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Inheritance

1

Autosomal recessive HP:0000007

Autosomal recessive inheritance is supported by homozygous affected individuals and heterozygous parents in the reported pedigrees. Consanguinity facilitated ascertainment but is not required for this inheritance pattern. When both parents carry a causal recessive allele, recurrence risk is 25% per pregnancy. The specific dominant DFNA21 allele has different counseling implications.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"If both parents are known to be heterozygous for an autosomal recessive hearing loss-related pathogenic variant, each sib of the proband has at conception a 25% chance of having hearing loss, a 50% chance of having no hearing loss and being a carrier, and a 25% chance of having no hearing loss..."

General recessive hearing-loss counseling applies after the causal variants and parental genotypes are established.

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Discussions and Knowledge Gaps

3

Do differing vestibular assays, alleles or compensatory mechanisms explain the human–model discrepancy?

HUMAN MODEL MISMATCH OPEN mismatch_vestibular_phenotype

Attached to

pathophysiology#Vestibular End-Organ Dysfunction animal_models#Fam65b/Ripor2 knockout mouse

Human vestibular areflexia was characterized with cVEMP and video head-impulse testing, whereas the null mouse was screened by behavior and rotarod. Stable exon-14 zebrafish lines had no overt hearing or balance behavioral difference at 5 dpf; the earlier morpholino experiment measured microphonics at 3 dpf. These are different alleles, developmental stages and assays. RIPOR1/RIPOR3 compensation is a proposed explanation, not a demonstrated mechanism.

Proposed experiments

Paralogue expression and compensation in mouse versus human vestibular epithelium

ripor_paralogue_expression_vestibular

First compare vestibular end-organ function with sensitive, age-appropriate assays across models and affected families. Test paralogue expression and combined perturbation only after distinguishing subtle sensory deficits from preserved overt balance behavior.

Would support

pathophysiology#Vestibular End-Organ Dysfunction

Supporting outcome

Combined paralogue perturbation reveals a vestibular deficit absent after Ripor2 loss alone, supporting compensation in the tested model.

Refuting outcome

Equivalent sensitive testing already detects dysfunction after Ripor2 loss alone, supporting an ascertainment contribution rather than complete model resistance.

Is the vestibular phenotype specific to the nonsense allele, or was it simply not looked for in the first family?

KNOWLEDGE GAP OPEN gap_allele_specific_vestibular

Attached to

phenotypes#Vestibular Areflexia genetic#RIPOR2

The two reported families differ on vestibular involvement and also differ on allele class and on how vestibular function was assessed. The Turkish kindred was reported as having no balance problems on clinical assessment; the Tunisian siblings were characterised with cervical VEMPs and video head-impulse testing, which detect dysfunction that a clinical balance history does not. So there are at least three live readings - an allele-specific effect, a genetic-background effect, and an ascertainment difference - and two families cannot distinguish them. The practical stake is whether to counsel a newly diagnosed RIPOR2 patient about vestibular involvement, and whether to test for it.

Proposed experiments

Uniform vestibular testing across all reported and newly ascertained RIPOR2 families

vestibular_testing_all_ripor2_families

Apply the same vestibular battery - cervical and ocular VEMPs, video head-impulse testing, and developmental motor milestones - to affected individuals from both published recessive families and any newly ascertained ones, and record the result against allele class.

Would support

phenotypes#Vestibular Areflexia

Supporting outcome

Formal testing finds vestibular dysfunction in splice-allele patients too, making vestibular involvement part of the disease rather than an allele-specific feature.

Refuting outcome

Splice-allele patients test normal on the same battery, which would support a real allele-specific difference and make variant class relevant to counselling.

Which structural and molecular dependencies directly mediate RIPOR2-related hearing loss?

KNOWLEDGE GAP OPEN gap_ripor2_domain_and_causal_intermediates

Attached to

pathophysiology#Biallelic RIPOR2 Loss-of-Function Variant pathophysiology#Reduced Cochlear MYH9 Abundance pathophysiology#Disorganisation of the Taper Compartment

The PX–BAR assignment was challenged by sequence/structure analysis, and the authors agreed that experimental confirmation was needed. MYH9 abundance, tubulin acetylation and taperin localization change in null mice, but their relative causal contributions are unresolved. The RL/AA construct alters both RhoC binding and basal self-association. Selective rescue and structural studies are needed to distinguish these possibilities.

Show evidence (1 reference)

PMID:25239234 SUPPORT Computational

"Secondary structure predictions of FAM65 do not reveal any similarity to the PX–BAR family of molecules."

The published computational challenge supports treating the initial domain assignment as unresolved.

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Pathophysiology

10

Biallelic RIPOR2 Loss-of-Function Variant

The Turkish NM_014722.2:c.102-1G>A allele causes exon 3 skipping in patient leukocyte RNA, producing p.Arg34_Asp86delinsSer, a net 52-residue deletion. The Tunisian NM_014722.4:c.1561C>T (p.Arg521*) allele is predicted to truncate RIPOR2 or reduce its abundance; patient protein absence and nonsense-mediated decay were not demonstrated. The proposed PX–BAR domain interpretation of the N-terminal deletion was challenged in published correspondence and remains unverified.

RIPOR2 hgnc:13872

Genetic context RIPOR2 hgnc:13872 variant_origin: GERMLINE zygosity: HOMOZYGOUS functional_impact_category: LOSS_OF_FUNCTION

Homozygous splice-acceptor and nonsense variants segregate in the reported recessive families. Loss of function includes defective localization of an in-frame deletion product; protein absence is not demonstrated for every human allele.

Downstream

Loss of RIPOR2 from the Stereociliary Taper Deletion constructs mislocalize in expression assays; null mice lack RIPOR2. The nonsense allele is predicted to reduce functional protein, but its molecular fate is unresolved.

Vestibular End-Organ Dysfunction Human segregation supports a RIPOR2-related vestibular phenotype. Its cellular intermediates and allele dependence are not established.

Show evidence (3 references)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

PMID:24958875 SUPPORT In Vitro

"Gel electrophoresis and sequence analysis of cDNA synthesized from leukocyte mRNA from family members revealed that exon 3 of FAM65B was absent in all affected relatives, whereas heterozygous individuals (III:9, III:10, IV:3, IV:4) carried both the wild-type and the mutant transcripts (Fig. 1 D and F)."

RNA from affected and heterozygous relatives demonstrates exon skipping; this is a patient-derived molecular assay, not only a splice prediction.

Loss of RIPOR2 from the Stereociliary Taper

RIPOR2 localizes around the basal stereociliary taper in mouse hair cells. Patient-deletion constructs accumulate in cytoplasmic inclusions in COS7 cells, and a related construct fails normal targeting in cultured mouse hair cells. These overexpression results support defective localization; they do not show endogenous mutant protein abundance or localization in the human cochlea. STORM ring geometry does not by itself establish direct lipid binding.

cochlear inner hair cell CL:0000589 cochlear outer hair cell CL:0000601

stereocilium GO:0032420

cochlea UBERON:0001844

Downstream

Disorganisation of the Taper Compartment RIPOR2 deficiency disrupts taperin localization, through an unresolved direct or secondary mechanism.

Reduced Cochlear MYH9 Abundance Ripor2-null cochleae have reduced MYH9 protein despite increased transcript.

Reduced Cochlear Tubulin Acetylation Ripor2-null cochlear extracts have reduced acetylated alpha-tubulin.

Stereocilia Disorganisation Loss of RIPOR2 causes abnormal stereocilia during early postnatal maturation; re-expression rescues morphology in explants.

Misorientation of Developing Hair Bundles Null mice show embryonic and postnatal bundle-orientation defects. The contribution of taper organization versus other RIPOR2 functions is unresolved.

Show evidence (2 references)

PMID:24958875 SUPPORT In Vitro

"The wild-type protein targets the plasma membrane, whereas the mutant protein accumulates in cytoplasmic inclusion bodies and does not reach the membrane."

Transfected COS7 cells expressing the deletion construct; this does not measure endogenous protein abundance in patients.

PMID:27269051 SUPPORT Model Organism

"Using biochemistry and stochastic optical reconstruction microscopy (STORM), we show here that Fam65b oligomers form a circumferential ring near the basal taper of the mechanically sensitive stereocilia of murine hair cells."

Mouse imaging and heterologous biochemistry support a ring-like oligomeric organization.

Disorganisation of the Taper Compartment

Taperin staining becomes reduced and diffuse in Ripor2-null hair cells, whereas espin staining is retained. No direct interaction with taperin, CLIC5, radixin, whirlin or the PTPRQ cytoplasmic domain was detected in the tested heterologous assays. RhoC enhances N-terminal RIPOR2 oligomerization in HEK293 cells, and tagged RhoC colocalizes with RIPOR2 in explants. The RL/AA construct fails rescue but also reduces basal homophilic binding, so it does not isolate a uniquely RhoC-dependent effect. A primary taper defect versus secondary disruption by abnormal bundle morphology remains unresolved.

cochlear inner hair cell CL:0000589 cochlear outer hair cell CL:0000601

auditory receptor cell stereocilium organization GO:0060088 ⚠ ABNORMAL

stereocilium GO:0032420

Animal models

Fam65b/Ripor2 knockout mouse Mouse recapitulates Reduced and diffuse taperin staining, with preserved espin.

Show evidence (2 references)

PMID:27269051 SUPPORT Model Organism

"The taperin signal is reduced and diffused in mutant hair cells, while the espin signal is similar."

Figure 5 distinguishes altered taperin localization from preserved espin staining; a direct RIPOR2–taperin interaction was not detected.

PMID:27269051 SUPPORT In Vitro

"In fact, the mutation appeared to even reduce the basal homophilic binding activity of Fam65b that is observed without expression of RhoC (Figure 9H,I)."

This control limits causal interpretation of the RhoC-binding-deficient rescue construct.

Reduced Cochlear MYH9 Abundance

MYH9 protein and its Ser1943-phosphorylated form are reduced in Ripor2-null cochleae despite increased Myh9 transcript. Tagged-protein co-immunoprecipitation supports association with RIPOR2. Reduced protein abundance is established; altered translation versus degradation and a causal role in kinocilium migration remain unresolved.

cochlear inner hair cell CL:0000589 cochlear outer hair cell CL:0000601

Animal models

Ripor2 knockout mouse (hair bundle morphogenesis) Mouse recapitulates Reduced protein abundance despite increased transcript.

Show evidence (2 references)

PMID:30280293 SUPPORT Model Organism

"Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount of Myh9 transcripts."

Cochlear protein and transcript measurements establish post-transcriptional discordance, without measuring protein turnover.

PMID:30280293 SUPPORT In Vitro

"The RIPOR2-MYH9 interaction was validated by co-immunoprecipitation using HEK293 cells overexpressing both proteins with two different tags (Fig. 3B) and by immunohistochemistry (Fig. 3C)."

Tagged proteins associate in heterologous cells; this does not establish purified direct binding.

Reduced Cochlear Tubulin Acetylation

K40-acetylated alpha-tubulin is reduced in Ripor2-null cochlear extracts. Kinocilium length was not detectably changed. A RIPOR2–HDAC6 mechanism was proposed from nonauditory work, but cochlear HDAC6 localization and activity were not established in this study.

kinocilium GO:0060091

Animal models

Ripor2 knockout mouse (hair bundle morphogenesis) Mouse recapitulates Reduced acetylated alpha-tubulin in cochlear extracts.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Western blot analysis shows a decrease on the content of alpha-acetyl-tubulin in protein extracts from cochleae of Ripor2 deficient mice (Fig. 5E, F)."

The measured acetylated-tubulin abundance is separate from the proposed HDAC6 mechanism.

Misorientation of Developing Hair Bundles

Ripor2-null cochleae have displaced kinocilia and increased deviations of hair-bundle orientation at E18.5 and P5. Reduced MYH9 and acetylated tubulin accompany the phenotype, but neither was selectively rescued to establish its contribution to polarity.

cochlear inner hair cell CL:0000589 cochlear outer hair cell CL:0000601

stereocilium bundle GO:0032421 kinocilium GO:0060091

Animal models

Ripor2 knockout mouse (hair bundle morphogenesis) Mouse recapitulates Embryonic and postnatal orientation defects.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects the orientation of this key subcellular structure."

Orientation and kinocilium-position defects are present at E18.5 and P5 in null mice.

Stereocilia Disorganisation

Inner-hair-cell bundles are already severely disorganized at P2 in Ripor2-null mice; outer-hair-cell bundles initially retain much of their staircase arrangement but show orientation defects. By P5 both cell types have abnormal length, thickness or arrangement of stereocilia. Deterioration occurs during maturation. Little hair-cell loss is evident at P16/P28, so bundle pathology is not equivalent to early wholesale hair-cell death.

cochlear inner hair cell CL:0000589 cochlear outer hair cell CL:0000601

stereocilium bundle GO:0032421

Animal models

Fam65b/Ripor2 knockout mouse Mouse recapitulates Early bundle abnormalities and deterioration during postnatal maturation.

Fam65b/Ripor2 knockout mouse Mouse rescues Wild-type RIPOR2 re-expression restores bundle morphology in P2 explants cultured for two days.

Downstream

Impaired Cochlear Mechanotransduction Abnormal bundle structure likely contributes to reduced mechanotransduction. The experiment does not resolve an additional direct transduction role for RIPOR2.

Show evidence (1 reference)

PMID:27269051 SUPPORT Model Organism

"Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected and stereocilia deteriorate."

The full-text time course shows early defects during maturation, rather than normal development followed only by adult maintenance failure.

Impaired Cochlear Mechanotransduction

P5 outer hair cells from Ripor2-null mice retain mechanically evoked currents, with reduced peak amplitude and a shifted, broadened displacement–open-probability curve. Mean saturated currents were approximately 233 pA in null cells and 417 pA in heterozygous controls. Re-expression in P2 explants restored fluid-jet-evoked GCaMP3 calcium responses; that rescue readout is not a direct measurement of restored transduction current.

cochlear outer hair cell CL:0000601

Animal models

Fam65b/Ripor2 knockout mouse Mouse recapitulates Reduced but retained mechanically evoked currents in P5 outer hair cells.

Fam65b/Ripor2 knockout mouse Mouse rescues Re-expression improves fluid-jet-evoked calcium responses in deficient explants.

Downstream

Sensorineural Hearing Loss Impaired hair-cell function provides a model-derived explanation for sensorineural hearing loss; corresponding human hair-cell currents have not been measured.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Mechanotransduction currents could also be evoked in OHCs fromFam65bLacZ/LacZmice but peak currents were reduced (Figure 6A)."

Whole-cell recordings in P5 outer hair cells show reduced, retained currents. The source extraction joins genotype text; this is an ex vivo recording.

Sensorineural Hearing Loss

Early-onset bilateral severe-to-profound hearing loss is the central clinical feature. Stability in the Turkish family cannot be generalized to the Tunisian sibship, whose clinical report describes progression. Mouse deafness was demonstrated at four weeks, not by a neonatal hearing test.

cochlea UBERON:0001844

Animal models

fam65b zebrafish morphant Zebrafish partially recapitulates Reduced inner-ear microphonic responses after knockdown.

Downstream

Bilateral Sensorineural Hearing Impairment The clinical auditory outcome involves both ears.

Profound Sensorineural Hearing Impairment Reported affected individuals have profound loss, including progression to profound severity.

Show evidence (2 references)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

Vestibular End-Organ Dysfunction

Mechanism confidence: Provisional

Vestibular areflexia is documented in the Tunisian siblings. The Turkish family had no reported balance symptoms and normal bedside tests, without an equivalent formal vestibular battery. The molecular explanation and whether this is allele-dependent remain unresolved.

internal ear UBERON:0001846

Animal models

Ripor2 knockout mouse (hair bundle morphogenesis) Mouse fails to recapitulate No overt circling or balance deficit and normal rotarod performance.

ripor2 exon 14 CRISPR zebrafish lines Zebrafish fails to recapitulate No overt vestibular behavioral phenotype in stable F2 larvae.

Downstream

Vestibular Areflexia Formal vestibular testing documents severe dysfunction in the Tunisian family.

Show evidence (1 reference)

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

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Pathograph

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

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Phenotypes

5

Ear 4

Profound Sensorineural Hearing Impairment HP:0011476

Show evidence (3 references)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

PMID:24958875 SUPPORT Human Clinical

"Available audiograms do not suggest progression of hearing loss."

Limited longitudinal evidence in the Turkish family only; it does not establish lifelong stability across RIPOR2 disease.

Prelingual Onset Prelingual sensorineural hearing impairment HP:0000399

Show evidence (1 reference)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

States the onset directly.

Bilateral Sensorineural Hearing Impairment HP:0008619

Show evidence (1 reference)

PMID:37864412 SUPPORT Human Clinical

"in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

States the hearing loss is bilateral and congenital.

Vestibular Areflexia HP:0008568

Show evidence (1 reference)

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

Nervous System 1

Delayed Independent Walking Delayed ability to walk HP:0031936

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Genetic Associations

1

RIPOR2 (Biallelic pathogenic RIPOR2 variants cause DFNB104. Reported alleles include NM_014722.2:c.102-1G>A, producing p.Arg34_Asp86delinsSer, and NM_014722.4:c.1561C>T (p.Arg521*). ClinVar RCV000190353 maps c.102-1G>A and NM_001286445.3:c.189-1G>A to the same genomic allele; these are transcript aliases, not independent variants. The distinct heterozygous c.1696_1707del (p.Gln566_Lys569del) allele causes DFNA21. In-frame deletion alone does not distinguish dominant from recessive disease; specific allele, segregation and phenotype must be considered.)

Gene: RIPOR2 hgnc:13872 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (2 references)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

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Medical Actions

6

Cochlear Implantation

Category: Therapeutic Action: cochlear device implantation Ontology label: Surgical Procedure NCIT:C15329

Platform: Surgery

Consider cochlear implantation according to hearing severity, aided benefit, anatomy and patient/family goals. The 2023 Tunisian report documents unilateral implantation in all three siblings with satisfactory results; this is a small uncontrolled experience, not a genotype-wide response estimate. An implant bypasses hair-cell transduction rather than restoring the stereociliary defect.

Mechanism Target:

BYPASSES Impaired Cochlear Mechanotransduction — Bypasses the failed transduction step by stimulating the auditory nerve directly.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"Cochlear implantation can be considered in children with severe-to-profound hearing loss who are older than age nine months."

General candidacy guidance. Disease-specific outcomes are recorded in the findings for PMID:37864412, whose publisher full text was reviewed.

Early Language Access and Habilitation

Category: Therapeutic Action: auditory habilitation Ontology label: Rehabilitation NCIT:C15315

Platform: Behavioral / lifestyle

Provide timely access to language and communication support, with spoken, signed or combined approaches reflecting patient and family goals. Audiology, speech-language support and educational services are complementary. Newborn screening and early assessment can support identification, but universal detection of every RIPOR2 presentation has not been demonstrated.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"On initial evaluation of individuals with hearing loss, the goals for communication must be established with a focus on equipping individuals with language and appropriate access to language."

General management guidance supports communication access, without restricting benefit to spoken language.

Vestibular Rehabilitation

Category: Therapeutic Action: vestibular rehabilitation Ontology label: Physical Therapy NCIT:C15302

Platform: Behavioral / lifestyle

Refer individuals with vestibular dysfunction or delayed motor development for individualized physical therapy and balance support. This is general management guidance; RIPOR2-specific rehabilitation efficacy has not been measured.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"The finding of vestibular dysfunction may guide physical therapy, particularly in children with delayed motor milestones."

General referral recommendation, rather than evidence that a specific intervention reverses vestibular areflexia.

Genetic Counselling

Category: Counseling / Informational Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Platform: Behavioral / lifestyle

Discuss recurrence risk after establishing the causal recessive variants and parental genotypes. Carrier testing of relatives and reproductive options can be offered according to family preferences. Counseling must distinguish recessive alleles from the specific dominant DFNA21 allele.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"If both parents are known to be heterozygous for an autosomal recessive hearing loss-related pathogenic variant, each sib of the proband has at conception a 25% chance of having hearing loss, a 50% chance of having no hearing loss and being a carrier, and a 25% chance of having no hearing loss..."

General recessive hearing-loss counseling applies after the causal variants and parental genotypes are established.

Audiologic Surveillance

Category: Monitoring

Follow hearing thresholds, communication needs and device benefit over time. Surveillance frequency should be individualized because the limited family reports include both apparently stable and progressive courses.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"Regular follow up is recommended for all individuals with genetic hearing loss in order to:"

General recommendation; sequential audiologic examinations document stability or progression.

Hearing Aids

Category: Therapeutic

Platform: Device

Offer amplification when residual hearing provides useful aided benefit, with reassessment as severity changes and consideration of implantation when indicated.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"Hearing aids (sound amplification), customized by an audiologist to the degree and frequency of hearing loss, can be used in individuals with mild-to-severe hearing loss."

General audiologic guidance; not a measured RIPOR2-specific response rate.

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Diagnosis

3

Comprehensive Hearing Loss Gene Panel or Exome Sequencing

Use a hearing-loss multigene panel or genomic testing, interpreting RIPOR2 variants with inheritance, phase, segregation and the clinical phenotype. Assess assay coverage for deletions and duplications when relevant. A variant of uncertain significance does not confirm or exclude DFNB104. Apparent homozygosity should be reconciled with parental testing. Exome sequencing identified both reported families.

Show evidence (3 references)

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"Recommended molecular genetic testing approaches include use of a multigene hearing loss panel and/or genomic testing."

General testing strategy; RIPOR2-specific causality still requires appropriate variant interpretation.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"The identification of variant(s) of uncertain significance cannot be used to confirm or rule out the diagnosis."

Diagnostic limitation applies to uncertain RIPOR2 findings.

Vestibular Function Testing

Assess vestibular function and motor development in affected individuals. Formal cVEMP and video head-impulse testing documented areflexia in the Tunisian siblings. Normal bedside balance or a negative symptom history cannot substitute for an equivalent vestibular battery.

Show evidence (2 references)

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"The finding of vestibular dysfunction may guide physical therapy, particularly in children with delayed motor milestones."

General care guidance supports assessment and referral; the primary family report supplies the RIPOR2-specific findings.

Audiologic Characterization

Use age-appropriate behavioral audiometry, auditory brainstem responses and otoacoustic emissions to define severity and hearing function. Repeat assessment to establish course; a stable pattern in one family does not predict all RIPOR2 cases.

pure-tone threshold audiometry LOINC:89015-2 hearing threshold, left ear, 500 Hz LOINC:89024-4 hearing threshold, right ear, 500 Hz LOINC:89025-1 hearing threshold, left ear, 1000 Hz LOINC:89016-0 hearing threshold, right ear, 1000 Hz LOINC:89017-8 hearing threshold, left ear, 2000 Hz LOINC:89018-6 hearing threshold, right ear, 2000 Hz LOINC:89019-4 hearing threshold, left ear, 4000 Hz LOINC:89022-8 hearing threshold, right ear, 4000 Hz LOINC:89023-6

Reference Ranges

(Grades recommended by the Global Burden of Disease Expert Group on Hearing Loss, better-ear average of 500, 1000, 2000 and 4000 Hz, as tabulated by Olusanya, Davis and Hoffman (WHO Bulletin))

Normal hearing (< 20 dB) Mild hearing loss (20–35 dB) Moderate hearing loss (35–50 dB) Moderately severe hearing loss (50–65 dB) Severe hearing loss (65–80 dB) Profound hearing loss (80–95 dB) Complete or total hearing loss (≥ 95 dB)

Values are dB hearing level (HL). The source gives each grade as a closed range to one decimal place (Mild hearing loss 20.0 to 34.9 dB hearing level, and so on up to Complete or total hearing loss 95.0 dB hearing level or greater); the half-open bands here are the same partition. The source splits normal hearing into -10.0 to 4.9 and 5.0 to 19.9 dB hearing level; both are folded into one Normal hearing band. Its Unilateral category (below 20.0 dB in the better ear, 35.0 dB or greater in the worse ear) needs both ears and is not representable as a band. Severity is set only where the grade name is mild, moderate or severe. Bonetti (PMID:41718341) applies the same boundaries, up to moderately severe, as the WHO-defined hearing loss categories; the WHO report itself is not PubMed-indexed, so the grades are quoted from these restatements. No LOINC code was found for the better-ear four-frequency pure-tone average these grades read: Monarch KG searches for pure tone average, threshold average, average hearing, PTA and hearing level returned none. The range therefore names no loinc_term. A numeric band on the panel LOINC:89015-2 would put a number on an instrument, and on any one frequency code would misstate what is graded; the average is computed from the eight per-frequency codes bound above. LOINC:98422-9 (Hearing loss degree Ear - left) and LOINC:98427-8 (Hearing loss degree Ear - right) exist but carry the category, not the dB value, so they are not bound. The grading is generic to hearing loss of any cause, not specific to this disease. The severity words this entry uses come from its cited clinical sources, which do not necessarily use these boundaries.

Show evidence (5 references)

PMID:31656340 SUPPORT REVIEW SYNTHESIS Other

"Mild hearing loss | 20.0 to 34.9 dB hearing level"

Table 2 row giving the lower boundary of hearing loss and the mild grade in the Global Burden of Disease Expert Group scheme.

PMID:31656340 SUPPORT REVIEW SYNTHESIS Other

"Profound hearing loss | 80.0 to 94.9 dB hearing level"

Table 2 row giving the profound grade.

PMID:31656340 SUPPORT REVIEW SYNTHESIS Other

"Complete or total hearing loss | 95.0 dB hearing level or greater"

Table 2 row giving the top, open-ended grade.

+ 2 more references

(Earlier WHO grades of hearing impairment (based on the 1991 version), better-ear average of 500, 1000, 2000 and 4000 Hz, as tabulated by Olusanya, Davis and Hoffman (WHO Bulletin))

Grade 0: no impairment (< 26 dB) Grade 1: slight impairment (26–41 dB) Grade 2: moderate impairment (41–61 dB) Grade 3: severe impairment (61–81 dB) Grade 4: profound impairment including deafness (≥ 81 dB)

Superseded scheme, recorded because older clinical literature reports severity on it and its boundaries differ from the Global Burden of Disease grades above. The source states whole-decibel ranges (25 dB or better, 26-40 dB, 41-60 dB, 61-80 dB, 81 dB or greater); an average falling between two stated ranges, such as 25.5 dB, is not assigned by the source and falls in the upper grade under the half-open convention used here. The same source records that only adults with a permanent unaided impairment above 40 dB hearing level in the better ear, and children with more than 30 dB, were regarded as having a disabling hearing impairment. Severity is set only where the grade name is moderate or severe. The grading is generic to hearing loss of any cause.

Show evidence (3 references)

PMID:31656340 SUPPORT REVIEW SYNTHESIS Other

"1: slight impairment | 26-40 dB | Able to hear and repeat words spoken in normal voice at 1 m"

Table 1 row giving the slight grade in the earlier WHO scheme.

PMID:31656340 SUPPORT REVIEW SYNTHESIS Other

"4: profound impairment including deafness | 81 dB or greater"

Table 1 row giving the top grade in the earlier WHO scheme.

PMID:31656340 SUPPORT REVIEW SYNTHESIS Other

"currently only adults (≥ 15 years) with a permanent unaided hearing impairment above 40 dB hearing level in the better ear and children (from birth to 14 years of age) with > 30 dB hearing level are regarded as having a disabling hearing impairment"

Places the earlier scheme's disabling-impairment cut-offs in the better ear.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"Hearing status can be determined at any age and is tailored to the individual's ability to participate (see Audiometric and Clinical Characteristics of Hearing Loss)."

General audiologic assessment guidance.

📊

Prevalence

1

Worldwide

Cases In Literature Not yet documented

Two published recessive families anchor the clinical evidence: six affected Turkish relatives with a splice variant and three Tunisian siblings with a nonsense variant. These family reports do not establish population prevalence, complete penetrance or that either allele is globally private.

Show evidence (2 references)

PMID:24958875 SUPPORT Human Clinical

"In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family."

Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.

PMID:37864412 SUPPORT Human Clinical

"A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound hearing and vestibular dysfunctions."

The abstract establishes the second family and cochleovestibular phenotype.

🔀

Differential Diagnoses

2

Conditions with similar clinical presentations that must be differentiated from Autosomal Recessive Nonsyndromic Hearing Loss 104:

Usher syndrome

Overlapping Features Usher syndrome type I can initially resemble early deafness with vestibular areflexia. Retinal degeneration may emerge later, so a normal early eye examination does not exclude it. Molecular testing and longitudinal clinical assessment distinguish the diagnoses.

Distinguishing Features

Pathogenic variants in an Usher-associated gene rather than recessive RIPOR2 alleles
Retinal degeneration supports Usher syndrome, but its absence early in life is not exclusionary

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"ophthalmology evaluation may be recommended, as individuals with hearing loss may depend more on vision for sensory input, as well as to evaluate for retinitis pigmentosa."

General hearing-loss evaluation includes assessment for retinal disease.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf SUPPORT REVIEW SYNTHESIS Other

"Nonsyndromic HL mimic: HL is congenital; RP begins in late adolescence or early adulthood."

The Usher type I row explicitly describes a nonsyndromic hearing-loss mimic before retinal disease emerges.

🐁

Animal Models

4

Fam65b/Ripor2 knockout mouse

Constitutive null model studied for taper organization, bundle morphology and hearing function. Heterologous-cell interaction assays and explant rescue are classified separately from intact-animal evidence.

Species

Mouse

Genotype

Homozygous Ripor2tm1(KOMP)Vlcg; exons 2–14 replaced by lacZ on a C57BL/6 background

Publication

PMID:27269051

Pathograph links

Disorganisation of the Taper Compartment recapitulates fidelity: moderate Reduced and diffuse taperin staining, with preserved espin.

Limitations: Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism, not complete clinical equivalence.

Readouts

Taperin localization

Direction: ALTERED

Interpretation: Taperin becomes diffuse in deficient hair cells.

Show evidence (1 reference)

PMID:27269051 SUPPORT Model Organism

"The taperin signal is reduced and diffused in mutant hair cells, while the espin signal is similar."

Figure 5 distinguishes altered taperin localization from preserved espin staining; a direct RIPOR2–taperin interaction was not detected.

Show evidence (1 reference)

PMID:27269051 SUPPORT Model Organism

"The taperin signal is reduced and diffused in mutant hair cells, while the espin signal is similar."

Figure 5 distinguishes altered taperin localization from preserved espin staining; a direct RIPOR2–taperin interaction was not detected.

Stereocilia Disorganisation recapitulates fidelity: moderate Early bundle abnormalities and deterioration during postnatal maturation.

Limitations: Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism, not complete clinical equivalence.

Readouts

Stereocilia morphology

Direction: ALTERED

Interpretation: Inner hair-cell defects are already present at P2 and affect both cell types by P5.

Show evidence (1 reference)

PMID:27269051 SUPPORT Model Organism

"Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected and stereocilia deteriorate."

The full-text time course shows early defects during maturation, rather than normal development followed only by adult maintenance failure.

Show evidence (1 reference)

PMID:27269051 SUPPORT Model Organism

"Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected and stereocilia deteriorate."

The full-text time course shows early defects during maturation, rather than normal development followed only by adult maintenance failure.

Impaired Cochlear Mechanotransduction recapitulates fidelity: moderate Reduced but retained mechanically evoked currents in P5 outer hair cells.

Limitations: Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism, not complete clinical equivalence.

Readouts

Peak mechanotransduction current

Direction: DECREASED

Interpretation: Null cells average approximately 233 pA versus 417 pA in heterozygous controls.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Mechanotransduction currents could also be evoked in OHCs fromFam65bLacZ/LacZmice but peak currents were reduced (Figure 6A)."

Whole-cell recordings in P5 outer hair cells show reduced, retained currents. The source extraction joins genotype text; this is an ex vivo recording.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Mechanotransduction currents could also be evoked in OHCs fromFam65bLacZ/LacZmice but peak currents were reduced (Figure 6A)."

Whole-cell recordings in P5 outer hair cells show reduced, retained currents. The source extraction joins genotype text; this is an ex vivo recording.

Stereocilia Disorganisation rescues fidelity: moderate Wild-type RIPOR2 re-expression restores bundle morphology in P2 explants cultured for two days.

Limitations: Ex vivo neonatal rescue does not establish in vivo hearing recovery, adult efficacy, delivery feasibility or a closed therapeutic window.

Readouts

Stereocilia morphology after re-expression

Direction: RESTORED

Interpretation: Wild-type construct restores bundle shape; RL/AA fails.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Note morphological defects of stereocilia were rescued by Fam65b-GFP but not by Fam65bRL/AA-GFP."

Figure 9 rescue in cultured hair cells. RL/AA also affects basal homophilic binding, limiting isolation of RhoC-specific causality.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Note morphological defects of stereocilia were rescued by Fam65b-GFP but not by Fam65bRL/AA-GFP."

Figure 9 rescue in cultured hair cells. RL/AA also affects basal homophilic binding, limiting isolation of RhoC-specific causality.

Impaired Cochlear Mechanotransduction rescues fidelity: moderate Re-expression improves fluid-jet-evoked calcium responses in deficient explants.

Limitations: Calcium response is a functional proxy; restored whole-cell current was not directly measured in this rescue.

Readouts

Fluid-jet-evoked calcium response

Direction: RESTORED

Interpretation: GCaMP3 response improves after re-expression.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Representative example demonstrating fluid–jet induced Ca2+response in G-CaMP3-expressing OHCs from controls,Fam65bmutants, andFam65bmutants following re-expression of Fam65b."

Figure 6 uses calcium imaging after P2 injectoporation and two days in culture.

Show evidence (1 reference)

PMID:27269051 SUPPORT In Vitro

"Representative example demonstrating fluid–jet induced Ca2+response in G-CaMP3-expressing OHCs from controls,Fam65bmutants, andFam65bmutants following re-expression of Fam65b."

Figure 6 uses calcium imaging after P2 injectoporation and two days in culture.

Ripor2 knockout mouse (hair bundle morphogenesis)

The same KOMP null allele studied for polarity, protein abundance and vestibular behavior.

Species

Mouse

Genotype

Homozygous Ripor2tm1(KOMP)Vlcg; exons 2–14 replaced by lacZ on a C57BL/6 background

Publication

PMID:30280293

Pathograph links

Misorientation of Developing Hair Bundles recapitulates fidelity: moderate Embryonic and postnatal orientation defects.

Limitations: Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism, not complete clinical equivalence.

Readouts

Hair-bundle orientation

Direction: ALTERED

Interpretation: Excess angular deviations and abnormal kinocilium position at E18.5 and P5.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects the orientation of this key subcellular structure."

Orientation and kinocilium-position defects are present at E18.5 and P5 in null mice.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects the orientation of this key subcellular structure."

Orientation and kinocilium-position defects are present at E18.5 and P5 in null mice.

Reduced Cochlear MYH9 Abundance recapitulates fidelity: moderate Reduced protein abundance despite increased transcript.

Limitations: Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism, not complete clinical equivalence.

Readouts

Cochlear MYH9 protein abundance

Direction: DECREASED

Interpretation: Protein/transcript discordance does not establish altered protein half-life.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount of Myh9 transcripts."

Cochlear protein and transcript measurements establish post-transcriptional discordance, without measuring protein turnover.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount of Myh9 transcripts."

Cochlear protein and transcript measurements establish post-transcriptional discordance, without measuring protein turnover.

Reduced Cochlear Tubulin Acetylation recapitulates fidelity: moderate Reduced acetylated alpha-tubulin in cochlear extracts.

Limitations: Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism, not complete clinical equivalence.

Readouts

Acetylated alpha-tubulin abundance

Direction: DECREASED

Interpretation: Immunoblot signal is reduced without demonstrated kinocilium shortening.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Western blot analysis shows a decrease on the content of alpha-acetyl-tubulin in protein extracts from cochleae of Ripor2 deficient mice (Fig. 5E, F)."

The measured acetylated-tubulin abundance is separate from the proposed HDAC6 mechanism.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Western blot analysis shows a decrease on the content of alpha-acetyl-tubulin in protein extracts from cochleae of Ripor2 deficient mice (Fig. 5E, F)."

The measured acetylated-tubulin abundance is separate from the proposed HDAC6 mechanism.

Vestibular End-Organ Dysfunction fails to recapitulate fidelity: moderate No overt circling or balance deficit and normal rotarod performance.

Limitations: Mouse behavioral tests are not equivalent to the human cVEMP and video head-impulse battery. A species-specific absence of vestibular pathology is not established.

Show evidence (1 reference)

PMID:30280293 SUPPORT Model Organism

"Absence of circling and balance defects as well as a normal performance in the rotating rod tests suggest a normal vestibular function for Ripor2 KO mouse (Fig. S1D)."

Behavioral screening does not exclude subtle vestibular end-organ dysfunction.

fam65b zebrafish morphant

Transient knockdown at 3 dpf reduces saccular hair-cell and neuromast numbers and microphonic amplitudes. Mild cardiac edema occurred. This experiment is distinct from the later stable CRISPR lines.

Species

Zebrafish

Genotype

Two splice-blocking morpholinos causing intron 2 or intron 3 retention

Publication

PMID:24958875

Pathograph links

Sensorineural Hearing Loss partially recapitulates fidelity: moderate Reduced inner-ear microphonic responses after knockdown.

Limitations: Transient morpholino exposure, nonhuman lateral-line anatomy and cell loss limit comparison with the human alleles. Both amplitudes fell, but only MO1 significantly raised threshold.

Show evidence (1 reference)

PMID:24958875 SUPPORT Model Organism

"After activation by 200-Hz stimulation, MO1 and MO2 morphants had weaker microphonic response than the controls did (Fig. 5 I and J)."

Both splice-blocking morpholinos reduce microphonic amplitudes at 3 dpf; only MO1 significantly increased threshold.

ripor2 exon 14 CRISPR zebrafish lines

Stable exon-14 CRISPR lines showed no hearing or balance behavioral difference at 5 dpf. This differs from the 2014 morphants. The publisher full text, rather than its compressed abstract, establishes the hearing result.

Species

Zebrafish

Genotype

Three stable exon 14 premature-stop lines; homozygous F2 larvae

Publication

PMID:37864412

Pathograph links

Vestibular End-Organ Dysfunction fails to recapitulate fidelity: moderate No overt vestibular behavioral phenotype in stable F2 larvae.

Limitations: Behavior at 5 dpf does not exclude subtle sensory dysfunction. Transient F0 circling was not retained in stable homozygotes; these are not promoter-deletion nulls.

Show evidence (1 reference)

PMID:37864412 SUPPORT Model Organism

"In contrast to the vestibular areflexia observed in our patients, deaf Ripor2 KO mouse model and our zebrafish model have normal vestibular function."

Abstract comparison; the full text specifies stable exon-14 F2 lines and behavioral assessment, with compensation proposed but untested.

{ }

Source YAML

click to show

name: Autosomal Recessive Nonsyndromic Hearing Loss 104
creation_date: "2026-08-26T14:00:00Z"
category: Mendelian
disease_term:
  preferred_term: autosomal recessive nonsyndromic hearing loss 104
  term:
    id: MONDO:0014675
    label: autosomal recessive nonsyndromic hearing loss 104
synonyms:
- DFNB104
- deafness, autosomal recessive 104
- RIPOR2-related autosomal recessive nonsyndromic hearing loss
- FAM65B-related deafness
description: >-
  Autosomal recessive hearing loss caused by biallelic pathogenic RIPOR2 (formerly FAM65B) variants. Reported
  families have early-onset bilateral severe-to-profound sensorineural hearing loss; vestibular areflexia occurs
  in the Tunisian sibship. Available audiograms suggested stability in the Turkish family, whereas the Tunisian
  report describes progression from severe to profound loss. Mouse and cell studies implicate stereociliary
  taper organization, hair-bundle morphogenesis and impaired mechanotransduction. Human inner-ear cellular
  mechanisms remain inferred from these models. The allele-specific dominant disorder DFNA21 is a differential
  diagnosis.

parents:
- Autosomal Recessive Nonsyndromic Hearing Loss
- Hereditary Hearing Loss

prevalence:
- population: Worldwide
  measure_type: CASES_IN_LITERATURE
  prevalence_class: NOT_YET_DOCUMENTED
  notes: >-
    Two published recessive families anchor the clinical evidence: six affected Turkish relatives with a splice
    variant and three Tunisian siblings with a nonsense variant. These family reports do not establish population
    prevalence, complete penetrance or that either allele is globally private.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss,
      we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates
      with the phenotype in the family.
    explanation: >-
      Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
pathophysiology:
- name: Biallelic RIPOR2 Loss-of-Function Variant
  role: trigger
  biological_scale: MOLECULAR
  description: >-
    The Turkish NM_014722.2:c.102-1G>A allele causes exon 3 skipping in patient leukocyte RNA, producing p.Arg34_Asp86delinsSer,
    a net 52-residue deletion. The Tunisian NM_014722.4:c.1561C>T (p.Arg521*) allele is predicted to truncate
    RIPOR2 or reduce its abundance; patient protein absence and nonsense-mediated decay were not demonstrated.
    The proposed PX–BAR domain interpretation of the N-terminal deletion was challenged in published correspondence
    and remains unverified.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss,
      we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates
      with the phenotype in the family.
    explanation: >-
      Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Gel electrophoresis and sequence analysis of cDNA synthesized from leukocyte mRNA from family members
      revealed that exon 3 of FAM65B was absent in all affected relatives, whereas heterozygous individuals
      (III:9, III:10, IV:3, IV:4) carried both the wild-type and the mutant transcripts (Fig. 1 D and F).
    explanation: >-
      RNA from affected and heterozygous relatives demonstrates exon skipping; this is a patient-derived molecular
      assay, not only a splice prediction.
  genetic_context:
    gene:
      preferred_term: RIPOR2
      term:
        id: hgnc:13872
        label: RIPOR2
    variant_origin: GERMLINE
    zygosity: HOMOZYGOUS
    functional_impact_category: LOSS_OF_FUNCTION
    description: >-
      Homozygous splice-acceptor and nonsense variants segregate in the reported recessive families. Loss of
      function includes defective localization of an in-frame deletion product; protein absence is not demonstrated
      for every human allele.
  downstream:
  - target: Loss of RIPOR2 from the Stereociliary Taper
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Deletion constructs mislocalize in expression assays; null mice lack RIPOR2. The nonsense allele is predicted
      to reduce functional protein, but its molecular fate is unresolved.
  - target: Vestibular End-Organ Dysfunction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Human segregation supports a RIPOR2-related vestibular phenotype. Its cellular intermediates and allele
      dependence are not established.
  genes:
  - preferred_term: RIPOR2
    term:
      id: hgnc:13872
      label: RIPOR2
- name: Loss of RIPOR2 from the Stereociliary Taper
  role: central_effector
  biological_scale: MOLECULAR
  description: >-
    RIPOR2 localizes around the basal stereociliary taper in mouse hair cells. Patient-deletion constructs
    accumulate in cytoplasmic inclusions in COS7 cells, and a related construct fails normal targeting in cultured
    mouse hair cells. These overexpression results support defective localization; they do not show endogenous
    mutant protein abundance or localization in the human cochlea. STORM ring geometry does not by itself establish
    direct lipid binding.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      The wild-type protein targets the plasma membrane, whereas the mutant protein accumulates in cytoplasmic
      inclusion bodies and does not reach the membrane.
    explanation: >-
      Transfected COS7 cells expressing the deletion construct; this does not measure endogenous protein abundance
      in patients.
  - reference: PMID:27269051
    reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Using biochemistry and stochastic optical reconstruction microscopy (STORM), we show here that Fam65b
      oligomers form a circumferential ring near the basal taper of the mechanically sensitive stereocilia
      of murine hair cells.
    explanation: >-
      Mouse imaging and heterologous biochemistry support a ring-like oligomeric organization.
  cell_types:
  - preferred_term: cochlear inner hair cell
    term:
      id: CL:0000589
      label: cochlear inner hair cell
  - preferred_term: cochlear outer hair cell
    term:
      id: CL:0000601
      label: cochlear outer hair cell
  cellular_components:
  - preferred_term: stereocilium
    term:
      id: GO:0032420
      label: stereocilium
  locations:
  - preferred_term: cochlea
    term:
      id: UBERON:0001844
      label: cochlea
  downstream:
  - target: Disorganisation of the Taper Compartment
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      RIPOR2 deficiency disrupts taperin localization, through an unresolved direct or secondary mechanism.
  - target: Reduced Cochlear MYH9 Abundance
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Ripor2-null cochleae have reduced MYH9 protein despite increased transcript.
  - target: Reduced Cochlear Tubulin Acetylation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Ripor2-null cochlear extracts have reduced acetylated alpha-tubulin.
  - target: Stereocilia Disorganisation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Loss of RIPOR2 causes abnormal stereocilia during early postnatal maturation; re-expression rescues morphology
      in explants.
  - target: Misorientation of Developing Hair Bundles
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Null mice show embryonic and postnatal bundle-orientation defects. The contribution of taper organization
      versus other RIPOR2 functions is unresolved.
- name: Disorganisation of the Taper Compartment
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    Taperin staining becomes reduced and diffuse in Ripor2-null hair cells, whereas espin staining is retained.
    No direct interaction with taperin, CLIC5, radixin, whirlin or the PTPRQ cytoplasmic domain was detected
    in the tested heterologous assays. RhoC enhances N-terminal RIPOR2 oligomerization in HEK293 cells, and
    tagged RhoC colocalizes with RIPOR2 in explants. The RL/AA construct fails rescue but also reduces basal
    homophilic binding, so it does not isolate a uniquely RhoC-dependent effect. A primary taper defect versus
    secondary disruption by abnormal bundle morphology remains unresolved.
  evidence:
  - reference: PMID:27269051
    reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The taperin signal is reduced and diffused in mutant hair cells, while the espin signal is similar.
    explanation: >-
      Figure 5 distinguishes altered taperin localization from preserved espin staining; a direct RIPOR2–taperin
      interaction was not detected.
  - reference: PMID:27269051
    reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      In fact, the mutation appeared to even reduce the basal homophilic binding activity of Fam65b that is
      observed without expression of RhoC (Figure 9H,I).
    explanation: >-
      This control limits causal interpretation of the RhoC-binding-deficient rescue construct.
  cell_types:
  - preferred_term: cochlear inner hair cell
    term:
      id: CL:0000589
      label: cochlear inner hair cell
  - preferred_term: cochlear outer hair cell
    term:
      id: CL:0000601
      label: cochlear outer hair cell
  cellular_components:
  - preferred_term: stereocilium
    term:
      id: GO:0032420
      label: stereocilium
  biological_processes:
  - preferred_term: auditory receptor cell stereocilium organization
    term:
      id: GO:0060088
      label: auditory receptor cell stereocilium organization
    modifier: ABNORMAL
- name: Reduced Cochlear MYH9 Abundance
  role: effector
  biological_scale: MOLECULAR
  description: >-
    MYH9 protein and its Ser1943-phosphorylated form are reduced in Ripor2-null cochleae despite increased
    Myh9 transcript. Tagged-protein co-immunoprecipitation supports association with RIPOR2. Reduced protein
    abundance is established; altered translation versus degradation and a causal role in kinocilium migration
    remain unresolved.
  evidence:
  - reference: PMID:30280293
    reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount
      of Myh9 transcripts.
    explanation: >-
      Cochlear protein and transcript measurements establish post-transcriptional discordance, without measuring
      protein turnover.
  - reference: PMID:30280293
    reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      The RIPOR2-MYH9 interaction was validated by co-immunoprecipitation using HEK293 cells overexpressing
      both proteins with two different tags (Fig. 3B) and by immunohistochemistry (Fig. 3C).
    explanation: >-
      Tagged proteins associate in heterologous cells; this does not establish purified direct binding.
  cell_types:
  - preferred_term: cochlear inner hair cell
    term:
      id: CL:0000589
      label: cochlear inner hair cell
  - preferred_term: cochlear outer hair cell
    term:
      id: CL:0000601
      label: cochlear outer hair cell
- name: Reduced Cochlear Tubulin Acetylation
  role: effector
  biological_scale: MOLECULAR
  description: >-
    K40-acetylated alpha-tubulin is reduced in Ripor2-null cochlear extracts. Kinocilium length was not detectably
    changed. A RIPOR2–HDAC6 mechanism was proposed from nonauditory work, but cochlear HDAC6 localization and
    activity were not established in this study.
  evidence:
  - reference: PMID:30280293
    reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Western blot analysis shows a decrease on the content of alpha-acetyl-tubulin in protein extracts from
      cochleae of Ripor2 deficient mice (Fig. 5E, F).
    explanation: >-
      The measured acetylated-tubulin abundance is separate from the proposed HDAC6 mechanism.
  cellular_components:
  - preferred_term: kinocilium
    term:
      id: GO:0060091
      label: kinocilium
- name: Misorientation of Developing Hair Bundles
  role: effector
  biological_scale: CELLULAR
  description: >-
    Ripor2-null cochleae have displaced kinocilia and increased deviations of hair-bundle orientation at E18.5
    and P5. Reduced MYH9 and acetylated tubulin accompany the phenotype, but neither was selectively rescued
    to establish its contribution to polarity.
  evidence:
  - reference: PMID:30280293
    reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects
      the orientation of this key subcellular structure.
    explanation: >-
      Orientation and kinocilium-position defects are present at E18.5 and P5 in null mice.
  cell_types:
  - preferred_term: cochlear inner hair cell
    term:
      id: CL:0000589
      label: cochlear inner hair cell
  - preferred_term: cochlear outer hair cell
    term:
      id: CL:0000601
      label: cochlear outer hair cell
  cellular_components:
  - preferred_term: stereocilium bundle
    term:
      id: GO:0032421
      label: stereocilium bundle
  - preferred_term: kinocilium
    term:
      id: GO:0060091
      label: kinocilium
- name: Stereocilia Disorganisation
  role: effector
  biological_scale: CELLULAR
  description: >-
    Inner-hair-cell bundles are already severely disorganized at P2 in Ripor2-null mice; outer-hair-cell bundles
    initially retain much of their staircase arrangement but show orientation defects. By P5 both cell types
    have abnormal length, thickness or arrangement of stereocilia. Deterioration occurs during maturation.
    Little hair-cell loss is evident at P16/P28, so bundle pathology is not equivalent to early wholesale hair-cell
    death.
  evidence:
  - reference: PMID:27269051
    reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected
      and stereocilia deteriorate.
    explanation: >-
      The full-text time course shows early defects during maturation, rather than normal development followed
      only by adult maintenance failure.
  cell_types:
  - preferred_term: cochlear inner hair cell
    term:
      id: CL:0000589
      label: cochlear inner hair cell
  - preferred_term: cochlear outer hair cell
    term:
      id: CL:0000601
      label: cochlear outer hair cell
  cellular_components:
  - preferred_term: stereocilium bundle
    term:
      id: GO:0032421
      label: stereocilium bundle
  downstream:
  - target: Impaired Cochlear Mechanotransduction
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Abnormal bundle structure likely contributes to reduced mechanotransduction. The experiment does not
      resolve an additional direct transduction role for RIPOR2.
- name: Impaired Cochlear Mechanotransduction
  role: effector
  biological_scale: CELLULAR
  description: >-
    P5 outer hair cells from Ripor2-null mice retain mechanically evoked currents, with reduced peak amplitude
    and a shifted, broadened displacement–open-probability curve. Mean saturated currents were approximately
    233 pA in null cells and 417 pA in heterozygous controls. Re-expression in P2 explants restored fluid-jet-evoked
    GCaMP3 calcium responses; that rescue readout is not a direct measurement of restored transduction current.
  evidence:
  - reference: PMID:27269051
    reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Mechanotransduction currents could also be evoked in OHCs fromFam65bLacZ/LacZmice but peak currents were
      reduced (Figure 6A).
    explanation: >-
      Whole-cell recordings in P5 outer hair cells show reduced, retained currents. The source extraction joins
      genotype text; this is an ex vivo recording.
  cell_types:
  - preferred_term: cochlear outer hair cell
    term:
      id: CL:0000601
      label: cochlear outer hair cell
  downstream:
  - target: Sensorineural Hearing Loss
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    description: >-
      Impaired hair-cell function provides a model-derived explanation for sensorineural hearing loss; corresponding
      human hair-cell currents have not been measured.
- name: Sensorineural Hearing Loss
  role: outcome
  biological_scale: ORGANISM
  description: >-
    Early-onset bilateral severe-to-profound hearing loss is the central clinical feature. Stability in the
    Turkish family cannot be generalized to the Tunisian sibship, whose clinical report describes progression.
    Mouse deafness was demonstrated at four weeks, not by a neonatal hearing test.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss,
      we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates
      with the phenotype in the family.
    explanation: >-
      Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
  locations:
  - preferred_term: cochlea
    term:
      id: UBERON:0001844
      label: cochlea
  downstream:
  - target: Bilateral Sensorineural Hearing Impairment
    causal_link_type: DIRECT
    description: >-
      The clinical auditory outcome involves both ears.
  - target: Profound Sensorineural Hearing Impairment
    causal_link_type: DIRECT
    description: >-
      Reported affected individuals have profound loss, including progression to profound severity.
- name: Vestibular End-Organ Dysfunction
  role: outcome
  biological_scale: ORGANISM
  description: >-
    Vestibular areflexia is documented in the Tunisian siblings. The Turkish family had no reported balance
    symptoms and normal bedside tests, without an equivalent formal vestibular battery. The molecular explanation
    and whether this is allele-dependent remain unresolved.
  evidence:
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
  mechanism_confidence: PROVISIONAL
  locations:
  - preferred_term: internal ear
    term:
      id: UBERON:0001846
      label: internal ear
  downstream:
  - target: Vestibular Areflexia
    causal_link_type: DIRECT
    description: >-
      Formal vestibular testing documents severe dysfunction in the Tunisian family.
phenotypes:
- category: Otologic
  name: Profound Sensorineural Hearing Impairment
  severity: SEVERE
  description: >-
    Profound loss was reported in the Turkish family. The Tunisian clinical report describes severe hearing
    loss progressing to profound levels. Universal lifelong stability is not established.
  phenotype_term:
    preferred_term: Profound sensorineural hearing impairment
    term:
      id: HP:0011476
      label: Profound sensorineural hearing impairment
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss,
      we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates
      with the phenotype in the family.
    explanation: >-
      Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Available audiograms do not suggest progression of hearing loss.
    explanation: >-
      Limited longitudinal evidence in the Turkish family only; it does not establish lifelong stability across
      RIPOR2 disease.
- category: Otologic
  name: Prelingual Onset
  phenotype_term:
    preferred_term: Prelingual sensorineural hearing impairment
    term:
      id: HP:0000399
      label: Prelingual sensorineural hearing impairment
  description: >-
    Prelingual hearing loss was reported in the Turkish kindred. Age at diagnosis may differ from onset, and
    family ascertainment does not establish a population frequency.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual,
      profound hearing loss, we identified in the gene FAM65B (MIM611410) a splice site
      mutation (c.102-1G>A) that perfectly cosegregates with the phenotype in the family.
    explanation: >-
      States the onset directly.

- category: Otologic
  name: Bilateral Sensorineural Hearing Impairment
  phenotype_term:
    preferred_term: Bilateral sensorineural hearing impairment
    term:
      id: HP:0008619
      label: Bilateral sensorineural hearing impairment
  evidence:
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      in RIPOR2 (RHO family interacting cell polarization regulator 2) has been identified
      by WES in Tunisian siblings suffering from congenital bilateral profound hearing and
      vestibular dysfunctions.
    explanation: >-
      States the hearing loss is bilateral and congenital.

- category: Otologic
  name: Vestibular Areflexia
  description: >-
    Documented in three Tunisian siblings. Absence of symptoms in the Turkish family is not equivalent to normal
    formal vestibular testing; frequency and allele specificity remain unknown.
  phenotype_term:
    preferred_term: Vestibular areflexia
    term:
      id: HP:0008568
      label: Vestibular areflexia
  evidence:
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
- category: Neurologic
  name: Delayed Independent Walking
  description: >-
    The three Tunisian siblings walked independently at 21–24 months. This finding is reported in the publisher
    full text of PMID:37864412, alongside vestibular areflexia; the cached abstract omits the milestone data.
    It is not a measured population frequency.
  phenotype_term:
    preferred_term: Delayed ability to walk
    term:
      id: HP:0031936
      label: Delayed ability to walk
genetic:
- name: RIPOR2
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  gene_term:
    preferred_term: RIPOR2
    term:
      id: hgnc:13872
      label: RIPOR2
  association: >-
    Biallelic pathogenic RIPOR2 variants cause DFNB104. Reported alleles include NM_014722.2:c.102-1G>A, producing
    p.Arg34_Asp86delinsSer, and NM_014722.4:c.1561C>T (p.Arg521*). ClinVar RCV000190353 maps c.102-1G>A and
    NM_001286445.3:c.189-1G>A to the same genomic allele; these are transcript aliases, not independent variants.
    The distinct heterozygous c.1696_1707del (p.Gln566_Lys569del) allele causes DFNA21. In-frame deletion alone
    does not distinguish dominant from recessive disease; specific allele, segregation and phenotype must be
    considered.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss,
      we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates
      with the phenotype in the family.
    explanation: >-
      Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Autosomal recessive inheritance is supported by homozygous affected individuals and heterozygous parents
    in the reported pedigrees. Consanguinity facilitated ascertainment but is not required for this inheritance
    pattern. When both parents carry a causal recessive allele, recurrence risk is 25% per pregnancy. The specific
    dominant DFNA21 allele has different counseling implications.
  evidence:
  - reference: PMID:24958875
    reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In a large consanguineous Turkish kindred with recessive nonsyndromic, prelingual, profound hearing loss,
      we identified in the gene FAM65B (MIM611410) a splice site mutation (c.102-1G>A) that perfectly cosegregates
      with the phenotype in the family.
    explanation: >-
      Segregation in the discovery pedigree supports recessive RIPOR2-associated hearing loss.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      If both parents are known to be heterozygous for an autosomal recessive hearing loss-related pathogenic
      variant, each sib of the proband has at conception a 25% chance of having hearing loss, a 50% chance
      of having no hearing loss and being a carrier, and a 25% chance of having no hearing loss and not being
      a carrier.
    explanation: >-
      General recessive hearing-loss counseling applies after the causal variants and parental genotypes are
      established.
    quote_role: REVIEW_SYNTHESIS
animal_models:
- name: Fam65b/Ripor2 knockout mouse
  species: Mouse
  genotype: Homozygous Ripor2tm1(KOMP)Vlcg; exons 2–14 replaced by lacZ on a C57BL/6 background
  publication: PMID:27269051
  description: >-
    Constitutive null model studied for taper organization, bundle morphology and hearing function. Heterologous-cell
    interaction assays and explant rescue are classified separately from intact-animal evidence.
  modeled_mechanisms:
  - target: Disorganisation of the Taper Compartment
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reduced and diffuse taperin staining, with preserved espin.
    limitations: >-
      Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism,
      not complete clinical equivalence.
    evidence:
    - reference: PMID:27269051
      reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        The taperin signal is reduced and diffused in mutant hair cells, while the espin signal is similar.
      explanation: >-
        Figure 5 distinguishes altered taperin localization from preserved espin staining; a direct RIPOR2–taperin
        interaction was not detected.
    readouts:
    - name: Taperin localization
      target: Disorganisation of the Taper Compartment
      direction: ALTERED
      interpretation: >-
        Taperin becomes diffuse in deficient hair cells.
      evidence:
      - reference: PMID:27269051
        reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          The taperin signal is reduced and diffused in mutant hair cells, while the espin signal is similar.
        explanation: >-
          Figure 5 distinguishes altered taperin localization from preserved espin staining; a direct RIPOR2–taperin
          interaction was not detected.
  - target: Stereocilia Disorganisation
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Early bundle abnormalities and deterioration during postnatal maturation.
    limitations: >-
      Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism,
      not complete clinical equivalence.
    evidence:
    - reference: PMID:27269051
      reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected
        and stereocilia deteriorate.
      explanation: >-
        The full-text time course shows early defects during maturation, rather than normal development followed
        only by adult maintenance failure.
    readouts:
    - name: Stereocilia morphology
      target: Stereocilia Disorganisation
      direction: ALTERED
      interpretation: >-
        Inner hair-cell defects are already present at P2 and affect both cell types by P5.
      evidence:
      - reference: PMID:27269051
        reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Stereocilia of Fam65b-deficient murine hair cells start to develop, but mechanotransduction is affected
          and stereocilia deteriorate.
        explanation: >-
          The full-text time course shows early defects during maturation, rather than normal development followed
          only by adult maintenance failure.
  - target: Impaired Cochlear Mechanotransduction
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reduced but retained mechanically evoked currents in P5 outer hair cells.
    limitations: >-
      Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism,
      not complete clinical equivalence.
    evidence:
    - reference: PMID:27269051
      reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Mechanotransduction currents could also be evoked in OHCs fromFam65bLacZ/LacZmice but peak currents
        were reduced (Figure 6A).
      explanation: >-
        Whole-cell recordings in P5 outer hair cells show reduced, retained currents. The source extraction
        joins genotype text; this is an ex vivo recording.
    readouts:
    - name: Peak mechanotransduction current
      target: Impaired Cochlear Mechanotransduction
      direction: DECREASED
      interpretation: >-
        Null cells average approximately 233 pA versus 417 pA in heterozygous controls.
      evidence:
      - reference: PMID:27269051
        reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Mechanotransduction currents could also be evoked in OHCs fromFam65bLacZ/LacZmice but peak currents
          were reduced (Figure 6A).
        explanation: >-
          Whole-cell recordings in P5 outer hair cells show reduced, retained currents. The source extraction
          joins genotype text; this is an ex vivo recording.
  - target: Stereocilia Disorganisation
    relationship: RESCUES
    fidelity: MODERATE
    description: >-
      Wild-type RIPOR2 re-expression restores bundle morphology in P2 explants cultured for two days.
    limitations: >-
      Ex vivo neonatal rescue does not establish in vivo hearing recovery, adult efficacy, delivery feasibility
      or a closed therapeutic window.
    evidence:
    - reference: PMID:27269051
      reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Note morphological defects of stereocilia were rescued by Fam65b-GFP but not by Fam65bRL/AA-GFP.
      explanation: >-
        Figure 9 rescue in cultured hair cells. RL/AA also affects basal homophilic binding, limiting isolation
        of RhoC-specific causality.
    readouts:
    - name: Stereocilia morphology after re-expression
      target: Stereocilia Disorganisation
      direction: RESTORED
      interpretation: >-
        Wild-type construct restores bundle shape; RL/AA fails.
      evidence:
      - reference: PMID:27269051
        reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Note morphological defects of stereocilia were rescued by Fam65b-GFP but not by Fam65bRL/AA-GFP.
        explanation: >-
          Figure 9 rescue in cultured hair cells. RL/AA also affects basal homophilic binding, limiting isolation
          of RhoC-specific causality.
  - target: Impaired Cochlear Mechanotransduction
    relationship: RESCUES
    fidelity: MODERATE
    description: >-
      Re-expression improves fluid-jet-evoked calcium responses in deficient explants.
    limitations: >-
      Calcium response is a functional proxy; restored whole-cell current was not directly measured in this
      rescue.
    evidence:
    - reference: PMID:27269051
      reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: >-
        Representative example demonstrating fluid–jet induced Ca2+response in G-CaMP3-expressing OHCs from
        controls,Fam65bmutants, andFam65bmutants following re-expression of Fam65b.
      explanation: >-
        Figure 6 uses calcium imaging after P2 injectoporation and two days in culture.
    readouts:
    - name: Fluid-jet-evoked calcium response
      target: Impaired Cochlear Mechanotransduction
      direction: RESTORED
      interpretation: >-
        GCaMP3 response improves after re-expression.
      evidence:
      - reference: PMID:27269051
        reference_title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
        supports: SUPPORT
        evidence_source: IN_VITRO
        snippet: >-
          Representative example demonstrating fluid–jet induced Ca2+response in G-CaMP3-expressing OHCs from
          controls,Fam65bmutants, andFam65bmutants following re-expression of Fam65b.
        explanation: >-
          Figure 6 uses calcium imaging after P2 injectoporation and two days in culture.
- name: Ripor2 knockout mouse (hair bundle morphogenesis)
  species: Mouse
  genotype: Homozygous Ripor2tm1(KOMP)Vlcg; exons 2–14 replaced by lacZ on a C57BL/6 background
  publication: PMID:30280293
  description: >-
    The same KOMP null allele studied for polarity, protein abundance and vestibular behavior.
  modeled_mechanisms:
  - target: Misorientation of Developing Hair Bundles
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Embryonic and postnatal orientation defects.
    limitations: >-
      Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism,
      not complete clinical equivalence.
    evidence:
    - reference: PMID:30280293
      reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects
        the orientation of this key subcellular structure.
      explanation: >-
        Orientation and kinocilium-position defects are present at E18.5 and P5 in null mice.
    readouts:
    - name: Hair-bundle orientation
      target: Misorientation of Developing Hair Bundles
      direction: ALTERED
      interpretation: >-
        Excess angular deviations and abnormal kinocilium position at E18.5 and P5.
      evidence:
      - reference: PMID:30280293
        reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Here, we demonstrate that during the morphogenesis of the hair cell bundle, absence of Ripor2 affects
          the orientation of this key subcellular structure.
        explanation: >-
          Orientation and kinocilium-position defects are present at E18.5 and P5 in null mice.
  - target: Reduced Cochlear MYH9 Abundance
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reduced protein abundance despite increased transcript.
    limitations: >-
      Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism,
      not complete clinical equivalence.
    evidence:
    - reference: PMID:30280293
      reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount
        of Myh9 transcripts.
      explanation: >-
        Cochlear protein and transcript measurements establish post-transcriptional discordance, without measuring
        protein turnover.
    readouts:
    - name: Cochlear MYH9 protein abundance
      target: Reduced Cochlear MYH9 Abundance
      direction: DECREASED
      interpretation: >-
        Protein/transcript discordance does not establish altered protein half-life.
      evidence:
      - reference: PMID:30280293
        reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Absence of Ripor2 is associated with low Myh9 abundance in the mouse cochlea despite increased amount
          of Myh9 transcripts.
        explanation: >-
          Cochlear protein and transcript measurements establish post-transcriptional discordance, without
          measuring protein turnover.
  - target: Reduced Cochlear Tubulin Acetylation
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reduced acetylated alpha-tubulin in cochlear extracts.
    limitations: >-
      Human cochlear cellular measurements are unavailable; fidelity concerns the model-derived mechanism,
      not complete clinical equivalence.
    evidence:
    - reference: PMID:30280293
      reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Western blot analysis shows a decrease on the content of alpha-acetyl-tubulin in protein extracts from
        cochleae of Ripor2 deficient mice (Fig. 5E, F).
      explanation: >-
        The measured acetylated-tubulin abundance is separate from the proposed HDAC6 mechanism.
    readouts:
    - name: Acetylated alpha-tubulin abundance
      target: Reduced Cochlear Tubulin Acetylation
      direction: DECREASED
      interpretation: >-
        Immunoblot signal is reduced without demonstrated kinocilium shortening.
      evidence:
      - reference: PMID:30280293
        reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: >-
          Western blot analysis shows a decrease on the content of alpha-acetyl-tubulin in protein extracts
          from cochleae of Ripor2 deficient mice (Fig. 5E, F).
        explanation: >-
          The measured acetylated-tubulin abundance is separate from the proposed HDAC6 mechanism.
  - target: Vestibular End-Organ Dysfunction
    relationship: FAILS_TO_RECAPITULATE
    fidelity: MODERATE
    description: >-
      No overt circling or balance deficit and normal rotarod performance.
    limitations: >-
      Mouse behavioral tests are not equivalent to the human cVEMP and video head-impulse battery. A species-specific
      absence of vestibular pathology is not established.
    evidence:
    - reference: PMID:30280293
      reference_title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Absence of circling and balance defects as well as a normal performance in the rotating rod tests suggest
        a normal vestibular function for Ripor2 KO mouse (Fig. S1D).
      explanation: >-
        Behavioral screening does not exclude subtle vestibular end-organ dysfunction.
- name: fam65b zebrafish morphant
  species: Zebrafish
  genotype: Two splice-blocking morpholinos causing intron 2 or intron 3 retention
  publication: PMID:24958875
  description: >-
    Transient knockdown at 3 dpf reduces saccular hair-cell and neuromast numbers and microphonic amplitudes.
    Mild cardiac edema occurred. This experiment is distinct from the later stable CRISPR lines.
  modeled_mechanisms:
  - target: Sensorineural Hearing Loss
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    description: >-
      Reduced inner-ear microphonic responses after knockdown.
    limitations: >-
      Transient morpholino exposure, nonhuman lateral-line anatomy and cell loss limit comparison with the
      human alleles. Both amplitudes fell, but only MO1 significantly raised threshold.
    evidence:
    - reference: PMID:24958875
      reference_title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        After activation by 200-Hz stimulation, MO1 and MO2 morphants had weaker microphonic response than
        the controls did (Fig. 5 I and J).
      explanation: >-
        Both splice-blocking morpholinos reduce microphonic amplitudes at 3 dpf; only MO1 significantly increased
        threshold.
- name: ripor2 exon 14 CRISPR zebrafish lines
  species: Zebrafish
  genotype: Three stable exon 14 premature-stop lines; homozygous F2 larvae
  publication: PMID:37864412
  description: >-
    Stable exon-14 CRISPR lines showed no hearing or balance behavioral difference at 5 dpf. This differs from
    the 2014 morphants. The publisher full text, rather than its compressed abstract, establishes the hearing
    result.
  modeled_mechanisms:
  - target: Vestibular End-Organ Dysfunction
    relationship: FAILS_TO_RECAPITULATE
    fidelity: MODERATE
    description: >-
      No overt vestibular behavioral phenotype in stable F2 larvae.
    limitations: >-
      Behavior at 5 dpf does not exclude subtle sensory dysfunction. Transient F0 circling was not retained
      in stable homozygotes; these are not promoter-deletion nulls.
    evidence:
    - reference: PMID:37864412
      reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        In contrast to the vestibular areflexia observed in our patients, deaf Ripor2 KO mouse model and our
        zebrafish model have normal vestibular function.
      explanation: >-
        Abstract comparison; the full text specifies stable exon-14 F2 lines and behavioral assessment, with
        compensation proposed but untested.
diagnosis:
- name: Comprehensive Hearing Loss Gene Panel or Exome Sequencing
  description: >-
    Use a hearing-loss multigene panel or genomic testing, interpreting RIPOR2 variants with inheritance, phase,
    segregation and the clinical phenotype. Assess assay coverage for deletions and duplications when relevant.
    A variant of uncertain significance does not confirm or exclude DFNB104. Apparent homozygosity should be
    reconciled with parental testing. Exome sequencing identified both reported families.
  evidence:
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Recommended molecular genetic testing approaches include use of a multigene hearing loss panel and/or
      genomic testing.
    explanation: >-
      General testing strategy; RIPOR2-specific causality still requires appropriate variant interpretation.
    quote_role: REVIEW_SYNTHESIS
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The identification of variant(s) of uncertain significance cannot be used to confirm or rule out the
      diagnosis.
    explanation: >-
      Diagnostic limitation applies to uncertain RIPOR2 findings.
    quote_role: REVIEW_SYNTHESIS
- name: Vestibular Function Testing
  description: >-
    Assess vestibular function and motor development in affected individuals. Formal cVEMP and video head-impulse
    testing documented areflexia in the Tunisian siblings. Normal bedside balance or a negative symptom history
    cannot substitute for an equivalent vestibular battery.
  evidence:
  - reference: PMID:37864412
    reference_title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A homozygous pathogenic variation c.1561C > T (p.Arg521*) in RIPOR2 (RHO family interacting cell polarization
      regulator 2) has been identified by WES in Tunisian siblings suffering from congenital bilateral profound
      hearing and vestibular dysfunctions.
    explanation: >-
      The abstract establishes the second family and cochleovestibular phenotype.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The finding of vestibular dysfunction may guide physical therapy, particularly in children with delayed
      motor milestones.
    explanation: >-
      General care guidance supports assessment and referral; the primary family report supplies the RIPOR2-specific
      findings.
    quote_role: REVIEW_SYNTHESIS
- name: Audiologic Characterization
  description: >-
    Use age-appropriate behavioral audiometry, auditory brainstem responses and otoacoustic emissions to define
    severity and hearing function. Repeat assessment to establish course; a stable pattern in one family does
    not predict all RIPOR2 cases.
  measurements:
  - preferred_term: pure-tone threshold audiometry
    term:
      id: LOINC:89015-2
      label: Pure tone threshold audiometry panel
  - preferred_term: hearing threshold, left ear, 500 Hz
    term:
      id: LOINC:89024-4
      label: Hearing threshold Ear - left --500 Hz
  - preferred_term: hearing threshold, right ear, 500 Hz
    term:
      id: LOINC:89025-1
      label: Hearing threshold Ear - right --500 Hz
  - preferred_term: hearing threshold, left ear, 1000 Hz
    term:
      id: LOINC:89016-0
      label: Hearing threshold Ear - left --1000 Hz
  - preferred_term: hearing threshold, right ear, 1000 Hz
    term:
      id: LOINC:89017-8
      label: Hearing threshold Ear - right --1000 Hz
  - preferred_term: hearing threshold, left ear, 2000 Hz
    term:
      id: LOINC:89018-6
      label: Hearing threshold Ear - left --2000 Hz
  - preferred_term: hearing threshold, right ear, 2000 Hz
    term:
      id: LOINC:89019-4
      label: Hearing threshold Ear - right --2000 Hz
  - preferred_term: hearing threshold, left ear, 4000 Hz
    term:
      id: LOINC:89022-8
      label: Hearing threshold Ear - left --4000 Hz
  - preferred_term: hearing threshold, right ear, 4000 Hz
    term:
      id: LOINC:89023-6
      label: Hearing threshold Ear - right --4000 Hz
  reference_ranges:
  - unit: dB
    population: >-
      Grades recommended by the Global Burden of Disease Expert Group on Hearing Loss, better-ear average
      of 500, 1000, 2000 and 4000 Hz, as tabulated by Olusanya, Davis and Hoffman (WHO Bulletin)
    interpretation_bands:
    - name: Normal hearing
      upper_bound: 20
      unit: dB
      abnormal_flag: NORMAL
    - name: Mild hearing loss
      lower_bound: 20
      upper_bound: 35
      unit: dB
      abnormal_flag: HIGH
      severity: MILD
    - name: Moderate hearing loss
      lower_bound: 35
      upper_bound: 50
      unit: dB
      abnormal_flag: HIGH
      severity: MODERATE
    - name: Moderately severe hearing loss
      lower_bound: 50
      upper_bound: 65
      unit: dB
      abnormal_flag: HIGH
    - name: Severe hearing loss
      lower_bound: 65
      upper_bound: 80
      unit: dB
      abnormal_flag: HIGH
      severity: SEVERE
    - name: Profound hearing loss
      lower_bound: 80
      upper_bound: 95
      unit: dB
      abnormal_flag: HIGH
    - name: Complete or total hearing loss
      lower_bound: 95
      unit: dB
      abnormal_flag: HIGH
    notes: >-
      Values are dB hearing level (HL). The source gives each grade as a closed range to one decimal place
      (Mild hearing loss 20.0 to 34.9 dB hearing level, and so on up to Complete or total hearing loss 95.0
      dB hearing level or greater); the half-open bands here are the same partition. The source splits
      normal hearing into -10.0 to 4.9 and 5.0 to 19.9 dB hearing level; both are folded into one Normal
      hearing band. Its Unilateral category (below 20.0 dB in the better ear, 35.0 dB or greater in the
      worse ear) needs both ears and is not representable as a band. Severity is set only where the grade
      name is mild, moderate or severe. Bonetti (PMID:41718341) applies the same boundaries, up to
      moderately severe, as the WHO-defined hearing loss categories; the WHO report itself is not
      PubMed-indexed, so the grades are quoted from these restatements. No LOINC code was found for the better-ear four-frequency pure-tone average these grades read: Monarch KG searches for pure tone average, threshold average, average hearing, PTA and hearing level returned none. The range therefore names no loinc_term. A numeric band on the panel LOINC:89015-2 would put a number on an instrument, and on any one frequency code would misstate what is graded; the average is computed from the eight per-frequency codes bound above. LOINC:98422-9 (Hearing loss degree Ear - left) and LOINC:98427-8 (Hearing loss degree Ear - right) exist but carry the category, not the dB value, so they are not bound. The grading is generic to hearing loss of any cause, not specific to this disease. The severity words this entry uses come from its cited clinical sources, which do not necessarily use these boundaries.
    evidence:
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "Mild hearing loss | 20.0 to 34.9 dB hearing level"
      explanation: >-
        Table 2 row giving the lower boundary of hearing loss and the mild grade in the Global Burden of
        Disease Expert Group scheme.
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "Profound hearing loss | 80.0 to 94.9 dB hearing level"
      explanation: Table 2 row giving the profound grade.
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "Complete or total hearing loss | 95.0 dB hearing level or greater"
      explanation: Table 2 row giving the top, open-ended grade.
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "b Average of 500, 1000, 2000 and 4000 Hz. Source: Global Burden of Disease Expert Group on Hearing Loss."
      explanation: >-
        Table 2 footnote naming the four frequencies averaged and the body that set the grades; footnote a
        places the measurement in the better ear.
    - reference: PMID:41718341
      reference_title: 'Self-Perceived Hearing Handicap and Audiometric Severity in Age-Related Hearing Loss: Associations with Age and Sex.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Moderate hearing loss (BE PTA-4 35 to <50 dB HL)"
      explanation: >-
        A clinical study stratifying patients by WHO hearing loss categories uses the same 35 to below 50 dB
        moderate band on the better-ear four-frequency average.
  - unit: dB
    population: >-
      Earlier WHO grades of hearing impairment (based on the 1991 version), better-ear average of 500, 1000,
      2000 and 4000 Hz, as tabulated by Olusanya, Davis and Hoffman (WHO Bulletin)
    interpretation_bands:
    - name: 'Grade 0: no impairment'
      upper_bound: 26
      unit: dB
      abnormal_flag: NORMAL
    - name: 'Grade 1: slight impairment'
      lower_bound: 26
      upper_bound: 41
      unit: dB
      abnormal_flag: HIGH
    - name: 'Grade 2: moderate impairment'
      lower_bound: 41
      upper_bound: 61
      unit: dB
      abnormal_flag: HIGH
      severity: MODERATE
    - name: 'Grade 3: severe impairment'
      lower_bound: 61
      upper_bound: 81
      unit: dB
      abnormal_flag: HIGH
      severity: SEVERE
    - name: 'Grade 4: profound impairment including deafness'
      lower_bound: 81
      unit: dB
      abnormal_flag: HIGH
    notes: >-
      Superseded scheme, recorded because older clinical literature reports severity on it and its
      boundaries differ from the Global Burden of Disease grades above. The source states whole-decibel
      ranges (25 dB or better, 26-40 dB, 41-60 dB, 61-80 dB, 81 dB or greater); an average falling between
      two stated ranges, such as 25.5 dB, is not assigned by the source and falls in the upper grade under
      the half-open convention used here. The same source records that only adults with a permanent
      unaided impairment above 40 dB hearing level in the better ear, and children with more than 30 dB,
      were regarded as having a disabling hearing impairment. Severity is set only where the grade name is
      moderate or severe. The grading is generic to hearing loss of any cause.
    evidence:
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "1: slight impairment | 26-40 dB | Able to hear and repeat words spoken in normal voice at 1 m"
      explanation: Table 1 row giving the slight grade in the earlier WHO scheme.
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: "4: profound impairment including deafness | 81 dB or greater"
      explanation: Table 1 row giving the top grade in the earlier WHO scheme.
    - reference: PMID:31656340
      reference_title: 'Hearing loss grades and the International classification of functioning, disability and health.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      snippet: >-
        currently only adults (≥ 15 years) with a permanent unaided hearing impairment above 40 dB hearing
        level in the better ear and children (from birth to 14 years of age) with > 30 dB hearing level are
        regarded as having a disabling hearing impairment
      explanation: Places the earlier scheme's disabling-impairment cut-offs in the better ear.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hearing status can be determined at any age and is tailored to the individual's ability to participate
      (see Audiometric and Clinical Characteristics of Hearing Loss).
    explanation: >-
      General audiologic assessment guidance.
    quote_role: REVIEW_SYNTHESIS
treatments:
- name: Cochlear Implantation
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: cochlear device implantation
    term:
      id: NCIT:C15329
      label: Surgical Procedure
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: cochlear implant
        term:
          id: NCIT:C157820
          label: Cochlear Implant
  description: >-
    Consider cochlear implantation according to hearing severity, aided benefit, anatomy and patient/family
    goals. The 2023 Tunisian report documents unilateral implantation in all three siblings with satisfactory
    results; this is a small uncontrolled experience, not a genotype-wide response estimate. An implant bypasses
    hair-cell transduction rather than restoring the stereociliary defect.
  target_mechanisms:
  - target: Impaired Cochlear Mechanotransduction
    treatment_effect: BYPASSES
    description: >-
      Bypasses the failed transduction step by stimulating the auditory nerve directly.
  action_category: THERAPEUTIC
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Cochlear implantation can be considered in children with severe-to-profound hearing loss who are older
      than age nine months.
    explanation: >-
      General candidacy guidance. Disease-specific outcomes are recorded in the findings for PMID:37864412,
      whose publisher full text was reviewed.
    quote_role: REVIEW_SYNTHESIS
- name: Early Language Access and Habilitation
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: auditory habilitation
    term:
      id: NCIT:C15315
      label: Rehabilitation
  description: >-
    Provide timely access to language and communication support, with spoken, signed or combined approaches
    reflecting patient and family goals. Audiology, speech-language support and educational services are complementary.
    Newborn screening and early assessment can support identification, but universal detection of every RIPOR2
    presentation has not been demonstrated.
  action_category: THERAPEUTIC
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      On initial evaluation of individuals with hearing loss, the goals for communication must be established
      with a focus on equipping individuals with language and appropriate access to language.
    explanation: >-
      General management guidance supports communication access, without restricting benefit to spoken language.
    quote_role: REVIEW_SYNTHESIS
- name: Vestibular Rehabilitation
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: vestibular rehabilitation
    term:
      id: NCIT:C15302
      label: Physical Therapy
  description: >-
    Refer individuals with vestibular dysfunction or delayed motor development for individualized physical
    therapy and balance support. This is general management guidance; RIPOR2-specific rehabilitation efficacy
    has not been measured.
  action_category: THERAPEUTIC
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The finding of vestibular dysfunction may guide physical therapy, particularly in children with delayed
      motor milestones.
    explanation: >-
      General referral recommendation, rather than evidence that a specific intervention reverses vestibular
      areflexia.
    quote_role: REVIEW_SYNTHESIS
- name: Genetic Counselling
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  description: >-
    Discuss recurrence risk after establishing the causal recessive variants and parental genotypes. Carrier
    testing of relatives and reproductive options can be offered according to family preferences. Counseling
    must distinguish recessive alleles from the specific dominant DFNA21 allele.

  action_category: COUNSELING_INFORMATIONAL
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      If both parents are known to be heterozygous for an autosomal recessive hearing loss-related pathogenic
      variant, each sib of the proband has at conception a 25% chance of having hearing loss, a 50% chance
      of having no hearing loss and being a carrier, and a 25% chance of having no hearing loss and not being
      a carrier.
    explanation: >-
      General recessive hearing-loss counseling applies after the causal variants and parental genotypes are
      established.
    quote_role: REVIEW_SYNTHESIS
- name: Audiologic Surveillance
  action_category: MONITORING
  description: >-
    Follow hearing thresholds, communication needs and device benefit over time. Surveillance frequency should
    be individualized because the limited family reports include both apparently stable and progressive courses.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Regular follow up is recommended for all individuals with genetic hearing loss in order to:
    explanation: >-
      General recommendation; sequential audiologic examinations document stability or progression.
    quote_role: REVIEW_SYNTHESIS
- name: Hearing Aids
  therapeutic_modality: DEVICE
  action_category: THERAPEUTIC
  description: >-
    Offer amplification when residual hearing provides useful aided benefit, with reassessment as severity
    changes and consideration of implantation when indicated.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Hearing aids (sound amplification), customized by an audiologist to the degree and frequency of hearing
      loss, can be used in individuals with mild-to-severe hearing loss.
    explanation: >-
      General audiologic guidance; not a measured RIPOR2-specific response rate.
    quote_role: REVIEW_SYNTHESIS
differential_diagnoses:
- name: RIPOR2-related autosomal dominant hearing loss (DFNA21)
  description: >-
    DFNA21 is associated with the heterozygous RIPOR2 c.1696_1707del (p.Gln566_Lys569del) founder allele. Onset
    was highly variable, from congenital to age 70, although typically later than recessive DFNB104. The dominant
    molecular mechanism remains uncertain.
  distinguishing_features:
  - Specific heterozygous p.Gln566_Lys569del allele and dominant segregation
  - Variable onset and progressive course; onset alone is not diagnostic
  - The recessive splice allele also produces an in-frame deletion, so broad variant class is insufficient
  evidence:
  - reference: PMID:32631815
    reference_title: "A RIPOR2 in-frame deletion is a frequent and highly penetrant cause of adult-onset hearing loss."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Hearing loss associated with the deletion in 63 subjects displayed variable audiometric characteristics
      and an average (SD) age of onset of 30.6 (14.9) years (range 0-70 years).
    explanation: >-
      The observed range precludes an absolute adult-onset distinction.
- name: Usher syndrome
  description: >-
    Usher syndrome type I can initially resemble early deafness with vestibular areflexia. Retinal degeneration
    may emerge later, so a normal early eye examination does not exclude it. Molecular testing and longitudinal
    clinical assessment distinguish the diagnoses.
  distinguishing_features:
  - Pathogenic variants in an Usher-associated gene rather than recessive RIPOR2 alleles
  - Retinal degeneration supports Usher syndrome, but its absence early in life is not exclusionary
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      ophthalmology evaluation may be recommended, as individuals with hearing loss may depend more on vision
      for sensory input, as well as to evaluate for retinitis pigmentosa.
    explanation: >-
      General hearing-loss evaluation includes assessment for retinal disease.
    quote_role: REVIEW_SYNTHESIS
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    reference_title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Nonsyndromic HL mimic: HL is congenital; RP begins in late adolescence or early adulthood.
    explanation: >-
      The Usher type I row explicitly describes a nonsyndromic hearing-loss mimic before retinal disease emerges.
    quote_role: REVIEW_SYNTHESIS
discussions:
- discussion_id: mismatch_vestibular_phenotype
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Vestibular End-Organ Dysfunction
  - animal_models#Fam65b/Ripor2 knockout mouse
  prompt: >-
    Do differing vestibular assays, alleles or compensatory mechanisms explain the human–model discrepancy?
  rationale: >-
    Human vestibular areflexia was characterized with cVEMP and video head-impulse testing, whereas the null
    mouse was screened by behavior and rotarod. Stable exon-14 zebrafish lines had no overt hearing or balance
    behavioral difference at 5 dpf; the earlier morpholino experiment measured microphonics at 3 dpf. These
    are different alleles, developmental stages and assays. RIPOR1/RIPOR3 compensation is a proposed explanation,
    not a demonstrated mechanism.
  proposed_experiments:
  - experiment_id: ripor_paralogue_expression_vestibular
    name: Paralogue expression and compensation in mouse versus human vestibular epithelium
    description: >-
      First compare vestibular end-organ function with sensitive, age-appropriate assays across models and
      affected families. Test paralogue expression and combined perturbation only after distinguishing subtle
      sensory deficits from preserved overt balance behavior.
    would_support:
    - pathophysiology#Vestibular End-Organ Dysfunction
    supporting_outcome:
    - >-
      Combined paralogue perturbation reveals a vestibular deficit absent after Ripor2 loss alone, supporting
      compensation in the tested model.
    refuting_outcome:
    - >-
      Equivalent sensitive testing already detects dysfunction after Ripor2 loss alone, supporting an ascertainment
      contribution rather than complete model resistance.
- discussion_id: gap_allele_specific_vestibular
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - phenotypes#Vestibular Areflexia
  - genetic#RIPOR2
  prompt: >-
    Is the vestibular phenotype specific to the nonsense allele, or was it simply not
    looked for in the first family?
  rationale: >-
    The two reported families differ on vestibular involvement and also differ on allele
    class and on how vestibular function was assessed. The Turkish kindred was reported as
    having no balance problems on clinical assessment; the Tunisian siblings were
    characterised with cervical VEMPs and video head-impulse testing, which detect
    dysfunction that a clinical balance history does not.

    So there are at least three live readings - an allele-specific effect, a
    genetic-background effect, and an ascertainment difference - and two families cannot
    distinguish them. The practical stake is whether to counsel a newly diagnosed RIPOR2
    patient about vestibular involvement, and whether to test for it.
  proposed_experiments:
  - experiment_id: vestibular_testing_all_ripor2_families
    name: Uniform vestibular testing across all reported and newly ascertained RIPOR2 families
    description: >-
      Apply the same vestibular battery - cervical and ocular VEMPs, video head-impulse
      testing, and developmental motor milestones - to affected individuals from both
      published recessive families and any newly ascertained ones, and record the result
      against allele class.
    would_support:
    - phenotypes#Vestibular Areflexia
    supporting_outcome:
    - >-
      Formal testing finds vestibular dysfunction in splice-allele patients too, making
      vestibular involvement part of the disease rather than an allele-specific feature.
    refuting_outcome:
    - >-
      Splice-allele patients test normal on the same battery, which would support a real
      allele-specific difference and make variant class relevant to counselling.

- discussion_id: gap_ripor2_domain_and_causal_intermediates
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Biallelic RIPOR2 Loss-of-Function Variant
  - pathophysiology#Reduced Cochlear MYH9 Abundance
  - pathophysiology#Disorganisation of the Taper Compartment
  prompt: >-
    Which structural and molecular dependencies directly mediate RIPOR2-related hearing loss?
  rationale: >-
    The PX–BAR assignment was challenged by sequence/structure analysis, and the authors agreed that experimental
    confirmation was needed. MYH9 abundance, tubulin acetylation and taperin localization change in null mice,
    but their relative causal contributions are unresolved. The RL/AA construct alters both RhoC binding and
    basal self-association. Selective rescue and structural studies are needed to distinguish these possibilities.
  evidence:
  - reference: PMID:25239234
    reference_title: Little evidence that FAM65B belongs to the family of phox homology (PX) and bin/amphiphysin/rvs (BAR) domain-containing proteins.
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    snippet: >-
      Secondary structure predictions of FAM65 do not reveal any similarity to the PX–BAR family of molecules.
    explanation: >-
      The published computational challenge supports treating the initial domain assignment as unresolved.
notes: >-
  RIPOR2 and FAM65B are current and historical symbols for the same gene. Primary family studies supply the
  disease-specific clinical baseline; the general GeneReviews hearing-loss chapter supplies diagnosis, management
  and recessive counseling guidance. No RIPOR2-specific clinical gene-replacement efficacy is established by
  neonatal explant rescue. The 2023 publisher full text was readable during review, but automated reference
  fetching returned HTTP 403; its clinical and stable-zebrafish details are recorded in publication findings
  without inventing cache-backed quotations.

references:
- reference: PMID:24958875
  title: "FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing."
- reference: PMID:27269051
  title: "Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function."
- reference: PMID:30280293
  title: "Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation."
- reference: PMID:37864412
  title: "RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models."
  findings:
  - statement: >-
      Publisher full text: three siblings had severe hearing loss progressing to profound levels, delayed walking
      at 21–24 months and vestibular areflexia. All received unilateral implants, at ages 15, 14 and 3, with
      satisfactory six-month results. Stable exon-14 zebrafish F2 lines lacked overt hearing or balance behavioral
      differences at 5 dpf. Detailed supplements were not reviewed.
- reference: PMID:32631815
  title: "A RIPOR2 in-frame deletion is a frequent and highly penetrant cause of adult-onset hearing loss."
- reference: PMID:25239234
  title: Little evidence that FAM65B belongs to the family of phox homology (PX) and bin/amphiphysin/rvs (BAR) domain-containing proteins.
  findings:
  - statement: >-
      Sequence searches, secondary-structure prediction and attempted homology modeling did not support assignment
      to the PX–BAR protein family.
- reference: PMID:25239233
  title: 'Reply to Teasdale and Collins: N-terminal region of FAM65B bears similarity to the PX-BAR module of SNX33.'
  findings:
  - statement: >-
      The authors defended their N-terminal homology model while acknowledging that experimental verification
      of a bona fide PX–BAR module was still required. Full correspondence read online; automated cache retrieval
      did not recover its body.
- reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
  title: https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf
  findings:
  - statement: >-
      Genetic Hearing Loss Overview, PMID:20301607. General care and counseling sections; not a RIPOR2-specific
      phenotype chapter.
- reference: PMID:20301607
  title: Genetic Hearing Loss Overview.
  tags:
  - GeneReviews
- reference: url:https://www.ncbi.nlm.nih.gov/clinvar/RCV000190353/
  title: "NM_001286445.3(RIPOR2):c.189-1G&gt;A AND Autosomal recessive nonsyndromic hearing loss 104 - ClinVar - NCBI"
  findings:
  - statement: >-
      ClinVar RCV000190353 maps NM_014722.2:c.102-1G>A and NM_001286445.3:c.189-1G>A to the same variant, NC_000006.12:g.24873800C>T.
      Used for transcript identity, not as independent clinical evidence or confirmation of the disputed PX-domain
      interpretation.

📚

References & Deep Research

References

10

PMID:24958875

FAM65B is a membrane-associated protein of hair cell stereocilia required for hearing.

No top-level findings curated for this source.

PMID:27269051

Murine Fam65b forms ring-like structures at the base of stereocilia critical for mechanosensory hair cell function.

No top-level findings curated for this source.

PMID:30280293

Ripor2 is involved in auditory hair cell stereociliary bundle structure and orientation.

No top-level findings curated for this source.

PMID:37864412

RIPOR2: A new gene of non-syndromic cochleovestibular dysfunction, discrepancy between human pathology and animal models.

1 finding

Publisher full text: three siblings had severe hearing loss progressing to profound levels, delayed walking at 21–24 months and vestibular areflexia. All received unilateral implants, at ages 15, 14 and 3, with satisfactory six-month results. Stable exon-14 zebrafish F2 lines lacked overt hearing or balance behavioral differences at 5 dpf. Detailed supplements were not reviewed.

PMID:32631815

A RIPOR2 in-frame deletion is a frequent and highly penetrant cause of adult-onset hearing loss.

No top-level findings curated for this source.

PMID:25239234

Little evidence that FAM65B belongs to the family of phox homology (PX) and bin/amphiphysin/rvs (BAR) domain-containing proteins.

1 finding

Sequence searches, secondary-structure prediction and attempted homology modeling did not support assignment to the PX–BAR protein family.

PMID:25239233

Reply to Teasdale and Collins: N-terminal region of FAM65B bears similarity to the PX-BAR module of SNX33.

1 finding

The authors defended their N-terminal homology model while acknowledging that experimental verification of a bona fide PX–BAR module was still required. Full correspondence read online; automated cache retrieval did not recover its body.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf

https://www.ncbi.nlm.nih.gov/sites/books/NBK1434/pdf/Bookshelf_NBK1434.pdf

1 finding

Genetic Hearing Loss Overview, PMID:20301607. General care and counseling sections; not a RIPOR2-specific phenotype chapter.

PMID:20301607

Genetic Hearing Loss Overview.

No top-level findings curated for this source.

url:https://www.ncbi.nlm.nih.gov/clinvar/RCV000190353/

NM_001286445.3(RIPOR2):c.189-1G>A AND Autosomal recessive nonsyndromic hearing loss 104 - ClinVar - NCBI

1 finding

ClinVar RCV000190353 maps NM_014722.2:c.102-1G>A and NM_001286445.3:c.189-1G>A to the same variant, NC_000006.12:g.24873800C>T. Used for transcript identity, not as independent clinical evidence or confirmation of the disputed PX-domain interpretation.

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 (2)

Review RIPOR2 clinical course and model mechanisms against full texts · 2026-09-23T17:29:32Z · View source

Reviewed the complete 1,186-line baseline and all five prior CREATE/EDIT histories; no REVIEW existed. Read the substantive deep-research report (lines 489–861) and the unique ten-reference citation appendix. The report has genuine provider metadata and narrative content, but some authors, ontology suggestions and variant nomenclature require correction against primary sources. Named-entity preflight passes for RIPOR2, MONDO:0014675 and OMIM:616515. Live open-PR preflight found no overlapping DFNB104 review. This Mendelian disease is within the user's noninfectious, nonenvironmental scope. The user subsequently restricted work to finishing this disorder and existing review PRs; no later disorder will be started. Refreshed PMID:24958875 and read the complete scientific main text, five figure captions and the brief methods section. Detailed supplementary methods were not read. Six Turkish relatives had symmetric profound prelingual/congenital loss; available audiograms suggested stability but did not prove lifelong nonprogression. Negative symptoms and bedside balance testing were not a formal vestibular battery. Temporal-bone CT was normal in two relatives only. Patient leukocyte cDNA directly demonstrates exon 3 skipping and p.Arg34_Asp86delinsSer; localization was tested in transfected COS7 cells, not patient cochlear tissue. The 2014 zebrafish experiment used two transient splice-blocking morpholinos, with reduced microphonic amplitudes for both but a significantly raised threshold only for MO1. Mild cardiac edema and developmental/assay differences limit generalization. Read all scientific text and methods, including nine main figure captions, from cached PMID:27269051. The KOMP null deletes exons 2–14 and replaces them with lacZ on a C57BL/6 background. Hearing was first tested at four weeks, not birth. P2 inner-hair-cell bundles are already severely abnormal; by P5 both hair-cell types are affected. Removed normal-development-then-adult-maintenance framing. P16/P28 preparations have little cell loss despite severe bundle abnormalities. P5 outer-hair-cell peak mechanotransduction currents are reduced, not absent (approximately 233 versus 417 pA), and the authors explicitly leave direct transduction effects versus secondary morphological effects unresolved. Re-expression at P2 plus two days of culture restores morphology and fluid-jet GCaMP3 responses; the functional rescue is calcium imaging, not direct restored-current recording or in vivo hearing recovery. The study does not establish adult efficacy or a closed treatment window. The 2016 taperin signal is reduced/diffuse while espin is retained. Tested heterologous assays did not detect direct association with taperin, CLIC5, radixin, whirlin or PTPRQ cytoplasmic domain. RhoC enhances N-terminal self-association in HEK293 cells; cochlear colocalization uses overexpressed tagged proteins. RL/AA also reduces basal homophilic binding, so failure of rescue cannot uniquely isolate RhoC binding. Ring-like STORM localization does not itself establish lipid binding or a PX domain. Separate supplements were not read. Read all cached scientific main text and methods of PMID:30280293; its XML extraction does not provide a complete separate figure-caption set. Orientation defects are present at E18.5 and P5. MYH9 protein and phospho-MYH9 decrease while Myh9 transcript increases, but turnover was not measured. Tagged-protein co-immunoprecipitation establishes association rather than purified direct binding. Acetylated alpha-tubulin is reduced without a detected kinocilium-length change. HDAC6-mediated effects and the causal contribution of these biochemical changes to polarity remain hypotheses. Split protein-abundance, tubulin-acetylation, bundle-orientation and stereociliary-morphology findings into separate nodes. Mouse vestibular evidence is behavioral/rotarod screening, which cannot exclude subtle end-organ dysfunction. Refreshed PMID:37864412, which still provides only an abstract in the local cache. Read the publisher's complete scientific main text, methods and two figure captions online at https://onlinelibrary.wiley.com/doi/full/10.1111/cge.14436. Its clinical results contradict universal stable/profound-at-birth wording: the three Tunisian siblings had severe loss progressing to profound loss, delayed walking at 21–24 months and vestibular areflexia. All three received unilateral cochlear implants with satisfactory six-month results. Stable exon-14 CRISPR F2 zebrafish lines lacked overt hearing and balance behavioral differences at 5 dpf; this is not the 2014 morphant experiment and does not prove entirely normal sensory physiology. Paralog compensation is proposed, not demonstrated. The supplemental Word document and detailed patient data were not read. Publisher full-text, PDF and alternative endpoint requests returned HTTP 403 or otherwise failed; no cache file was fabricated. Detailed manually verified findings are recorded under the publication, and the delayed-walking phenotype transparently lacks a cached exact quote. Abstract quotations are limited to claims the abstract actually supports. Fetched PMID:25239234 and read its full correspondence challenging the PX–BAR assignment through sequence searches, secondary-structure prediction and unsuccessful homology modeling. Read the complete reply, PMID:25239233, online: the authors defend their N-terminal model but acknowledge that experimental verification remains necessary. Automated fetching of the reply did not recover its body; several URL attempts yielded CAPTCHA pages, which are excluded from the commit. The entry no longer treats the original domain prediction as established. ClinVar RCV000190353 was fetched and its HGVS/coordinate block checked: NM_014722.2:c.102-1G>A and NM_001286445.3:c.189-1G>A are aliases of NC_000006.12:g.24873800C>T. This record is used for identity, not as independent proof of the disputed domain annotation. Read all cached scientific text and methods of PMID:32631815 for the DFNA21 differential; separate supplements and figure images were not read. The specific dominant four-residue deletion has variable onset from congenital to 70 years, incomplete penetrance remains possible, and its molecular mode of action is unresolved. Both dominant and recessive alleles can produce in-frame deletions, so broad variant class cannot distinguish the diseases. Do not transfer Dutch founder prevalence or dominant penetrance estimates to DFNB104. Removed assertions that recessive alleles are necessarily globally private or that consanguinity is required. Fetched the GeneReviews Genetic Hearing Loss Overview PDF, PMID:20301607. Read the relevant diagnostic/genetic-testing, habilitation/communication, surveillance and recessive-counseling sections and the Usher type I table row; the whole chapter and other disease-specific tables were not read. Exact quotations support broad-panel/genomic testing, VUS limitations, age-appropriate audiology, vestibular-directed physical therapy, cochlear implantation, hearing aids, communication choices, follow-up and conditional 25/50/25 recurrence risk. This is a general chapter, not a RIPOR2 phenotype baseline. A normal early retinal examination cannot exclude Usher syndrome. No phase II or later RIPOR2 intervention trial was identified in the report or audited primary sources, and neonatal explant rescue is not clinical gene therapy evidence. Completeness cross-check: major auditory, vestibular and motor-milestone findings, atomic mechanisms, allele identity, diagnostic assessment, supportive care and central references are covered. No established disease subtypes or proven human modifier alleles require additional records. Sparse pedigrees do not support numerical phenotype frequencies or complete penetrance. Unknown causal intermediates are not replaced by invented edges: MYH9 and tubulin changes are observations, not proven drivers of polarity; prelingual onset and delayed walking remain unwired. The gene is explicitly connected to the triggering mechanism. New evidence/publication titles were matched to source identity. All cache additions/refreshes came from just fetch-reference; the frozen dataset accession file was not accessed. Schema, terms and all 63 cached quotations pass. Two targeted disorder-data tests passed before the final small additions; final checks, node-class verification, repository evidence gates and commit hooks are recorded in the PR/worktree. REVIEW history and PR linkage will be validated before completion.

Create: Autosomal Recessive Nonsyndromic Hearing Loss 104 · 2026-08-26T13:41:17Z · View source

De-novo curation of DFNB104, RIPOR2-related autosomal recessive nonsyndromic hearing loss. Deep research was run with the claude_code provider; the report is committed at research/Autosomal_Recessive_Nonsyndromic_Hearing_Loss_104-deep-research-claude_code.md. The report suggested CL:0000601 for inner hair cell and CL:0000602 for outer hair cell; OLS lookup shows CL:0000601 is cochlear outer hair cell and CL:0000602 is pressoreceptor cell, so the entry binds CL:0000589 and CL:0000601 instead. Two further suggestions (UBERON:0002106 for organ of Corti, HP:0002321 for vestibular areflexia) were also wrong and were replaced. The entry is scoped to the recessive disease; the allelic dominant in-frame-deletion disorder DFNA21 is curated under differential diagnoses only, and PMID:32631815 is cited for what it actually reports rather than for any phenotype of this disease. The reported mouse and zebrafish models are deaf with normal vestibular function while the human patients with a nonsense allele have vestibular areflexia, so that link is curated as FAILS_TO_RECAPITULATE with a HUMAN_MODEL_MISMATCH discussion rather than smoothed over. Evidence comes from PMID:24958875, PMID:27269051, PMID:30280293, PMID:37864412 and PMID:32631815. All 37 snippets verified against the reference cache. Validated with just validate plus the offline gates check-duplicate-keys, check-entity-refs, check-folded-hyphens, check-snippet-length, check-title-snippets and check-environmental-evidence.

Claude Code ▸

Autosomal Recessive Nonsyndromic Hearing Loss 104 (DFNB104) — Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 10 citations 2026-08-26T13:00:28.367751

Autosomal Recessive Nonsyndromic Hearing Loss 104 (DFNB104) — Comprehensive Research Report

1. Disease Information

Overview: Autosomal Recessive Nonsyndromic Hearing Loss 104 (DFNB104), also designated Deafness, Autosomal Recessive 104, is a form of prelingual, congenital, profound sensorineural hearing loss caused by biallelic (homozygous or compound heterozygous) loss-of-function variants in RIPOR2 (formerly known as FAM65B), located on chromosome 6p22.3. The disorder was first mapped and the causal gene identified in 2014 by Diaz-Horta and colleagues in a large consanguineous Turkish kindred (Diaz-Horta et al. 2014, PNAS, PMID 24958875). RIPOR2 encodes a plasma-membrane-associated actin-cytoskeletal regulatory protein that localizes to the base of the stereocilia in cochlear (and vestibular) hair cells and is required for normal stereocilia bundle structure and maintenance.

Key Identifiers: - OMIM: #616515 (DFNB104); gene entry 611410 (RIPOR2) (OMIM 616515; OMIM 611410) - MONDO: MONDO:0014675 - MedGen (NCBI): C4225298 — "Autosomal recessive nonsyndromic hearing loss 104" (MedGen) - HGNC: HGNC:13872 (RIPOR2; formerly FAM65B) - Gene locus: 6p22.3 - Orphanet: Grouped under the generic "Autosomal recessive non-syndromic sensorineural deafness type DFNB" umbrella entries; a DFNB104-specific ORPHA code was not independently confirmed in primary Orphanet sources during this research and should be verified directly against Orphadata before citation. - ICD-10:* H90.3 (Sensorineural hearing loss, bilateral) — generic code; no disease-specific ICD-10/11 code exists for DFNB104.

Synonyms/Alternative Names: - DFNB104 - Deafness, Autosomal Recessive 104 - FAM65B-related deafness - RIPOR2-related nonsyndromic hearing loss (recessive form; distinct from the dominant RIPOR2-related DFNA21)

Data source note: All published information derives from aggregated disease-level resources — pedigree/cosegregation studies in a small number of consanguineous families (Turkish, Tunisian) — plus complementary murine and zebrafish model data, rather than large EHR-derived cohorts. This is consistent with an ultra-rare monogenic recessive deafness gene.

Important nomenclature distinction: RIPOR2 causes two clinically and genetically distinct hearing-loss entities: - DFNB104 — biallelic (recessive) loss-of-function variants → congenital, profound, non-progressive hearing loss (this report's focus). - DFNA21 — heterozygous, dominant-negative in-frame deletion (c.1696_1707del) → adult-onset, progressive hearing loss, described as a frequent Dutch founder variant (Oonk et al. 2020, PMID 32631815).

2. Etiology

Disease Causal Factors: DFNB104 is purely genetic/monogenic — caused by biallelic loss-of-function (null or severely hypomorphic) variants in RIPOR2. No environmental, infectious, or multifactorial contribution has been reported.

Genetic Risk Factors: - Causal variants identified to date (small number of families): - c.102-1G>A (splice acceptor, intron 2) — homozygous in the original consanguineous Turkish family, causing in-frame skipping of exon 3 and deletion of residues 34–86 (p.R34_D86delinsS) within the core PX membrane-localization domain (Diaz-Horta et al. 2014, PMID 24958875). - c.189-1G>A (splice acceptor variant) — reported in ClinVar as pathogenic for DFNB104 (ClinVar RCV000190353). - c.1561C>T (p.Arg521) — homozygous nonsense variant identified in three Tunisian siblings with congenital profound hearing loss and* vestibular areflexia, the third reported RIPOR2 pathogenic allele and the first with a documented vestibular phenotype (Morel et al. 2023, Clinical Genetics, DOI 10.1111/cge.14436). - Consanguinity is a strong risk factor for exposing biallelic RIPOR2 variants, consistent with the Turkish and Tunisian consanguineous pedigrees in which the condition has been reported. - The mutation was absent from dbSNP, the Exome Variant Server, and 330 Turkish population controls in the original report, consistent with a rare, family-restricted (non-founder) allele in that population — in contrast to the common Dutch dominant founder deletion causing DFNA21.

Environmental Risk Factors: None identified; this is a purely Mendelian condition with no reported environmental modifiers of penetrance.

Protective Factors: None reported specific to RIPOR2/DFNB104. Speculative genetic compensation by paralogs RIPOR1 and RIPOR3 (~70% sequence similarity) has been proposed as a possible explanation for milder or absent vestibular phenotypes in some model systems, but this has not been demonstrated as a true protective mechanism in humans (Morel et al. 2023).

Gene-Environment Interactions: None documented; no CTD or GxE database entries were identified linking RIPOR2 to environmental modifiers.

3. Phenotypes

Auditory phenotype (core feature)

Type: Clinical sign / sensory (audiometric) abnormality.
Onset: Congenital / prelingual — hearing loss is present from birth.
Severity: Profound, and in the founding Turkish family, symmetric across affected individuals.
Progression: Notably non-progressive — "available audiograms did not suggest progression of the hearing loss" in the original family, distinguishing DFNB104 from many other DFNB forms and from the dominant DFNA21 (which is progressive).
Frequency: All 6 affected individuals in the index Turkish kindred; all 3 affected siblings in the Tunisian kindred — i.e., fully penetrant in reported biallelic carriers.
Suggested HPO terms:
HP:0001739 Sensorineural hearing impairment
HP:0008625 Bilateral sensorineural hearing impairment
HP:0000456 Prelingual sensorineural hearing impairment (or the more general HP:0008527 congenital sensorineural hearing impairment)
HP:0001737 Profound sensorineural hearing impairment (if distinguishing profound severity)

Audiological test findings

Absent otoacoustic emissions (OAEs) — HP:0025400 or descriptor "absent OAEs" (no dedicated HPO term; document as laboratory abnormality).
Absent/abnormal acoustic reflexes.
Absent/abnormal auditory brainstem responses (ABR).

Vestibular phenotype (variant-dependent, not uniform)

The original Turkish family: normal vestibular function — negative Romberg test, normal tandem gait, no balance complaints ("None had balance problems").
The Tunisian family (p.Arg521 nonsense variant): vestibular areflexia*, delayed independent walking (21–24 months), abnormal cervical VEMPs, and abnormal video head-impulse testing showing negative gains and covert saccades on posterior and lateral semicircular canals (Morel et al. 2023).
This indicates variable expressivity/phenotypic heterogeneity across RIPOR2 alleles — possibly allele-specific (nonsense/truncating vs. splice-site) or genetic-background-dependent.
Suggested HPO terms:
HP:0000763 or HP:0002321 Vertigo / Vestibular dysfunction
HP:0002321 Vestibular areflexia (if a specific term is used) — verify exact HPO ID at curation time
HP:0001270 Motor delay (for delayed walking, if attributable)

Quality of life impact

No dedicated EQ-5D/SF-36/disease-specific QOL studies were identified for DFNB104 specifically. As with other forms of congenital profound sensorineural deafness, the expected impact includes impaired spoken-language acquisition without early intervention (hearing aids/cochlear implantation), and — in the vestibular-areflexia subset — additional impact on gross motor development and balance-dependent activities (data extrapolated from general profound-deafness and vestibular-areflexia literature; no RIPOR2-specific QOL instrument data located).

4. Genetic/Molecular Information

Causal Gene: RIPOR2 (RHO Family Interacting Cell Polarization Regulator 2), formerly FAM65B. - HGNC: HGNC:13872 - OMIM gene: 611410 - Locus: 6p22.3 - Ensembl:* ENSG00000111913

Pathogenic Variants (recessive, DFNB104): | Variant | Effect | Family/Population | Source | |---|---|---|---| | c.102-1G>A | Splice acceptor → exon 3 skipping, in-frame deletion of aa 34-86 (p.R34_D86delinsS), disrupting the PX membrane-localization domain | Consanguineous Turkish family (6 affected) | PMID 24958875 | | c.189-1G>A | Splice acceptor variant, pathogenic | ClinVar-reported | ClinVar RCV000190353 | | c.1561C>T (p.Arg521*) | Nonsense/premature stop, exon 14 | Consanguineous Tunisian family (3 affected siblings) | Morel et al. 2023, Clin Genet |

Variant classification (ACMG/AMP): All reported variants classified pathogenic per cosegregation with disease, absence from population databases/controls, and functional evidence of protein mislocalization (for the splice variant).
Variant type/class: Splice-site (2 variants) and nonsense (1 variant) — all predicted/demonstrated loss-of-function, consistent with a haploinsufficiency-independent, biallelic-null recessive mechanism (contrasting with the dominant-negative in-frame deletion causing DFNA21).
Allele frequency: The recessive DFNB104 alleles are private/family-restricted and were absent from gnomAD/ExAC/dbSNP-scale population databases at the time of reporting — consistent with ultra-rare recessive alleles rather than founder variants (unlike the DFNA21 c.1696_1707del founder deletion, common in the Dutch population).
Somatic vs. germline: Germline only; no somatic RIPOR2 hearing-loss association reported.
Functional consequence: Loss of function — the mutant protein (from the splice variant) accumulates in cytoplasmic inclusion bodies and fails to reach the plasma membrane, in contrast to wild-type RIPOR2/FAM65B, which targets the stereocilia plasma membrane (PMID 24958875).
ClinGen Gene-Disease Validity: RIPOR2 has an Expert Panel "Definitive"/"Strong"-tier classification for autosomal recessive nonsyndromic deafness 104 (reported as ClinGen "Expert Review Green" via PanelApp aggregation).
Modifier genes: RIPOR1 and RIPOR3 (paralogs, ~70% sequence similarity to RIPOR2) have been proposed as potential functional compensators explaining phenotypic variability (e.g., absence of vestibular phenotype in some carriers/models), though this is hypothesis-generating rather than directly demonstrated in humans.
Epigenetic information: None reported specific to RIPOR2/DFNB104.
Chromosomal abnormalities: None reported; DFNB104 is caused by sequence-level variants, not large structural/chromosomal rearrangements.

Protein structure/function: - RIPOR2/FAM65B contains a PX(-like)-BAR module region implicated in membrane targeting and curvature sensing (though a later PNAS letter disputed strict PX-BAR domain classification — PMID for "Little evidence that FAM65B belongs to the family of PX and BAR domain-containing proteins," PNAS 2014 — a caveat worth noting for structural claims). - RIPOR2 is an atypical inhibitor of the small GTPase RhoA, implicated (in non-auditory contexts) in myoblast fusion and leukocyte polarization/migration. - In hair cells, RIPOR2 forms circumferential ring-like oligomeric structures (~229 ± 7 nm diameter) at the basal taper of stereocilia, distinct from taperin's intra-stereociliary core localization; RhoC (not RhoA) co-localizes with and regulates RIPOR2 oligomerization in this compartment (Krey et al. 2016, eLife, PMID for "Murine Fam65b forms ring-like structures..."). - RIPOR2 interacts with MYH9 (a known deafness gene, DFNA17); loss of Ripor2 in mice is associated with reduced MYH9 protein abundance (despite increased transcript) and aberrant kinocilium localization during hair-bundle morphogenesis (Xiong et al. 2018, J Mol Med, PMID 30280293).

Suggested ontology terms: - Gene: hgnc:13872 (RIPOR2) - GO Molecular Function: GO:0005096 (GTPase activator activity) — for RhoA/RhoC-modulating activity; verify precise GO term at curation - GO Cellular Component: GO:0032420 (stereocilium), GO:0060091 (kinocilium) - GO Biological Process: GO:0032420-related stereocilium organization; GO:0060088 auditory receptor cell stereocilium organization

5. Environmental Information

No environmental factors, lifestyle factors, or infectious agents have been implicated in DFNB104 causation — it is a fully penetrant monogenic recessive disorder. No CTD, TOXNET, or epidemiological database entries link RIPOR2/DFNB104 to environmental exposures.

6. Mechanism / Pathophysiology

Causal chain (upstream → downstream):

Molecular trigger: Biallelic loss-of-function RIPOR2 variants (splice-site or nonsense) → absent or non-functional RIPOR2 protein, or protein that fails to reach its normal subcellular destination (mutant protein retained in cytoplasmic inclusion bodies rather than trafficking to the plasma membrane) — PMID 24958875.
Subcellular/structural consequence: Loss of the RIPOR2 circumferential ring structure at the base of stereocilia (normally regulated by RhoC-dependent oligomerization) — PMID for Krey et al. 2016 eLife.
Cytoskeletal/interactome consequence: Disrupted interaction with MYH9 (myosin heavy chain 9), reduced MYH9 protein levels in the cochlea, and mislocalization of the kinocilium during hair-bundle morphogenesis — PMID 30280293.
Cellular/organelle consequence: Abnormal stereociliary bundle structure and orientation; in mouse models, this manifests as disorganized, misoriented hair bundles from early development (structural/developmental defect) rather than a purely late, degenerative process — PMID 30280293; complementary evidence from the paralogous EPS8L2/DFNB106 pathway shows a distinct maintenance-phase mechanism (see note below).
Functional consequence: Impaired mechanotransduction — reduced mechanotransduction currents in RIPOR2-deficient hair cells, with re-expression rescue demonstrated experimentally (eLife 2016), directly linking RIPOR2 loss to sensory transduction failure rather than only structural malformation.
Clinical manifestation: Congenital, profound, non-progressive sensorineural hearing loss (± vestibular areflexia in some allelic variants).

Note on module conformance (dismech context): This causal chain — stereociliary actin-cytoskeleton disruption → hair-bundle structural/mechanotransduction failure → profound congenital deafness — is mechanistically analogous to, but molecularly distinct from, the EPS8/EPS8L2 (DFNB102/DFNB106) pathway, which involves stereocilia elongation and maintenance via direct actin-bundling rather than RhoA/RhoC-regulated membrane-ring formation. If a "stereocilia structure/maintenance" mechanism module exists in dismech, DFNB104 nodes should specify the RIPOR2/RhoC/MYH9 axis distinctly from the EPS8/EPS8L2/actin-elongation axis.

Cellular processes involved: - Actin cytoskeleton organization/regulation (via Rho-family GTPase signaling) - Stereocilia bundle morphogenesis and maintenance - Mechanotransduction (sensory transduction in hair cells) - Possibly cell polarity establishment (kinocilium positioning)

Protein dysfunction: Loss of function via (a) failed membrane trafficking/localization (splice variant) or (b) truncation/nonsense-mediated decay (nonsense variant) — net effect is absence of functional RIPOR2 at the stereociliary base.

Biochemical abnormalities: Reduced MYH9 protein abundance despite normal/increased Myh9 transcript levels in Ripor2-null mouse cochlea — a post-transcriptional/protein-stability defect downstream of RIPOR2 loss.

Molecular profiling: No transcriptomic, proteomic, metabolomic, or single-cell/spatial datasets specific to human DFNB104 tissue were identified (expected, given the rarity of the condition and inaccessibility of human inner-ear tissue); mechanistic molecular data derive from mouse and zebrafish models.

Suggested GO terms: - GO:0060088 — auditory receptor cell stereocilium organization - GO:0035090 — maintenance of apical/basal cell polarity (if applicable to kinocilium positioning) - GO:0007266 — Rho protein signal transduction

Suggested CL terms: - CL:0000601 — inner hair cell - CL:0000602 — outer hair cell - CL:0000855 — sensory hair cell (general, if subtype not specified)

7. Anatomical Structures Affected

Organ level: - Primary organ: inner ear (cochlea) — auditory portion. - Secondary/variant-dependent involvement: vestibular labyrinth (semicircular canals, otolith organs) — affected in the Tunisian p.Arg521* family but not the original Turkish splice-variant family, indicating allele-dependent penetrance of the vestibular phenotype. - Body system: sensory/auditory-vestibular system (cranial nerve VIII pathway secondarily, via sensory input loss, not primary neuronal pathology).

Tissue and cell level: - Sensory epithelium of the organ of Corti (cochlea) — inner and outer hair cells (CL:0000601, CL:0000602). - Vestibular sensory epithelium (cristae ampullares, maculae) in variant-affected individuals.

Subcellular level: - Stereocilia — specifically the basal taper/base region where RIPOR2 forms its ring-like oligomeric structure (distinct from the stereocilia tips, where EPS8/EPS8L2 act). - Plasma membrane (site of normal RIPOR2 localization; site of failed trafficking for the mutant splice-variant protein). - Cytoplasmic inclusion bodies (site of pathological mutant-protein accumulation). - Kinocilium (secondarily mislocalized in Ripor2-deficient mice).

Localization: - Bilateral, symmetric involvement of both ears (consistent across all reported human cases). - No lateralization/asymmetry reported.

Suggested UBERON terms: - UBERON:0001846 — cochlea - UBERON:0002106 — spiral organ (organ of Corti) - UBERON:0002418 — stereocilium bundle / UBERON:0009866 stereocilium (verify precise term) - UBERON:0001838 — vestibular apparatus (for the variant-associated phenotype)

Suggested GO Cellular Component terms: - GO:0032420 — stereocilium - GO:0005886 — plasma membrane

8. Temporal Development

Onset: Congenital/prelingual — hearing loss is present from birth or the earliest testable age (universal newborn hearing screening range), consistent with a developmental/structural stereociliary defect rather than a late degenerative process.

Onset pattern: Not acute or insidious in the usual sense — it is a static congenital deficit.

Progression: - Auditory phenotype: Non-progressive in the original (splice-variant) family — audiograms performed at multiple ages did not show worsening. This is a notable point of contrast with the RIPOR2-associated dominant DFNA21, which is explicitly progressive with average onset age 30.6 years (range 0–70 years) in the Dutch founder-variant cohort (PMID 32631815). - Vestibular phenotype (where present): Static congenital areflexia with developmental consequence (delayed independent walking at 21–24 months in the Tunisian siblings) rather than progressive vestibular decline.

Disease course pattern: Stable, chronic, lifelong sensorineural hearing loss.

Disease stages: Not formally staged (unlike some progressive conditions); severity is described simply as profound at diagnosis and remains profound.

Remission patterns: None — this is a structural/developmental sensory deficit with no spontaneous remission; management is via habilitation (hearing aids, cochlear implantation), not disease-modifying treatment.

Critical periods: As with all forms of prelingual profound deafness, early identification (newborn hearing screening) and early intervention (hearing aids/cochlear implant, before ~2–3 years of age) represent the critical window for optimizing spoken-language outcomes — a general principle for congenital SNHL, not RIPOR2-specific data.

9. Inheritance and Population

Epidemiology: - No population-level prevalence or incidence estimates exist for DFNB104 specifically; it is described only via individual case families (an ultra-rare, "cases in literature" level of epidemiological documentation — likely fewer than 10 families reported worldwide as of 2023–2024: 1 Turkish family with 6 affected, 1 Tunisian family with 3 affected, plus scattered additional ClinVar-reported variants of uncertain full clinical documentation). - Suggested prevalence_class: NOT_YET_DOCUMENTED or CASES_IN_LITERATURE (per dismech's PrevalenceMeasureEnum), given the case-family-level evidence base.

Inheritance pattern: Autosomal recessive (biallelic variants required; heterozygous carriers are unaffected for DFNB104, in contrast to the dominant DFNA21 allele in the same gene).

Penetrance: Complete in all reported biallelic carriers (100% penetrance for the auditory phenotype across both reported families).

Expressivity: Variable — specifically regarding the vestibular component (present in the Tunisian p.Arg521* family, absent in the Turkish c.102-1G>A family), suggesting possible allele-specific or genetic-background-dependent expressivity. The auditory phenotype (profound, congenital, non-progressive) appears consistent across families.

Genetic anticipation: Not applicable/not reported (not a repeat-expansion disorder).

Germline mosaicism: Not reported in the literature reviewed.

Founder effects: Not established for the recessive DFNB104 alleles (each reported variant appears private to its family) — this contrasts with the well-characterized Dutch founder deletion causing the dominant DFNA21.

Consanguinity role: Central — both reported families (Turkish, Tunisian) are consanguineous, which is the mechanism by which rare private recessive alleles became biallelic and phenotypically manifest.

Carrier frequency: Not established in population databases (gnomAD) given the rarity/private nature of reported alleles.

Population demographics: - Reported affected families: Turkish (original discovery family) and Tunisian (second reported vestibular-affected family) — both from populations with documented elevated rates of consanguineous marriage, consistent with ascertainment bias toward populations where recessive conditions are more readily unmasked and studied. - No broader geographic/ethnic prevalence data available. - Sex ratio: Autosomal recessive — expected 1:1 male:female; no skew reported (consistent with the 6 and 3 affected individuals reported, though gender breakdown was not the emphasized detail in these papers).

10. Diagnostics

Clinical/audiological tests: - Auditory brainstem response (ABR): absent, consistent with profound SNHL. - Otoacoustic emissions (OAE): absent/negative. - Acoustic reflex testing: absent. - Pure-tone audiometry: profound bilateral symmetric SNHL. - Vestibular testing (where indicated): cervical VEMPs (abnormal in Tunisian family), video head-impulse test (vHIT) — negative gains, covert saccades on posterior/lateral canals in the vestibular-areflexia subgroup.

Genetic testing: - Recommended approach: Given DFNB104's genetic and phenotypic overlap with dozens of other DFNB loci (e.g., GJB2, MYO15A, OTOF, and the mechanistically related EPS8/EPS8L2/DFNB102/106), a multi-gene nonsyndromic hearing loss panel or exome sequencing (especially in consanguineous families, where autozygosity mapping/homozygosity-region analysis is powerful — as used in both the original Turkish and Tunisian discovery studies) is the standard diagnostic approach rather than single-gene RIPOR2 testing. - Whole exome sequencing (WES): Was the discovery method in both published families (combined with linkage/homozygosity mapping). - Gene panels: RIPOR2 is included in clinical "monogenic hearing loss" gene panels (e.g., Genomics England PanelApp lists RIPOR2 under its Monogenic hearing loss panel). - Chromosomal microarray/karyotyping/FISH: Not applicable — DFNB104 arises from sequence-level (not structural chromosomal) variants. - Mitochondrial DNA testing: Not applicable (nuclear gene).

Clinical criteria: No RIPOR2/DFNB104-specific diagnostic criteria exist beyond standard nonsyndromic hearing loss workup; diagnosis is genetically confirmed (biallelic pathogenic RIPOR2 variants in a proband with congenital nonsyndromic profound SNHL, especially with consanguinity or homozygosity by descent).

Differential diagnosis: - Other DFNB loci causing congenital profound nonsyndromic SNHL (GJB2/DFNB1, MYO15A/DFNB3, OTOF/DFNB9, TMC1/DFNB7/11, and many others). - Usher syndrome (if vestibular areflexia is present in an affected individual — must be distinguished from RP-associated Usher syndrome by absence of retinal/ophthalmologic findings, since the Tunisian RIPOR2 phenotype mimics a Usher-like cochleovestibular presentation without retinitis pigmentosa). - The mechanistically related but molecularly distinct EPS8-family disorders (DFNB102/EPS8, DFNB106/EPS8L2) — clinically distinguishable by their typically progressive (rather than congenital-stable) course.

Screening: Universal newborn hearing screening (standard of care generally, not RIPOR2-specific) would detect the congenital profound hearing loss; cascade genetic testing/carrier screening is relevant in consanguineous families with a known proband variant.

11. Outcome/Prognosis

Survival/mortality: No excess mortality — DFNB104 is an isolated (nonsyndromic) sensory disorder with no reported systemic or life-limiting comorbidity.

Morbidity/function: - Primary morbidity is profound congenital deafness, with attendant impact on spoken-language development if unaddressed by early habilitation. - In the vestibular-areflexia subset (Tunisian family), additional morbidity includes delayed gross motor/balance milestones (delayed independent walking) and likely lifelong absence of the vestibulo-ocular reflex, which may affect balance in low-visual/proprioceptive-input conditions (e.g., darkness, uneven surfaces) — extrapolated from general vestibular-areflexia literature, not RIPOR2-specific outcome studies.

Disease course: Stable — the hearing loss does not progress further once established (a favorable prognostic feature relative to progressive DFNB/DFNA forms), meaning habilitative interventions (hearing aids, cochlear implants) are not expected to need escalation due to further hearing decline.

Complications: None specific reported beyond the sensory/developmental consequences above; cochlear implantation is expected to be effective given the absence of documented cochlear structural malformation beyond the stereociliary/hair-cell level (though implant-specific outcome data for RIPOR2/DFNB104 patients specifically were not identified in this search).

Prognostic factors: Early cochlear implantation/hearing amplification is the major modifiable prognostic factor for language outcomes, per general principles of congenital profound SNHL management (not RIPOR2-specific trial data).

12. Treatment

No RIPOR2/DFNB104-specific gene therapy, pharmacotherapy, or targeted molecular treatment currently exists or is in registered clinical trials (no ClinicalTrials.gov entries or AAV inner-ear gene-therapy programs targeting RIPOR2 were identified in this search, in contrast to genes like OTOF, which has advanced AAV gene-therapy programs).

Standard of care (supportive/rehabilitative, non-gene-specific): - Hearing amplification: Hearing aids for residual hearing (typically limited benefit given profound loss). - NCIT term: NCIT:C15302 (Physical Therapy) is not correct; more appropriate would be a hearing-device/audiologic-rehabilitation NCIT term if available, or leave treatment_term free-text if no exact NCIT match exists (device-based interventions currently lack a precise NCIT clinical-action term per dismech's own documented gap for "DEVICE" modality). - Cochlear implantation: The mainstay definitive intervention for congenital profound bilateral SNHL. - NCIT: no exact single term found in this search; consider NCIT:C15329 (Surgical Procedure) as the treatment_term with device/implant specified in description, or search NCIT specifically for "Cochlear Implantation" at curation time. - Vestibular rehabilitation (for the vestibular-areflexia subgroup): standard balance/vestibular physical therapy. - NCIT:C15302 (Physical Therapy) applicable here. - Genetic counseling: Recommended for consanguineous families with an identified proband, given the autosomal recessive inheritance and elevated recurrence risk (25% per pregnancy for carrier parents). - NCIT:C15240 (Genetic Counseling).

Experimental/preclinical therapeutic direction (mechanistic rationale, not yet RIPOR2-specific): - Mouse model rescue experiments have shown that re-expression of Fam65b/Ripor2 in deficient hair cells can rescue mechanotransduction defects (Krey et al. 2016, eLife), providing proof-of-concept rationale for a future AAV-mediated gene-replacement approach analogous to those in advanced development for OTOF, TMC1, and other DFNB genes — but no RIPOR2-specific vector or preclinical inner-ear gene-therapy publication was identified as of this search.

Treatment outcomes: No RIPOR2-specific treatment-response, adverse-event, or comparative-effectiveness data located.

13. Prevention

Primary prevention: Not applicable in the traditional sense (monogenic disorder); the only "prevention" avenue is reproductive genetic counseling and reduction of consanguineous-union recurrence risk awareness in affected families.
Secondary prevention/early detection: Universal newborn hearing screening (general standard of care, not RIPOR2-specific) enables early diagnosis and prompt habilitative intervention.
Genetic screening: Carrier screening and prenatal/preimplantation genetic diagnosis (PGD) are options for known-carrier consanguineous families once a familial RIPOR2 variant is identified, per standard ACMG-style recessive-disorder counseling principles.
Tertiary prevention: Early cochlear implantation/amplification to prevent language-developmental complications of unaddressed profound deafness; vestibular rehabilitation to mitigate balance-related complications in the vestibular-areflexia subgroup.
Public health/behavioral/immunization/prophylaxis: Not applicable — no infectious, immunizable, or behavioral risk-modification component to this monogenic disorder.

14. Other Species / Natural Disease

Taxonomy: No naturally occurring RIPOR2-associated hearing loss has been reported in companion animals or wildlife (no OMIA entry identified in this search) — all non-human data derive from engineered/induced models (see Section 15), not spontaneous natural disease.
Comparative biology: The RIPOR2 gene and its role in stereociliary actin regulation appear evolutionarily conserved (functional orthologs studied in mouse and zebrafish), and the RhoC-RIPOR2-MYH9 interaction network appears conserved across these model systems, though the notable species discrepancy in vestibular phenotype (human vestibular areflexia in some RIPOR2-null patients vs. normal vestibular function in Ripor2-knockout mice and zebrafish) is a documented cross-species divergence meriting explicit note (Morel et al. 2023) — a candidate HUMAN_MODEL_MISMATCH discussion for dismech curation.
Zoonotic/transmission relevance: Not applicable (non-infectious monogenic disorder).

15. Model Organisms

Mouse models: - Ripor2 (Fam65b) knockout mice: Complete deafness; hair bundle morphological defects (disorganized/misoriented stereocilia bundles), reduced mechanotransduction currents, aberrant kinocilium localization, and reduced MYH9 protein abundance in the cochlea (Xiong et al. 2018, J Mol Med, PMID 30280293; Krey et al. 2016, eLife). - Phenotype recapitulation: High fidelity for the auditory phenotype (deafness, hair-bundle/stereocilia structural defects, mechanotransduction failure) — closely mirrors human DFNB104. - Model limitation: Vestibular phenotype is NOT recapitulated — Ripor2-knockout mice show normal balance/vestibular function (no circling behavior), unlike the vestibular areflexia documented in at least one human family. This is an explicit, well-documented human-model mismatch meriting HUMAN_MODEL_MISMATCH classification (per dismech schema conventions) rather than a generic KNOWLEDGE_GAP, since the evidence (mouse vestibular testing) exists but its translational validity to the human vestibular phenotype is the open question. Proposed explanations in the primary literature include incomplete/insensitive vestibular testing in mice and genetic compensation by paralogs RIPOR1/RIPOR3. - Rescue experiments: Re-expression of wild-type Fam65b/Ripor2 in deficient hair cells rescues mechanotransduction current defects, demonstrating causality and supporting the eventual therapeutic feasibility of gene replacement (eLife 2016).

Zebrafish models: - fam65b knockdown (morpholino) zebrafish: Significant reduction in saccular hair cell numbers and neuromasts, and hearing loss, reported in the original discovery paper (Diaz-Horta et al. 2014, PMID 24958875). - fam65b nonsense-mutant zebrafish (from the Tunisian-family follow-up study): No circling behavior or balance abnormality at 5 days post-fertilization, again showing the auditory-but-not-vestibular phenotype discrepancy relative to at least one human RIPOR2 family (Morel et al. 2023).

Applications: These models have been used to establish causality (loss-of-function → hearing loss), define the subcellular localization and oligomeric ring structure of RIPOR2 at the stereociliary base, dissect the RhoC-dependent regulatory mechanism, identify the MYH9 interaction, and demonstrate rescue of mechanotransduction by gene re-expression — the last providing direct preclinical proof-of-concept for a future gene-therapy approach.

Resources: MGI (Mouse Genome Informatics) for Ripor2 knockout allele records; ZFIN for zebrafish fam65b/ripor2 mutant/morphant lines (specific allele/stock IDs not retrieved in this search — recommend direct MGI/ZFIN query at curation time for exact resource identifiers).

Summary of Key Evidence Citations

Citation	Key Contribution
Diaz-Horta O, et al. PNAS 2014. PMID: 24958875	Discovery of FAM65B/RIPOR2 as DFNB104 gene; c.102-1G>A splice variant; Turkish family clinical/audiometric characterization; zebrafish knockdown model
Xiong W, et al. J Mol Med 2018. PMID: 30280293	Ripor2 mouse knockout: hair-bundle structure/orientation defects; MYH9 interaction
Krey JF, et al. eLife 2016. DOI 10.7554/eLife.14222	RIPOR2 ring-like stereociliary base structure; RhoC-dependent oligomerization; mechanotransduction rescue
Oonk AMM, et al. 2020. PMID: 32631815	Dominant RIPOR2 founder deletion causing DFNA21 (adult-onset, progressive) — important nosological contrast to DFNB104
Morel N, et al. Clin Genet 2023. DOI 10.1111/cge.14436	Third RIPOR2 variant (p.Arg521*); Tunisian family with vestibular areflexia; explicit human-vs-animal-model vestibular-phenotype discrepancy discussion
OMIM #616515	Clinical synopsis and molecular genetics summary for DFNB104
OMIM *611410	RIPOR2 gene entry

Notable curation caveats for dismech entry construction: 1. The Orphanet-specific identifier for DFNB104 could not be independently confirmed in this research pass and should be verified directly against Orphadata/ORPHA before citation (avoid citing an unverified ORPHA code). 2. The PX-BAR domain structural classification for RIPOR2/FAM65B has been directly disputed in the literature (PNAS 2014 technical comment) — cite this nuance if describing protein domain structure in detail. 3. The vestibular phenotype is not uniform across reported DFNB104 families — this is a genuine expressivity finding, not an error, and should be modeled as such (e.g., via subtype-level or evidence-item-level distinction between the Turkish and Tunisian families) rather than collapsed into a single uniform phenotype claim. 4. No RIPOR2-specific prevalence, treatment-trial, or QOL data exist beyond the two published case families — this is an ultra-rare, "cases-in-literature" level disorder, and prevalence/epidemiology fields should be populated conservatively (e.g., CASES_IN_LITERATURE / NOT_YET_DOCUMENTED).

Autosomal Recessive Nonsyndromic Hearing Loss 104

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Autosomal Recessive Nonsyndromic Hearing Loss 104 (DFNB104) — Comprehensive Research Report

1. Disease Information

2. Etiology

3. Phenotypes

Auditory phenotype (core feature)

Audiological test findings

Vestibular phenotype (variant-dependent, not uniform)

Quality of life impact

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Summary of Key Evidence Citations