| Domain | Best-supported finding | Evidence type/strength | Key source/date |
|---|---|---|---|
| Disease identity and inheritance | DFNB35 is autosomal-recessive nonsyndromic sensorineural hearing loss caused by biallelic germline **ESRRB** variants; locus **14q24.3**. | **Strong:** linkage, segregation, multiple independent families, and functional evidence. | Collin et al., Jan 2008, [DOI](https://doi.org/10.1016/j.ajhg.2007.09.008) (pqac-00000004, pqac-00000007); Choi et al., Sep 2024, [DOI](https://doi.org/10.1038/s41598-024-70795-8) (pqac-00000006) |
| Core phenotype | Usually congenital/prelingual, bilateral, approximately symmetric severe-to-profound SNHL; moderate-to-severe and asymmetric progressive disease also occur. Vestibular dysfunction was absent in the original families. | **Moderate:** consistent case-series evidence, but few patients and incomplete longitudinal characterization. | Collin et al., Jan 2008 (pqac-00000007, pqac-00000008); Choi et al., Sep 2024 (pqac-00000009, pqac-00000010) |
| Rarity and populations | Fewer than 20 affected families had been reported before the 2024 Korean case; many early families were consanguineous and Pakistani or Turkish. Disease-specific prevalence, incidence, and carrier frequency are unknown. | **Moderate for extreme rarity; limited for population estimates:** ascertainment is strongly family- and ancestry-biased. | Choi et al., Sep 2024 (pqac-00000006, pqac-00000011); Collin et al., Jan 2008 (pqac-00000004, pqac-00000007) |
| Causal gene and protein | **ESRRB** encodes estrogen-related receptor β (ERRβ), an orphan nuclear-receptor transcription factor with a C4 zinc-finger DNA-binding domain and a C-terminal ligand-binding domain. | **Strong:** established molecular genetics and protein-domain biology. | Collin et al., Jan 2008, [DOI](https://doi.org/10.1016/j.ajhg.2007.09.008) (pqac-00000007); Choi et al., Sep 2024 (pqac-00000006) |
| Variant spectrum | A 2024 synthesis identified **25 reported alleles representing 22 unique variants**: 90.9% SNVs; 72.7% missense, 4.5% nonsense, 9.1% frameshift, 9.1% splice, and 4.5% in-frame. Nine coding variants mapped to each of the DNA- and ligand-binding domains. | **Moderate-to-strong:** literature synthesis backed by reported pedigrees; classifications may change with new population or functional evidence. | Choi et al., Sep 2024 (pqac-00000012) |
| Exemplar pathogenic variants | Segregating examples include **c.1018_1024dupGAGTTTG (p.Val342GlyfsTer44)**, **p.Ala110Val**, **p.Leu320Pro**, **p.Val342Leu**, **p.Leu347Pro**, **c.397+2T>G**, and **p.Arg382Cys** in trans with a loss-of-function allele. **p.Pro386Ser** was found in controls and treated as polymorphic; **p.Thr389Met** remained uncertain. | **Strong for segregating loss-of-function/domain variants; variable for missense variants.** | Collin et al., Jan 2008 (pqac-00000007); Choi et al., Sep 2024 (pqac-00000001, pqac-00000015) |
| 2024 functional advance | **c.397+2T>G** caused exon-4 skipping, premature termination, and nonsense-mediated decay. **p.Arg382Cys** destabilized ERRβ and abolished/reduced transcriptional activity; authors assigned **PS3-supporting** but retained a “warm VUS” rather than pathogenic classification. Its gnomAD v4.1 East-Asian frequency was **0.007065**, versus **0.002095** overall. | **Strong functional evidence for splicing; moderate supporting evidence for p.Arg382Cys:** patient cells, minigene, reporter, protein, and computational assays, but one family and no knock-in animal. | Choi et al., Sep 2024, [DOI](https://doi.org/10.1038/s41598-024-70795-8) (pqac-00000009, pqac-00000012, pqac-00000015) |
| Molecular mechanism | Biallelic loss or hypomorphic dysfunction reduces ERRβ-dependent transcription. In patient cells, **ATP1B1** and **EGR1** decreased 55.1% and 45.4% versus the father; splice-allele-associated targets **NRP1**, **TBX3**, and **SPARC** fell approximately 48–53%. Disruption of cochlear ion/fluid homeostasis is plausible, but the complete human causal pathway remains partly inferred. | **Moderate:** direct cellular transcriptional evidence plus animal/anatomical support; downstream electrophysiology has not been demonstrated in affected humans. | Choi et al., Sep 2024 (pqac-00000002, pqac-00000012); Collin et al., Jan 2008 (pqac-00000008) |
| Anatomy and cell types | ESRRB localizes to cochlear supporting and nonsensory tissues, stria vascularis/spiral ligament, nerve fibers, and spiral-ganglion cells; it was not detected in inner or outer hair cells. Absent otoacoustic emissions therefore likely reflect secondary outer-hair-cell dysfunction. | **Moderate:** developmental mouse RNA localization and postnatal rat immunohistochemistry, supported by human audiology; direct human cochlear tissue evidence is lacking. | Collin et al., Jan 2008 (pqac-00000008, pqac-00000013) |
| Model-organism evidence | Complete **Esrrb** loss is embryonically lethal; rescued or conditional-null mice show impaired hearing and balance, circling/head tossing, and defective stria-vascularis development. | **Moderate-to-strong mechanistic support:** mammalian loss-of-function phenotype, although it does not precisely model every human allele or the nonsyndromic presentation. | Collin et al., Jan 2008 (pqac-00000008) |
| Diagnosis | Confirm SNHL audiologically, exclude acquired causes and structural anomalies as indicated, then use a comprehensive hearing-loss panel or exome/genome sequencing with CNV analysis. Establish **biallelic variants in trans**, perform segregation testing, and use RNA/minigene or other functional assays for splice variants and unresolved VUSs. | **Strong for molecular approach; disease-specific evidence derives mainly from targeted sequencing/WES and functional follow-up.** | Ghasemnejad et al., Feb 2022, [DOI](https://doi.org/10.1186/s12920-022-01165-4) (pqac-00000003); Choi et al., Sep 2024 (pqac-00000014) |
| Treatment and trials | No disease-modifying or ESRRB-specific therapy is established. Current care is individualized hearing aids, cochlear-implant evaluation for severe-to-profound loss, speech/language and auditory rehabilitation, educational support, and serial audiometry. Searches identified no ESRRB/DFNB35-specific interventional trial. | **General standard-of-care evidence; very limited DFNB35-specific outcome evidence.** Absence of a retrieved trial is search-limited, not proof that none exists. | Choi et al., Sep 2024 (pqac-00000011, pqac-00000016) |
| Major evidence gaps | No reliable prevalence, penetrance, carrier-frequency, sex-ratio, natural-history, cochlear-implant outcome, modifier-gene, gene–environment, protective-factor, biomarker, epigenomic, metabolomic, or human single-cell dataset is available specifically for DFNB35. Dental-decay association and variant-specific genotype–phenotype correlations remain insufficiently established. | **Evidence insufficient:** conclusions should not be extrapolated from general SNHL without qualification. | Variant and family limitations summarized by Choi et al., Sep 2024 (pqac-00000010, pqac-00000011, pqac-00000015) |


*Table: Compact evidence-grade synthesis of the disease identity, phenotype, genetics, mechanism, clinical implementation, and principal knowledge gaps in ESRRB-related DFNB35.*