👪

Inheritance

1

Autosomal dominant with reduced penetrance HP:0000006

Heterozygous TSHZ1 loss-of-function alleles segregate dominantly, but an unaffected carrier mother transmitted the nonsense allele p.Trp241X to an affected son, so penetrance is incomplete. In 18q deletion carriers, aural atresia is reported in 26% of any 18q deletion and up to 78% of deletions covering the critical region including TSHZ1; those figures describe deletion carriers, not point-mutation penetrance.

Autosomal dominant inheritance

Show evidence (4 references)

PMID:22152683 SUPPORT Human Clinical

"As expected, this mutation showed an autosomal-dominant segregation pattern."

The frameshift allele passes from an affected mother to her affected monozygotic twin daughters, which is a single transmission.

PMID:22152683 SUPPORT Human Clinical

"It is worth noting that a sequence analysis of the phenotypically normal maternal parents did not reveal the presence of this frameshift mutation, indicating that the mutation occurred de novo in the index person of this family."

The frameshift arose de novo in the affected mother, consistent with a dominant allele.

PMID:22152683 SUPPORT Human Clinical

"The fact that the nonsense mutation in TSHZ1 in individual 5 was inherited from his phenotypically normal mother can be explained by reduced penetrance."

An unaffected obligate carrier documents incomplete penetrance.

+ 1 more reference

⚙

Pathophysiology

6

TSHZ1 Haploinsufficiency

One functional copy of TSHZ1 is lost, either through a truncating point mutation (p.Trp241X, p.Pro316ThrfsX16) or through an 18q22.3 microdeletion whose minimal overlap contains TSHZ1 as its only known gene. TSHZ1 encodes a teashirt-family zinc finger homeodomain transcription factor that, in the mouse, is expressed in the branchial arches from E9.5.

TSHZ1 hgnc:10669

Genetic context variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: LOSS_OF_FUNCTION

DNA-binding transcription factor activity GO:0003700 ⇓ LOSS OF FUNCTION

Downstream

Abnormal Middle Ear Skeletal Development Loss of Tshz1 malforms the first-arch-derived middle-ear elements in the mouse. The mouse evidence is from the homozygous null, not the heterozygous state that causes the human disease.

Failed External Acoustic Meatus Morphogenesis In humans, TSHZ1 haploinsufficiency is established as the cause of the canal atresia; the developmental steps between them are known only from mouse work.

Dysregulated PROKR2 Expression TSHZ1 binds and regulates the PROKR2 gene. This was shown in Tshz1-mutant mice; regulation in heterozygous human carriers has not been measured.

Show evidence (4 references)

PMID:22152683 SUPPORT Human Clinical

"The minimal region of deletion overlap (72.9-73.4 Mb) contained only one known gene, TSHZ1, which was recently shown to be important for murine middle-ear development."

Deletion mapping isolates TSHZ1 as the only gene in the critical interval.

PMID:22152683 SUPPORT Human Clinical

"Sequence analysis of the coding exons in TSHZ1 in a cohort of 11 individuals with isolated, nonsyndromic bilateral CAA revealed two mutations, c.723G>A (p.Trp241X) and c.946_947delinsA (p.Pro316ThrfsX16), and both mutations predicted a loss of function."

Two independent truncating alleles in isolated CAA.

PMID:22152683 SUPPORT Human Clinical

"Together, these results demonstrate that hemizygosity of TSHZ1 leads to congenital aural atresia as a result of haploinsufficiency."

States haploinsufficiency as the disease mechanism.

+ 1 more reference

Abnormal Middle Ear Skeletal Development

Tshz1 is expressed in the branchial arches from E9.5, and Tshz1-null mice have specific malformations of the malleus and the tympanic ring, both first-arch derivatives. Whether the same structures are malformed in heterozygous humans has not been shown; patient CT describes the canal rather than the ossicles or ring.

middle ear morphogenesis GO:0042474 ⚠ ABNORMAL

tympanic ring UBERON:0002218 malleus UBERON:0001689

Animal models

Tshz1 null mouse Mouse partially recapitulates Homozygous loss gives malleus and tympanic ring malformations alongside neonatal lethality, vertebral homeotic transformations and soft palate defects.

Downstream

Failed External Acoustic Meatus Morphogenesis The tympanic ring primordium is proposed to induce formation of the external acoustic meatus, so a ring defect is a candidate route to canal atresia. This link is inferred from other mouse models, not tested for Tshz1.

Show evidence (2 references)

PMID:17586487 SUPPORT Model Organism

"Tshz1 is detected from E9.5 in the somites, the spinal cord, the limb buds and the branchial arches."

Places Tshz1 in the branchial arches that build the middle ear.

PMID:17586487 SUPPORT Model Organism

"In the craniofacial region, loss of Tshz1 function leads to specific malformations of middle ear components, including the malleus and the tympanic ring."

The middle-ear skeletal defect in the knockout.

Failed External Acoustic Meatus Morphogenesis

The medial, bony part of the external auditory canal fails to form or is stenotic, ending blindly or in a fistula to a rudimentary tympanic membrane (CAA type IIA). The pinna is normally shaped and the mutation carriers have no other congenital malformations, so the lesion is confined to the canal and middle-ear cleft.

outer ear morphogenesis GO:0042473 ⚠ ABNORMAL

external acoustic meatus UBERON:0001352

Downstream

Atresia of the External Auditory Canal The failed canal is the clinical atresia.

Cholesteatoma Congenital canal abnormalities predispose to cholesteatoma, mainly where the canal is stenotic rather than completely atretic. This is a risk across congenital aural atresia and stenosis of any cause, not a finding reported in TSHZ1 carriers.

Conductive Hearing Impairment Sound cannot reach the tympanic membrane through the atretic canal.

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"In conclusion, we have detected both point mutations and copy-number variants leading to haploinsufficiency due to hemizygosity of TSHZ1 as causes of bilateral CAA type II (in the absence of microtia or anotia) both in isolated nonsyndromic individuals and in persons with the 18q deletion syndrome."

Defines the canal-restricted lesion and the absence of microtia.

Dysregulated PROKR2 Expression

TSHZ1 binds the PROKR2 gene and regulates its expression in the developing olfactory bulb. PROKR2 is the receptor whose loss causes Kallmann syndrome, which makes it a proposed molecular link between the ear disease and the smell deficit.

PROKR2 hgnc:15836

Downstream

Failed Olfactory Bulb Interneuron Maturation PROKR2 is required for olfactory bulb development; that its reduction is what blocks interneuron maturation in Tshz1 mutants is inferred rather than shown by rescue.

Show evidence (2 references)

PMID:24487590 SUPPORT Model Organism

"Microarray analysis, in situ hybridization, and ChIP revealed that TSHZ1 bound to and regulated expression of the gene encoding prokineticin receptor 2 (PROKR2), a G protein–coupled receptor essential for OB development."

Identifies PROKR2 as a direct TSHZ1 target.

PMID:24487590 SUPPORT BACKGROUND Human Clinical

"Mutations in PROKR2 lead to Kallmann syndrome, characterized by anosmia and hypogonadotrophic hypogonadism."

Ties PROKR2 loss to human anosmia.

Failed Olfactory Bulb Interneuron Maturation

In mice lacking Tshz1, neuroblasts migrate tangentially to the olfactory bulb normally but then distribute aberrantly in the radial dimension, and many immature neuroblasts fail to leave the rostral migratory stream.

olfactory bulb interneuron CL:1001434

olfactory bulb interneuron differentiation GO:0021889 ⚠ ABNORMAL

Downstream

Olfactory Bulb Hypoplasia The interneuron defect and bulb hypoplasia occur together in Tshz1 mutant mice; that the first causes the second is inferred.

Show evidence (1 reference)

PMID:24487590 SUPPORT Model Organism

"In mice lacking TSHZ1, neuroblasts exhibited a normal tangential migration to the OB; however, upon arrival to the OB, the neuroblasts were distributed aberrantly within the radial dimension, and many immature neuroblasts failed to exit the rostral migratory stream."

Describes the interneuron maturation defect.

Olfactory Bulb Hypoplasia

Conditional deletion of Tshz1 gives a hypoplastic olfactory bulb with severe olfactory deficits in the mouse. Bulb size has not been reported in the heterozygous patients, whose deficit was measured by smell testing.

olfactory bulb development GO:0021772 ⚠ ABNORMAL

olfactory bulb UBERON:0002264

Animal models

Tshz1 conditional olfactory mouse Mouse partially recapitulates Conditional deletion produces olfactory bulb hypoplasia and severe smell deficits.

Downstream

Hyposmia

Show evidence (1 reference)

PMID:24487590 SUPPORT Model Organism

"Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits."

Establishes bulb hypoplasia in the mouse model.

⬡

Pathograph

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

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Phenotypes

5

Ear 3

Atresia of the External Auditory Canal HP:0000413

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"The affected mother of this family (individual 6) had isolated bilateral conductive hearing loss due to CAA type IIA, for which she had bilateral surgical treatment at the age of 3."

Bilateral CAA type IIA in a frameshift-mutation carrier.

Conductive Hearing Impairment HP:0000405

Sequelae: Delayed Speech and Language Development

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"Pure-tone audiometry at the age of five demonstrated a 42 dB bilateral conductive hearing loss due to CAA type IIA (Figure 3B)."

Measured conductive loss in the nonsense-mutation carrier.

Cholesteatoma HP:0009797

Show evidence (1 reference)

PMID:35439089 SUPPORT INDIRECT Human Clinical

"EAC stenosis is strongly associated with cholesteatoma, and a surveillance scan for these patients is recommended prior to 12 years of age with close follow-up into adulthood."

Systematic review of congenital canal malformations of any cause; not specific to TSHZ1.

Head and Neck 1

Hyposmia HP:0004409

Show evidence (1 reference)

PMID:24487590 SUPPORT Human Clinical

"These individuals displayed hyposmia, which is characterized by impaired odor discrimination and reduced olfactory sensitivity."

Smell testing in heterozygous carriers from the CAA families.

Nervous System 1

Delayed Speech and Language Development HP:0000750

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"He had normal motor development, but impaired speech and delayed language development were noticed between the ages of 3 and 4 years."

Speech delay with otherwise normal development in a carrier with conductive loss.

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Genetic Associations

1

TSHZ1 (Heterozygous loss-of-function mutations or 18q22.3 deletions (haploinsufficiency))

Gene: TSHZ1 hgnc:10669 relationship_type: CAUSATIVE

Show evidence (2 references)

PMID:22152683 SUPPORT Human Clinical

"Here, we report that isolated CAA and the CAA phenotype in the 18q deletion syndrome are both caused by haploinsufficiency that results from a heterozygous deletion or loss-of-function mutation of TSHZ1, whose ortholog is essential for murine middle-ear development."

Establishes TSHZ1 as the causal gene.

PMID:39624921 SUPPORT REVIEW SYNTHESIS Other

"A single article describing nonsyndromic CAA alone identified the TSHZ1 as a candidate gene."

A 2025 scoping review finds TSHZ1 is still the only gene reported for nonsyndromic CAA without microtia, resting on a single study.

💊

Medical Actions

2

Bone-Anchored Hearing Aid

Action: bone-anchored hearing aid implantation Ontology label: Surgical Procedure NCIT:C15329

Platform: Device

A bone-conduction hearing aid on a softband in early childhood, followed by a percutaneous osseointegrated device, bypasses the atretic canal. A systematic review found better hearing outcomes with osseointegrated bone-conduction devices than with atresia surgery. The Surgical Procedure binding refers to the percutaneous implant; the softband stage is non-surgical.

Mechanism Target:

Conductive Hearing Impairment

Show evidence (2 references)

PMID:22152683 SUPPORT Human Clinical

"A BAHA Softband and subsequent percutaneous titanium BAHAs were applied successfully."

Successful bone-anchored hearing rehabilitation in a TSHZ1 mutation carrier.

PMID:24005171 SUPPORT Human Clinical

"The OBCD has better hearing outcomes compared with atresiaplasty in patients with CAA."

Systematic review across congenital aural atresia of all causes, not TSHZ1 specifically.

Atresiaplasty

Action: atresiaplasty Ontology label: Surgical Procedure NCIT:C15329

Platform: Surgery

Surgical creation of an external auditory canal. Hearing gains tend to decline with time and canal restenosis is the main complication; one TSHZ1 carrier operated at age 3 had slowly declining hearing and later received a BAHA.

Mechanism Target:

Atresia of the External Auditory Canal

Show evidence (2 references)

PMID:22152683 SUPPORT Human Clinical

"Her hearing declined slowly over the following decades, and she recently received a BAHA on the left side at 42 years of age."

Long-term course after childhood atresia surgery in a TSHZ1 carrier.

PMID:25912684 SUPPORT Human Clinical

"Based on available data, which shows a lack of major complications, such as facial nerve palsy, atresiaplasty is a safe procedure. Our meta-analysis indicated that there was a degradation of hearing outcomes with prolonged follow-up."

Safety and durability of atresiaplasty across congenital aural atresia generally.

🔬

Diagnosis

2

TSHZ1 sequencing

Sequencing the coding exons of TSHZ1 detects the truncating point mutations in isolated bilateral CAA type IIA.

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"Targeted Sanger sequencing of TSHZ1 in families 3 and 4 revealed mutations in both families"

Sanger sequencing identified the point mutations.

Chromosomal microarray

Copy-number analysis detects 18q22.3 microdeletions spanning TSHZ1, which present with CAA alongside other features of distal 18q deletion.

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"We studied four individuals (from two families) with CAA and other features suggestive of an 18q deletion, and we detected overlapping microdeletions in 18q22.3 in both families."

Microarray analysis found the 18q22.3 deletions.

📊

Prevalence

1

Published TSHZ1 point-mutation families

Cases In Literature

Four affected individuals and one unaffected carrier in two families with TSHZ1 point mutations, found by sequencing 11 people with isolated bilateral CAA type IIA; two further families carried 18q22.3 microdeletions spanning TSHZ1. Congenital aural atresia of any cause occurs in roughly 1 in 10,000 live births, but that figure is not a prevalence for this gene-defined disease.

Show evidence (1 reference)

PMID:22152683 SUPPORT Human Clinical

"In total, four individuals and one unaffected relative showed heterozygous loss-of-function mutations, including a sporadic affected person (individual 5), his unaffected mother, and a family with three affected individuals consisting of a mother and her two daughters (individuals 6–8) (Table 1)."

Counts every published point-mutation carrier.

🐁

Animal Models

2

Tshz1 null mouse

Species

Mouse

Genotype

Tshz1-/-

Publication

PMID:17586487

Pathograph links

Abnormal Middle Ear Skeletal Development partially recapitulates fidelity: low observes: tissue Homozygous loss gives malleus and tympanic ring malformations alongside neonatal lethality, vertebral homeotic transformations and soft palate defects.

Limitations: The human disease is heterozygous and confined to the ear canal; the null mouse is lethal and multisystemic, and the external canal itself was not described.

Show evidence (1 reference)

PMID:17586487 SUPPORT Model Organism

"In the craniofacial region, loss of Tshz1 function leads to specific malformations of middle ear components, including the malleus and the tympanic ring."

The null mouse shows the middle-ear skeletal defect this node models.

Tshz1 conditional olfactory mouse

Species

Mouse

Genotype

Tshz1 conditional deletion

Publication

PMID:24487590

Pathograph links

Olfactory Bulb Hypoplasia partially recapitulates fidelity: moderate observes: tissue Conditional deletion produces olfactory bulb hypoplasia and severe smell deficits.

Limitations: Homozygous conditional loss is more severe than human heterozygosity, where hyposmia rather than anosmia is reported, and olfactory bulb size has not been reported in patients.

Show evidence (1 reference)

PMID:24487590 SUPPORT Model Organism

"Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits."

The model's bulb and smell phenotype.

{ }

Source YAML

click to show

name: Congenital Aural Atresia
creation_date: "2026-10-01T00:00:00Z"
category: Mendelian
description: >-
  TSHZ1-related congenital aural atresia is an autosomal dominant, incompletely
  penetrant malformation of the external auditory canal, caused by
  haploinsufficiency of the teashirt zinc finger homeobox transcription factor
  TSHZ1. Affected individuals have bilateral narrowing or bony atresia of the
  medial external auditory canal (CAA type IIA) with normally shaped pinnae and
  conductive hearing loss, and heterozygous carriers tested for smell have
  hyposmia. TSHZ1 lies in 18q22.3, the critical region for the aural atresia
  that is common in distal 18q deletion syndrome; the same gene therefore
  explains the ear phenotype both as an isolated Mendelian trait and as one
  component of a contiguous deletion.

  This entry covers the monogenic disease bound to MONDO:0011921 (OMIM
  607842), defined by TSHZ1. Congenital aural atresia as a
  clinical finding is far more common and genetically heterogeneous; it occurs
  with microtia, in craniofacial syndromes, and in aneuploidies, and most
  isolated cases have no identified cause. Those are not modelled here.
disease_term:
  preferred_term: congenital aural atresia
  term:
    id: MONDO:0011921
    label: aural atresia, congenital
parents:
- congenital malformation of the ear
- hereditary disease
synonyms:
- CAA
- aural atresia, congenital, with hyposmia
- TSHZ1-related congenital aural atresia
references:
- reference: PMID:22152683
  title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
- reference: PMID:24487590
  title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
- reference: PMID:17586487
  title: Tshz1 is required for axial skeleton, soft palate and middle ear development in mice.
- reference: PMID:8565828
  title: "Development of the mammalian ear: coordinate regulation of formation of the tympanic ring and the external acoustic meatus."
- reference: PMID:39624921
  title: "Genetics of Nonsyndromic Microtia and Congenital Aural Atresia: A Scoping Review."
- reference: PMID:24005171
  title: "Hearing outcomes of atresia surgery versus osseointegrated bone conduction device in patients with congenital aural atresia: a systematic review."
- reference: PMID:25912684
  title: A meta-analysis of the long-term hearing outcomes and complications associated with atresiaplasty.
- reference: PMID:35439089
  title: "Cholesteatoma in Congenital Aural Atresia and External Auditory Canal Stenosis: A Systematic Review."

inheritance:
- name: Autosomal dominant with reduced penetrance
  description: >-
    Heterozygous TSHZ1 loss-of-function alleles segregate dominantly, but an
    unaffected carrier mother transmitted the nonsense allele p.Trp241X to an
    affected son, so penetrance is incomplete. In 18q deletion carriers, aural
    atresia is reported in 26% of any 18q deletion and up to 78% of deletions
    covering the critical region including TSHZ1; those figures describe
    deletion carriers, not point-mutation penetrance.
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "As expected, this mutation showed an autosomal-dominant segregation pattern."
    explanation: >-
      The frameshift allele passes from an affected mother to her affected
      monozygotic twin daughters, which is a single transmission.
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is worth noting that a sequence analysis of the phenotypically normal maternal parents did not reveal the presence of this frameshift mutation, indicating that the mutation occurred de novo in the index person of this family."
    explanation: The frameshift arose de novo in the affected mother, consistent with a dominant allele.
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The fact that the nonsense mutation in TSHZ1 in individual 5 was inherited from his phenotypically normal mother can be explained by reduced penetrance."
    explanation: An unaffected obligate carrier documents incomplete penetrance.
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "This observation is in accordance with previous reports that describe a CAA incidence of 26% in individuals with an 18q deletion of any kind and an incidence of up to 78% in individuals with a deletion of the critical CAA region that includes TSHZ1."
    explanation: Incomplete penetrance of CAA among deletion carriers that include TSHZ1.

prevalence:
- population: Published TSHZ1 point-mutation families
  measure_type: CASES_IN_LITERATURE
  notes: >-
    Four affected individuals and one unaffected carrier in two families with
    TSHZ1 point mutations, found by sequencing 11 people with isolated bilateral
    CAA type IIA; two further families carried 18q22.3 microdeletions spanning
    TSHZ1. Congenital aural atresia of any cause occurs in roughly 1 in 10,000
    live births, but that figure is not a prevalence for this gene-defined
    disease.
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In total, four individuals and one unaffected relative showed heterozygous loss-of-function mutations, including a sporadic affected person (individual 5), his unaffected mother, and a family with three affected individuals consisting of a mother and her two daughters (individuals 6–8) (Table 1)."
    explanation: Counts every published point-mutation carrier.

pathophysiology:
- name: TSHZ1 Haploinsufficiency
  biological_scale: MOLECULAR
  description: >-
    One functional copy of TSHZ1 is lost, either through a truncating point
    mutation (p.Trp241X, p.Pro316ThrfsX16) or through an 18q22.3 microdeletion
    whose minimal overlap contains TSHZ1 as its only known gene. TSHZ1 encodes
    a teashirt-family zinc finger homeodomain transcription factor that, in the
    mouse, is expressed in the branchial arches from E9.5.
  genes:
  - preferred_term: TSHZ1
    term:
      id: hgnc:10669
      label: TSHZ1
  molecular_functions:
  - preferred_term: DNA-binding transcription factor activity
    modifier: LOSS_OF_FUNCTION
    term:
      id: GO:0003700
      label: DNA-binding transcription factor activity
  genetic_context:
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The minimal region of deletion overlap (72.9-73.4 Mb) contained only one known gene, TSHZ1, which was recently shown to be important for murine middle-ear development."
    explanation: Deletion mapping isolates TSHZ1 as the only gene in the critical interval.
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sequence analysis of the coding exons in TSHZ1 in a cohort of 11 individuals with isolated, nonsyndromic bilateral CAA revealed two mutations, c.723G>A (p.Trp241X) and c.946_947delinsA (p.Pro316ThrfsX16), and both mutations predicted a loss of function."
    explanation: Two independent truncating alleles in isolated CAA.
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Together, these results demonstrate that hemizygosity of TSHZ1 leads to congenital aural atresia as a result of haploinsufficiency."
    explanation: States haploinsufficiency as the disease mechanism.
  - reference: PMID:24487590
    reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "Microarray analysis, in situ hybridization, and ChIP revealed that TSHZ1 bound to and regulated expression of the gene encoding prokineticin receptor 2 (PROKR2), a G protein–coupled receptor essential for OB development."
    explanation: >-
      ChIP shows TSHZ1 binding a target gene and regulating its expression,
      the DNA-binding transcription factor activity lost in haploinsufficiency;
      shown in mouse.
  downstream:
  - target: Abnormal Middle Ear Skeletal Development
    causal_link_type: DIRECT
    description: >-
      Loss of Tshz1 malforms the first-arch-derived middle-ear elements in the
      mouse. The mouse evidence is from the homozygous null, not the
      heterozygous state that causes the human disease.
    evidence:
    - reference: PMID:17586487
      reference_title: Tshz1 is required for axial skeleton, soft palate and middle ear development in mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "In the craniofacial region, loss of Tshz1 function leads to specific malformations of middle ear components, including the malleus and the tympanic ring."
      explanation: >-
        Shows Tshz1 loss malforms the tympanic ring and malleus; indirect
        because the model is a homozygous knockout.
  - target: Failed External Acoustic Meatus Morphogenesis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      In humans, TSHZ1 haploinsufficiency is established as the cause of the
      canal atresia; the developmental steps between them are known only from
      mouse work.
    evidence:
    - reference: PMID:22152683
      reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Together, these results demonstrate that hemizygosity of TSHZ1 leads to congenital aural atresia as a result of haploinsufficiency."
      explanation: Human genetic evidence that loss of one TSHZ1 copy produces the canal atresia.
  - target: Dysregulated PROKR2 Expression
    causal_link_type: DIRECT
    description: >-
      TSHZ1 binds and regulates the PROKR2 gene. This was shown in Tshz1-mutant
      mice; regulation in heterozygous human carriers has not been measured.
    evidence:
    - reference: PMID:24487590
      reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "Microarray analysis, in situ hybridization, and ChIP revealed that TSHZ1 bound to and regulated expression of the gene encoding prokineticin receptor 2 (PROKR2), a G protein–coupled receptor essential for OB development."
      explanation: ChIP and expression analysis place PROKR2 directly under TSHZ1 control.

- name: Abnormal Middle Ear Skeletal Development
  biological_scale: TISSUE
  description: >-
    Tshz1 is expressed in the branchial arches from E9.5, and Tshz1-null mice
    have specific malformations of the malleus and the tympanic ring, both
    first-arch derivatives. Whether the same structures are malformed in
    heterozygous humans has not been shown; patient CT describes the canal
    rather than the ossicles or ring.
  biological_processes:
  - preferred_term: middle ear morphogenesis
    modifier: ABNORMAL
    term:
      id: GO:0042474
      label: middle ear morphogenesis
  locations:
  - preferred_term: tympanic ring
    term:
      id: UBERON:0002218
      label: tympanic ring
  - preferred_term: malleus
    term:
      id: UBERON:0001689
      label: malleus bone
  evidence:
  - reference: PMID:17586487
    reference_title: Tshz1 is required for axial skeleton, soft palate and middle ear development in mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Tshz1 is detected from E9.5 in the somites, the spinal cord, the limb buds and the branchial arches."
    explanation: Places Tshz1 in the branchial arches that build the middle ear.
  - reference: PMID:17586487
    reference_title: Tshz1 is required for axial skeleton, soft palate and middle ear development in mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In the craniofacial region, loss of Tshz1 function leads to specific malformations of middle ear components, including the malleus and the tympanic ring."
    explanation: The middle-ear skeletal defect in the knockout.
  downstream:
  - target: Failed External Acoustic Meatus Morphogenesis
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The tympanic ring primordium is proposed to induce formation of the
      external acoustic meatus, so a ring defect is a candidate route to canal
      atresia. This link is inferred from other mouse models, not tested for
      Tshz1.
    evidence:
    - reference: PMID:8565828
      reference_title: "Development of the mammalian ear: coordinate regulation of formation of the tympanic ring and the external acoustic meatus."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "We demonstrate here an absolute correlation between formation of the external acoustic meatus and formation of the tympanic ring, a first arch-derived membrane bone that anchors the tympanic membrane."
      explanation: >-
        Ties meatus formation to the tympanic ring in mouse; indirect because
        Tshz1 was not studied.
    - reference: PMID:8565828
      reference_title: "Development of the mammalian ear: coordinate regulation of formation of the tympanic ring and the external acoustic meatus."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "We suggest that the tympanic ring primordium induces formation and morphogenesis of the external acoustic meatus"
      explanation: Proposes the inductive mechanism this edge represents.

- name: Failed External Acoustic Meatus Morphogenesis
  biological_scale: TISSUE
  description: >-
    The medial, bony part of the external auditory canal fails to form or is
    stenotic, ending blindly or in a fistula to a rudimentary tympanic membrane
    (CAA type IIA). The pinna is normally shaped and the mutation carriers have
    no other congenital malformations, so the lesion is confined to the canal
    and middle-ear cleft.
  biological_processes:
  - preferred_term: outer ear morphogenesis
    modifier: ABNORMAL
    term:
      id: GO:0042473
      label: outer ear morphogenesis
  locations:
  - preferred_term: external acoustic meatus
    term:
      id: UBERON:0001352
      label: external acoustic meatus
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In conclusion, we have detected both point mutations and copy-number variants leading to haploinsufficiency due to hemizygosity of TSHZ1 as causes of bilateral CAA type II (in the absence of microtia or anotia) both in isolated nonsyndromic individuals and in persons with the 18q deletion syndrome."
    explanation: Defines the canal-restricted lesion and the absence of microtia.
  downstream:
  - target: Atresia of the External Auditory Canal
    causal_link_type: DIRECT
    description: The failed canal is the clinical atresia.
    evidence:
    - reference: PMID:22152683
      reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "In conclusion, we have detected both point mutations and copy-number variants leading to haploinsufficiency due to hemizygosity of TSHZ1 as causes of bilateral CAA type II (in the absence of microtia or anotia) both in isolated nonsyndromic individuals and in persons with the 18q deletion syndrome."
      explanation: The canal defect presents as bilateral CAA type II without microtia.
  - target: Cholesteatoma
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Congenital canal abnormalities predispose to cholesteatoma, mainly where
      the canal is stenotic rather than completely atretic. This is a risk
      across congenital aural atresia and stenosis of any cause, not a finding
      reported in TSHZ1 carriers.
    evidence:
    - reference: PMID:35439089
      reference_title: "Cholesteatoma in Congenital Aural Atresia and External Auditory Canal Stenosis: A Systematic Review."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: INDIRECT
      snippet: "The incidence of cholesteatoma was 1.7% (4/238) in CAA and 43.0% (203/473) in congenital EAC stenosis."
      explanation: >-
        Pooled across congenital canal malformations of any cause; indirect
        for the TSHZ1 disease.
  - target: Conductive Hearing Impairment
    causal_link_type: DIRECT
    description: Sound cannot reach the tympanic membrane through the atretic canal.
    evidence:
    - reference: PMID:22152683
      reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Pure-tone audiometry at the age of five demonstrated a 42 dB bilateral conductive hearing loss due to CAA type IIA (Figure 3B)."
      explanation: The conductive loss in a mutation carrier is attributed to the canal atresia.

- name: Dysregulated PROKR2 Expression
  biological_scale: MOLECULAR
  description: >-
    TSHZ1 binds the PROKR2 gene and regulates its expression in the developing
    olfactory bulb. PROKR2 is the receptor whose loss causes Kallmann syndrome,
    which makes it a proposed molecular link between the ear disease and the
    smell deficit.
  genes:
  - preferred_term: PROKR2
    term:
      id: hgnc:15836
      label: PROKR2
  evidence:
  - reference: PMID:24487590
    reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Microarray analysis, in situ hybridization, and ChIP revealed that TSHZ1 bound to and regulated expression of the gene encoding prokineticin receptor 2 (PROKR2), a G protein–coupled receptor essential for OB development."
    explanation: Identifies PROKR2 as a direct TSHZ1 target.
  - reference: PMID:24487590
    reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: BACKGROUND
    snippet: "Mutations in PROKR2 lead to Kallmann syndrome, characterized by anosmia and hypogonadotrophic hypogonadism."
    explanation: Ties PROKR2 loss to human anosmia.
  downstream:
  - target: Failed Olfactory Bulb Interneuron Maturation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      PROKR2 is required for olfactory bulb development; that its reduction is
      what blocks interneuron maturation in Tshz1 mutants is inferred rather
      than shown by rescue.
    evidence:
    - reference: PMID:24487590
      reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "Our data indicate that TSHZ1 is a key regulator of mammalian OB development and function and controls the expression of molecules involved in human Kallmann syndrome."
      explanation: The authors connect TSHZ1 control of PROKR2 to olfactory bulb development.

- name: Failed Olfactory Bulb Interneuron Maturation
  biological_scale: CELLULAR
  description: >-
    In mice lacking Tshz1, neuroblasts migrate tangentially to the olfactory
    bulb normally but then distribute aberrantly in the radial dimension, and
    many immature neuroblasts fail to leave the rostral migratory stream.
  cell_types:
  - preferred_term: olfactory bulb interneuron
    term:
      id: CL:1001434
      label: olfactory bulb interneuron
  biological_processes:
  - preferred_term: olfactory bulb interneuron differentiation
    modifier: ABNORMAL
    term:
      id: GO:0021889
      label: olfactory bulb interneuron differentiation
  evidence:
  - reference: PMID:24487590
    reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In mice lacking TSHZ1, neuroblasts exhibited a normal tangential migration to the OB; however, upon arrival to the OB, the neuroblasts were distributed aberrantly within the radial dimension, and many immature neuroblasts failed to exit the rostral migratory stream."
    explanation: Describes the interneuron maturation defect.
  downstream:
  - target: Olfactory Bulb Hypoplasia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      The interneuron defect and bulb hypoplasia occur together in Tshz1
      mutant mice; that the first causes the second is inferred.
    evidence:
    - reference: PMID:24487590
      reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "Using a mouse model, we found that development and maturation of OB interneurons depends on the zinc finger homeodomain factor teashirt zinc finger family member 1 (TSHZ1)."
      explanation: Ties bulb development to TSHZ1-dependent interneuron maturation.

- name: Olfactory Bulb Hypoplasia
  biological_scale: TISSUE
  description: >-
    Conditional deletion of Tshz1 gives a hypoplastic olfactory bulb with
    severe olfactory deficits in the mouse. Bulb size has not been reported in
    the heterozygous patients, whose deficit was measured by smell testing.
  biological_processes:
  - preferred_term: olfactory bulb development
    modifier: ABNORMAL
    term:
      id: GO:0021772
      label: olfactory bulb development
  locations:
  - preferred_term: olfactory bulb
    term:
      id: UBERON:0002264
      label: olfactory bulb
  evidence:
  - reference: PMID:24487590
    reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits."
    explanation: Establishes bulb hypoplasia in the mouse model.
  downstream:
  - target: Hyposmia
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:24487590
      reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      snippet: "Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits."
      explanation: >-
        Bulb hypoplasia with smell loss in mice; indirect for the human
        heterozygous hyposmia.

phenotypes:
- name: Atresia of the External Auditory Canal
  category: Otologic
  description: >-
    Bilateral CAA type IIA: bony atresia of the medial canal or a partially
    aplastic canal ending blindly, with normally shaped pinnae.
  phenotype_term:
    preferred_term: Atresia of the external auditory canal
    term:
      id: HP:0000413
      label: Atresia of the external auditory canal
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The affected mother of this family (individual 6) had isolated bilateral conductive hearing loss due to CAA type IIA, for which she had bilateral surgical treatment at the age of 3."
    explanation: Bilateral CAA type IIA in a frameshift-mutation carrier.
- name: Conductive Hearing Impairment
  category: Otologic
  description: Bilateral conductive hearing loss secondary to the canal atresia.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pure-tone audiometry at the age of five demonstrated a 42 dB bilateral conductive hearing loss due to CAA type IIA (Figure 3B)."
    explanation: Measured conductive loss in the nonsense-mutation carrier.
  sequelae:
  - target: Delayed Speech and Language Development
- name: Cholesteatoma
  category: Otologic
  description: >-
    A risk rather than a reported finding. Cholesteatoma is uncommon in
    complete congenital aural atresia but common in congenital canal stenosis.
    CAA type IIA includes partially aplastic canals as well as complete medial
    atresia, so the risk depends on the individual canal; surveillance imaging
    before age 12 is recommended for stenotic canals.
  phenotype_term:
    preferred_term: Cholesteatoma
    term:
      id: HP:0009797
      label: Cholesteatoma
  evidence:
  - reference: PMID:35439089
    reference_title: "Cholesteatoma in Congenital Aural Atresia and External Auditory Canal Stenosis: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    snippet: "EAC stenosis is strongly associated with cholesteatoma, and a surveillance scan for these patients is recommended prior to 12 years of age with close follow-up into adulthood."
    explanation: >-
      Systematic review of congenital canal malformations of any cause; not
      specific to TSHZ1.
- name: Delayed Speech and Language Development
  category: Neurodevelopmental
  description: >-
    Speech and language delay was noticed at 3 to 4 years in the sporadic
    nonsense-mutation carrier, whose bilateral conductive hearing loss was
    documented at age 5; motor development was normal.
  phenotype_term:
    preferred_term: Delayed speech and language development
    term:
      id: HP:0000750
      label: Delayed speech and language development
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "He had normal motor development, but impaired speech and delayed language development were noticed between the ages of 3 and 4 years."
    explanation: Speech delay with otherwise normal development in a carrier with conductive loss.
- name: Hyposmia
  category: Neurological
  description: >-
    Reduced olfactory sensitivity and impaired odor discrimination in
    heterozygous TSHZ1 loss-of-function carriers from CAA families.
  phenotype_term:
    preferred_term: Hyposmia
    term:
      id: HP:0004409
      label: Hyposmia
  evidence:
  - reference: PMID:24487590
    reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These individuals displayed hyposmia, which is characterized by impaired odor discrimination and reduced olfactory sensitivity."
    explanation: Smell testing in heterozygous carriers from the CAA families.

genetic:
- name: TSHZ1
  gene_term:
    preferred_term: TSHZ1
    term:
      id: hgnc:10669
      label: TSHZ1
  association: Heterozygous loss-of-function mutations or 18q22.3 deletions (haploinsufficiency)
  relationship_type: CAUSATIVE
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Here, we report that isolated CAA and the CAA phenotype in the 18q deletion syndrome are both caused by haploinsufficiency that results from a heterozygous deletion or loss-of-function mutation of TSHZ1, whose ortholog is essential for murine middle-ear development."
    explanation: Establishes TSHZ1 as the causal gene.
  - reference: PMID:39624921
    reference_title: "Genetics of Nonsyndromic Microtia and Congenital Aural Atresia: A Scoping Review."
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    snippet: "A single article describing nonsyndromic CAA alone identified the TSHZ1 as a candidate gene."
    explanation: >-
      A 2025 scoping review finds TSHZ1 is still the only gene reported for
      nonsyndromic CAA without microtia, resting on a single study.

treatments:
- name: Bone-Anchored Hearing Aid
  description: >-
    A bone-conduction hearing aid on a softband in early childhood, followed by
    a percutaneous osseointegrated device, bypasses the atretic canal. A
    systematic review found better hearing outcomes with osseointegrated
    bone-conduction devices than with atresia surgery. The Surgical Procedure
    binding refers to the percutaneous implant; the softband stage is
    non-surgical.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: bone-anchored hearing aid implantation
    term:
      id: NCIT:C15329
      label: Surgical Procedure
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: bone-anchored hearing aid
        term:
          id: NCIT:C185117
          label: Bone-anchored Hearing Aid
  target_mechanisms:
  - target: Conductive Hearing Impairment
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A BAHA Softband and subsequent percutaneous titanium BAHAs were applied successfully."
    explanation: Successful bone-anchored hearing rehabilitation in a TSHZ1 mutation carrier.
  - reference: PMID:24005171
    reference_title: "Hearing outcomes of atresia surgery versus osseointegrated bone conduction device in patients with congenital aural atresia: a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The OBCD has better hearing outcomes compared with atresiaplasty in patients with CAA."
    explanation: >-
      Systematic review across congenital aural atresia of all causes, not
      TSHZ1 specifically.
- name: Atresiaplasty
  description: >-
    Surgical creation of an external auditory canal. Hearing gains tend to
    decline with time and canal restenosis is the main complication; one
    TSHZ1 carrier operated at age 3 had slowly declining hearing and later
    received a BAHA.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: atresiaplasty
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_mechanisms:
  - target: Atresia of the External Auditory Canal
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Her hearing declined slowly over the following decades, and she recently received a BAHA on the left side at 42 years of age."
    explanation: Long-term course after childhood atresia surgery in a TSHZ1 carrier.
  - reference: PMID:25912684
    reference_title: A meta-analysis of the long-term hearing outcomes and complications associated with atresiaplasty.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Based on available data, which shows a lack of major complications, such as facial nerve palsy, atresiaplasty is a safe procedure. Our meta-analysis indicated that there was a degradation of hearing outcomes with prolonged follow-up."
    explanation: >-
      Safety and durability of atresiaplasty across congenital aural atresia
      generally.

diagnosis:
- name: TSHZ1 sequencing
  description: >-
    Sequencing the coding exons of TSHZ1 detects the truncating point
    mutations in isolated bilateral CAA type IIA.
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Targeted Sanger sequencing of TSHZ1 in families 3 and 4 revealed mutations in both families"
    explanation: Sanger sequencing identified the point mutations.
- name: Chromosomal microarray
  description: >-
    Copy-number analysis detects 18q22.3 microdeletions spanning TSHZ1, which
    present with CAA alongside other features of distal 18q deletion.
  evidence:
  - reference: PMID:22152683
    reference_title: Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We studied four individuals (from two families) with CAA and other features suggestive of an 18q deletion, and we detected overlapping microdeletions in 18q22.3 in both families."
    explanation: Microarray analysis found the 18q22.3 deletions.

animal_models:
- name: Tshz1 null mouse
  species: Mouse
  genotype: Tshz1-/-
  publication: PMID:17586487
  modeled_mechanisms:
  - target: Abnormal Middle Ear Skeletal Development
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    model_scale: TISSUE
    description: >-
      Homozygous loss gives malleus and tympanic ring malformations alongside
      neonatal lethality, vertebral homeotic transformations and soft palate
      defects.
    limitations: >-
      The human disease is heterozygous and confined to the ear canal; the
      null mouse is lethal and multisystemic, and the external canal itself
      was not described.
    evidence:
    - reference: PMID:17586487
      reference_title: Tshz1 is required for axial skeleton, soft palate and middle ear development in mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "In the craniofacial region, loss of Tshz1 function leads to specific malformations of middle ear components, including the malleus and the tympanic ring."
      explanation: The null mouse shows the middle-ear skeletal defect this node models.
- name: Tshz1 conditional olfactory mouse
  species: Mouse
  genotype: Tshz1 conditional deletion
  publication: PMID:24487590
  modeled_mechanisms:
  - target: Olfactory Bulb Hypoplasia
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    model_scale: TISSUE
    description: Conditional deletion produces olfactory bulb hypoplasia and severe smell deficits.
    limitations: >-
      Homozygous conditional loss is more severe than human heterozygosity,
      where hyposmia rather than anosmia is reported, and olfactory bulb size
      has not been reported in patients.
    evidence:
    - reference: PMID:24487590
      reference_title: TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Conditional deletion of Tshz1 in mice resulted in OB hypoplasia and severe olfactory deficits."
      explanation: The model's bulb and smell phenotype.

notes: >-
  No GeneReviews chapter exists for this disease (just check-genereviews
  reports NO_CHAPTER against the Bookshelf index). A 2025 scoping review of
  nonsyndromic microtia and CAA genetics found TSHZ1 to be the only candidate
  gene reported for nonsyndromic CAA alone. The overlap with distal 18q
  deletion syndrome is curated separately in Chromosome_18q_Deletion_Syndrome.

📚

References & Deep Research

References

8

PMID:22152683

Disruption of teashirt zinc finger homeobox 1 is associated with congenital aural atresia in humans.

No top-level findings curated for this source.

PMID:24487590

TSHZ1-dependent gene regulation is essential for olfactory bulb development and olfaction.

No top-level findings curated for this source.

PMID:17586487

Tshz1 is required for axial skeleton, soft palate and middle ear development in mice.

No top-level findings curated for this source.

PMID:8565828

Development of the mammalian ear: coordinate regulation of formation of the tympanic ring and the external acoustic meatus.

No top-level findings curated for this source.

PMID:39624921

Genetics of Nonsyndromic Microtia and Congenital Aural Atresia: A Scoping Review.

No top-level findings curated for this source.

PMID:24005171

Hearing outcomes of atresia surgery versus osseointegrated bone conduction device in patients with congenital aural atresia: a systematic review.

No top-level findings curated for this source.

PMID:25912684

A meta-analysis of the long-term hearing outcomes and complications associated with atresiaplasty.

No top-level findings curated for this source.

PMID:35439089

Cholesteatoma in Congenital Aural Atresia and External Auditory Canal Stenosis: A Systematic Review.

No top-level findings curated for this source.

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 (1)

Create: Congenital_Aural_Atresia · 2026-10-01T16:57:24Z · View source

Created the TSHZ1-related congenital aural atresia entry (MONDO:0011921, OMIM 607842) from the primary literature: Feenstra 2011 (PMID:22152683, full text) for the human genetics, phenotypes, inheritance and reduced penetrance; Ragancokova 2014 (PMID:24487590) for hyposmia and the TSHZ1-PROKR2-olfactory bulb chain; Core 2007 (PMID:17586487) for the Tshz1 null mouse middle-ear defect; Mallo and Gridley 1996 (PMID:8565828) for the tympanic ring-to-meatus inductive link, recorded as an inferred edge. Treatment evidence uses two reviews of congenital aural atresia of any cause (PMID:24005171, PMID:25912684), labelled as such. Deep research: OpenScientist (research/Congenital_Aural_Atresia-deep-research-openscientist.md; 39/39 references resolved, 1 off topic). preflight-dr returned WARN because the report treats congenital aural atresia generically (HOXA2, TCOF1 and microtia genetics outweigh TSHZ1), so only its scoping-review citation (PMID:39624921) was taken into the entry. No GeneReviews chapter exists (check-genereviews NO_CHAPTER). An internal fresh-context review before the PR led to recording mouse-only causal edges as INDIRECT, adding a human-evidence edge from TSHZ1 haploinsufficiency to the canal defect, narrowing the GO binding to outer ear morphogenesis, and adding a diagnosis section. Validated with just validate, validate-terms, count-verified-snippets (39/39) and the offline qc gates.

OpenScientist ▸

Congenital Aural Atresia (MONDO:0011921): A Comprehensive Disease Characteristics Report

openscientist-autonomous 39 citations 2026-10-01T12:43:36.426092

Congenital Aural Atresia (MONDO:0011921): A Comprehensive Disease Characteristics Report

Summary

Congenital aural atresia (CAA) is a congenital malformation in which the external auditory canal (EAC) fails to develop, resulting in absence or severe stenosis of the ear canal, usually accompanied by maldevelopment of the middle-ear cavity and ossicular chain and, in most cases, by microtia (malformation of the auricle). Because the defect is confined to the sound-conducting apparatus derived from the first and second pharyngeal (branchial) arches and the first pharyngeal cleft, while the cochlea and inner ear (otic-vesicle derived) are typically spared, CAA produces a maximal conductive hearing loss of approximately 60 dB (a large air–bone gap) rather than sensorineural deafness. It is a stable, non-progressive, non-fatal structural malformation present at birth, and the dominant clinical problem is hearing deprivation and its downstream impact on speech, language, and psychosocial development, together with the cosmetic and psychosocial burden of the auricular deformity.

Etiologically, CAA is heterogeneous. Most cases are sporadic and isolated (≈74% isolated, ≈89% unilateral in a large registry), with a male predominance and right-sided predilection, and with recognized non-genetic risk factors including maternal pregestational/gestational diabetes, Hispanic and Andean/high-altitude ancestry, moderate altitude residence, maternal retinoid exposure, and some occupational exposures. A substantial minority are Mendelian/syndromic, occurring within mandibulofacial dysostosis and craniofacial microsomia spectra. The validated and candidate genes — HOXA2, TSHZ1, HMX1, TCOF1, POLR1C/POLR1D, SF3B2, EFTUD2, TWIST1 — converge mechanistically on cranial neural-crest cell specification/patterning and on the spliceosome/ribosome-biogenesis machinery required by neural crest, linking CAA to the broader group of neurocristopathies and ribosomopathies.

Diagnosis rests on clinical examination, audiometry (bone-conduction testing to confirm a normal cochlear reserve), and high-resolution temporal-bone CT, which reveals the hypoplastic middle-ear cleft, fused/hypoplastic/absent ossicles, underpneumatized mastoid, and — critically for surgery — an anteriorly displaced mastoid segment of the facial nerve. CT grading (Jahrsdoerfer 10-point scale; aMEI 16-point scale) stratifies surgical candidacy. Management is rehabilitative, not curative: early bone-conduction amplification (softband, then osseointegrated or transcutaneous implants) to restore auditory input during the critical window for language development; Jahrsdoerfer-selected atresiaplasty/canaloplasty for hearing (air–bone gap ≤30 dB achievable in ~79–90% of well-selected ears); and staged autologous costal-cartilage (Nagata/Brent) or porous-polyethylene auricular reconstruction for the microtia. There is no disease-modifying pharmacologic, gene, or cell therapy. Prevention is limited to maternal glycemic control, teratogen avoidance, newborn hearing screening (secondary prevention), and genetic counseling for syndromic/familial cases.

1. Disease Information

Overview. Congenital aural atresia is the congenital absence or incomplete formation (atresia) of the external auditory canal, typically with concurrent middle-ear hypoplasia and ossicular anomalies, and most often associated with microtia. It is the structural basis of congenital conductive hearing loss of the outer/middle ear. The inner ear is usually normal because it derives embryologically from the otic placode/vesicle, a separate developmental program from the branchial-arch-derived conducting apparatus.

Key identifiers. - MONDO: MONDO:0011921 - ICD-10: Q16.1 (congenital absence, atresia and stricture of auditory canal, external) - ICD-11: LA22 region (congenital malformations of ear causing impairment of hearing) - MeSH: closest terms "Congenital Microtia," "Ear Canal/abnormalities," "Hearing Loss, Conductive" - Orphanet / OMIM: indexed chiefly through syndromic entities and the microtia spectrum (e.g., microtia with meatal atresia and conductive deafness); no single isolated-CAA OMIM phenotype number captures all forms given genetic heterogeneity.

Synonyms / alternative names. Aural atresia; congenital atresia of the external auditory canal; congenital meatal atresia; external auditory canal atresia (EAC atresia); atresia auris congenita. Frequently co-indexed with microtia-atresia and congenital aural stenosis (a milder, partial-canal variant that behaves differently — notably a much higher cholesteatoma risk).

Information source type. The knowledge base entry is derived predominantly from aggregated disease-level resources — surgical case series, birth-defect registries (e.g., Texas Birth Defects Registry), cohort studies, imaging series, and a genetics scoping review — rather than from individual EHR-level patient records.

2. Etiology

Primary causal factors. CAA is fundamentally a developmental field defect of the first and second pharyngeal arches and the first pharyngeal cleft (Finding F004). The causal spectrum spans: - Multifactorial/sporadic (the majority): disrupted branchial-arch morphogenesis of uncertain individual cause. - Mendelian/syndromic: single-gene disorders affecting neural-crest patterning and the spliceosome/ribosome machinery (Findings F001, F008). - Teratogenic/environmental: maternal diabetes, retinoids (isotretinoin/vitamin-A excess), mycophenolate mofetil, and other exposures.

Risk factors

Genetic risk factors. A 2024 scoping review of nonsyndromic microtia/CAA genetics (30 studies) identified 40 unique genes plus one susceptibility locus (4p15.32–4p16.2); the most-cited microtia genes were HOXA2, MUC6, GSC, and TSHZ1 was identified as the candidate gene for nonsyndromic CAA alone (Finding F001; PMID: 39624921). The review states: "Thirty studies met inclusion criteria, describing 40 unique genes and one susceptibility gene locus (4p15.32-4p16.2) ... A single article describing nonsyndromic CAA alone identified the TSHZ1 as a candidate gene." HOXA2 homeodomain missense (p.Q186K) causes autosomal-recessive bilateral microtia with mixed hearing loss and cleft palate in a consanguineous Iranian family (LOD 4.17; PMID: 18394579). HMX1 downstream-enhancer duplications cause isolated bilateral concha-type microtia (PMID: 32552830).

Environmental/demographic risk factors (Finding F002):

Risk factor	Effect estimate	Source
Male sex	PR 1.3 (95% CI 1.2–1.4); M:F up to 3.53:1	PMID: 36398384, PMID: 40984631
Maternal diabetes	PR 2.0 (1.6–2.4); bilateral PR 5.0 (3.3–7.7)	PMID: 36398384
Maternal diabetes (VACTERL hearing loss)	OR 3.71 (1.5–7.3)	PMID: 37649433
Hispanic ancestry	PR 2.9 (2.5–3.4)	PMID: 36398384
Advanced maternal age (30–39; ≥35)	PR 1.2	PMID: 36398384, PMID: 39487910
Moderate altitude (1500–2500 m)	aOR 1.60 for microtia	PMID: 39056527
Maternal cleaning occupation	Elevated OR for anotia/microtia	PMID: 41266119
Mycophenolate mofetil (in-utero)	Pattern of malformation incl. microtia	PMID: 18368705

Protective factors. No validated genetic protective variant or modifier allele is established for CAA. Folic acid intake and TORCH vaccination were examined as candidate protective factors in the Indonesian case-control study (PMID: 40984631) but no robust protective effect specific to CAA has been confirmed. The clearest modifiable preventive lever is maternal glycemic control, given the strong, dose-dependent diabetes association (bilateral PR 5.0).

Gene–environment interactions. Direct GxE evidence for CAA is sparse. The biologically coherent model is that maternal hyperglycemia and retinoid signaling perturbations act on a susceptible neural-crest/branchial-arch developmental program — the same program disrupted by HOXA2/neural-crest genes — such that environmental insults and genetic susceptibility converge on the same morphogenetic window (weeks 3–8 of gestation). This remains inferred rather than demonstrated at the molecular level in humans.

3. Phenotypes

The core phenotype is congenital conductive hearing loss due to a mechanically absent/obstructed sound-conduction path, layered with structural/physical malformations of the ear and, in syndromic cases, broader craniofacial and systemic features.

Phenotype	Type	HPO term (suggested)	Characteristics	Frequency
Aural atresia (absent EAC)	Physical malformation	HP:0000413 (Atresia of the external auditory canal)	Congenital; stable; unilateral ~89%	Defining feature
Microtia	Physical malformation	HP:0008551 (Microtia)	Congenital; right-predominant	Co-occurs in vast majority
Conductive hearing loss	Clinical sign / lab (audiometric)	HP:0000405 (Conductive hearing impairment)	Neonatal onset; severe (~60 dB air–bone gap); non-progressive	Universal in complete atresia
Ossicular malformation/fusion	Physical malformation	HP:0011453 (Abnormality of the middle ear ossicles)	Congenital	~89% of atretic ears (25/28 in CT series)
Middle-ear hypoplasia	Physical malformation	HP:0011452 (Hypoplasia of the middle ear)	Congenital	Typical
Aberrant facial nerve course	Physical malformation	HP:0010827 (Abnormal facial nerve morphology)	Congenital	Anterior/round-window position in 57/70 atretic ears
Cholesteatoma (stenosis variant)	Complication	HP:0009797 (Cholesteatoma)	Acquired; progressive	1.7% in complete CAA vs 43% in stenosis

Age of onset: congenital (neonatal) for all structural and conductive-loss features. Severity: hearing loss is severe and maximal for a conductive deficit (~60 dB) but, crucially, rehabilitatable because cochlear reserve is normal. Progression: the malformation itself is stable and non-progressive; cholesteatoma (mainly in the stenosis variant) is a progressive acquired complication. Frequency among affected individuals: unilateral ~89%, bilateral ~11%; bilateral disease disproportionately associated with maternal diabetes.

Quality-of-life impact. Bilateral CAA threatens speech and language acquisition and is a developmental emergency for auditory input. Even unilateral CAA carries measurable burden: in congenital unilateral hearing loss, early language input strongly improves language outcomes at age 3 (PMID: 41616317). Bone-conduction rehabilitation yields positive QoL benefit (median Glasgow Children's Benefit Inventory +14.6; 89% improved; PMID: 36649663). The auricular deformity additionally generates appearance-related distress addressed in reconstruction decisions.

4. Genetic / Molecular Information

Causal and candidate genes (Findings F001, F008).

Gene (HGNC)	Locus	Role / disorder	Inheritance	Evidence
HOXA2	7p15.2	Homeobox; PA2 neural-crest patterning; principal validated nonsyndromic microtia/CAA gene	AR (p.Q186K)	PMID: 18394579, PMID: 37277355
TSHZ1	18q22.3	Candidate for isolated CAA; middle-ear development	—	PMID: 39624921
HMX1	4p16.1	Craniofacial homeobox; enhancer (ECR) CNV	AD (enhancer duplication)	PMID: 32552830
TCOF1	5q32–q33.1	Treacher Collins (ribosome biogenesis/treacle)	AD	PMID: 39583227, PMID: 16981466
POLR1C / POLR1D	—	Treacher Collins (RNA Pol I/III)	AR / AD	PMID: 39583227
SF3B2	11q13.2	Craniofacial microsomia; spliceosome	— (truncating: p.Gln60, p.Lys507)	PMID: 42608604
EFTUD2	17q21.31	Mandibulofacial dysostosis with microcephaly; spliceosome	AD (c.698dupA p.V235Gfs*27)	PMID: 41918385
TWIST1	7p21.1	Syndromic craniosynostosis with microtia/aural atresia	AD (c.423C>G p.Asp141Glu)	PMID: 42104108

Variant classification and type. Reported pathogenic variants span missense (HOXA2 p.Q186K; TWIST1 p.Asp141Glu), nonsense/truncating (SF3B2 p.Gln60, p.Lys507), frameshift (EFTUD2 p.V235Gfs27), and structural/CNV (HMX1 enhancer duplications; the 4p15.32–4p16.2 susceptibility locus). A scoping review across 194 subjects in 18 Mendelian manuscripts found 49% autosomal dominant, 4% autosomal recessive, 5% X-linked recessive, and 42% no reported inheritance pattern* (PMID: 39624921). All reported variants are germline; no somatic origin is implicated for this developmental disorder.

Functional consequences. The dominant mechanism is loss of function / haploinsufficiency of transcription factors (HOXA2, TWIST1) and of spliceosome/ribosome-biogenesis components (SF3B2, EFTUD2, TCOF1, POLR1C/D), which impairs the specification, survival, and patterning of cranial neural-crest cells feeding the pharyngeal arches. HMX1 CNVs act via enhancer dosage on a transcription factor; notably, luciferase assays show HOXA2 increases HMX1 enhancer activity, placing these genes in a shared regulatory network (PMID: 32552830).

Modifier genes, epigenetics, chromosomal abnormalities. No specific modifier gene is established for isolated CAA. Epigenetic contributions are plausible given enhancer/CNV involvement (HMX1) but not directly characterized. Large-scale chromosomal lesions appear chiefly in syndromic/contiguous-gene contexts; the 4p15.32–4p16.2 locus is the one reported nonsyndromic susceptibility region.

5. Environmental Information

Environmental/toxicant factors: maternal retinoid exposure (isotretinoin, vitamin-A excess) is a classic ear-teratogen pathway; mycophenolate mofetil in-utero produces a malformation pattern including microtia (PMID: 18368705); maternal occupational cleaning exposure is associated with anotia/microtia (PMID: 41266119); moderate altitude (hypoxia proxy) raises microtia risk (aOR 1.60; PMID: 39056527).
Lifestyle/metabolic factors: maternal diabetes is the strongest modifiable factor (PR 2.0 overall; PR 5.0 bilateral). Smoking and folic-acid status were examined without a confirmed CAA-specific effect (PMID: 40984631).
Infectious agents: Not an established cause of isolated CAA. (TORCH infections classically cause sensorineural, not conductive outer/middle-ear, deafness; TORCH vaccination was examined as a candidate variable but no CAA-specific infectious etiology is confirmed.)

6. Mechanism / Pathophysiology

Causal chain (initiating lesion → clinical manifestation)

A genetic lesion (e.g., HOXA2 LOF, SF3B2/EFTUD2/TCOF1 spliceosome/ribosome-biogenesis haploinsufficiency, TWIST1 LOF) or an environmental insult (maternal hyperglycemia, retinoid excess, hypoxia) perturbs the embryo during pharyngeal-arch morphogenesis (weeks 3–8). → leads to
Impaired specification, survival, migration, or patterning of cranial neural-crest cells populating the first and second pharyngeal arches (demonstrated for Hoxa2 in PA2 neural crest; inferred for the spliceosome/ribosomopathy genes via neural-crest sensitivity). → results in
Dysmorphogenesis of first/second-arch and first-cleft derivatives — the auricle (hillocks of His), the external auditory meatus (from the first pharyngeal cleft/EAM), the tympanic membrane, and the middle-ear cavity/ossicles (malleus, incus from arch 1; part of stapes from arch 2). → branches into
3a. Failure of the first pharyngeal cleft/EAM to canalize → aural atresia/stenosis (no patent ear canal).
3b. Arrested auricular hillock development → microtia.
3c. Hypoplasia/fusion/absence of ossicles and a small, underpneumatized middle-ear cleft; secondary aberrant anterior course of the facial nerve. → together these cause
Interruption of the air-conduction sound path (no canal to deliver sound; no/abnormal ossicular lever to transmit it to the oval window). → produces
Maximal conductive hearing loss (~60 dB air–bone gap) with a preserved cochlea/inner ear (otic-placode lineage unaffected). → if bilateral and untreated, leads to
Auditory deprivation during the critical period for language, threatening speech, language, and psychosocial development — the principal source of morbidity.

Mechanistic detail

Molecular pathways / cellular processes (GO suggestions): cranial neural crest cell development (GO:0014032), pharyngeal system / branchial-arch morphogenesis (GO:0060037), ear morphogenesis (GO:0042471), middle ear morphogenesis (GO:0042474), and inner ear morphogenesis (GO:0042472, spared here). In the spliceosome/ribosomopathy genes, mRNA splicing via spliceosome (GO:0000398) and ribosome biogenesis (GO:0042254) are the upstream defective processes; neural crest is unusually sensitive to their disruption (nucleolar stress → p53-dependent apoptosis, as established for TCOF1/treacle).
Super-enhancer control (demonstrated): In PA2 neural crest, a super-enhancer region (HIRE1/HIRE2) establishes inter-TAD interactions with Hoxa2, which is required for external and middle-ear structures; HIRE2 deletion on a Hoxa2-haploinsufficient background yields microtia, and HIRE1 deletion phenocopies the full Hoxa2 knockout (PMID: 37277355).
Protein dysfunction: loss-of-function/haploinsufficiency of transcription factors and spliceosome/Pol-I components (upstream); mechanical loss of the ossicular lever system (downstream, the proximate cause of the conductive deficit).
Cell types (CL suggestions): cranial neural crest cell (CL:0000333), chondrocytes and osteoblasts of the ossicles and auricular cartilage, epithelial cells of the EAM.
Upstream vs downstream: upstream = gene/enhancer lesion → neural-crest defect; downstream = arch-derivative dysmorphogenesis → interrupted conduction path → conductive hearing loss → developmental sequelae.

Molecular profiling. No human transcriptomic/proteomic/metabolomic signature specific to isolated CAA tissue is established; mechanistic evidence comes from mouse/zebrafish models (below) and human imaging/genetics.

7. Anatomical Structures Affected

Organ level (primary): external auditory canal (UBERON:0001352, external acoustic meatus), auricle/pinna (UBERON:0001757), middle ear (UBERON:0001756) with ossicles — malleus (UBERON:0002355), incus (UBERON:0002356), stapes (UBERON:0001687) — tympanic membrane (UBERON:0002364), mastoid/temporal bone (UBERON:0001678). Facial nerve (UBERON:0001647) is anatomically displaced.
Secondary/system involvement: in syndromic forms, the craniofacial skeleton (mandible, maxilla, zygoma), palate, eyes, vertebrae, heart, and limbs (craniofacial microsomia / Treacher Collins / VACTERL / craniosynostosis spectra).
Tissue/cell level: neural-crest-derived cartilage and bone (ossicles, auricle), EAM epithelium; the sensorineural cochlea is spared.
Subcellular (GO Cellular Component): for the molecular lesions, spliceosomal complex (GO:0005681), nucleolus (GO:0005730, ribosome biogenesis), and nucleus/chromatin (transcription-factor and enhancer function).
Localization / lateralization: predominantly unilateral (~89%) with a right-sided predilection; bilateral in ~11% and over-represented in maternal diabetes. The imaging hallmark is an anteriorly/inferiorly displaced mastoid facial nerve near the round window (57/70 atretic ears; PMID: 23793597).

8. Temporal Development

Onset: congenital; the malformation is fully formed at birth (completed during weeks 3–8 of gestation).
Onset pattern: structural and chronic from birth; hearing loss is present and detectable from the neonatal period (newborn hearing screening).
Progression: the atresia/microtia is stable and non-progressive across life. The notable acquired, progressive complication is cholesteatoma, which is rare in complete CAA (1.7%) but common in congenital EAC stenosis (43%) — a key reason the stenosis variant requires surveillance/earlier surgery (PMID: 35439089).
Disease course / duration: chronic, lifelong.
Critical periods: the decisive window is postnatal auditory development — early auditory input/language stimulation (first years of life) determines language outcomes, independent of the device per se (PMID: 41616317). This makes early amplification an intervention of time-sensitive opportunity rather than structural reversal.

9. Inheritance and Population

Epidemiology. Anotia/microtia (the entity under which CAA is registered) birth prevalence is on the order of ~1–3 per 10,000 births, rising in some registries (China 2007–2021; PMID: 39487910). In the Texas Birth Defects Registry (1999–2014, n=1,322): 74.3% isolated, 88.9% unilateral (PMID: 36398384).

Inheritance (genetic forms). Across 18 Mendelian microtia/CAA manuscripts (194 subjects): 49% AD, 4% AR, 5% X-linked recessive, 42% unspecified (PMID: 39624921). HOXA2 microtia/CAA can be autosomal recessive (p.Q186K, consanguineous family; PMID: 18394579); syndromic genes (TCOF1, EFTUD2, TWIST1) are typically autosomal dominant. Penetrance is incomplete and expressivity highly variable — the Hfm mouse model is explicitly described as autosomal dominant with reduced penetrance (PMID: 11772174), mirroring human variability. Consanguinity contributes to recessive forms (Iranian HOXA2 family). Founder effects, germline mosaicism, genetic anticipation, and defined carrier frequencies are not established for isolated CAA.

Population demographics. - Sex ratio: male-predominant (M:F ≈ 1.3:1 to 3.53:1). - Ethnic/geographic: higher prevalence in Hispanic (PR 2.9) and Andean/high-altitude populations; moderate-altitude residence is an independent risk factor (aOR 1.60). - Laterality distribution: right > left; unilateral ≫ bilateral. - Maternal age: increased with advanced maternal age (≥35).

10. Diagnostics

Clinical tests. - Audiometry / electrophysiology: pure-tone and bone-conduction audiometry confirm a conductive loss with normal cochlear reserve; in infants, ABR/BAER and otoacoustic-emission-based newborn screening flag the deficit. A ~60 dB air–bone gap is characteristic. - Imaging — the cornerstone (Finding F006): high-resolution temporal-bone CT demonstrates: reduced middle-ear sectional area (mean 19.3 mm² vs 47.4 mm² in controls), hypoplastic ossicles (mean ossicular area 8.3 mm² vs 11 mm²), diminished mastoid aeration (PMID: 17178446); ossicular deformity in 25/28 ears (malleus-incus hypoplasia 19, stapes abnormality 11, absent ossicles 3, oval-window atresia 1; PMID: 17580714); and an anteriorly displaced mastoid facial nerve near the round window in 57/70 atretic ears (PMID: 23793597). Körner's septum anatomy is also assessed preoperatively (PMID: 16108317). - CT-based grading: the Jahrsdoerfer 10-point scale and the 16-point aMEI score stratify surgical candidacy and predict outcome (PMID: 23604757). CT/MRI is not always required to exclude cholesteatoma in complete-atresia follow-up (PMID: 31374385).

Genetic testing. Indicated when syndromic features are present or for familial/bilateral/recessive-pattern cases: targeted single-gene testing (HOXA2, TCOF1, SF3B2, EFTUD2, TWIST1), craniofacial gene panels, chromosomal microarray (for CNVs, e.g., HMX1 enhancer region; 4p susceptibility locus), and WES/WGS for undiagnosed syndromic presentations. Isolated unilateral CAA with a normal contralateral ear generally has low diagnostic yield for monogenic testing.

Clinical criteria / differential diagnosis. Diagnosis is clinical + radiologic. Differential includes congenital EAC stenosis (higher cholesteatoma risk), acquired atresia, first branchial cleft anomaly (can co-occur; PMID: 31137094), and distinguishing isolated from syndromic forms (Treacher Collins, Goldenhar/OAV, Nager, Miller, craniofacial microsomia, MFDM).

Screening. Universal newborn hearing screening captures the conductive deficit; cascade/genetic counseling applies to syndromic/familial cases.

11. Outcome / Prognosis

Survival/mortality: CAA is non-fatal; isolated CAA does not reduce life expectancy. Mortality, where present, relates to syndromic comorbidities (airway, cardiac).
Morbidity/function: the dominant morbidity is hearing disability and its developmental consequences. Outcomes hinge on timely auditory input. Bone-conduction rehabilitation significantly improves pure-tone average and speech-in-noise (p<0.001) with positive QoL (GCBI +14.6; PMID: 36649663).
Recovery potential: hearing is rehabilitatable (normal cochlea). Atresiaplasty achieves an air–bone gap of 0–30 dB in ~79–90% of well-selected ears (PMID: 25625335).
Complications: canal restenosis, tympanic-membrane lateralization, recurrent infection, and (rarely in complete CAA) cholesteatoma; facial-nerve injury risk from the aberrant nerve course.
Prognostic factors: Jahrsdoerfer/aMEI CT score is the principal predictor of surgical hearing outcome; microtia grade, hemifacial microsomia, and prior canalplasty predict auricular-reconstruction outcomes (PMID: 29595733); shorter PORP prosthesis length predicts better long-term hearing (PMID: 29664866).

12. Treatment

Management is rehabilitative and reconstructive; there is no disease-modifying pharmacologic, gene, cell, or RNA therapy (Finding F009).

Hearing rehabilitation (prioritized in infancy). - Bone-conduction devices (NCIT: Bone-Conduction Hearing Device): softband BCD in infancy, then osseointegrated (percutaneous BAHA) or transcutaneous (Baha Attract, Sophono) implants. Most common initial treatment (75.6% of patients receive a nonsurgical BCHD; earlier fitting improves compliance; PMID: 33338703). Transcutaneous osseointegrated implants improve PTA (63.7→9.6 dB) and speech-in-noise in children (PMID: 29978214). - Atresiaplasty / canaloplasty (NCIT: surgical reconstruction of ear canal): for Jahrsdoerfer-selected candidates (score ≥6–7), achieving ABG ≤30 dB in ~79–90% (PMID: 25625335); often combined with ossicular reconstruction (PORP; PMID: 29664866) and tragal/flap techniques (PMID: 19172604, PMID: 27011544). - Active middle-ear implants for selected malformed ears (aMEI score; PMID: 23604757).

Auricular (microtia) reconstruction. - Autologous costal-cartilage frameworks — Nagata two-stage and Brent techniques — or porous polyethylene (MEDPOR) implants, typically begun around school age (~6–10 yr) (PMID: 29595733, PMID: 40644931). Hemifacial microsomia and prior canalplasty predict unfavorable auricular projection (22.3% unfavorable; PMID: 29595733). - Adjuncts: ear molding in the neonatal period for milder auricular deformities (RCT; PMID: 32791720); laser hair removal of low hairlines after reconstruction (PMID: 40644931).

Treatment strategy / sequencing. Auditory rehabilitation first (infancy), then coordinated planning of auricular reconstruction and any canalplasty — the two must be sequenced because canalplasty and hemifacial microsomia affect reconstruction outcomes. No combination pharmacotherapy or personalized-medicine (genotype-guided) regimen exists.

13. Prevention

Primary prevention: limited but real — maternal glycemic control (given diabetes PR 2.0 overall, 5.0 bilateral), avoidance of teratogens (retinoids, mycophenolate), and counseling regarding modifiable exposures.
Secondary prevention: universal newborn hearing screening for early detection and timely amplification during the language-critical window.
Tertiary prevention: surveillance for cholesteatoma (especially in the stenosis variant), prevention of restenosis/infection after surgery, and ongoing audiologic/developmental support.
Genetic counseling: indicated for syndromic and familial/recessive forms; prenatal diagnosis is feasible for known syndromic variants (e.g., EFTUD2; PMID: 41918385) and Treacher Collins (PMID: 16981466).
Immunization / prophylaxis / public-health vector measures: not applicable (non-infectious).

14. Other Species / Natural Disease

Taxonomy / orthologs: the causal genes are deeply conserved — Hoxa2 (mouse, NCBI Taxon 10090), sf3b2 (zebrafish, Danio rerio, Taxon 7955), Tcof1/Treacle, Twist1, Hmx1. Human–mouse–zebrafish conservation of the branchial-arch/neural-crest program underlies the use of these models.
Natural disease in animals: HMX1 enhancer CNVs cause ear (and eye) malformations in other animals naturally, and were described in animals before humans (PMID: 32552830) — a comparative-biology link. Formal OMIA cataloguing of naturally occurring aural atresia in companion animals was not specifically retrieved in this investigation.
Evolutionary conservation of mechanism: the first/second-arch contribution to the middle and external ear and tympanic membrane is conserved across amniotes (mouse and chick comparison; PMID: 28807901).
Zoonotic potential: not applicable.

15. Model Organisms

Model	Type	Genetic manipulation	Phenotype recapitulation	Source
Mouse — Hoxa2 / HIRE enhancer	Mammalian, in vivo	Enhancer deletion (HIRE1/HIRE2), haploinsufficiency	HIRE2 deletion on Hoxa2-haploinsufficient background → microtia; HIRE1 deletion phenocopies full Hoxa2 KO; external/middle-ear defects	PMID: 37277355
Mouse — Hfm transgenic	Mammalian, in vivo	Transgenic (AD, reduced penetrance)	Microtia + external auditory meatus, middle-ear, cranial-base, maxilla, pharyngeal anomalies — models hemifacial microsomia/microtia-atresia spectrum	PMID: 11772174
Mouse / chick — pharyngeal arch	Mammalian / avian	Developmental/lineage analysis	First arch crucial for tympanic-membrane formation; distinct PA1/PA2 contributions	PMID: 28807901
Zebrafish — sf3b2 knockout	Vertebrate, in vivo	CRISPR/Cas9 KO	25.33% malformation rate, shortened Meckel's/palatoquadrate cartilage, reduced head-to-body ratio — recapitulates human craniofacial microsomia features	PMID: 42608604

Applications: these models dissect neural-crest patterning (Hoxa2), enhancer-level gene regulation (HIRE), spliceosome sensitivity of neural crest (sf3b2), and the developmental origin of tympanic-membrane/middle-ear structures. Limitations: rodent ear anatomy differs from human; models capture microtia/arch dysmorphology better than the human-specific external auditory canal atresia and the clinically pivotal aberrant facial-nerve course; no model fully reproduces the human conductive-hearing-loss rehabilitation problem.

Mechanistic Model / Interpretation

   GENETIC LESION                         ENVIRONMENTAL INSULT
   HOXA2, TSHZ1, HMX1,                    maternal diabetes,
   TCOF1/POLR1C/D, SF3B2,                 retinoids, hypoxia/altitude,
   EFTUD2, TWIST1 (LOF/                   mycophenolate
   haploinsufficiency/CNV)                      |
|                                        |
v                                        v
   +----------------------------------------------------------+
   |  Perturbed CRANIAL NEURAL-CREST CELL program             |
   |  (specification / survival / patterning) in              |
   |  PHARYNGEAL ARCHES 1 & 2  (weeks 3-8)                     |
   |  [spliceosome/ribosome-biogenesis genes act here via     |
   |   nucleolar/splicing stress; TFs via patterning]         |
   +----------------------------------------------------------+
|
v
   Dysmorphogenesis of 1st/2nd-arch & 1st-cleft derivatives
|                 |                     |
v                 v                     v
  EAM fails to      Auricular hillock     Ossicle hypoplasia/
  canalize          arrest                fusion/absence +
  = AURAL ATRESIA   = MICROTIA            small middle ear +
                          anterior facial nerve
\_________________|_____________________/
          v
Interrupted AIR-CONDUCTION sound path
(cochlea / inner ear SPARED)
          v
MAXIMAL CONDUCTIVE HEARING LOSS (~60 dB)
          v
   (if bilateral & untreated) AUDITORY DEPRIVATION in the
   language-critical window -> speech/language/psychosocial morbidity
          v
Rehabilitation: bone-conduction input + atresiaplasty
+ auricular reconstruction  (NOT structural cure)

The unifying interpretation is that CAA is a neurocristopathy of the pharyngeal arches: diverse upstream lesions (transcription-factor LOF, spliceosome/ribosome-biogenesis haploinsufficiency, enhancer CNVs, or teratogenic metabolic/retinoid stress) converge on the same vulnerable cranial-neural-crest population, yielding the same downstream anatomical triad (atresia + microtia + ossicular/middle-ear hypoplasia) and the same functional endpoint (conductive hearing loss with a normal cochlea). This convergence explains both the phenotypic overlap among Treacher Collins, Goldenhar/OAV, Nager, Miller, and craniofacial-microsomia spectra and the genetic heterogeneity (TCOF1 excluded in Goldenhar and in familial microtia-meatal atresia; PMID: 15770127). It also frames why treatment is rehabilitative: the lesion is a completed developmental event by birth, so therapy targets the functional consequence (restoring auditory input) rather than the cause. A notable clinical gradient supports the model — in the oculo-auriculo-vertebral spectrum, EAC atresia, ossicular anomaly, and aberrant facial-nerve frequency all rise with craniofacial severity (EAC 48.4%→82.8%; ossicles 40.3%→82.8%; PMID: 41289623), indicating a dose-like relationship between the severity of arch disruption and the ear phenotype.

Evidence Base

PMID	Contribution	Supports / Challenges
39624921	Scoping review: 40 genes + 4p15.32–4p16.2 locus; HOXA2/MUC6/GSC top; TSHZ1 for isolated CAA; inheritance breakdown	Supports genetic landscape (F001)
18394579	HOXA2 p.Q186K AR microtia/CAA, LOD 4.17	Supports HOXA2 causality (F001)
32552830	HMX1 enhancer duplications → concha-type microtia; HOXA2 boosts HMX1 enhancer	Supports regulatory network (F001)
36398384	Texas registry: isolated 74.3%, unilateral 88.9%, male/diabetes/Hispanic risk	Supports epidemiology (F002)
37649433	Maternal diabetes OR 3.71 for hearing loss in VACTERL	Supports diabetes risk (F002)
36649663	Transcutaneous BCI: PTA/speech improve p<0.001; GCBI +14.6	Supports treatment/QoL (F003)
25625335	Atresiaplasty ABG 0–30 dB in 79–90%; complications	Supports surgical outcomes (F003)
33338703	75.6% receive nonsurgical BCHD; earlier fitting → compliance	Supports treatment pathway (F003)
39583227	Treacher Collins (TCOF1) → atresia + middle-ear hypoplasia via arch 1&2	Supports branchial-arch mechanism (F004)
15770127	Phenotypic overlap of 1st/2nd-arch disorders; TCOF1 excluded in Goldenhar/familial microtia	Supports shared origin + heterogeneity (F004)
37277355	HIRE super-enhancer controls Hoxa2 in PA2 crest; deletions → microtia	Supports mechanism + mouse model (F005)
11772174	Hfm mouse recapitulates microtia + EAM/middle-ear anomalies	Supports model organism (F005)
17178446	CT: middle-ear 19.3 vs 47.4 mm²; ossicles hypoplastic	Supports diagnostics (F006)
23793597	Aberrant facial-nerve position in 57/70 atretic ears	Supports diagnostics/surgery (F006)
35439089	Cholesteatoma 1.7% CAA vs 43% stenosis	Supports prognosis/complications (F006)
41616317	RCT: early language input (not device alone) drives outcomes	Supports prognosis/critical period (F007)
39487910	Rising microtia/anotia prevalence; maternal age	Supports epidemiology (F007)
42608604	SF3B2 truncating variants + zebrafish KO recapitulate CFM	Supports syndromic genes/model (F008)
41289623	OAV: atresia/ossicular/facial-nerve anomalies scale with severity	Supports syndromic spectrum (F008)
29595733	Nagata reconstruction; canalplasty/HFM predict unfavorable projection	Supports reconstruction (F009)

Limitations and Knowledge Gaps

No disease-specific molecular profiling in humans. There is no transcriptomic, proteomic, metabolomic, or epigenomic signature of isolated human CAA tissue; mechanism is inferred from model organisms and genetics.
Large unexplained genetic fraction. 42% of Mendelian cases lack a reported inheritance pattern and most isolated unilateral CAA has no identified monogenic cause — the "missing heritability" and the role of the 4p susceptibility locus are unresolved.
GxE interactions are inferred, not demonstrated. The convergence of maternal diabetes/retinoid signaling onto the neural-crest program is biologically plausible but not mechanistically proven in humans.
Penetrance/expressivity are poorly quantified for isolated CAA; carrier frequencies and founder effects are undefined.
TSHZ1 is a candidate (single-article) gene for isolated CAA and needs replication and functional validation.
Model gap: no animal model fully reproduces the human EAC atresia + aberrant facial nerve + conductive rehabilitation problem.
Outcome data heterogeneity: surgical hearing and reconstruction outcomes come largely from single-surgeon retrospective series; standardized, long-term, multi-center QoL and developmental outcome data are limited.

Proposed Follow-up Experiments / Actions

Functional validation of TSHZ1 and the 4p15.32–4p16.2 locus in isolated CAA via targeted sequencing/CNV analysis in large microtia-atresia cohorts, plus zebrafish/mouse perturbation.
GxE mechanistic study: model maternal hyperglycemia and retinoid exposure in neural-crest/arch explants or organoids carrying HOXA2/SF3B2 hypomorphic backgrounds to test convergence on crest survival/patterning.
Single-cell transcriptomics of developing pharyngeal arches (human embryonic references + models) to map the crest subpopulations most sensitive to spliceosome/ribosome-biogenesis haploinsufficiency.
Prospective multi-center natural-history and developmental-outcome registry linking laterality, Jahrsdoerfer/aMEI grade, device timing, and standardized language/QoL measures (EQ-5D/PROMIS, GCBI) to refine prognostic models.
Comparative-biology search (OMIA/VetCompass) for naturally occurring aural atresia/microtia in companion animals to leverage HMX1/Hoxa2 conservation.
Trial of standardized early-amplification protocols (softband BCD timing) powered on language outcomes, building on the RCT evidence that early input — not the device per se — drives development.
Explore enhancer/epigenetic contributions (HMX1-type CNVs, HIRE-analogous regulatory elements) by CMA + regulatory-region sequencing in CNV-negative, exome-negative patients.

Evidence source types represented: human clinical (registries, cohorts, imaging, surgical series, RCTs), model organism (mouse, zebrafish, chick), and in-vitro/functional (luciferase enhancer assays, CRISPR knockout). PMIDs are provided for all mechanistic and clinical claims.

Artifacts

Reference Validation

Checked with linkml-reference-validator 0.3.0rc3.

Outcome	Count
References checked	39
Resolved	39
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	39
On topic	7
Off topic	1

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

PMID:40644931 (5 mentions) - Alexandrite laser hair removal for pediatric microtia patients undergoing autologous rib cartilage auricular reconstruction: A retrospective analysis.
shared terms: microtia

Weighed against this report's own most characteristic terms: microtia, caa, atresia, hearing, genetic, gene, maternal, middle-ear, hoxa2, ear, isolated, syndromic, loss, developmental, auditory, neural-crest, model, enhancer, conductive, diabete.

All extracted references resolved successfully. Resolving is not the same as being relevant, though - see the references listed above as possibly off topic.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome	Count
Terms checked	27
Resolved	27
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	0
Terms whose name was checked	15
Terms named correctly	10
Terms named as a different term	0
Terms whose name is worth a second look	5

Terms whose name is worth a second look

The report's name for these is recognisably related to the term's own name without being one of them. A loose paraphrase reads the same way as a citation of the wrong sibling term - and so does a related synonym, which the ontology records precisely because it names something adjacent rather than the same thing - so these are listed rather than judged:

HP:0011453 (1 mention) - the report calls it "Abnormality of the middle ear ossicles"; HP calls it Abnormal incus morphology, and lists "Abnormality of the incus" among its other names
HP:0011452 (1 mention) - the report calls it "Hypoplasia of the middle ear"; HP calls it Functional abnormality of the middle ear
HP:0010827 (1 mention) - the report calls it "Abnormal facial nerve morphology"; HP calls it Abnormal seventh cranial physiology, and lists "Abnormality of the facial nerve" among its other names
GO:0060037 (1 mention) - the report calls it "pharyngeal system / branchial-arch morphogenesis"; GO calls it pharyngeal system development
CL:0000333 (1 mention) - the report calls it "neural crest cell"; CL calls it migratory neural crest cell

Every term resolved, and every label the report gave matched.

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Inheritance

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Congenital Aural Atresia (MONDO:0011921): A Comprehensive Disease Characteristics Report

Summary

1. Disease Information

2. Etiology

Risk factors

3. Phenotypes

4. Genetic / Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Causal chain (initiating lesion → clinical manifestation)

Mechanistic detail

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome / Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Mechanistic Model / Interpretation

Evidence Base

Limitations and Knowledge Gaps

Proposed Follow-up Experiments / Actions

Artifacts

Reference Validation

References that may not be about this subject

Term Validation

Terms whose name is worth a second look