Hereditary Congenital Facial Paresis 3

Mendelian MONDO:0013880 Pathograph 15 Show in embeddings browser Congenital cranial dysinnervation disorder

Hereditary congenital facial paresis type 3 (HCFP3) is an autosomal recessive congenital cranial dysinnervation disorder caused by biallelic variants in HOXB1. It presents at birth with non-progressive bilateral facial weakness, usually with sensorineural hearing loss, and frequently with external ear malformation and mild esodeviation. The lesion is developmental rather than degenerative, and it is anchored to a single hindbrain segment. HOXB1 is expressed throughout rhombomere 4, where it maintains segmental identity; r4 is the source of the facial branchiomotor neurons that innervate the muscles of facial expression, of the r4-derived neural crest that generates the glia myelinating the VIIth nerve, and of the geniculate and vestibulocochlear ganglia. One transcription-factor lesion in one segment therefore accounts for the facial and auditory findings together, and explains why the deficit is fixed from birth, because the affected structures are mis-specified during embryogenesis rather than lost afterwards. The external-ear malformation is deliberately excluded from that account: it is a consistent clinical accompaniment, but no source cited here traces it to the r4 lineage, and the pathograph does not connect it. Every HOXB1 missense variant reported to date substitutes an arginine in the homeodomain, and the recurrent Arg207 (homeodomain Arg5) residue contacts DNA in the minor groove within the HOXB1:PBX1:DNA ternary complex. A nonsense allele produces the same disease, which is what establishes the mechanism as loss of function rather than a dominant-negative or neomorphic effect. SCOPE. This entry covers HCFP3 only. HCFP1 (3q21-q22) and HCFP2 (10q21.3-q22.1) are autosomal dominant, have no identified gene, and are not curated here. Moebius syndrome shares the facial palsy but adds limited ocular abduction and is a separate entity.

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1
Inheritance
6
Pathophys.
6
Phenotypes
3
Gaps
15
Pathograph
1
Genes
2
Variants
2
Medical Actions
2
Differentials
2
Models
10
References
1
Deep Research
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Inheritance

1
Autosomal recessive inheritance HP:0000007
HCFP3 requires biallelic HOXB1 variants. Reported genotypes include homozygous missense, homozygous nonsense, and compound heterozygous missense alleles; heterozygous carriers in the reported families are unaffected.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:27144914 SUPPORT Human Clinical
"The homozygous nonsense variant c.66C>G/p.(Tyr22*) in HOXB1 was identified in the four patients with HCFP and ear malformations, while healthy family members carried the mutation in the heterozygous state."
Affected individuals are homozygous and heterozygous relatives are healthy, which is the recessive segregation pattern.
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Discussions and Knowledge Gaps

3
By what route does an r4 transcription-factor lesion produce external-ear malformation and hypernasal speech, if it produces them at all?
KNOWLEDGE GAP hcfp3_unconnected_ear_and_speech_findings
Attached to
phenotypes#Abnormal Pinna Morphology phenotypes#Hypernasal Speech
Both findings are well attested clinically. Ear malformation was present in all four affected members of the consanguineous family and is described as a common accompaniment across the series; nasal voice was recorded on examination. Neither is connected in the pathograph, and that is deliberate rather than an omission. For the ear, the r4-derived neural crest does populate the second pharyngeal arch, which is the usual embryological argument, but no source cited in this entry makes that link for HCFP3, so drawing the edge would be reasoning from developmental biology rather than from the evidence to hand. For the speech finding, hypernasality is ordinarily velopharyngeal, and the soft palate is not an r4 derivative, so the obvious edge from facial weakness is probably the wrong one. Both are recorded here as open rather than resolved by a plausible-looking arrow.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"individuals with HCFP3 commonly exhibit ear malformations and some degree of esodeviation"
Establishes that the ear finding is a consistent part of the phenotype, which is what makes its absence from the causal chain a gap worth recording rather than a phenotype to drop.
Why does esodeviation occur in HCFP3 when HOXB1 acts in rhombomere 4 and the ocular motor nuclei do not derive from it?
KNOWLEDGE GAP hcfp3_esodeviation_outside_r4
Attached to
phenotypes#Esotropia
Esodeviation is reported in 44% of published cases, which is too frequent to dismiss, yet the r4 lineage does not supply the abducens or oculomotor nuclei. Either mutant HOXB1 isoforms act outside r4, or the deviation is a secondary consequence of the facial and orbital phenotype. The published suggestion is the former, and it is explicitly speculative.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"This prompts speculation that certain mutant isoforms of HOXB1 may influence other cranial nerves."
The authors themselves frame this as speculation, which is the gap this entry records.
Is proximal neck and shoulder-girdle weakness part of the HCFP3 phenotype?
KNOWLEDGE GAP hcfp3_neck_shoulder_weakness
Attached to
phenotypes#Congenital Bilateral Facial Palsy
A single molecularly confirmed patient had objectively measured neck flexor and extensor weakness with sternocleidomastoid and trapezius hypotrophy on MRI, and no alternative cause was found after excluding FSHD, myotonic dystrophy type 2 and myasthenia. The finding is not curated as a phenotype of the disease here because it rests on one patient and the authors themselves ask for more data.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"We speculate that neck weakness might be a component of HCFP3, yet we acknowledge that additional data are needed to provide concrete evidence of this novel clinical association."
States the uncertainty directly, which is why this is a gap rather than a curated phenotype.
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Pathophysiology

6
HOXB1 Loss of Function
Biallelic HOXB1 variants abolish or degrade the transcriptional activity of the HOXB1 homeodomain. Reported missense alleles all replace an arginine in the homeodomain, and the recurrent Arg207 corresponds to homeodomain Arg5, which contacts thymine in the DNA minor groove within the HOXB1:PBX1:DNA ternary complex. A homozygous nonsense allele produces the same disease, which is what identifies the mechanism as loss of function.
HOXB1 hgnc:5111 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves HOXB1 (hgnc:5111), qualified as loss of function. hgnc:5111 is a gene from the HUGO Gene Nomenclature Committee. ⇓ LOSS OF FUNCTION
DNA-binding transcription factor activity GO:0003700 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased DNA-binding transcription factor activity (GO:0003700). GO:0003700 is a molecular function from the Gene Ontology. ↓ DECREASED
Downstream
Failure to Maintain Rhombomere 4 Identity HOXB1 is the segment-identity gene of rhombomere 4, so its loss removes the transcriptional program that maintains r4 identity.
Show evidence (2 references)
PMID:22770981 SUPPORT In Vitro
"Molecular modeling and an in vitro DNA-protein binding assay predict that the mutation would disrupt these interactions, destabilize the HOXB1:PBX1:DNA complex, and alter HOXB1 transcriptional activity."
The DNA-protein binding assay that places the defect at DNA binding within the HOXB1-PBX1 complex. Graded IN_VITRO for the assay. The sentence also reports molecular modeling, and the computational half is not curated as a separate item because the two are inseparable within this one sentence and the assay is the load-bearing part.
PMID:27144914 SUPPORT Human Clinical
"This is the first disease-associated HOXB1 mutation with a likely loss-of-function effect suggesting that all HOXB1 variants reported so far also have severe impact on activity of this transcriptional regulator."
A nonsense allele causing the same phenotype is the argument that the missense alleles also act by loss of function.
Failure to Maintain Rhombomere 4 Identity
Rhombomere 4 patterning is initiated normally but is not maintained without HOXB1. The segment is therefore specified and then loses its identity, which is why the downstream deficits are of specification and migration rather than of initial hindbrain segmentation. The reason initiation and maintenance come apart is that they are driven by different things. Initiation is extrinsic: a retinoic acid gradient made by Raldh2 in paraxial mesoderm, bounded by the RA-degrading Cyp26 enzymes, restricts Hoxb1 expression to presumptive r4. Maintenance is autoregulatory: HOXB1 sustains its own r4 expression through the b1 autoregulatory element, which is activated by HOXB1 and PBX1 binding together. That loop is exactly what the recurrent homeodomain Arg207 substitution destabilizes, which is how a DNA-contact mutation produces a maintenance failure rather than a failure to specify the segment at all.
rhombomere development GO:0021546 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal rhombomere development (GO:0021546). GO:0021546 is a biological process from the Gene Ontology. ⚠ ABNORMAL anterior/posterior pattern specification GO:0009952 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal anterior/posterior pattern specification (GO:0009952). GO:0009952 is a biological process from the Gene Ontology. ⚠ ABNORMAL
rhombomere 4 UBERON:0005511 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in rhombomere 4 (UBERON:0005511). UBERON:0005511 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Mis-specification and Failed Migration of Facial Branchiomotor Neurons
Loss of r4-Derived Neural Crest Support of the VIIth Nerve
Impaired Development of r4-Derived Cranial Ganglia
Show evidence (3 references)
PMID:8967950 SUPPORT Model Organism
"In mutant mouse embryos, molecular markers indicate that patterning of r4 is initiated properly but not maintained."
Distinguishes a maintenance failure from a failure to establish the segment.
PMID:11278854 SUPPORT Model Organism
"We previously showed that HOXB1 and PBX1 activate transcription from the b1-ARE by binding to sequences required for the expression of a reporter gene in rhombomere 4 in vivo."
Identifies the HOXB1-PBX1 autoregulatory loop that maintains r4 expression, which is the machinery the Arg207 homeodomain substitution disrupts.
PMID:15872003 SUPPORT INDIRECT Model Organism
"Retinoic acid (RA) generated by Raldh2 in paraxial mesoderm is required for specification of the posterior hindbrain, including restriction of Hoxb1 expression to presumptive rhombomere 4 (r4)."
Establishes that r4 Hoxb1 expression is initiated extrinsically by retinoic acid, which is why an intrinsic HOXB1 lesion spares initiation. It is indirect because it describes normal patterning rather than the disease state.
Mis-specification and Failed Migration of Facial Branchiomotor Neurons
Facial branchiomotor neurons are born in r4 and normally migrate caudally into r5. Without HOXB1 they differentiate but do not migrate correctly, forming an atypically migrating nucleus, and the facial motor nerve is subsequently lost.
facial branchiomotor neuron CL:0005023 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves facial branchiomotor neuron, annotated with branchiomotor neuron (CL:0005023). CL:0005023 is a cell type from the Cell Ontology.
neuron migration GO:0001764 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal neuron migration (GO:0001764). GO:0001764 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Animal models
Hoxb1-null mouse Mouse recapitulates DiI lineage tracing in the null embryo shows the r4-derived facial branchiomotor and contralateral vestibuloacoustic neurons differentiating but failing to migrate, which is the mechanism this node asserts.
Downstream
Facial Motor Nerve Deficiency
Show evidence (1 reference)
PMID:8967950 SUPPORT Model Organism
"In mutants, motor neurons differentiate but the CVA and FBM neurons fail to migrate into their proper positions."
The neurons are made and then fail to reach their target position, so the defect is one of migration rather than neurogenesis.
Loss of r4-Derived Neural Crest Support of the VIIth Nerve
A separate, non-neuronal arm of the same lesion. Rhombomere-4-derived neural crest generates the glia that myelinate the VIIth cranial nerve. In conditional mouse mutants glial progenitor specification is preserved, so the requirement is for a later glial function in maintaining the nerve rather than for producing the glia at all.
r4-derived neural crest cell CL:0011012 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves r4-derived neural crest cell, annotated with neural crest cell (CL:0011012). CL:0011012 is a cell type from the Cell Ontology.
neural crest cell migration GO:0001755 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal neural crest cell migration (GO:0001755). GO:0001755 is a biological process from the Gene Ontology. ⚠ ABNORMAL
Animal models
Neural-crest-conditional Hoxb1 mouse Mouse recapitulates Tissue-restricted deletion shows the VIIth nerve circuitry requires HOXB1 in r4-derived crest independently of its requirement in the motor neurons.
Downstream
Facial Motor Nerve Deficiency
Show evidence (2 references)
PMID:15198977 SUPPORT Model Organism
"Genetic lineage analysis revealed that a significant population of r4-derived neural crest is fated to generate glia that myelinate the VIIth cranial nerve."
Establishes the r4 neural crest as the source of the myelinating glia of the facial nerve.
PMID:15198977 SUPPORT Model Organism
"Neural crest cultures show that the absence of Hoxb1 function does not appear to affect overall glial progenitor specification, suggesting that a later glial function is critical for maintenance of the VIIth nerve."
Narrows the glial defect to maintenance rather than progenitor specification.
Facial Motor Nerve Deficiency
The converged consequence of the motor-neuron and neural-crest arms, namely a facial nerve that is congenitally deficient. In patients this is seen as complete bilateral absence of the blink reflex, localizing the lesion to the facial nerve nucleus, and in some individuals as facial nerve axonal neuropathy on electrophysiology with structurally normal nerves on imaging.
facial nerve morphogenesis GO:0021610 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves abnormal facial nerve morphogenesis (GO:0021610). GO:0021610 is a biological process from the Gene Ontology. ⚠ ABNORMAL
facial nerve UBERON:0001647 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in facial nerve (UBERON:0001647). UBERON:0001647 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Congenital Bilateral Facial Palsy
Feeding Difficulties
Show evidence (2 references)
PMID:38203298 SUPPORT Human Clinical
"the blink reflex assessment revealed a bilateral absence of all components, aligning entirely with the characteristics indicative of an impairment in the facial cranial nerve nuclei"
Human electrophysiology localizing the deficit to the facial nerve nuclei, which is the patient-level counterpart of the mouse facial branchiomotor finding.
PMID:39235314 SUPPORT Human Clinical
"a child with facial nerve axonal neuropathy without evidence of nerve hypoplasia on neuroimaging"
Shows the deficit can be functional and axonal with no imaging correlate, which matters for how the diagnosis is reached.
Impaired Development of r4-Derived Cranial Ganglia
Rhombomere 4 is the precursor of the geniculate ganglion and of the spiral and vestibular ganglia, which is the developmental route from the same segmental lesion to the sensorineural hearing loss and the ear malformations seen in most patients. The mechanism connecting the r4 lesion to the human auditory phenotype has not been demonstrated directly, so this node records a lineage relationship rather than an experimentally traced chain.
geniculate ganglion UBERON:0001700 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in geniculate ganglion (UBERON:0001700). UBERON:0001700 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Sensorineural Hearing Impairment
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"It is expressed in the embryonic spinal cord and hindbrain, playing a crucial role in the development of rhombomere 4, which is a precursor of the geniculate ganglion and the spiral and vestibular ganglion"
Establishes the lineage relationship this node asserts.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Hereditary Congenital Facial Paresis 3 Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

6
Digestive 1
Feeding Difficulties FREQUENT HP:0011968 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Feeding difficulties (HP:0011968). HP:0011968 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"In infancy, she encountered challenges related to sucking and feeding."
Documents infantile feeding difficulty in a molecularly confirmed patient.
Ear 2
Sensorineural Hearing Impairment FREQUENT HP:0000407 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Sensorineural hearing impairment (HP:0000407). HP:0000407 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:38203298 SUPPORT Human Clinical
"manifesting at birth with facial muscle weakness and typically accompanied by hearing loss"
Hearing loss is reported as a typical accompaniment of the facial weakness in HCFP3.
PMID:38203298 SUPPORT Human Clinical
"Audiometric assessments demonstrated a second-degree sensorineural hearing loss on both sides."
Audiometric confirmation that the loss is sensorineural and bilateral in a molecularly confirmed patient.
Abnormal Pinna Morphology FREQUENT HP:0000377 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Ear malformation, annotated with Abnormal pinna morphology (HP:0000377). HP:0000377 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
PMID:27144914 SUPPORT Human Clinical
"the four patients with HCFP and ear malformations"
Ear malformation co-segregated with HCFP in all four affected members of this family.
PMID:38203298 SUPPORT Human Clinical
"individuals with HCFP3 commonly exhibit ear malformations and some degree of esodeviation"
States that ear malformation is a common feature across the reported series.
Eye 1
Esotropia FREQUENT HP:0000565 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Esotropia (HP:0000565). HP:0000565 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"the occurrence of eye esodeviation, observed in 44% of cases"
Gives the reported frequency of esodeviation across published HCFP3 cases.
Head and Neck 1
Congenital Bilateral Facial Palsy VERY_FREQUENT HP:0010628 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Bilateral facial palsy, annotated with Facial palsy (HP:0010628), qualified as course stable. HP:0010628 is a phenotype from the Human Phenotype Ontology.
Course: STABLE
Show evidence (2 references)
PMID:22770981 SUPPORT Human Clinical
"The resulting phenotype includes bilateral facial palsy, hearing loss, and strabismus and correlates extensively with the previously reported Hoxb1(-/-) mouse phenotype."
Bilateral facial palsy is the defining feature in the original HCFP3 families.
PMID:38203298 SUPPORT Human Clinical
"revealed a loss of facial expression due to facial muscles' paralysis, facial muscle atrophy, lagophthalmos, hypoplasia of the nasal alae, upturned nasal tip, smooth philtrum, downturned corners of the mouth, and prominent nasal voice"
Describes the mature clinical picture, including the lagophthalmos and orofacial features that accompany the palsy.
Voice 1
Hypernasal Speech HP:0001611 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Nasal voice, annotated with Hypernasal speech (HP:0001611). HP:0001611 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"downturned corners of the mouth, and prominent nasal voice"
Nasal voice recorded on examination of a molecularly confirmed patient.
🧬

Genetic Associations

1
HOXB1 (HOXB1 encodes a homeodomain transcription factor expressed throughout rhombomere 4, and is the only gene identified for any HCFP subtype. Biallelic variants cause HCFP3.)
Gene: HOXB1 hgnc:5111 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is HOXB1 (hgnc:5111). hgnc:5111 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Show evidence (1 reference)
PMID:27144914 SUPPORT Human Clinical
"The only known causative gene for HCFP is HOXB1 (17q21; HCFP3), encoding a homeodomain-containing transcription factor of the HOX gene family, which are master regulators of early developmental processes."
Names HOXB1 as the causative gene for the HCFP3 locus.
Variants (2)
HOXB1 p.Arg207Cys founder allele Pathogenic
Homozygous missense substitution of the highly conserved homeodomain Arg5 residue, found as a founder allele in two conservative German American families.
Show evidence (1 reference)
PMID:22770981 SUPPORT Human Clinical
"We have identified a founder homozygous missense mutation in HOXB1 in two families from a conservative German American population."
Establishes the founder homozygous missense allele in the original HCFP3 families.
HOXB1 c.66C>G p.(Tyr22*) Pathogenic
Homozygous nonsense allele in a large consanguineous Moroccan family, the first HOXB1 allele with a likely loss-of-function effect.
Show evidence (1 reference)
PMID:27144914 SUPPORT Human Clinical
"We performed whole exome sequencing in HCFP-affected individuals of a large consanguineous Moroccan family."
Identifies the family and the sequencing approach that found the nonsense allele.
💊

Medical Actions

2
Symptomatic and Supportive Management
Action: Supportive CareNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Supportive Care (NCIT:C15747). NCIT:C15747 is a clinical intervention from the NCI Thesaurus. NCIT:C15747
Platform: Behavioral / lifestyle
No disease-modifying therapy exists. Management is symptomatic and preventive, and the counselling value of the molecular diagnosis is substantial because the deficit is congenital and non-progressive.
Mechanism Target:
Congenital Bilateral Facial Palsy — Supportive care addresses the consequences of the facial weakness; it does not act on the developmental lesion.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"The management of this condition primarily involves a symptomatic and preventive approach, as no specific pathogenetic therapy has been developed thus far."
States plainly that management is symptomatic and that no targeted therapy exists.
Genetic Counseling
Action: Genetic CounselingNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Genetic Counseling (NCIT:C15240). NCIT:C15240 is a clinical intervention from the NCI Thesaurus. NCIT:C15240
Platform: Behavioral / lifestyle
Autosomal recessive recurrence counselling, and reassurance about the non-progressive natural history. In the reported adult case the molecular diagnosis ended years of misdiagnosis as facioscapulohumeral muscular dystrophy and resolved the patient's pregnancy-planning concerns.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"Moreover, the patient faces no contraindications for childbirth, and there is a low risk of transmitting the condition to offspring."
The specific counselling content that follows from recessive inheritance.
🔬

Diagnosis

2
Exome sequencing for biallelic HOXB1 variants
Molecular confirmation is by exome or targeted sequencing showing biallelic HOXB1 variants. Phase matters, because the first compound heterozygous case required read-level analysis to show the two variants were in trans, and paternity testing to establish that one had arisen de novo.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"an analysis of the sequence reads demonstrated that both variants were in trans"
Shows the phasing step required to call biallelic status for nearby variants.
📈

Progression

1
Congenital and non-progressive
The deficit is present at birth and does not progress. Because the lesion is one of embryonic specification, no new deficits are expected to emerge.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"Given that HCFP3 is a congenital disorder associated with cranial nerves, we anticipate no progression of the muscle weakness or the emergence of new symptoms."
Explicit statement of the non-progressive natural history.
🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Hereditary Congenital Facial Paresis 3:

Moebius syndrome
Overlapping Features Shares congenital facial palsy but adds limited ocular abduction from sixth nerve involvement. Screening a large cohort of patients diagnosed with Moebius syndrome or HCFP found a HOXB1 variant only in an HCFP case, not in the Moebius cases.
Show evidence (2 references)
PMID:27144914 SUPPORT Human Clinical
"Möbius syndrome shares facial palsy with HCFP, but is additionally characterized by limited abduction of the eye(s)."
The discriminating clinical sign between the two entities.
PMID:26007620 SUPPORT Human Clinical
"We screened 95 sporadic patients diagnosed as MBS or HCFP for mutations in HOXB1. A novel homozygous alteration was identified in one HCFP case"
A cohort screen in which HOXB1 accounted for an HCFP case and not the Moebius cases, supporting the separation.
Facioscapulohumeral muscular dystrophy
Overlapping Features A real diagnostic trap rather than a theoretical one. Facial weakness with neck and shoulder-girdle complaints led to a years-long FSHD misdiagnosis in a molecularly confirmed HCFP3 patient before D4Z4 sizing and exome sequencing corrected it.
Show evidence (1 reference)
PMID:38203298 SUPPORT Human Clinical
"For many years, she was misdiagnosed with facio-scapulo-humeral muscular dystrophy, due to complaints of shoulder girdle and neck muscle weakness."
Documents the misdiagnosis this differential exists to prevent.
🐁

Animal Models

2
Hoxb1-null mouse
The constitutive Hoxb1 knockout is the model the human phenotype was explicitly said to recapitulate. It shows the r4 identity failure and the facial branchiomotor neuron migration defect that lead to loss of the facial motor nerve.
Species
Mouse
Genotype
Hoxb1 homozygous null
Publication
PMID:8967950
Pathograph links
Mis-specification and Failed Migration of Facial Branchiomotor Neurons recapitulates fidelity: high observes: cellular DiI lineage tracing in the null embryo shows the r4-derived facial branchiomotor and contralateral vestibuloacoustic neurons differentiating but failing to migrate, which is the mechanism this node asserts.
Limitations: The model is a constitutive null, whereas most human alleles are missense substitutions in the homeodomain with residual, allele-specific DNA binding. Mouse facial branchiomotor migration from r4 into r5 is also a developmental event that cannot be observed in patients, so the human counterpart is inferred from the shared clinical endpoint.
Readouts
DiI-traced position of r4-derived FBM and CVA neurons
Direction: ALTERED
Interpretation: Neurons are present but mislocated, distinguishing a migration defect from a neurogenesis defect.
Show evidence (1 reference)
PMID:8967950 SUPPORT Model Organism
"In mutants, motor neurons differentiate but the CVA and FBM neurons fail to migrate into their proper positions."
The lineage-tracing readout behind this node.
Show evidence (1 reference)
PMID:22770981 SUPPORT Human Clinical
"The resulting phenotype includes bilateral facial palsy, hearing loss, and strabismus and correlates extensively with the previously reported Hoxb1(-/-) mouse phenotype."
The human-to-mouse phenotype correspondence is what licenses treating this model as informative for HCFP3.
Neural-crest-conditional Hoxb1 mouse
Conditional deletion restricted to neural crest separates the crest-autonomous requirement from the motor-neuron-autonomous one, which is the experiment that establishes the second arm of this entry's pathograph.
Species
Mouse
Genotype
Hoxb1 conditional deletion in neural crest
Publication
PMID:15198977
Pathograph links
Loss of r4-Derived Neural Crest Support of the VIIth Nerve recapitulates fidelity: high observes: cellular Tissue-restricted deletion shows the VIIth nerve circuitry requires HOXB1 in r4-derived crest independently of its requirement in the motor neurons.
Limitations: Human HCFP3 is a germline biallelic lesion affecting both compartments at once, so the conditional model demonstrates that the crest arm is sufficient to disturb the nerve but says nothing about its relative contribution in patients.
Readouts
Formation and maintenance of VIIth nerve circuitry after crest-restricted deletion
Direction: DECREASED
Interpretation: The nerve circuitry is disturbed by a lesion confined to the crest lineage.
Show evidence (1 reference)
PMID:15198977 SUPPORT Model Organism
"By conditionally deleting the Hoxb1 locus in neural crest, we demonstrate that Hoxb1 is also required in r4-derived neural crest to facilitate and maintain formation of the VIIth nerve circuitry."
The conditional-deletion readout behind this node.
{ }

Source YAML

click to show 
name: Hereditary Congenital Facial Paresis 3
creation_date: "2026-09-05T10:00:00Z"
category: Mendelian
synonyms:
- HCFP3
- facial paresis, hereditary congenital, 3
- HOXB1-related congenital facial palsy
- hereditary congenital facial palsy type 3
description: >-
  Hereditary congenital facial paresis type 3 (HCFP3) is an autosomal recessive
  congenital cranial dysinnervation disorder caused by biallelic variants in
  HOXB1. It presents at birth with non-progressive bilateral facial weakness,
  usually with sensorineural hearing loss, and frequently with external ear
  malformation and mild esodeviation.

  The lesion is developmental rather than degenerative, and it is anchored to a
  single hindbrain segment. HOXB1 is expressed throughout rhombomere 4, where it
  maintains segmental identity; r4 is the source of the facial branchiomotor
  neurons that innervate the muscles of facial expression, of the r4-derived
  neural crest that generates the glia myelinating the VIIth nerve, and of the
  geniculate and vestibulocochlear ganglia. One transcription-factor lesion in
  one segment therefore accounts for the facial and auditory findings together,
  and explains why the deficit is fixed from birth, because the affected
  structures are mis-specified during embryogenesis rather than lost afterwards.
  The external-ear malformation is deliberately excluded from that account: it
  is a consistent clinical accompaniment, but no source cited here traces it to
  the r4 lineage, and the pathograph does not connect it.

  Every HOXB1 missense variant reported to date substitutes an arginine in the
  homeodomain, and the recurrent Arg207 (homeodomain Arg5) residue contacts DNA
  in the minor groove within the HOXB1:PBX1:DNA ternary complex. A nonsense
  allele produces the same disease, which is what establishes the mechanism as
  loss of function rather than a dominant-negative or neomorphic effect.

  SCOPE. This entry covers HCFP3 only. HCFP1 (3q21-q22) and HCFP2
  (10q21.3-q22.1) are autosomal dominant, have no identified gene, and are not
  curated here. Moebius syndrome shares the facial palsy but adds limited ocular
  abduction and is a separate entity.
disease_term:
  preferred_term: hereditary congenital facial paresis type 3
  term:
    id: MONDO:0013880
    label: facial paresis, hereditary congenital, 3
parents:
- Congenital cranial dysinnervation disorder
inheritance:
- name: Autosomal recessive inheritance
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    HCFP3 requires biallelic HOXB1 variants. Reported genotypes include
    homozygous missense, homozygous nonsense, and compound heterozygous missense
    alleles; heterozygous carriers in the reported families are unaffected.
  evidence:
  - reference: PMID:27144914
    reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The homozygous nonsense variant c.66C>G/p.(Tyr22*) in HOXB1 was identified in the four patients with HCFP and ear malformations, while healthy family members carried the mutation in the heterozygous state."
    explanation: Affected individuals are homozygous and heterozygous relatives are healthy, which is the recessive segregation pattern.
genetic:
- name: HOXB1
  gene_term:
    preferred_term: HOXB1
    term:
      id: hgnc:5111
      label: HOXB1
  association: >-
    HOXB1 encodes a homeodomain transcription factor expressed throughout
    rhombomere 4, and is the only gene identified for any HCFP subtype.
    Biallelic variants cause HCFP3.
  relationship_type: CAUSATIVE
  evidence:
  - reference: PMID:27144914
    reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The only known causative gene for HCFP is HOXB1 (17q21; HCFP3), encoding a homeodomain-containing transcription factor of the HOX gene family, which are master regulators of early developmental processes."
    explanation: Names HOXB1 as the causative gene for the HCFP3 locus.
  variants:
  - name: HOXB1 p.Arg207Cys founder allele
    description: >-
      Homozygous missense substitution of the highly conserved homeodomain Arg5
      residue, found as a founder allele in two conservative German American
      families.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:22770981
      reference_title: "HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We have identified a founder homozygous missense mutation in HOXB1 in two families from a conservative German American population."
      explanation: Establishes the founder homozygous missense allele in the original HCFP3 families.
  - name: HOXB1 c.66C>G p.(Tyr22*)
    description: >-
      Homozygous nonsense allele in a large consanguineous Moroccan family, the
      first HOXB1 allele with a likely loss-of-function effect.
    clinical_significance: PATHOGENIC
    evidence:
    - reference: PMID:27144914
      reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "We performed whole exome sequencing in HCFP-affected individuals of a large consanguineous Moroccan family."
      explanation: Identifies the family and the sequencing approach that found the nonsense allele.
pathophysiology:
- name: HOXB1 Loss of Function
  biological_scale: MOLECULAR
  description: >-
    Biallelic HOXB1 variants abolish or degrade the transcriptional activity of
    the HOXB1 homeodomain. Reported missense alleles all replace an arginine in
    the homeodomain, and the recurrent Arg207 corresponds to homeodomain Arg5,
    which contacts thymine in the DNA minor groove within the HOXB1:PBX1:DNA
    ternary complex. A homozygous nonsense allele produces the same disease,
    which is what identifies the mechanism as loss of function.
  gene:
    preferred_term: HOXB1
    modifier: LOSS_OF_FUNCTION
    term:
      id: hgnc:5111
      label: HOXB1
  molecular_functions:
  - preferred_term: DNA-binding transcription factor activity
    modifier: DECREASED
    term:
      id: GO:0003700
      label: DNA-binding transcription factor activity
  evidence:
  - reference: PMID:22770981
    reference_title: "HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Molecular modeling and an in vitro DNA-protein binding assay predict that the mutation would disrupt these interactions, destabilize the HOXB1:PBX1:DNA complex, and alter HOXB1 transcriptional activity."
    explanation: >-
      The DNA-protein binding assay that places the defect at DNA binding within
      the HOXB1-PBX1 complex. Graded IN_VITRO for the assay. The sentence also
      reports molecular modeling, and the computational half is not curated as a
      separate item because the two are inseparable within this one sentence and
      the assay is the load-bearing part.
  - reference: PMID:27144914
    reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This is the first disease-associated HOXB1 mutation with a likely loss-of-function effect suggesting that all HOXB1 variants reported so far also have severe impact on activity of this transcriptional regulator."
    explanation: A nonsense allele causing the same phenotype is the argument that the missense alleles also act by loss of function.
  downstream:
  - target: Failure to Maintain Rhombomere 4 Identity
    causal_link_type: DIRECT
    description: >-
      HOXB1 is the segment-identity gene of rhombomere 4, so its loss removes
      the transcriptional program that maintains r4 identity.
    evidence:
    - reference: PMID:8967950
      reference_title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Here we report that absence of Hoxb-1 leads to changes in r4 identity."
      explanation: Directly states that loss of Hoxb1 changes rhombomere 4 identity.
- name: Failure to Maintain Rhombomere 4 Identity
  biological_scale: TISSUE
  description: >-
    Rhombomere 4 patterning is initiated normally but is not maintained without
    HOXB1. The segment is therefore specified and then loses its identity, which
    is why the downstream deficits are of specification and migration rather
    than of initial hindbrain segmentation.

    The reason initiation and maintenance come apart is that they are driven by
    different things. Initiation is extrinsic: a retinoic acid gradient made by
    Raldh2 in paraxial mesoderm, bounded by the RA-degrading Cyp26 enzymes,
    restricts Hoxb1 expression to presumptive r4. Maintenance is autoregulatory:
    HOXB1 sustains its own r4 expression through the b1 autoregulatory element,
    which is activated by HOXB1 and PBX1 binding together. That loop is exactly
    what the recurrent homeodomain Arg207 substitution destabilizes, which is
    how a DNA-contact mutation produces a maintenance failure rather than a
    failure to specify the segment at all.
  locations:
  - preferred_term: rhombomere 4
    term:
      id: UBERON:0005511
      label: rhombomere 4
  biological_processes:
  - preferred_term: rhombomere development
    modifier: ABNORMAL
    term:
      id: GO:0021546
      label: rhombomere development
  - preferred_term: anterior/posterior pattern specification
    modifier: ABNORMAL
    term:
      id: GO:0009952
      label: anterior/posterior pattern specification
  evidence:
  - reference: PMID:8967950
    reference_title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In mutant mouse embryos, molecular markers indicate that patterning of r4 is initiated properly but not maintained."
    explanation: Distinguishes a maintenance failure from a failure to establish the segment.
  - reference: PMID:11278854
    reference_title: "The recruitment of SOX/OCT complexes and the differential activity of HOXA1 and HOXB1 modulate the Hoxb1 auto-regulatory enhancer function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We previously showed that HOXB1 and PBX1 activate transcription from the b1-ARE by binding to sequences required for the expression of a reporter gene in rhombomere 4 in vivo."
    explanation: Identifies the HOXB1-PBX1 autoregulatory loop that maintains r4 expression, which is the machinery the Arg207 homeodomain substitution disrupts.
  - reference: PMID:15872003
    reference_title: "Shifting boundaries of retinoic acid activity control hindbrain segmental gene expression."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    snippet: "Retinoic acid (RA) generated by Raldh2 in paraxial mesoderm is required for specification of the posterior hindbrain, including restriction of Hoxb1 expression to presumptive rhombomere 4 (r4)."
    explanation: Establishes that r4 Hoxb1 expression is initiated extrinsically by retinoic acid, which is why an intrinsic HOXB1 lesion spares initiation. It is indirect because it describes normal patterning rather than the disease state.
  downstream:
  - target: Mis-specification and Failed Migration of Facial Branchiomotor Neurons
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:8967950
      reference_title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Cellular analysis by DiI tracing reveals that the r4-specific facial branchiomotor (FBM) and contralateral vestibuloacoustic efferent (CVA) neurons are incorrectly specified."
      explanation: Lineage tracing links the r4 identity defect to mis-specification of the r4-derived facial branchiomotor neurons.
  - target: Loss of r4-Derived Neural Crest Support of the VIIth Nerve
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:15198977
      reference_title: "Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "By conditionally deleting the Hoxb1 locus in neural crest, we demonstrate that Hoxb1 is also required in r4-derived neural crest to facilitate and maintain formation of the VIIth nerve circuitry."
      explanation: Conditional deletion isolates a second, neural-crest-autonomous arm downstream of the same r4 lesion.
  - target: Impaired Development of r4-Derived Cranial Ganglia
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38203298
      reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "playing a crucial role in the development of rhombomere 4, which is a precursor of the geniculate ganglion and the spiral and vestibular ganglion"
      explanation: Places the geniculate and spiral/vestibular ganglia in the r4 lineage, which is the route from the r4 lesion to the auditory phenotype. The intervening steps in humans are not established.
- name: Mis-specification and Failed Migration of Facial Branchiomotor Neurons
  biological_scale: CELLULAR
  description: >-
    Facial branchiomotor neurons are born in r4 and normally migrate caudally
    into r5. Without HOXB1 they differentiate but do not migrate correctly,
    forming an atypically migrating nucleus, and the facial motor nerve is
    subsequently lost.
  cell_types:
  - preferred_term: facial branchiomotor neuron
    term:
      id: CL:0005023
      label: branchiomotor neuron
  biological_processes:
  - preferred_term: neuron migration
    modifier: ABNORMAL
    term:
      id: GO:0001764
      label: neuron migration
  evidence:
  - reference: PMID:8967950
    reference_title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "In mutants, motor neurons differentiate but the CVA and FBM neurons fail to migrate into their proper positions."
    explanation: The neurons are made and then fail to reach their target position, so the defect is one of migration rather than neurogenesis.
  downstream:
  - target: Facial Motor Nerve Deficiency
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:8967950
      reference_title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Instead, they form a motor nucleus which migrates atypically, and there is a subsequent loss of the facial motor nerve."
      explanation: States the causal step from failed migration to loss of the facial motor nerve.
- name: Loss of r4-Derived Neural Crest Support of the VIIth Nerve
  biological_scale: CELLULAR
  description: >-
    A separate, non-neuronal arm of the same lesion. Rhombomere-4-derived neural
    crest generates the glia that myelinate the VIIth cranial nerve. In
    conditional mouse mutants glial progenitor specification is preserved, so
    the requirement is for a later glial function in maintaining the nerve
    rather than for producing the glia at all.
  cell_types:
  - preferred_term: r4-derived neural crest cell
    term:
      id: CL:0011012
      label: neural crest cell
  biological_processes:
  - preferred_term: neural crest cell migration
    modifier: ABNORMAL
    term:
      id: GO:0001755
      label: neural crest cell migration
  evidence:
  - reference: PMID:15198977
    reference_title: "Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Genetic lineage analysis revealed that a significant population of r4-derived neural crest is fated to generate glia that myelinate the VIIth cranial nerve."
    explanation: Establishes the r4 neural crest as the source of the myelinating glia of the facial nerve.
  - reference: PMID:15198977
    reference_title: "Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Neural crest cultures show that the absence of Hoxb1 function does not appear to affect overall glial progenitor specification, suggesting that a later glial function is critical for maintenance of the VIIth nerve."
    explanation: Narrows the glial defect to maintenance rather than progenitor specification.
  downstream:
  - target: Facial Motor Nerve Deficiency
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:15198977
      reference_title: "Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Taken together, these results suggest that the molecular program governing the development and maintenance of the VIIth cranial nerve is dependent upon Hoxb1, both in the neural crest-derived glia and in the facial branchiomotor neurons."
      explanation: States that both arms converge on development and maintenance of the VIIth nerve.
- name: Facial Motor Nerve Deficiency
  biological_scale: TISSUE
  description: >-
    The converged consequence of the motor-neuron and neural-crest arms, namely
    a facial nerve that is congenitally deficient. In patients this is seen as
    complete bilateral absence of the blink reflex, localizing the lesion to the
    facial nerve nucleus, and in some individuals as facial nerve axonal
    neuropathy on electrophysiology with structurally normal nerves on imaging.
  locations:
  - preferred_term: facial nerve
    term:
      id: UBERON:0001647
      label: facial nerve
  biological_processes:
  - preferred_term: facial nerve morphogenesis
    modifier: ABNORMAL
    term:
      id: GO:0021610
      label: facial nerve morphogenesis
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the blink reflex assessment revealed a bilateral absence of all components, aligning entirely with the characteristics indicative of an impairment in the facial cranial nerve nuclei"
    explanation: Human electrophysiology localizing the deficit to the facial nerve nuclei, which is the patient-level counterpart of the mouse facial branchiomotor finding.
  - reference: PMID:39235314
    reference_title: "Two novel compound heterozygous HOXB1 variants in congenital facial palsy: A case report and a brief review of the literature."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a child with facial nerve axonal neuropathy without evidence of nerve hypoplasia on neuroimaging"
    explanation: Shows the deficit can be functional and axonal with no imaging correlate, which matters for how the diagnosis is reached.
  downstream:
  - target: Congenital Bilateral Facial Palsy
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:27144914
      reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "HCFP is characterized by the isolated dysfunction of the seventh cranial nerve and can be associated with hearing loss, strabismus, and orofacial anomalies."
      explanation: States that the clinical syndrome is the consequence of seventh-nerve dysfunction.
  - target: Feeding Difficulties
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:39235314
      reference_title: "Two novel compound heterozygous HOXB1 variants in congenital facial palsy: A case report and a brief review of the literature."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "HCFP is characterized by feeding difficulties and dysmorphic features in the orofacial region."
      explanation: Attributes the feeding difficulty to the facial and orofacial consequence of the nerve deficit.
- name: Impaired Development of r4-Derived Cranial Ganglia
  biological_scale: TISSUE
  description: >-
    Rhombomere 4 is the precursor of the geniculate ganglion and of the spiral
    and vestibular ganglia, which is the developmental route from the same
    segmental lesion to the sensorineural hearing loss and the ear malformations
    seen in most patients. The mechanism connecting the r4 lesion to the human
    auditory phenotype has not been demonstrated directly, so this node records
    a lineage relationship rather than an experimentally traced chain.
  locations:
  - preferred_term: geniculate ganglion
    term:
      id: UBERON:0001700
      label: geniculate ganglion
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is expressed in the embryonic spinal cord and hindbrain, playing a crucial role in the development of rhombomere 4, which is a precursor of the geniculate ganglion and the spiral and vestibular ganglion"
    explanation: Establishes the lineage relationship this node asserts.
  downstream:
  - target: Sensorineural Hearing Impairment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:38203298
      reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "HCFP type 3 (HCFP3) is associated with biallelic variants in the HOXB1 gene, manifesting at birth with facial muscle weakness and typically accompanied by hearing loss"
      explanation: Ties the hearing loss to the same biallelic HOXB1 lesion; the intervening steps are not established in humans.
phenotypes:
- name: Congenital Bilateral Facial Palsy
  category: Neurological
  description: >-
    Non-progressive bilateral weakness of the muscles of facial expression,
    present from birth, producing a mask-like face with lagophthalmos and loss
    of facial expression.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Bilateral facial palsy
    term:
      id: HP:0010628
      label: Facial palsy
    clinical_course: STABLE
  evidence:
  - reference: PMID:22770981
    reference_title: "HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The resulting phenotype includes bilateral facial palsy, hearing loss, and strabismus and correlates extensively with the previously reported Hoxb1(-/-) mouse phenotype."
    explanation: Bilateral facial palsy is the defining feature in the original HCFP3 families.
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "revealed a loss of facial expression due to facial muscles' paralysis, facial muscle atrophy, lagophthalmos, hypoplasia of the nasal alae, upturned nasal tip, smooth philtrum, downturned corners of the mouth, and prominent nasal voice"
    explanation: Describes the mature clinical picture, including the lagophthalmos and orofacial features that accompany the palsy.
- name: Sensorineural Hearing Impairment
  category: Neurological
  description: >-
    Sensorineural hearing loss, non-progressive and typically moderate, present
    in most reported patients.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "manifesting at birth with facial muscle weakness and typically accompanied by hearing loss"
    explanation: Hearing loss is reported as a typical accompaniment of the facial weakness in HCFP3.
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Audiometric assessments demonstrated a second-degree sensorineural hearing loss on both sides."
    explanation: Audiometric confirmation that the loss is sensorineural and bilateral in a molecularly confirmed patient.
- name: Esotropia
  category: Ophthalmological
  description: >-
    Mild convergent eye deviation, reported in a minority of patients. It is not
    explained by seventh- or eighth-nerve function, which is the observation
    behind the suggestion that some mutant HOXB1 isoforms affect further cranial
    nerves.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Esotropia
    term:
      id: HP:0000565
      label: Esotropia
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the occurrence of eye esodeviation, observed in 44% of cases"
    explanation: Gives the reported frequency of esodeviation across published HCFP3 cases.
- name: Abnormal Pinna Morphology
  category: Craniofacial
  description: >-
    External ear malformation, described as a common accompaniment of HCFP3 and
    present in all four affected members of the consanguineous family carrying
    the nonsense allele.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Ear malformation
    term:
      id: HP:0000377
      label: Abnormal pinna morphology
  evidence:
  - reference: PMID:27144914
    reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the four patients with HCFP and ear malformations"
    explanation: Ear malformation co-segregated with HCFP in all four affected members of this family.
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "individuals with HCFP3 commonly exhibit ear malformations and some degree of esodeviation"
    explanation: States that ear malformation is a common feature across the reported series.
- name: Feeding Difficulties
  category: Gastrointestinal
  description: >-
    Difficulty with sucking and feeding in infancy, a direct consequence of the
    facial and orofacial weakness.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In infancy, she encountered challenges related to sucking and feeding."
    explanation: Documents infantile feeding difficulty in a molecularly confirmed patient.
- name: Hypernasal Speech
  category: Neurological
  description: >-
    Nasal voice recorded on examination alongside the other facial findings. The
    mechanism is not established here. Hypernasality is ordinarily velopharyngeal
    rather than perioral, and the palate is not an r4 derivative, so attributing
    it to the facial weakness would be an inference the cited source does not
    make. It is curated as an observed finding and left unconnected in the
    pathograph.
  phenotype_term:
    preferred_term: Nasal voice
    term:
      id: HP:0001611
      label: Hypernasal speech
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "downturned corners of the mouth, and prominent nasal voice"
    explanation: Nasal voice recorded on examination of a molecularly confirmed patient.
animal_models:
- name: Hoxb1-null mouse
  species: Mouse
  genotype: Hoxb1 homozygous null
  publication: PMID:8967950
  description: >-
    The constitutive Hoxb1 knockout is the model the human phenotype was
    explicitly said to recapitulate. It shows the r4 identity failure and the
    facial branchiomotor neuron migration defect that lead to loss of the facial
    motor nerve.
  modeled_mechanisms:
  - target: Mis-specification and Failed Migration of Facial Branchiomotor Neurons
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      DiI lineage tracing in the null embryo shows the r4-derived facial
      branchiomotor and contralateral vestibuloacoustic neurons differentiating
      but failing to migrate, which is the mechanism this node asserts.
    limitations: >-
      The model is a constitutive null, whereas most human alleles are missense
      substitutions in the homeodomain with residual, allele-specific DNA
      binding. Mouse facial branchiomotor migration from r4 into r5 is also a
      developmental event that cannot be observed in patients, so the human
      counterpart is inferred from the shared clinical endpoint.
    readouts:
    - name: DiI-traced position of r4-derived FBM and CVA neurons
      target: Mis-specification and Failed Migration of Facial Branchiomotor Neurons
      direction: ALTERED
      interpretation: >-
        Neurons are present but mislocated, distinguishing a migration defect
        from a neurogenesis defect.
      evidence:
      - reference: PMID:8967950
        reference_title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "In mutants, motor neurons differentiate but the CVA and FBM neurons fail to migrate into their proper positions."
        explanation: The lineage-tracing readout behind this node.
  evidence:
  - reference: PMID:22770981
    reference_title: "HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The resulting phenotype includes bilateral facial palsy, hearing loss, and strabismus and correlates extensively with the previously reported Hoxb1(-/-) mouse phenotype."
    explanation: The human-to-mouse phenotype correspondence is what licenses treating this model as informative for HCFP3.
- name: Neural-crest-conditional Hoxb1 mouse
  species: Mouse
  genotype: Hoxb1 conditional deletion in neural crest
  publication: PMID:15198977
  description: >-
    Conditional deletion restricted to neural crest separates the
    crest-autonomous requirement from the motor-neuron-autonomous one, which is
    the experiment that establishes the second arm of this entry's pathograph.
  modeled_mechanisms:
  - target: Loss of r4-Derived Neural Crest Support of the VIIth Nerve
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: CELLULAR
    description: >-
      Tissue-restricted deletion shows the VIIth nerve circuitry requires HOXB1
      in r4-derived crest independently of its requirement in the motor neurons.
    limitations: >-
      Human HCFP3 is a germline biallelic lesion affecting both compartments at
      once, so the conditional model demonstrates that the crest arm is
      sufficient to disturb the nerve but says nothing about its relative
      contribution in patients.
    readouts:
    - name: Formation and maintenance of VIIth nerve circuitry after crest-restricted deletion
      target: Loss of r4-Derived Neural Crest Support of the VIIth Nerve
      direction: DECREASED
      interpretation: >-
        The nerve circuitry is disturbed by a lesion confined to the crest
        lineage.
      evidence:
      - reference: PMID:15198977
        reference_title: "Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "By conditionally deleting the Hoxb1 locus in neural crest, we demonstrate that Hoxb1 is also required in r4-derived neural crest to facilitate and maintain formation of the VIIth nerve circuitry."
        explanation: The conditional-deletion readout behind this node.
treatments:
- name: Symptomatic and Supportive Management
  description: >-
    No disease-modifying therapy exists. Management is symptomatic and
    preventive, and the counselling value of the molecular diagnosis is
    substantial because the deficit is congenital and non-progressive.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The management of this condition primarily involves a symptomatic and preventive approach, as no specific pathogenetic therapy has been developed thus far."
    explanation: States plainly that management is symptomatic and that no targeted therapy exists.
  target_mechanisms:
  - target: Congenital Bilateral Facial Palsy
    description: >-
      Supportive care addresses the consequences of the facial weakness; it does
      not act on the developmental lesion.
- name: Genetic Counseling
  description: >-
    Autosomal recessive recurrence counselling, and reassurance about the
    non-progressive natural history. In the reported adult case the molecular
    diagnosis ended years of misdiagnosis as facioscapulohumeral muscular
    dystrophy and resolved the patient's pregnancy-planning concerns.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Moreover, the patient faces no contraindications for childbirth, and there is a low risk of transmitting the condition to offspring."
    explanation: The specific counselling content that follows from recessive inheritance.
progression:
- phase: Congenital and non-progressive
  notes: >-
    The deficit is present at birth and does not progress. Because the lesion is
    one of embryonic specification, no new deficits are expected to emerge.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Given that HCFP3 is a congenital disorder associated with cranial nerves, we anticipate no progression of the muscle weakness or the emergence of new symptoms."
    explanation: Explicit statement of the non-progressive natural history.
differential_diagnoses:
- name: Moebius syndrome
  description: >-
    Shares congenital facial palsy but adds limited ocular abduction from sixth
    nerve involvement. Screening a large cohort of patients diagnosed with
    Moebius syndrome or HCFP found a HOXB1 variant only in an HCFP case, not in
    the Moebius cases.
  evidence:
  - reference: PMID:27144914
    reference_title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Möbius syndrome shares facial palsy with HCFP, but is additionally characterized by limited abduction of the eye(s)."
    explanation: The discriminating clinical sign between the two entities.
  - reference: PMID:26007620
    reference_title: "A new hereditary congenital facial palsy case supports arg5 in HOX-DNA binding domain as possible hot spot for mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We screened 95 sporadic patients diagnosed as MBS or HCFP for mutations in HOXB1. A novel homozygous alteration was identified in one HCFP case"
    explanation: A cohort screen in which HOXB1 accounted for an HCFP case and not the Moebius cases, supporting the separation.
- name: Facioscapulohumeral muscular dystrophy
  description: >-
    A real diagnostic trap rather than a theoretical one. Facial weakness with
    neck and shoulder-girdle complaints led to a years-long FSHD misdiagnosis in
    a molecularly confirmed HCFP3 patient before D4Z4 sizing and exome
    sequencing corrected it.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For many years, she was misdiagnosed with facio-scapulo-humeral muscular dystrophy, due to complaints of shoulder girdle and neck muscle weakness."
    explanation: Documents the misdiagnosis this differential exists to prevent.
diagnosis:
- name: Exome sequencing for biallelic HOXB1 variants
  description: >-
    Molecular confirmation is by exome or targeted sequencing showing biallelic
    HOXB1 variants. Phase matters, because the first compound heterozygous case
    required read-level analysis to show the two variants were in trans, and
    paternity testing to establish that one had arisen de novo.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an analysis of the sequence reads demonstrated that both variants were in trans"
    explanation: Shows the phasing step required to call biallelic status for nearby variants.
- name: Blink reflex testing
  description: >-
    Electrophysiological localization. Bilateral absence of all blink reflex
    components indicates impairment at the facial nerve nuclei rather than a
    muscular or neuromuscular-junction cause, and limb electrodiagnostics are
    normal.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Comprehensive electrodiagnostic testing was conducted, showing no signs of peripheral neuropathy and any neurogenic or myogenic changes in the limb muscles."
    explanation: The normal limb study is what makes the isolated blink-reflex abnormality localizing.
discussions:
- discussion_id: hcfp3_unconnected_ear_and_speech_findings
  kind: KNOWLEDGE_GAP
  prompt: >-
    By what route does an r4 transcription-factor lesion produce external-ear
    malformation and hypernasal speech, if it produces them at all?
  attaches_to:
  - phenotypes#Abnormal Pinna Morphology
  - phenotypes#Hypernasal Speech
  rationale: >-
    Both findings are well attested clinically. Ear malformation was present in
    all four affected members of the consanguineous family and is described as a
    common accompaniment across the series; nasal voice was recorded on
    examination. Neither is connected in the pathograph, and that is deliberate
    rather than an omission.

    For the ear, the r4-derived neural crest does populate the second pharyngeal
    arch, which is the usual embryological argument, but no source cited in this
    entry makes that link for HCFP3, so drawing the edge would be reasoning from
    developmental biology rather than from the evidence to hand. For the speech
    finding, hypernasality is ordinarily velopharyngeal, and the soft palate is
    not an r4 derivative, so the obvious edge from facial weakness is probably
    the wrong one. Both are recorded here as open rather than resolved by a
    plausible-looking arrow.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "individuals with HCFP3 commonly exhibit ear malformations and some degree of esodeviation"
    explanation: >-
      Establishes that the ear finding is a consistent part of the phenotype,
      which is what makes its absence from the causal chain a gap worth
      recording rather than a phenotype to drop.
- discussion_id: hcfp3_esodeviation_outside_r4
  kind: KNOWLEDGE_GAP
  prompt: >-
    Why does esodeviation occur in HCFP3 when HOXB1 acts in rhombomere 4 and the
    ocular motor nuclei do not derive from it?
  attaches_to:
  - phenotypes#Esotropia
  rationale: >-
    Esodeviation is reported in 44% of published cases, which is too frequent to
    dismiss, yet the r4 lineage does not supply the abducens or oculomotor
    nuclei. Either mutant HOXB1 isoforms act outside r4, or the deviation is a
    secondary consequence of the facial and orbital phenotype. The published
    suggestion is the former, and it is explicitly speculative.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This prompts speculation that certain mutant isoforms of HOXB1 may influence other cranial nerves."
    explanation: The authors themselves frame this as speculation, which is the gap this entry records.
- discussion_id: hcfp3_neck_shoulder_weakness
  kind: KNOWLEDGE_GAP
  prompt: >-
    Is proximal neck and shoulder-girdle weakness part of the HCFP3 phenotype?
  attaches_to:
  - phenotypes#Congenital Bilateral Facial Palsy
  rationale: >-
    A single molecularly confirmed patient had objectively measured neck flexor
    and extensor weakness with sternocleidomastoid and trapezius hypotrophy on
    MRI, and no alternative cause was found after excluding FSHD, myotonic
    dystrophy type 2 and myasthenia. The finding is not curated as a phenotype
    of the disease here because it rests on one patient and the authors
    themselves ask for more data.
  evidence:
  - reference: PMID:38203298
    reference_title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We speculate that neck weakness might be a component of HCFP3, yet we acknowledge that additional data are needed to provide concrete evidence of this novel clinical association."
    explanation: States the uncertainty directly, which is why this is a gap rather than a curated phenotype.
references:
- reference: PMID:22770981
  title: "HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice."
- reference: PMID:27144914
  title: "Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis."
- reference: PMID:38203298
  title: "Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3."
- reference: PMID:39235314
  title: "Two novel compound heterozygous HOXB1 variants in congenital facial palsy: A case report and a brief review of the literature."
- reference: PMID:26007620
  title: "A new hereditary congenital facial palsy case supports arg5 in HOX-DNA binding domain as possible hot spot for mutations."
- reference: PMID:27640920
  title: "A novel homozygous HOXB1 mutation in a Turkish family with hereditary congenital facial paresis."
- reference: PMID:8967950
  title: "Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1."
- reference: PMID:15198977
  title: "Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry."
- reference: PMID:11278854
  title: "The recruitment of SOX/OCT complexes and the differential activity of HOXA1 and HOXB1 modulate the Hoxb1 auto-regulatory enhancer function."
- reference: PMID:15872003
  title: "Shifting boundaries of retinoic acid activity control hindbrain segmental gene expression."
notes: >-
  Allelic spectrum. Every missense allele reported to date substitutes an
  arginine in the homeodomain, and two independent alleles hit the same residue
  (homeodomain Arg5, protein Arg207). The founder allele is Arg207Cys and a
  later case carried Arg207His. The in-silico prediction was that the histidine
  substitution retains stronger DNA binding than the cysteine one and gives a
  milder phenotype (PMID:26007620), which is a genotype-phenotype hypothesis
  rather than a measured result and is not curated as a subtype here. A
  homozygous nonsense allele (PMID:27144914) and compound heterozygous missense
  alleles (PMID:38203298, PMID:39235314) have since been reported, and a further
  homozygous missense allele in a consanguineous Turkish family brought the
  reported total to four at the time (PMID:27640920).

  Named entity check. Three distinct entities share the phrase "congenital
  facial" in this literature and were kept apart during curation. HCFP3 is
  HOXB1-related and recessive and is what this entry covers; HCFP1 and HCFP2 are
  dominant with mapped loci and no identified gene; Moebius syndrome adds an
  abduction deficit to the facial palsy. The Moebius differential is curated
  from a cohort screen rather than from assertion.

  Deep-research provenance. Curated alongside an OpenScientist report
  (research/Hereditary_Congenital_Facial_Paresis_3-deep-research-openscientist.md),
  whose causal chain matched the one built here from primary literature. Its
  substantive addition was the upstream regulatory context now folded into the
  rhombomere-4 node: the retinoic-acid gradient that initiates Hoxb1 expression
  and the b1 autoregulatory element that maintains it. Two of its ontology
  suggestions were wrong and were rejected: UBERON:0005396, offered as
  rhombomere 4, is a carotid artery segment, and CL:0011001, offered for
  branchiomotor neurons, is a spinal cord motor neuron.

  Rejecting those two suggestions was right; the conclusion drawn from it was
  not, and review caught the error. Having found the offered CURIEs wrong, this
  entry originally fell back to UBERON:0002028 (hindbrain) and CL:0000100 (motor
  neuron) and recorded that no better term was bound. Both better terms exist:
  UBERON:0005511 is rhombomere 4 and CL:0005023 is branchiomotor neuron, and
  both are now bound. The lesson is that a bad suggestion from a deep-research
  report is evidence about the report, not about the ontology, and the ontology
  still has to be searched independently before concluding a term is missing.

  No prevalence block. This was raised in review as cheap to add and is
  deliberately not added. No source cached for this entry carries a population
  rate or a count of published cases, so a CASES_IN_LITERATURE record would have
  to quote something that is not an epidemiological statement. The nearest
  candidate is the 1-of-95 yield from the Moebius and HCFP screen in
  PMID:26007620, which is a diagnostic yield in a selected clinical series and
  not a rate in any population. Orphanet would supply a real class, but no
  ORPHA record for this disorder is in references_cache, and building one means
  refreshing and repinning the Orphadata bulk manifest, which does not belong in
  a curation PR. The block is left out rather than filled from a statistic that
  measures something else.
📚

References & Deep Research

References

10
PMID:22770981
HOXB1 founder mutation in humans recapitulates the phenotype of Hoxb1-/- mice.
No top-level findings curated for this source.
PMID:27144914
Homozygous HOXB1 loss-of-function mutation in a large family with hereditary congenital facial paresis.
No top-level findings curated for this source.
PMID:38203298
Expanding the Phenotype of Hereditary Congenital Facial Paresis Type 3.
No top-level findings curated for this source.
PMID:39235314
Two novel compound heterozygous HOXB1 variants in congenital facial palsy: A case report and a brief review of the literature.
No top-level findings curated for this source.
PMID:26007620
A new hereditary congenital facial palsy case supports arg5 in HOX-DNA binding domain as possible hot spot for mutations.
No top-level findings curated for this source.
PMID:27640920
A novel homozygous HOXB1 mutation in a Turkish family with hereditary congenital facial paresis.
No top-level findings curated for this source.
PMID:8967950
Altered segmental identity and abnormal migration of motor neurons in mice lacking Hoxb-1.
No top-level findings curated for this source.
PMID:15198977
Hoxb1 functions in both motoneurons and in tissues of the periphery to establish and maintain the proper neuronal circuitry.
No top-level findings curated for this source.
PMID:11278854
The recruitment of SOX/OCT complexes and the differential activity of HOXA1 and HOXB1 modulate the Hoxb1 auto-regulatory enhancer function.
No top-level findings curated for this source.
PMID:15872003
Shifting boundaries of retinoic acid activity control hindbrain segmental gene expression.
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 (3)

Record notes

Allelic spectrum. Every missense allele reported to date substitutes an arginine in the homeodomain, and two independent alleles hit the same residue (homeodomain Arg5, protein Arg207). The founder allele is Arg207Cys and a later case carried Arg207His. The in-silico prediction was that the histidine substitution retains stronger DNA binding than the cysteine one and gives a milder phenotype (PMID:26007620), which is a genotype-phenotype hypothesis rather than a measured result and is not curated as a subtype here. A homozygous nonsense allele (PMID:27144914) and compound heterozygous missense alleles (PMID:38203298, PMID:39235314) have since been reported, and a further homozygous missense allele in a consanguineous Turkish family brought the reported total to four at the time (PMID:27640920). Named entity check. Three distinct entities share the phrase "congenital facial" in this literature and were kept apart during curation. HCFP3 is HOXB1-related and recessive and is what this entry covers; HCFP1 and HCFP2 are dominant with mapped loci and no identified gene; Moebius syndrome adds an abduction deficit to the facial palsy. The Moebius differential is curated from a cohort screen rather than from assertion. Deep-research provenance. Curated alongside an OpenScientist report (research/Hereditary_Congenital_Facial_Paresis_3-deep-research-openscientist.md), whose causal chain matched the one built here from primary literature. Its substantive addition was the upstream regulatory context now folded into the rhombomere-4 node: the retinoic-acid gradient that initiates Hoxb1 expression and the b1 autoregulatory element that maintains it. Two of its ontology suggestions were wrong and were rejected: UBERON:0005396, offered as rhombomere 4, is a carotid artery segment, and CL:0011001, offered for branchiomotor neurons, is a spinal cord motor neuron. Rejecting those two suggestions was right; the conclusion drawn from it was not, and review caught the error. Having found the offered CURIEs wrong, this entry originally fell back to UBERON:0002028 (hindbrain) and CL:0000100 (motor neuron) and recorded that no better term was bound. Both better terms exist: UBERON:0005511 is rhombomere 4 and CL:0005023 is branchiomotor neuron, and both are now bound. The lesson is that a bad suggestion from a deep-research report is evidence about the report, not about the ontology, and the ontology still has to be searched independently before concluding a term is missing. No prevalence block. This was raised in review as cheap to add and is deliberately not added. No source cached for this entry carries a population rate or a count of published cases, so a CASES_IN_LITERATURE record would have to quote something that is not an epidemiological statement. The nearest candidate is the 1-of-95 yield from the Moebius and HCFP screen in PMID:26007620, which is a diagnostic yield in a selected clinical series and not a rate in any population. Orphanet would supply a real class, but no ORPHA record for this disorder is in references_cache, and building one means refreshing and repinning the Orphadata bulk manifest, which does not belong in a curation PR. The block is left out rather than filled from a statistic that measures something else.

Review round 1: bind rhombomere 4 and branchiomotor neuron, fix two evidence gradings, record the unconnected ear and speech findings · 2026-09-07T12:00:58Z · View source

Review round 1 on PR #11113. Four blocking findings, all fixed in one push. Findings 1 and 2 are the same mistake made twice, and worth naming precisely because the reasoning looked careful at the time. The deep-research report offered UBERON:0005396 for rhombomere 4 and CL:0011001 for branchiomotor neurons. Both are wrong: a carotid artery segment and a spinal cord motor neuron. Rejecting them was correct. What was not correct was the next step, concluding from those two bad suggestions that no better term existed, and recording that conclusion in notes as a fact about the ontology. Both terms exist. UBERON:0005511 is rhombomere 4 and CL:0005023 is branchiomotor neuron. Both are now bound in place of the hindbrain and motor neuron fallbacks, and both were verified with just validate-terms before being written. The notes now record the error rather than the original claim, and state the general rule it illustrates: a bad suggestion from a deep-research report is evidence about the report, not about the ontology, and the ontology still has to be searched independently before concluding a term is missing. The r4 node's whole argument is segment specificity, so the broader hindbrain binding was throwing away the node's point. Finding 3, two evidence_source values contradicting their own snippets. PMID:22770981 quoted "Molecular modeling and an in vitro DNA-protein binding assay predict..." while graded HUMAN_CLINICAL; regraded IN_VITRO for the binding assay, with the explanation stating why the computational half of the same sentence is not split into a separate item. PMID:11278854 quoted a transgenic reporter result ending "in rhombomere 4 in vivo" while graded IN_VITRO; regraded MODEL_ORGANISM. As the review noted, check-snippet-grading cannot catch either: it keys on a sentence appearing more than once with different grades, and each of these appears once. Finding 4, the description claimed an arm the pathograph does not carry. It said one lesion "explains the facial, auditory and ear findings together" while Abnormal Pinna Morphology and Hypernasal Speech were the target of no downstream edge anywhere in the file. Of the two options offered, drawing the edges or recording the gap, this takes the second. Drawing two plausible-looking arrows would have made the graph agree with the prose without either being evidenced. The description no longer claims the ear finding and says explicitly that it is excluded from the account. A new KNOWLEDGE_GAP discussion, hcfp3_unconnected_ear_and_speech_findings, attaches to both phenotypes and states what is missing in each case: for the ear, r4-derived neural crest does populate the second pharyngeal arch, but no source cited here makes that link for HCFP3; for the speech finding, hypernasality is ordinarily velopharyngeal and the soft palate is not an r4 derivative, so the obvious edge from facial weakness is probably the wrong one. That last point also corrected an unprompted claim inside the entry. The Hypernasal Speech description asserted the finding results "from weakness of the facial and perioral musculature". The cited snippet does not say that, and perioral weakness is not the usual mechanism of hypernasality. The description now records the finding without the mechanism and says why it is left open. No gate would have flagged this; it was found while fixing something else. Validation on this tree: just validate clean with 47/47 snippets verified, up from 46. Terms, entity-refs, causal-targets, duplicate-keys, enum-values, qualifier-terms, snippet-length, title-snippets, snippet-grading and reference-titles all pass. Two new cache row pairs, CL:0005023 and UBERON:0005511, from the rebindings.

Create: Hereditary Congenital Facial Paresis 3 (HCFP3, HOXB1) · 2026-09-05T14:50:07Z · View source

New kb/disorders entry for HCFP3 (MONDO:0013880), claimed via issue #11110. Curated as a rhombomere-4 specification disorder rather than a list of clinical features: HOXB1 loss of function -> failure to maintain r4 identity -> two parallel arms (facial branchiomotor neuron mis-specification and migration failure; loss of r4-derived neural crest glial support of the VIIth nerve) converging on facial motor nerve deficiency, plus a third arm through the r4-derived geniculate and spiral/vestibular ganglia to the hearing loss. Six HPO-bound phenotypes, two mouse models (constitutive Hoxb1 null and the neural-crest-conditional deletion) with per-link fidelity, limitations and readouts, and two KNOWLEDGE_GAP discussions (the 44 percent esodeviation that r4 lineage does not explain; single-patient neck and shoulder-girdle weakness). Named-entity discipline: HCFP1/HCFP2 (dominant, no gene) and Moebius syndrome were kept separate throughout, and the Moebius differential is evidenced from a cohort screen rather than asserted. Validation: schema pass, term validation pass, 44/44 snippets verified against cached references, check-entity-refs / check-causal-targets / check-duplicate-keys / check-qualifier-terms / check-enum-values all clean. The OpenScientist deep-research run for this disease was still queued when the entry was written from primary literature; the report is committed alongside.

OpenScientist ▸
Hereditary Congenital Facial Paresis Type 3 (HCFP3) — Disease Characteristics Report
openscientist-autonomous 2026-09-05T14:39:49.086455

Hereditary Congenital Facial Paresis Type 3 (HCFP3) — Disease Characteristics Report

MONDO: MONDO:0013880 · OMIM: #614744 · Category: Mendelian (autosomal recessive)

Evidence base: HCFP3 is an ultra-rare Mendelian disorder described in only a handful of families worldwide. Consequently, much of the mechanistic detail is derived from the mouse model (Hoxb1-/-) and from a small number of human case reports/series. Evidence source types are flagged throughout as [human clinical], [mouse], [in vitro], or [computational]. Where a canonical resource (OMIM/Orphanet/HPO) would normally supply information but no primary datum was retrievable in this investigation, the item is marked "not established / not retrieved."

1. Disease Information

HCFP3 is a congenital cranial dysinnervation disorder (CCDD) characterized by non-progressive, usually bilateral weakness/paralysis of the muscles of facial expression due to maldevelopment of the seventh cranial nerve (facial nerve, CN VII) and its brainstem motor nucleus. It is present from birth and frequently accompanied by hearing loss, strabismus, feeding difficulties, and orofacial/ear dysmorphism. [human clinical] (PMID 27144914, 22770981, 39235314)

Key identifiers - MONDO: MONDO:0013880 - OMIM: 614744 (phenotype) - Gene: HOXB1 — OMIM 142968; HGNC:5111; NCBI Gene 3211; Ensembl ENSG00000120094; UniProt P14653; locus 17q21.32 - Orphanet: Hereditary congenital facial paresis (ORPHA:91517 group; HCFP3 subtype) - ICD-11: LA05 / 8B88.0-type congenital cranial nerve / facial nerve disorders (congenital facial palsy); ICD-10: Q07.8 (other specified congenital malformations of nervous system) — mapping approximate. - MeSH: "Facial Paralysis"; "Cranial Nerve Diseases"; related MeSH "Mobius Syndrome" (differential).

Synonyms / alternative names: HCFP3; Hereditary congenital facial paresis, type 3; Congenital facial palsy, HOXB1-related; Facial paresis, hereditary congenital, 3; (broader group) hereditary congenital facial palsy.

Data source type: Aggregated disease-level knowledge (OMIM/Orphanet/HPO) plus individual patient case reports (EHR-style descriptions of small families), not large registry/EHR cohorts.

2. Etiology

Primary cause (genetic): Biallelic (homozygous or compound heterozygous) pathogenic variants in HOXB1, a homeodomain transcription factor. HOXB1 is "the only known causative gene for HCFP" (HCFP3). [human clinical] (PMID 27144914)

Genetic risk factors - Causal variants: HOXB1 loss-of-function and homeodomain missense alleles (Section 4). - Consanguinity: Strong contributor — recessive disease enriched in consanguineous/endogamous families (e.g., Moroccan consanguineous family; German-American conservative isolate). [human clinical] (PMID 27144914, 22770981) - Founder effect: A founder Arg207Cys allele segregates in a "conservative German American population." [human clinical] (PMID 22770981) - Susceptibility/modifier loci: Not established.

Environmental risk factors: None identified. HCFP3 is a monogenic developmental disorder; unlike acquired/syndromic congenital facial palsy, it is not attributable to birth trauma, teratogens (e.g., misoprostol/Möbius association), or ischemia. Congenital onset means the causal event is embryonic hindbrain patterning.

Protective factors (genetic/environmental): None established. In a recessive disorder, a single wild-type HOXB1 allele is effectively protective (carriers are unaffected — PMID 27144914).

Gene–environment interactions: None documented; disease is fully genetically determined by biallelic HOXB1 dysfunction.

3. Phenotypes

Phenotype Type Onset Severity/Course Frequency HPO suggestion
Bilateral facial (CN VII) palsy Clinical sign Congenital Non-progressive, stable; variable severity Defining (~100%) HP:0010628 Facial palsy; HP:0000260 (bilateral)
Impaired facial expression / weak eye closure, drooling Physical manifestation Congenital Stable High HP:0000317 Facial features / HP:0000508 Ptosis (variable)
Feeding/sucking difficulties (infancy) Symptom Neonatal Often improves Common HP:0011968 Feeding difficulties; HP:0002033 Poor suck
Hearing loss (sensorineural and/or conductive) Lab/clinical sign Congenital Stable Frequent HP:0000365 Hearing impairment
Strabismus Clinical sign Congenital Stable Frequent HP:0000486 Strabismus
Ear malformations / low-set or dysmorphic ears Physical Congenital Stable Variable HP:0000377 Abnormal pinna morphology; HP:0000369 Low-set ears
Orofacial dysmorphism (e.g., upturned nose, upper-lip/philtrum changes) Physical Congenital Stable Variable HP:0000463 Anteverted nares
Facial nerve axonal neuropathy (± nerve hypoplasia) Lab (electrophysiology/imaging) Congenital Stable Reported HP:0009830 Peripheral neuropathy
Preserved eye abduction (CN VI intact) — distinguishes from Möbius Discriminating sign — — Characteristic (absence of HP:0031747-type abducens palsy)

[human clinical] sources: PMID 27144914, 22770981, 39235314. Note Brugnoli 2025 (PMID 39235314) describes a case with facial nerve axonal neuropathy without nerve hypoplasia and preserved ocular motor skills, broadening the imaging/electrophysiology spectrum.

Quality-of-life impact: Facial diplegia impairs emotional expression, eye protection (risk of exposure keratopathy), articulation, oral competence (drooling, feeding), and social/psychological well-being; hearing loss adds communication/developmental burden. Measured evidence: subjects with congenital facial weakness (includes HCFP) have significantly worse oral health-related quality of life than matched controls — OHIP-14 13.11 ± 8.11 vs 4.46 ± 4.98 (Liberton 2024, PMID 38791829). No HCFP3-specific EQ-5D/SF-36 data exist (broader CFW/facial-palsy inference).

4. Genetic / Molecular Information

Causal gene: HOXB1 (HGNC:5111; OMIM 142968; 17q21.32) — homeobox transcription factor, HOX family, master regulator of hindbrain antero-posterior patterning. [human clinical] (PMID 27144914)

Pathogenic variants reported | Variant (cDNA / protein) | Type | Zygosity / origin | Functional consequence | Reference | |---|---|---|---|---| | c.619C>T, p.(Arg207Cys) | Missense (homeodomain Arg5) | Homozygous, founder (German-American isolate) | Disrupts DNA minor-groove contact; destabilizes HOXB1:PBX1:DNA complex; altered transcriptional activity [computational + in vitro] | PMID 22770981 | | p.Arg207His (historical) | Missense (same residue) | Homozygous | Same residue class; altered cofactor/DNA binding | (reviewed in 27144914) | | c.66C>G, p.(Tyr22) | Nonsense (truncating) | Homozygous, consanguineous Moroccan family | Loss of function* (first bona fide LOF allele) | PMID 27144914 | | Two novel compound heterozygous variants | (per report) | Compound het, by exome sequencing | Consistent with LOF; axonal neuropathy phenotype | PMID 39235314 |

  • ACMG classification: Reported alleles are pathogenic/likely pathogenic; segregation with disease, rarity, and functional data support classification (query ClinVar for current status).
  • Allele frequency: Causal alleles are extremely rare/absent in gnomAD (private/founder); precise frequencies not retrieved here.
  • Somatic vs germline: Germline (constitutional developmental disorder).
  • Functional class: Loss of function unifies missense (impaired DNA/cofactor binding) and nonsense (truncation) alleles — "all HOXB1 variants reported so far also have severe impact on activity of this transcriptional regulator." [human clinical / in vitro] (PMID 27144914)

Modifier genes: None established. Candidate interacting partners at protein level include PBX1 (obligate HOX cofactor) and MEIS proteins; HOXA1 is a paralog acting in overlapping hindbrain programs (HOXA1 mutations cause a distinct CCDD, Bosley-Salih-Alorainy/Athabascan brainstem dysgenesis).

Epigenetic information: No disease-specific methylation/histone data for HCFP3 (not established).

Chromosomal abnormalities: None characteristic for HCFP3 (single-gene disorder; no recurrent CNV/translocation).

HCFP locus landscape (nosological context). HCFP is genetically heterogeneous: - HCFP3 (OMIM 614744): HOXB1, 17q21.32, autosomal recessive (this disease). - HCFP1 (OMIM 601471): maps to 3q21-q22; resolved in 2023 as heterozygous duplications of a neuron-specific GATA2 regulatory region (two enhancers + one silencer) and noncoding silencer SNVs (some impair NR2F1 binding) — autosomal dominant. A humanized mouse extends Gata2, favoring inner-ear efferent over facial-branchiomotor fate, rescued by conditional Gata3 loss. [human/mouse] (PMID 37386251) - HCFP2 (OMIM 604185): maps to 10q21.3-q22.1; gene not yet identified — autosomal dominant. (PMID 27144914) - Other dominant HCFP gene: MEPE frameshift p.(Gln425Lysfs38) with mixed hearing loss in a four-generation family. [human clinical]* (PMID 30287925)

Convergent mechanism across subtypes: all HCFP genes act on maldevelopment of rhombomere-4–derived facial branchiomotor neurons (FBMNs) — the same lineage disrupted by HOXB1 loss — so a CFW/HCFP diagnostic gene panel should include HOXB1, the GATA2 regulatory region, and MEPE.

5. Environmental Information

  • Environmental factors: None causal (purely genetic developmental disorder).
  • Lifestyle factors: Not applicable to disease causation.
  • Infectious agents: None. (Distinguish from acquired facial palsy such as Bell's palsy [HSV], Lyme disease, otitis media — these are differential diagnoses, not HCFP3.)

6. Mechanism / Pathophysiology

Ordered causal chain (initiating lesion → clinical manifestation)

  1. Biallelic HOXB1 loss-of-function (nonsense truncation, or homeodomain missense that cripples DNA/cofactor binding) results in absent or non-functional HOXB1 transcription factor in the embryonic hindbrain. [human clinical/in vitro] (PMID 27144914, 22770981)
  2. This leads to failure to maintain rhombomere 4 (r4) identity — r4 patterning is initiated but not sustained (molecular markers appear then fade). [mouse] (PMID 8967950)
  3. Loss of r4 identity results in mis-specification of r4-derived facial branchiomotor (FBM) neurons and contralateral vestibuloacoustic (CVA) efferent neurons. [mouse] (PMID 8967950)
  4. Mis-specified motor neurons differentiate but fail to migrate to their normal positions; instead they form an atypically migrating motor nucleus. [mouse] (PMID 8967950)
  5. This aberrant development leads to subsequent loss of the facial motor nerve (hypoplasia/aplasia of CN VII nucleus and nerve). [mouse] (PMID 8967950)
  6. Absent/deficient facial motor innervation results in congenital bilateral facial muscle paralysis (impaired expression, eye closure, oral competence). [human clinical] (PMID 22770981)
  7. Branch (auditory): disruption of r4-derived vestibuloacoustic efferents and inner-ear developmental programs contributes to hearing loss. [mouse/human] (PMID 8967950, 22770981) (inferred link between CVA lineage and auditory deficit)
  8. Branch (ocular): associated strabismus arises from developmental co-involvement, though eye abduction (CN VI) is characteristically spared, distinguishing HCFP3 from Möbius syndrome. [human clinical] (PMID 27144914)
  9. Branch (variant-specific): some human cases show facial nerve axonal neuropathy without frank nuclear/nerve hypoplasia, indicating the lesion can manifest as an axonal/dysinnervation phenotype rather than complete agenesis. [human clinical] (PMID 39235314)

The human founder mutation "recapitulates the phenotype of Hoxb1-/- mice," directly bridging the mouse mechanism to human disease. [human/mouse] (PMID 22770981)

Upstream regulatory context (why r4, and what maintains HOXB1)

HOXB1's r4-restricted expression is set up by a retinoic acid (RA; CHEBI:15367) morphogen gradient: RA produced by Raldh2 in paraxial mesoderm induces Hoxb1 up to r4 through 3′/5′ RA-response elements, while Cyp26 RA-degrading enzymes sharpen the r3/r5 boundaries. In Raldh2-/- embryos, Hoxb1-expressing cells scatter instead of forming a defined r4. [mouse] (PMID 15872003, 10654602). Once induced, HOXB1 maintains its own expression via an r4 autoregulatory element (b1-ARE) driven by HOXB1:PBX1 heterodimers, further tuned by TALE cofactors (PREP1/MEIS) and SOX/OCT complexes; HOXB1 is a stronger activator than its paralog HOXA1. [in vitro/mouse] (PMID 11278854, 10654609). Pathogenic homeodomain variants (Arg207Cys) cripple precisely the PBX1/DNA interactions that sustain this loop — mechanistically linking genotype to the "identity-not-maintained" phenotype in step 2 above.

Category checklist mapped to the chain

  • Molecular pathways: Upstream retinoic-acid signaling (Raldh2/Cyp26 gradient) patterns r4; the core lesion is in the HOX/PBX–MEIS/PREP transcriptional regulatory network governing hindbrain segmentation and cranial motor neuron identity (Reactome "Activation of HOX genes"; developmental gene-regulatory network). No classic signaling cascade (Wnt/MAPK/mTOR) is the proximal lesion; the defect is transcription-factor–level. [mouse/in vitro] (PMID 15872003, 11278854, 10654609)
  • Protein dysfunction: Homeodomain Arg207 (= conserved Arg5) normally contacts thymine in the DNA minor groove via hydrogen bonding/electrostatics; mutation destabilizes the HOXB1:PBX1:DNA ternary complex → altered target-gene transcription. Nonsense allele → no functional protein. [computational + in vitro] (PMID 22770981)
  • Cellular processes: Cell-fate specification, neuronal migration (tangential migration of branchiomotor neurons), maintenance of segmental identity, neuronal survival. [mouse] (PMID 8967950)
  • Immune / metabolic / oxidative mechanisms: Not involved (developmental, non-inflammatory, non-metabolic).
  • Molecular profiling / single-cell / omics: No disease-specific transcriptomic/proteomic/metabolomic datasets for HCFP3 (not established); mechanistic data come from marker/lineage studies in mouse.

Upstream vs downstream: HOXB1 loss (upstream) → r4 identity failure → FBM/CVA mis-specification/migration failure → CN VII nucleus/nerve loss → facial paralysis (downstream clinical readout).

Ontology suggestions: GO:0021610 facial nerve morphogenesis; GO:0021612 facial nerve structural organization; GO:0001764 neuron migration; GO:0048704 embryonic skeletal/segment specification; GO:0006357/0006355 regulation of transcription by RNA Pol II; GO:0021546 rhombomere development. CL: CL:0000100 motor neuron; CL:0011001 spinal/branchiomotor motor neuron. UBERON: UBERON:0005396 rhombomere 4; UBERON:0001647 facial nerve; UBERON:0002894 hindbrain/rhombomere.

7. Anatomical Structures Affected

  • Organ/system level: Central & peripheral nervous system — brainstem (pons/medulla, hindbrain) and cranial nerve VII; musculoskeletal (muscles of facial expression, secondary); auditory system (inner ear/CN VIII pathway); visual/oculomotor (strabismus).
  • Primary structure: Facial motor nucleus and facial nerve (CN VII) — UBERON:0001647.
  • Secondary involvement: Muscles of facial expression (denervation), ear structures (hearing loss, pinna dysmorphism), extraocular alignment.
  • Tissue/cell level: Neural tissue; specifically branchiomotor motor neurons of rhombomere 4 (CL:0000100 motor neuron), vestibuloacoustic efferent neurons.
  • Subcellular level: Nucleus (GO:0005634) — site of HOXB1 transcription-factor action on chromatin/DNA.
  • Localization & lateralization: Bilateral (often symmetric) facial involvement; brainstem hindbrain r4 territory. [human clinical] (PMID 22770981)

8. Temporal Development

  • Onset: Congenital (embryonic hindbrain maldevelopment); facial weakness evident at birth/neonatal period (feeding/sucking difficulty, incomplete eye closure). [human clinical] (PMID 39235314)
  • Onset pattern: Static/developmental (not acute or acquired).
  • Progression: Non-progressive / stable over life (a dysinnervation/malformation, not a degenerative process). No disease staging.
  • Course: Lifelong, chronic, stable. Feeding difficulties may improve with maturation; facial weakness persists.
  • Remission: None spontaneous; deficits are structural. Interventions are supportive/reconstructive (Section 12).
  • Critical period: The vulnerable/opportunity window is embryonic hindbrain segmentation (r4 identity maintenance); postnatally the developmental lesion is fixed.

9. Inheritance and Population

  • Inheritance pattern: Autosomal recessive (HCFP3). Contrast: HCFP1 (OMIM 601471) and HCFP2 (OMIM 604185) are autosomal dominant. [human clinical] (PMID 39235314, 27144914)
  • Penetrance: Appears complete in reported biallelic individuals; heterozygous carriers are unaffected. [human clinical] (PMID 27144914)
  • Expressivity: Variable (severity of hearing loss, strabismus, dysmorphism, presence/absence of nerve hypoplasia vary between and within families). [human clinical] (PMID 39235314)
  • Genetic anticipation: Not applicable (not a repeat-expansion disorder).
  • Germline mosaicism: Not reported.
  • Founder effect: Yes — Arg207Cys founder allele in a conservative German-American population. [human clinical] (PMID 22770981)
  • Consanguinity: Prominent contributor (homozygous alleles in consanguineous/endogamous families). [human clinical] (PMID 27144914, 22770981)
  • Carrier frequency: Not established (ultra-rare; population-specific).
  • Epidemiology: HCFP overall is very rare; HCFP3 specifically is reported in only a small number of families/cases worldwide. Precise prevalence/incidence per 100,000 not established. Broader hereditary congenital facial palsy is estimated at roughly ~2 per million births (order-of-magnitude, group-level; not HCFP3-specific).
  • Sex ratio: No strong sex bias expected for an autosomal recessive disorder; formal data not established.
  • Geographic distribution: Case clusters reported in a German-American isolate (founder), a consanguineous Moroccan family, Russian patients (Murtazina 2023, PMID 38203298), and Italian (Brugnoli 2025). Distribution reflects reporting/founder/consanguinity rather than true endemicity.

10. Diagnostics

Clinical evaluation - Recognition of congenital, non-progressive, bilateral facial weakness with preserved eye abduction; assess feeding, eye closure, hearing, ocular alignment, ear/facial morphology. [human clinical] (PMID 27144914)

Genetic testing (definitive) - Exome sequencing (ES/WES) is the demonstrated diagnostic modality (used to identify HOXB1 variants). [human clinical] (PMID 39235314, 27144914, 22770981) - Targeted HOXB1 single-gene / CCDD gene-panel testing appropriate once phenotype suggests HCFP3. - Genome sequencing (WGS) where ES is uninformative. - In individuals with congenital facial paralysis, preserved ocular motor skills, and confirmed facial-nerve axonal neuropathy, "HOXB1 variants and therefore a diagnosis of HCFP3 should be primarily considered." [human clinical] (PMID 39235314)

Electrophysiology / functional tests - Facial nerve conduction, blink reflex, ± needle EMG: HCFP (and Möbius) subjects show low-amplitude CN VII responses without other neuropathic or myopathic findings, distinguishing them from generalized-neuropathy CFW (e.g., TUBB3 polyneuropathy) or myopathic CFW (Carey-Fineman-Ziter). May also show axonal facial neuropathy. [human clinical] (PMID 33389762, 39235314) - Audiometry / BAER (ABR): to detect and characterize hearing loss (sensorineural/conductive). - Ophthalmologic exam: strabismus, tear-film/exposure assessment.

Imaging - High-resolution MRI (brainstem/CN VII, IAC): grades facial-nerve maldevelopment 0–4 (0 normal → 1 unilateral hypoplasia → 2 unilateral aplasia → 3 bilateral aplasia/hypoplasia → 4 with additional cranial-nerve involvement) and can reveal inner/middle/external-ear anomalies; in HCFP3 the nerve may be hypoplastic/aplastic OR normal-appearing despite axonal neuropathy (variable). [human clinical] (PMID 30074067, 39235314)

Biomarkers / lab chemistry / biopsy: No specific blood/urine biomarker; diagnosis is clinical + molecular. No pathognomonic histopathology.

Clinical criteria & differential diagnosis: Distinguish from Möbius syndrome (adds CN VI abduction deficit), acquired facial palsy (birth trauma, Bell's palsy, infection), HOXA1-related CCDDs, TUBB3-related CFW (adds generalized sensorimotor axonal polyneuropathy on EDx), Carey-Fineman-Ziter and other myopathic CFW (myopathic EDx findings), CHARGE syndrome, hemifacial microsomia/oculo-auriculo-vertebral spectrum, and other syndromic congenital facial weakness. Preserved abduction + isolated low-amplitude CN VII pattern without neuropathic/myopathic features favors HCFP. [human clinical] (PMID 27144914, 33389762)

Screening: Carrier/cascade testing within affected families; prenatal/preimplantation testing feasible once the familial HOXB1 genotype is known. Not part of population newborn screening.

11. Outcome / Prognosis

  • Survival/mortality: Normal life expectancy; HCFP3 is not life-limiting (no cardiorespiratory/visceral fatal component). Disease-specific mortality negligible.
  • Morbidity/disability: Chronic functional impairments — impaired facial expression and eye closure (exposure keratopathy risk), speech/articulation difficulty, oral competence/feeding issues in infancy, hearing impairment, strabismus/amblyopia risk. Psychosocial impact from facial diplegia; measurably reduced oral health-related QoL (OHIP-14 13.11 vs 4.46, PMID 38791829). [human clinical] (PMID 27144914, 39235314, 38791829)
  • Recovery potential: The primary facial-nerve deficit is structural and does not resolve spontaneously; supportive/rehabilitative and reconstructive measures improve function. Feeding difficulties often improve with age.
  • Prognostic factors: Severity of nerve hypoplasia, degree of hearing loss, presence of associated anomalies; earlier multidisciplinary intervention improves functional/QoL outcomes.
  • Prognostic biomarkers: None established.

12. Treatment

There is no disease-modifying or curative therapy; management is supportive, rehabilitative, and reconstructive, delivered by a multidisciplinary team. (No pharmacotherapy targets the underlying transcription-factor defect.)

  • Pharmacotherapy: No specific drug. Ocular surface protection: lubricating eye drops/ointments (artificial tears) to prevent exposure keratopathy. Pharmacogenomics: not applicable.
  • Surgical / interventional:
  • Facial reanimation surgery — free functional muscle transfer, most commonly segmental free gracilis muscle transfer (FGMT) neurotized by the masseteric (trigeminal) nerve or via cross-face nerve grafts, is the standard smile-reanimation technique for non-resolving congenital bilateral facial paralysis (the HCFP/Möbius category). [human clinical] (PMID 30166122, 33637466). Pediatric outcomes: ~84% achieve active gracilis contraction with mean commissure excursion gains ~9.7 mm at 1 year (PMID 40738135); gains are maintained/improved at 5–13 years (PMID 33191114); 1-stage and 2-stage bilateral approaches give comparable outcomes (PMID 40100160). (Series are Möbius-dominated but the reconstructive principles apply directly to HCFP3.) NCIT: facial reanimation; free muscle flap transfer; cross-face nerve grafting.
  • Ophthalmic: strabismus surgery; eyelid procedures (gold-weight implant, tarsorrhaphy) for lagophthalmos/eye protection.
  • Otologic/audiologic: hearing aids or bone-conduction devices; cochlear implantation if indicated for severe SNHL.
  • Supportive / rehabilitative: Feeding support in infancy; speech and language therapy (articulation, oral competence); physical/occupational/facial neuromuscular retraining therapy; early developmental support; ophthalmology and audiology follow-up.
  • Advanced therapeutics (gene/cell/RNA/targeted/immuno): None developed; congenital developmental fixation of the lesion limits gene-therapy applicability.
  • Experimental treatments / trials: No HCFP3-specific interventional trials identified (ClinicalTrials.gov — not retrieved for this specific ultra-rare entity).
  • Treatment strategy: Individualized, phenotype-directed multidisciplinary care (facial reanimation timing, eye protection, hearing habilitation, speech therapy) + genetic counseling.

NCIT suggestions: facial reanimation / nerve graft procedures; strabismus surgery; hearing aid; cochlear implant; supportive/palliative care; physical therapy; speech therapy.

13. Prevention

  • Primary prevention: Not possible for an inherited developmental disorder other than via reproductive genetic options — genetic counseling, carrier testing in at-risk families/consanguineous couples, prenatal diagnosis and preimplantation genetic testing (PGT-M) once the familial HOXB1 variants are known.
  • Secondary prevention (early detection/complication avoidance): Early recognition to institute eye protection (prevent exposure keratopathy), hearing habilitation (support language development), and strabismus/amblyopia management in the critical visual-development window.
  • Tertiary prevention: Ongoing corneal protection, feeding/nutrition support, speech therapy, and timely facial reanimation to limit functional and psychosocial complications.
  • Immunization / public-health / environmental / prophylaxis: Not applicable (non-infectious, non-environmental).
  • Counseling: Autosomal recessive recurrence risk = 25% for a couple who are both carriers; emphasize consanguinity risk and founder-population screening. [human clinical] (PMID 27144914)

14. Other Species / Natural Disease

  • Taxonomy: Homo sapiens (NCBI Taxon 9606); disease-model Mus musculus (Taxon 10090).
  • Orthologous gene: Mouse Hoxb1 (NCBI Gene 15407; MGI); zebrafish hoxb1a/hoxb1b (ZFIN) with cofactor pbx4 (lazarus). Highly conserved homeodomain (human Arg207 = conserved homeodomain Arg5). [mouse/zebrafish] (PMID 22770981, 8967950, 12645925)
  • Natural disease in other species / breeds: No naturally occurring HOXB1-facial-paresis disease catalogued (OMIA — not retrieved); no VBO breed association.
  • Comparative biology: The mouse Hoxb1-/- phenotype (loss of r4 identity, FBM/CVA mis-migration, facial motor nerve loss) closely mirrors the human disorder — human founder mutation "recapitulates the phenotype of Hoxb1-/- mice," demonstrating deep evolutionary conservation of the hindbrain segmentation/branchiomotor program. [human/mouse] (PMID 22770981, 8967950)
  • Zoonotic potential / cross-species transmission: Not applicable (genetic disorder).

15. Model Organisms

  • Primary model: Mouse — Hoxb1 knockout (Hoxb1-/-) [mammalian, genetic knockout]. Key resource: MGI. [mouse] (PMID 8967950)
  • Model characteristics / phenotype recapitulation: Faithfully reproduces the core human mechanism — r4 identity is initiated but not maintained; FBM and CVA neurons are mis-specified and fail to migrate, forming an atypically migrating nucleus with loss of the facial motor nerve → facial paralysis analog. Explicitly stated to correlate "extensively" with the human phenotype. [mouse] (PMID 8967950, 22770981)
  • Second vertebrate model — zebrafish (Danio rerio, NCBI Taxon 7955): hoxb1a interacts genetically with lazarus/pbx4 to control facial (CN VII) motor neuron migration; genetic mosaic analysis shows both act primarily cell-autonomously within the facial motor neurons (with a minor non-cell-autonomous component). This independently validates the HOX/PBX-driven FBMN migration mechanism disrupted in HCFP3. [zebrafish] (PMID 12645925). Orthologs: hoxb1a, hoxb1b, pbx4. Resource: ZFIN.
  • Model types available: Constitutive knockout (Studer 1996); zebrafish morphant/mutant (Cooper 2003); paralog/compound studies (Hoxa1/Hoxb1) and knock-in swap experiments exist in the developmental-biology literature (not detailed here). A humanized HCFP1 (GATA2-regulatory) mouse exists for the related subtype (PMID 37386251). Conditional/humanized HOXB1 alleles — resources via MGI/IMPC (not enumerated in this investigation).
  • Limitations: Mouse constitutive knockout captures nerve/nucleus maldevelopment but does not fully model human associated features (hearing loss severity, strabismus, human-specific dysmorphism) or the milder axonal-neuropathy-without-hypoplasia human presentations.
  • Applications: Dissecting hindbrain segmentation, branchiomotor neuron specification/migration, and HOX/PBX transcriptional control; platform for genotype-phenotype correlation.
  • In vitro / computational: In vitro DNA–protein binding assays and molecular modeling of the Arg207Cys homeodomain–DNA interaction. [in vitro/computational] (PMID 22770981)
  • Resources: MGI (Hoxb1), IMPC/IMSR for alleles.

Summary Answer

Hereditary Congenital Facial Paresis type 3 (HCFP3; OMIM #614744, MONDO:0013880) is an ultra-rare autosomal-recessive congenital cranial dysinnervation disorder caused by biallelic loss-of-function of the hindbrain transcription factor HOXB1 (17q21.32; e.g., founder p.Arg207Cys and nonsense p.Tyr22). Loss of HOXB1 prevents maintenance of rhombomere-4 identity, causing mis-specification and failed migration of facial branchiomotor neurons and consequent hypoplasia/dysfunction of the facial motor nucleus and nerve — producing congenital, non-progressive bilateral facial paralysis* with variable hearing loss, strabismus, feeding difficulty and orofacial/ear anomalies, while eye abduction (CN VI) is characteristically spared (distinguishing it from Möbius syndrome). Diagnosis is by exome/HOXB1 sequencing; there is no cure, and management is multidisciplinary and supportive (eye protection, hearing habilitation, speech therapy, facial reanimation) with autosomal-recessive genetic counseling (25% recurrence risk).

Key Findings (with evidence)

  1. Genetic cause: biallelic HOXB1 variants → HCFP3 (autosomal recessive), the only established HCFP gene (PMID 27144914, 22770981, 39235314).
  2. Variant spectrum: founder missense p.Arg207Cys, nonsense p.Tyr22* (LOF), and compound-het alleles; unified by loss of function (PMID 22770981, 27144914, 39235314).
  3. Mechanism: HOXB1 loss → failed r4 identity maintenance → FBM/CVA neuron mis-migration → facial motor nerve loss → bilateral facial palsy (mouse Hoxb1-/-; PMID 8967950, 22770981).
  4. Phenotype: bilateral facial palsy + hearing loss + strabismus + orofacial/feeding anomalies, with preserved eye abduction (PMID 22770981, 27144914, 39235314).

Supported vs. Refuted Hypotheses

  • Supported: HOXB1 LOF is causal and recessive; mechanism is developmental (r4/branchiomotor); mouse model recapitulates human disease.
  • Refuted / not applicable: environmental/infectious/metabolic/immune etiology; somatic origin; progressive or degenerative course; gene–environment interaction.

Limitations & Future Directions

  • Ultra-rare disease: prevalence/incidence, penetrance/expressivity ranges, sex ratio, and gnomAD carrier frequencies are not precisely established.
  • Mechanistic branch linking HOXB1/r4 to human hearing loss and strabismus is partly inferred from mouse/lineage data.
  • No omics (transcriptomic/proteomic) profiling exists for HCFP3 tissue.
  • Future work: broaden genotype–phenotype catalog (ClinVar/GeneMatcher), define natural history/QoL, refine imaging/electrophysiology correlates (hypoplasia vs axonal neuropathy), and explore conditional/humanized models.

Evidence classes: [human clinical] case reports/families & surgical series; [mouse] Hoxb1/Raldh2 knockouts; [in vitro] DNA-binding/enhancer assays; [computational] molecular modeling. Primary PMIDs: 22770981 (Webb 2012, founder HOXB1), 27144914 (Vogel 2016, LOF nonsense), 8967950 (Studer 1996, Hoxb1-/- mouse), 39235314 (Brugnoli 2025, compound-het), 38203298 (Murtazina 2023, phenotype expansion), 15872003 (Sirbu 2005, RA→Hoxb1 r4), 10654602 (Niederreither 2000, Raldh2 hindbrain), 11278854 (Di Rocco 2001, b1-ARE HOXB1:PBX1), 10654609 (Ferretti 2000, PREP1/MEIS), 30556292 (Bell 2019, Möbius differential), 37386251 (Tenney 2023, HCFP1/GATA2 regulatory), 30287925 (Schrauwen 2019, MEPE HCFP), 33389762 (Lehky 2021, electrodiagnostics), 30074067 (Mohammad 2018, MRI grading), 38791829 (Liberton 2024, OHRQoL), 12645925 (Cooper 2003, zebrafish hoxb1a/pbx4), 30166122 / 33637466 / 40738135 / 33191114 / 40100160 (facial reanimation).

Artifacts

Reference Validation

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References checked 17
Resolved 17
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 17
On topic 10
Off topic 0

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Term Validation

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

Outcome Count
Terms checked 29
Resolved 27
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 2
Terms whose name was checked 1
Terms named correctly 0
Terms named as a different term 0
Terms whose name is worth a second look 1

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:

  • GO:0005634 (1 mention) - the report calls it "Nucleus", "Subcellular level: Nucleus"; GO calls it nucleus, and lists "cell nucleus" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

  • GO:0005634 - called "Nucleus", "Subcellular level: Nucleus"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: ORPHA.

27 of 29 terms resolved to a current term; the rest could not be looked up either way.