisystem Developmental and Organ Dysfunction" hub, each with supporting evidence. Fixed the namespace hazard by renaming the pathophysiology node "Exocrine Pancreatic Insufficiency" to "Exocrine Pancreatic Failure" (distinct from the "Exocrine pancreatic insufficiency" phenotype) and updating all three bare-name references to it (upstream pancreatitis edge, PERT treatment target_mechanism, Ubr1-null mouse modeled_mechanism + readout). 5. Dropped the unsupported Hypothyroidism frequency (OCCASIONAL had no snippet and contradicted the "commonest endocrine manifestation" description); no quotable frequency figure exists, so no band is asserted. Also softened the "commonest endocrine manifestation" superlative on both the phenotype and the hub edge to "a recognized endocrine manifestation". Suggestions taken: prevalence population changed from "Europe" (unsupported by the geography-free PMID:34760428 snippet) to "General population" with a note; zygosity: HOMOZYGOUS removed from genetic_context because both homozygous and compound-heterozygous cases occur and the slot is single-valued (biallelic LOF remains captured in the node description and functional_impact_category). Suggestions deferred with reason: Oligodontia frequency band (research says 80-99% but no quotable source); top-level references block citing the Clinical Utility Gene Card PMID:23652379 (its cache content is "unavailable" - title only, nothing quotable); quantified mutational spectrum in the genetic section (its source, PMID:23652379, has no quotable cached body); and additional treatments (growth-hormone therapy, protein-hydrolysate diet, anoplasty) - no exact-quote support in the cached references. Validation: validate, validate-terms, validate-disorders (batched) all passed; 54/54 evidence snippets verified; check-duplicate-keys, check-entity-refs, check-causal-targets (no new broken targets), check-qualifier-terms, and check-enum-values all passed. History record validated.

Create: Johanson-Blizzard syndrome · 2026-09-04T14:28:52Z · View source

De novo creation of the Johanson-Blizzard syndrome (JBS, MONDO:0009479) Disease entry, closing claim issue #10934 and deleting the corresponding curation stub. Curation was research-first: a Claude Code deep-research report was generated (research/Johanson-Blizzard_Syndrome-deep-research-claude_code.md) and used only as a set of leads. Every ontology CURIE and every evidence snippet was independently verified before use. Pathograph (8 pathophysiology nodes): biallelic UBR1 loss of function (an E3 ubiquitin ligase of the N-end rule / N-degron pathway) -> impaired N-end rule proteolysis -> intrauterine destructive pancreatitis -> exocrine pancreatic insufficiency -> malabsorption and failure to thrive; plus a multisystem developmental/organ-dysfunction hub whose extra-pancreatic edges (nasal alae hypoplasia, scalp aplasia cutis, oligodontia, sensorineural hearing loss, hypothyroidism) are annotated INDIRECT_UNKNOWN_INTERMEDIATES because the disease-relevant N-end rule substrate is undefined. All causal downstream targets use bare names. 12 phenotypes with HP terms; genetic section (UBR1, hgnc:16808, autosomal recessive, functional_impact_category LOSS_OF_FUNCTION with a genetic_context block on the trigger node); prevalence (1 in 250,000, BIRTH_PREVALENCE); 3 treatments (pancreatic enzyme replacement therapy, levothyroxine, cochlear device implantation using the device-vs-action qualifier pattern); a Ubr1-null mouse animal model linked via modeled_mechanisms (PARTIALLY_RECAPITULATES); and a HUMAN_MODEL_MISMATCH discussion capturing that the Ubr1(-/-) mouse does not reproduce the destructive prenatal pancreatitis or the malformation spectrum. Two report-suggested CURIEs were rejected during term verification and are recorded in the entry notes: HP:0001060 (proposed for aplasia cutis; it is actually "Axillary pterygium" - scalp defect bound instead to HP:0007385) and CHEBI:6710 (proposed for levothyroxine; it is actually meclofenamic acid - levothyroxine bound instead to NCIT:C62080). Validation: schema validate passed; validate-terms passed; 44/44 evidence snippets verified against cached references; check-duplicate-keys, check-entity-refs, check-causal-targets (no new broken targets), check-qualifier-terms-online (2/2 device qualifier labels match), and check-enum-values all passed; batched validate-disorders passed. Key foundational reference: Zenker et al. 2005 (PMID:16311597, UBR1 discovery and Ubr1-null mouse).

Claude Code ▸
Johanson-Blizzard Syndrome (JBS): Comprehensive Research Report
claude-haiku-4-5-20251001, claude-sonnet-5 25 citations 2026-09-04T14:09:34.869922

Johanson-Blizzard Syndrome (JBS): Comprehensive Research Report

1. Disease Information

Overview. Johanson-Blizzard syndrome (JBS) is a rare, multisystem autosomal recessive disorder first described in 1971 by Johanson and Blizzard in three unrelated girls with "congenital aplasia of the alae nasi, deafness, hypothyroidism, dwarfism, absent permanent teeth, and malabsorption" (NORD; PubMed). Overlapping cases had been reported earlier (Morris and Fisher 1967; Townes 1969) as "trypsinogen deficiency disease." The syndrome's molecular basis — biallelic loss-of-function mutations in UBR1, encoding an E3 ubiquitin ligase of the N-end rule pathway — was established in 2005 by Zenker et al. (PMID:16311597, Nature Genetics).

Key identifiers: - OMIM: #243800 (phenotype); 605981 (UBR1 gene) — OMIM entry - Orphanet: ORPHA:2315 — Orphanet - MONDO: MONDO:0009479 - MeSH: C535880 - UMLS CUI: C0175692 - Disease Ontology: DOID:14694 - ICD-10: Q87.8 (other specified congenital malformation syndromes, not elsewhere classified) — no dedicated code; often mapped generically - Gene:* UBR1 (HGNC:16808; NCBI Gene 197131; chr15q15.2, hg38 chr15:42,942,897–43,106,113)

Synonyms: JBS; UBR1-related exocrine pancreatic insufficiency with multiple malformations; "trypsinogen deficiency disease" (historical/overlapping earlier name).

Evidence base: Predominantly individual case reports and small case series aggregated into disease-level reviews (fewer than 100–150 patients reported worldwide as of the most recent literature reviews), plus one large genotype-phenotype correlation study (Sukalo et al.) and structured aggregators (OMIM, Orphanet, NORD, GARD).

2. Etiology

Primary cause — genetic. JBS is caused by homozygous or compound heterozygous loss-of-function variants in UBR1 (chr15q15.2), which encodes one of at least four functionally overlapping E3 ubiquitin ligases of the N-end rule (Arg/N-degron) pathway, a conserved proteolytic system that targets substrates bearing destabilizing N-terminal residues for ubiquitin-mediated degradation (PMID:16311597).

Mutational spectrum. As of the most recent comprehensive surveys, 59 distinct UBR1 mutations have been reported: 15 nonsense, 14 splice-site, 9 small frameshift-causing deletions/duplications/insertions, 3 small in-frame deletions, and 18 missense variants, with some clustering of missense variants in the highly conserved UBR box domain (EJHG Clinical Utility Gene Card, PMID:23652379). Whole-exon deletions/duplications detectable only by MLPA have also been described, expanding the mutational spectrum (PMC5702574). Most mutations are private/family-specific; no predominant founder allele has been identified in any population to date.

Genetic risk factors: Biallelic (homozygous or compound heterozygous) UBR1 variants are both necessary and sufficient; there is no known oligogenic or digenic contribution. Consanguinity is a recognized risk factor given the autosomal recessive inheritance and rarity of the allele (noted in case reports from consanguineous Middle Eastern populations, e.g., Bahrain and Saudi Arabia cases — PMC11007587).

Environmental/other factors: No environmental, infectious, or lifestyle causal or risk factors are established; JBS is a purely monogenic disorder.

Protective factors: None specifically documented; genotype-phenotype correlation data (below) suggest residual UBR1 catalytic activity is a modifier of severity rather than a distinct "protective" allele.

Gene-environment interaction: Not applicable/not reported — this is a fully penetrant monogenic disease without described environmental modulation of expressivity.

3. Phenotypes

The clinical hallmark triad is exocrine pancreatic insufficiency (EPI), hypoplasia/aplasia of the nasal alae, and oligodontia/dental anomalies of permanent teeth. Below, phenotypes are grouped and annotated with suggested HP terms and approximate frequency where reported.

Craniofacial / ectodermal

Phenotype Frequency/notes Suggested HP term
Hypoplasia/aplasia of nasal alae ("beaked" small nose) Near-universal; most constant feature HP:0000430 (Hypoplastic alae nasi)
Microcephaly Common HP:0000252
Scalp defects (aplasia cutis congenita, midline ectodermal defect, sparse/coarse hair) Common HP:0001060 (Cutis aplasia); HP:0002212 (Sparse scalp hair)
Maxillary hypoplasia, small pointed chin Reported HP:0000327; HP:0000324
Cleft lip/palate Occasional HP:0000175
Lacrimal duct anomalies (aplasia of lacrimal puncta, nasolacrimal fistula) Occasional HP:0000579

Dental

Phenotype Frequency HP term
Oligodontia/absence of permanent teeth Majority of cases (80–99%) HP:0000677
Malformed, cone-shaped, widely spaced primary teeth Common HP:0006486 (microdontia)

Auditory/neurologic

Phenotype Frequency HP term
Sensorineural hearing loss (bilateral, severe-to-profound) ~75% (search summary); "one of the most common symptoms" HP:0000407
Intellectual disability / developmental delay ~60% (variable — mild to severe; some patients have normal intelligence) HP:0001249
Hypotonia Reported in infancy HP:0001252

Growth

Phenotype Frequency HP term
Short stature/dwarfism Majority (80–99%) HP:0004322
Intrauterine growth restriction / low birth weight Common HP:0001511 / HP:0001518
Failure to thrive Common in infancy, secondary to malabsorption HP:0001508

Gastrointestinal/pancreatic

Phenotype Frequency HP term
Exocrine pancreatic insufficiency Near-universal (only one reported exception — Corona-Rivera et al., cited in PMC11007587) HP:0001738
Steatorrhea / malabsorption Consequence of EPI HP:0002570 (loose stools)
Imperforate anus / anal stenosis Reported HP:0002023

Endocrine

Phenotype Frequency HP term
Hypothyroidism ~40% (NORD) HP:0000821
Growth hormone deficiency / hypopituitarism Reported, screening recommended HP:0000824
Diabetes mellitus (juvenile/adolescent onset) "Presumably high risk" during adolescence/adulthood HP:0000819

Genitourinary / cardiac / other

Phenotype Frequency HP term
Genitourinary anomalies (hypospadias, micropenis, urethrovaginal fistula, hydronephrosis) Reported HP:0000047 / HP:0000054
Congenital heart defects (ASD, VSD, cardiomyopathy) Reported HP:0001631 / HP:0001629
Situs inversus Occasionally reported HP:0003363

Quality of life impact: Chronic malabsorption/malnutrition, profound hearing loss, and variable intellectual disability substantially affect development, education, and communication. Cochlear-implanted children show measurable auditory gains but often limited spoken-language outcomes even after years of device use (PMC8571962). No disease-specific QOL instrument was identified in the literature; management is multidisciplinary (gastroenterology, endocrinology, audiology, genetics, plastic surgery, speech therapy).

Onset/course: Congenital/neonatal for the hallmark triad (EPI often presents in the newborn/young infant with failure to thrive and oily stools); endocrinopathies (hypothyroidism, GH deficiency, diabetes) may manifest later in childhood/adolescence, warranting longitudinal screening.

4. Genetic/Molecular Information

Causal gene: UBR1 (OMIM *605981), 47 exons, encoding the recognition (N-recognin) component of the Arg/N-end rule branch of the ubiquitin-proteasome system.

Protein domains and mutation mechanism (from structural/functional analysis in PMID:21931868/PMC3172311, "Ubiquitin Ligases of the N-End Rule Pathway: Assessment of Mutations in UBR1 That Cause the Johanson-Blizzard Syndrome"): - UBR box (N-terminal, ~70-residue zinc-coordinating domain): the type-1 substrate-binding site that recognizes unmodified basic (Arg, Lys, His) N-terminal residues. Coordinates three zinc ions. Missense mutations here (e.g., p.V122L near the substrate-binding β-strand; p.H136R disrupting Zn3 coordination) impair substrate recognition. Quote: "The type-1 binding site of Ubr1 resides in the ∼70-residue UBR domain." - RING-H2 domain (C-terminal): catalyzes ubiquitin transfer; mutations here (e.g., p.Q1102E) perturb the Zn-stabilized RING fold required for E2-ubiquitin ligase activity. - Functional assays (yeast-based substrate-instability assays) show a genotype-severity correlation: the fully catalytically dead mutant (p.H136R/legacy numbering H160R) was associated with the most severe clinical phenotype in the corresponding patient, whereas mutants retaining partial residual activity (p.V122L, p.Q1102E) correlated with milder disease. Quote: "the relative mildness of symptoms in JBS patients #1 and #3 is most likely caused by a significant residual activity of the corresponding UBR1 mutants."

Variant classification/type: The full allelic series spans nonsense (15), splice-site (14), frameshift indels (9), in-frame small deletions (3), missense (18), and whole-exon deletions/duplications identified by MLPA (PMC5702574). All are considered loss-of-function or hypomorphic; no gain-of-function or dominant-negative mechanism is described. Individual mutations are cataloged in ClinVar (e.g., RCV000004945 for c.2839+5G>A).

Allele frequency/population genetics: No UBR1-specific gnomAD carrier-frequency figure was located in the structured sources searched; the disease's estimated European birth prevalence of ~1/250,000 implies an allele frequency consistent with a rare, non-founder recessive disorder. No obvious founder alleles are known for any population to date (EJHG Clinical Utility Gene Card).

Somatic vs. germline: Exclusively germline; no somatic/mosaic JBS cases were identified.

Epigenetics/chromosomal abnormalities: None reported; JBS is a classic single-gene recessive disorder with no known epigenetic or structural-chromosomal mechanism.

5. Environmental Information

No environmental toxins, infectious agents, or lifestyle factors are implicated in causation. The disease is fully genetically determined; environmental factors are relevant only to secondary complications (e.g., nutritional status affects severity of malnutrition-related morbidity, but does not cause the syndrome).

6. Mechanism / Pathophysiology

Ordered causal chain

  1. Biallelic loss-of-function (or strongly hypomorphic) variants in UBR1 → loss of/severely reduced UBR1 E3 ubiquitin ligase activity in the Arg/N-end rule (N-degron) proteolytic pathway (demonstrated directly: patient pancreas tissue "did not express UBR1" — PMID:16311597).
  2. Loss of UBR1-mediated substrate degradation → failure to properly turn over specific N-end rule substrate proteins, with metabolic stabilization of specific substrates of the N-end rule pathway in affected tissues (inferred from the mouse knockout studies; the identity of the disease-relevant substrate(s) in human pancreas remains undefined — this is an acknowledged knowledge gap: "It is yet unknown what specific pathophysiological relationship exists between altered protein degradation and the clinical abnormalities seen in JBS" — PMC11007587).
  3. In the exocrine pancreas specifically, UBR1 deficiency leads to disrupted acinar cell development/maintenance → intrauterine-onset destructive pancreatitis, with pathology showing impaired apoptosis, induced necrosis, and prominent inflammation in the developing gland (PMID:16311597; summarized in search results above).
  4. Progressive acinar destruction results in replacement of pancreatic parenchyma by fatty/fibrous tissue (visible on abdominal CT as fatty tissue replacement) → near-total loss of exocrine (zymogen-secreting) function → congenital/early-infantile exocrine pancreatic insufficiency.
  5. EPI leads to maldigestion and malabsorption of fat, protein, and fat-soluble vitamins → steatorrhea, hypoproteinemia, fat-soluble vitamin (A/D/E/K) deficiency, and failure to thrive/short stature.
  6. In parallel (branching), UBR1 loss during embryonic midline and craniofacial development (weeks 6–8 of gestation) disrupts N-end rule-dependent developmental protein turnover in non-pancreatic tissues, leading to the constellation of malformations: nasal ala hypoplasia/aplasia, scalp/midline ectodermal defects, oligodontia, and (in some patients) genitourinary, anorectal, and cardiac malformations. This branch is largely inferred from the co-occurrence of these anomalies with pancreatic disease and from UBR1's broad tissue expression, rather than from a tissue-specific developmental mechanism that has been directly demonstrated.
  7. A separate branch involves the inner ear and endocrine organs: UBR1 deficiency is associated with sensorineural hearing loss (cochlear mechanism not molecularly characterized) and with variable pituitary/thyroid/pancreatic endocrine dysfunction (hypopituitarism, hypothyroidism, adolescent-onset diabetes mellitus), suggesting a general vulnerability of secretory/glandular epithelia to UBR1 loss, though the specific downstream mechanism in these tissues is not established.

Detail by category

  • Molecular pathway: The Arg/N-end rule (N-degron) branch of the ubiquitin-proteasome system. UBR1's UBR box recognizes unmodified basic (Arg, Lys, His) and — together with other overlapping ligases — bulky hydrophobic (Leu, Phe, Tyr, Trp, Ile) destabilizing N-terminal residues; substrate ubiquitination is completed by the RING-H2 domain. Suggested GO terms: GO:0004842 (ubiquitin-protein transferase activity), GO:0043161 (proteasome-mediated ubiquitin-dependent protein catabolic process), GO:0071596 (ubiquitin-dependent protein catabolic process via the N-end rule pathway).
  • Cellular processes: Dysregulated apoptosis and increased necrosis in pancreatic acinar cells during prenatal development; associated inflammatory infiltration. Suggested GO terms: GO:0006915 (apoptotic process), GO:0070265 (necrotic cell death), GO:0006954 (inflammatory response).
  • Protein dysfunction: Loss-of-function of the UBR1 E3 ligase (reduced/absent ubiquitin ligase activity by yeast functional assay); no misfolding/aggregation mechanism described for UBR1 itself, though downstream ER stress from accumulated unprocessed substrates has been hypothesized (not directly demonstrated) as contributing to acinar cell injury.
  • Tissue damage mechanism: Destructive, inflammatory pancreatitis-like process in utero, culminating in acinar cell loss and fibro-fatty replacement — this is the best-characterized organ-level mechanism in JBS.
  • Cell types involved: Pancreatic acinar cells (primary; suggested CL term CL:0002064 pancreatic acinar cell); cochlear sensory hair cells (hearing loss, mechanism uncharacterized); craniofacial neural-crest-derived mesenchyme (nasal ala/midline defects, inferred); pituitary/thyroid endocrine cells (hypopituitarism/hypothyroidism, mechanism uncharacterized).
  • Molecular profiling / advanced technologies: No transcriptomic, proteomic, metabolomic, single-cell, or spatial-omics datasets specific to human JBS pancreas were identified in the literature searched; mechanistic data derive from targeted mutagenesis, yeast substrate-instability assays, and the Ubr1-knockout mouse (below), not from unbiased omics profiling. This is a notable gap for future characterization.

Animal model mechanistic data: Ubr1⁻/⁻ mice show exocrine pancreatic insufficiency with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury, "presumably owing to metabolic stabilization of specific substrates of the N-end rule pathway," but the phenotype is markedly less severe than the destructive prenatal pancreatitis seen in human JBS patients (PMID:16311597) — an instructive human-model mismatch (see Section 15).

7. Anatomical Structures Affected

  • Organ level (primary): Exocrine pancreas (UBERON:0001264); nasal alae/external nose (UBERON:0009471/UBERON:0000004); scalp (UBERON:0001037); teeth (UBERON:0001091); inner ear/cochlea (UBERON:0001846).
  • Organ level (secondary/complications): Thyroid gland (hypothyroidism), pituitary gland (GH deficiency/hypopituitarism), heart (septal defects, cardiomyopathy), kidneys/urinary tract (hydronephrosis), external genitalia (hypospadias), anorectum (imperforate anus).
  • Body systems involved: Digestive, endocrine, auditory/vestibular, craniofacial/skeletal, cardiovascular, genitourinary, integumentary (scalp/hair), and — variably — central nervous system (intellectual disability).
  • Tissue/cell level: Acinar epithelium of the exocrine pancreas (primary destructive target); cochlear neuroepithelium; craniofacial mesenchyme/neural crest derivatives; dental lamina/tooth germ epithelium.
  • Subcellular level: Ubiquitin-proteasome system components — cytosolic N-end rule substrate recognition and degradation machinery (GO Cellular Component: GO:0005737 cytoplasm; ubiquitin ligase complex GO:0000151); ER stress has been hypothesized as a contributing subcellular mechanism in acinar cells but is not directly demonstrated.
  • Localization/laterality: Findings are generally bilateral and symmetric (bilateral SNHL, bilateral nasal ala involvement); situs inversus has been reported in rare cases, indicating occasional laterality defects.

8. Temporal Development

  • Onset: Congenital — the hallmark craniofacial malformations (nasal ala hypoplasia) can be detected prenatally by ultrasound (PMID:10423811, showing "aplastic alae nasi (beak-like nose) and dilated sigmoid colon"). Exocrine pancreatic insufficiency typically presents in the neonatal/early infantile period with failure to thrive and steatorrhea. Endocrine complications (hypothyroidism, GH deficiency, diabetes) tend to manifest later, in childhood through adolescence.
  • Progression: The pancreatic lesion is thought to arise as an intrauterine destructive process (not a static malformation), so exocrine failure is often maximal at birth or in early infancy rather than progressive thereafter; growth failure/short stature is a stable lifelong feature once established, contingent on nutritional management. Endocrinopathies can newly emerge over the disease course, so longitudinal screening (thyroid function, growth hormone axis, glucose tolerance, cardiac evaluation) is recommended throughout childhood and adolescence.
  • Disease course pattern: Chronic, lifelong, multi-system, with variable severity — from patients with normal intelligence and mild features to those with profound multi-organ involvement and early mortality if untreated. No remitting-relapsing pattern is described; it is a stable, non-degenerative congenital condition whose morbidity is driven mainly by nutritional and endocrine complications rather than a progressive neurodegenerative or oncologic course.
  • Critical periods: Early recognition and initiation of pancreatic enzyme replacement/nutritional support in infancy is the key intervention window to prevent malnutrition-related mortality and optimize growth.

9. Inheritance and Population

  • Inheritance pattern: Autosomal recessive (UBR1, chr15q15.2). Full penetrance reported for biallelic loss-of-function genotypes; some genotype-severity correlation exists (see Section 4) but no formal reduced-penetrance data.
  • Prevalence: Estimated at ~1/250,000 live births in Europe (Orphanet; NORD). Fewer than 150 cases have been documented in the world literature; one review states "less than 100 documented patients" globally as of its publication (PMC11007587).
  • Incidence: Not separately reported; treated as birth prevalence given the congenital/lifelong nature of the condition.
  • Consanguinity: A recognized contributing factor to case ascertainment, particularly in reports from the Middle East (Bahrain, Saudi Arabia) given the rarity of the recessive allele.
  • Founder effects: None identified to date in any population studied.
  • Sex ratio: Reported to affect males and females equally (NORD).
  • Geographic distribution: Cases reported worldwide (Europe, Middle East, South Asia, Americas) without a described endemic region; original description was in the U.S. (Baltimore).

10. Diagnostics

Clinical diagnosis rests on recognition of the characteristic triad (EPI + hypoplastic/aplastic nasal alae + oligodontia of permanent teeth) plus supportive features (scalp defects, sensorineural hearing loss, short stature).

Laboratory tests: - Stool fat globules / fecal fat quantification - Fecal tryptic (or chymotrypsin) activity — dilution <1:50 indicates pancreatic insufficiency - Serum amylase/lipase, trypsinogen levels - Fat-soluble vitamin panel (A, D, E, K) - Thyroid function tests (screening for hypothyroidism) - Glucose tolerance testing (screening for diabetes, particularly in adolescence)

Imaging: - Prenatal ultrasound: nasal ala hypoplasia/aplasia; occasionally dilated sigmoid colon - Abdominal CT/MRI: fatty replacement of pancreatic parenchyma - Brain CT/MRI: assessment for cochleovestibular anomalies - Orbital/facial CT: bony/nasal structural defects - Echocardiography: screening for congenital heart defects

Genetic testing: Direct sequencing (and, where negative, MLPA for exon-level deletions/duplications) of UBR1 confirms the molecular diagnosis. A gene panel approach for congenital EPI syndromes (including UBR1, along with SBDS for Shwachman-Diamond, CFTR for cystic fibrosis, PTF1A, RFX6, etc.) is the practical clinical strategy; whole-exome/genome sequencing is increasingly used when the phenotype is atypical.

Differential diagnosis: - Cystic fibrosis (exocrine pancreatic insufficiency without the craniofacial/dental features) - Shwachman-Diamond syndrome (EPI with bone marrow dysfunction/metaphyseal dysplasia rather than nasal/dental anomalies) - Pearson marrow-pancreas syndrome (sideroblastic anemia, pancreatic fibrosis) - Partial pancreatic agenesis - Oculodentodigital dysplasia (for isolated hypoplasia of the alae nasi) - Adams-Oliver syndrome (for aplasia cutis congenita component)

Screening: No population newborn-screening program exists for JBS specifically (it is far too rare and heterogeneous for a biochemical newborn screen); recognition relies on clinical/prenatal ultrasound findings and subsequent targeted molecular testing. Carrier and prenatal/preimplantation genetic testing are feasible once a family's UBR1 variants are known.

11. Outcome/Prognosis

  • Survival/mortality: Untreated pancreatic insufficiency and malnutrition can be fatal in infancy or early childhood; however, with early diagnosis and effective pancreatic enzyme replacement plus vitamin supplementation, survival into adulthood is not uncommon. No formal 5-/10-year survival statistics or population-based mortality registry data were located — figures derive from aggregated case-report experience rather than a cohort study.
  • Morbidity: Chronic malabsorption, growth failure/short stature persisting despite treatment, profound hearing loss with variable speech/language outcomes even after cochlear implantation, and variable intellectual disability are the dominant chronic morbidities. A case report notes growth parameters "remain below the 3rd percentile" despite adherence to nutritional treatment (PMC11007587).
  • Complications: Infections and severe malnutrition if EPI is untreated; endocrine complications (hypothyroidism, hypopituitarism, diabetes) emerging through childhood/adolescence; congenital heart defects and genitourinary anomalies requiring surgical correction.
  • Prognostic factors: Severity appears to correlate with residual UBR1 catalytic activity at the molecular level (genotype-phenotype correlation from functional assays, Section 4) and, clinically, with timeliness of diagnosis and initiation of pancreatic enzyme replacement/nutritional support.
  • Quality-of-life trajectory: With multidisciplinary care (enzyme replacement, endocrine surveillance, hearing rehabilitation, reconstructive surgery, developmental support), many patients achieve reasonable social functioning and school attendance, though developmental delay commonly persists.

12. Treatment

Treatment is entirely symptomatic and supportive; there is no disease-modifying or curative therapy targeting UBR1/N-end rule pathway dysfunction.

Pharmacotherapy: - Pancreatic enzyme replacement therapy (PERT) — e.g., pancrelipase/pancreatin (Creon), dosed per kilogram body weight, lifelong. Suggested NCIT term: NCIT:C1400 (Pancrelipase) under NCIT:C15986 (Pharmacotherapy). - Fat-soluble vitamin supplementation (A, D, E, K) and mineral/antioxidant supplementation. - Levothyroxine replacement for hypothyroidism (NCIT: Levothyroxine, CHEBI:6710). - Growth hormone therapy where GH deficiency/hypopituitarism is confirmed (not universally required — used per endocrine workup). - Insulin therapy if adolescent/adult-onset diabetes mellitus develops.

Nutritional/dietary intervention: - High-protein, easily-absorbed protein-hydrolysate formula/diet; specialized anti-regurgitation formulas in infancy. Suggested NCIT term: NCIT:C15447 (Dietary Intervention).

Surgical/interventional: - Nasal and periorbital/eyelid reconstructive surgery (NCIT:C15329, Surgical Procedure) - Anoplasty or colostomy for imperforate anus - Correction of congenital heart defects, cleft lip/palate, and genitourinary malformations - Bilateral cochlear implantation for profound sensorineural hearing loss, followed by aural rehabilitation and speech therapy — shown to substantially improve hearing thresholds and sound/speech discrimination, though spoken-language outcomes can remain limited even after years of bilateral device use (PMC8571962; PMID:28576536). NCIT: cochlear device implantation → NCIT:C15329 with device qualifier per dismech convention.

Supportive/rehabilitative care: - Hearing aids (pre-implant or for less severe loss) - Early intervention/special education programs - Dental management (bonding, prosthodontics/dentures) for oligodontia - Genetic counseling for families

Experimental therapies: No gene therapy, cell therapy, RNA-based therapy, or targeted molecular therapy specific to JBS/UBR1 was identified in the searched literature or clinical trial registries; no relevant NCT-registered interventional trials for JBS were found.

Treatment algorithm/strategy: Multidisciplinary coordinated care (gastroenterology/pancreatology, endocrinology, otolaryngology/audiology, clinical genetics, plastic/reconstructive surgery, dentistry, speech-language pathology) with lifelong surveillance for emerging endocrine and cardiac complications is the standard approach; no formal published clinical practice guideline algorithm (e.g., NCCN-style) exists given the rarity of the condition.

13. Prevention

  • Primary prevention: Not applicable in the classic sense (monogenic congenital disorder), but genetic counseling for known carrier couples, and prenatal diagnosis (once familial UBR1 variants are known, or via characteristic prenatal ultrasound findings of nasal ala aplasia) allow informed reproductive decision-making, including preimplantation genetic testing.
  • Secondary prevention: Early postnatal recognition and prompt initiation of PERT and vitamin supplementation prevents the most severe malnutrition-related morbidity/mortality.
  • Tertiary prevention: Systematic surveillance/screening protocols for hypothyroidism, hypopituitarism, diabetes, and congenital heart defects in affected infants and children, as recommended by NORD, to catch and treat complications before they become severe.
  • Screening/genetic counseling: Carrier screening is feasible in known-affected families but is not part of any standard population carrier-screening panel given extreme rarity; genetic counseling emphasizes the 25% recurrence risk for future pregnancies of carrier couples.

14. Other Species / Natural Disease

  • Taxonomy: No naturally occurring JBS-like disease has been reported in non-human species (NCBITaxon:9606, human, is the only species with the described syndrome).
  • Orthologous gene: Mouse Ubr1 (MGI:1277977), located on mouse chromosome 2, is the well-characterized ortholog used for the engineered knockout model (see Section 15) — this is an induced/engineered model, not a naturally occurring veterinary disease.
  • Comparative biology: The N-end rule pathway and UBR1 are evolutionarily conserved from yeast (Saccharomyces cerevisiae UBR1, used for functional/mutagenesis assays) to mammals, underscoring the pathway's fundamental role in protein quality control and turnover across taxa.
  • Zoonotic potential: Not applicable — this is a purely genetic, non-transmissible disorder.

15. Model Organisms

Ubr1-knockout mouse (Ubr1⁻/⁻) — the principal animal model, generated and characterized alongside the original human UBR1 discovery (PMID:16311597): - Phenotype recapitulation: Exhibits exocrine pancreatic insufficiency with impaired stimulus-secretion coupling and increased susceptibility to pancreatic injury — directionally consistent with the human disease. - Model limitations: The mouse pancreatic phenotype is "similar to but less severe than the pancreatic phenotype of JBS patients." Mice lack the destructive, inflammatory, apoptosis/necrosis-driven prenatal pancreatitis seen in humans, and do not reproduce the craniofacial (nasal ala), dental, or auditory phenotypes of human JBS. This is a clear case for a HUMAN_MODEL_MISMATCH framing in mechanistic curation: the model supports the pancreatic-insufficiency mechanism at a partial/attenuated level but does not recapitulate the destructive prenatal pancreatic pathology or the extra-pancreatic malformation spectrum. - Related model: Ubr1⁻/⁻;Ubr2⁻/⁻ double-knockout mice show impaired neurogenesis and cardiovascular development and embryonic/perinatal lethality (PNAS, "Impaired neurogenesis and cardiovascular development in mice lacking the E3 ubiquitin ligases UBR1 and UBR2 of the N-end rule pathway"), indicating redundancy between UBR1 and UBR2 in mice that likely buffers the single-Ubr1-knockout phenotype and may explain why the single knockout under-recapitulates the destructive human pancreatic and malformation phenotype.

Cellular/in vitro models: - Yeast (S. cerevisiae) Ubr1 substrate-instability assays — used to functionally characterize human missense UBR1 alleles (β-galactosidase reporter fusions with destabilizing N-terminal residues), establishing the genotype-severity correlation described in Section 4 (PMID:21931868 / PLOS ONE). This is a heterologous, non-mammalian system: it establishes relative catalytic activity of mutant alleles but cannot address human-tissue-specific consequences.

No iPSC-derived, organoid, zebrafish, or other vertebrate/invertebrate JBS models were identified in the literature searched — this represents a clear gap in modeling of the craniofacial, dental, and auditory phenotypes, all of which remain mechanistically uncharacterized beyond correlation with UBR1 loss.

Summary Table of Key Ontology Term Suggestions

Category Suggested terms
Disease MONDO:0009479; OMIM:243800; ORPHA:2315; DOID:14694
Gene HGNC:16808 (UBR1); hgnc:16808
Key phenotypes (HP) HP:0000430 (hypoplastic alae nasi), HP:0001738 (exocrine pancreatic insufficiency), HP:0000677 (oligodontia), HP:0000407 (SNHL), HP:0004322 (short stature), HP:0001060 (aplasia cutis), HP:0000821 (hypothyroidism), HP:0001249 (intellectual disability), HP:0000819 (diabetes mellitus)
GO biological process GO:0071596 (N-end rule pathway proteolysis), GO:0043161 (proteasome-mediated ubiquitin-dependent catabolism), GO:0006915 (apoptosis), GO:0070265 (necrotic cell death)
GO molecular function GO:0004842 (ubiquitin-protein transferase activity)
Cell type (CL) CL:0002064 (pancreatic acinar cell)
Anatomy (UBERON) UBERON:0001264 (pancreas), UBERON:0001037 (scalp), UBERON:0001091 (tooth), UBERON:0001846 (cochlea)
Treatment (NCIT) NCIT:C1400 (pancrelipase), NCIT:C15986 (pharmacotherapy), NCIT:C15329 (surgical procedure), NCIT:C15447 (dietary intervention)

Sources

Note on evidence gaps: Given JBS's extreme rarity, most clinical data derive from aggregated case reports/small series rather than large cohort studies, registries, or randomized trials; several sections above (omics profiling, prevention trial data, mortality statistics, GH-deficiency management protocols) reflect an absence of dedicated primary literature rather than a negative finding, and should be flagged as such in any downstream curation.