Osteootohepatoenteric Syndrome (OOHE / O2HE) — Comprehensive Research Report

1. Disease Information

Overview. Osteootohepatoenteric syndrome (OOHE, also styled O2HE or "osteo-oto-hepato-enteric syndrome") is an ultra-rare autosomal recessive multisystem disorder first delineated in 2018. It is defined by a variable combination of four core features reflected in its name: bone fragility (osteo-), sensorineural hearing loss (oto-), cholestasis (hepato-), and congenital/severe diarrhea (enteric-), sometimes accompanied by mild developmental delay and intellectual disability. It is caused by biallelic (compound heterozygous or homozygous) loss-of-function variants in UNC45A (Unc-45 Myosin Chaperone A), a myosin co-chaperone gene on chromosome 15q26.1 OMIM #619377; PMID:29429573.

Key identifiers: - OMIM: #619377 (phenotype), 611219 (UNC45A gene) - MONDO: MONDO:0859164 - MedGen: C5543557 (UID 1785846) - Gene:* UNC45A, HGNC gene ID 55898 approx. (NCBI Gene 55898), 15q26.1 - Orphanet-specific numeric entry was not retrievable through available search (not confirmed in this session — treat as unresolved rather than fabricate an ORPHA code)

Synonyms: O2HE syndrome; OOHE; osteo-oto-hepato-enteric syndrome; UNC45A-related disorder / UNC45A deficiency syndrome. A related but phenotypically distinct allelic entity — Aagenaes syndrome (cholestasis-lymphedema syndrome) presenting with neonatal cholestasis and lymphedema — has recently been linked to a UNC45A 5′-UTR regulatory variant (c.-88G>A) in combination with a loss-of-function allele, suggesting an expanding UNC45A-related allelic/phenotypic spectrum distinct from classic OOHE (PMID:39887522).

Evidence basis. Nearly all published data derive from individual case reports and small case series (aggregated literature review, not a large disease registry), supplemented by patient-derived cellular/organoid models and animal (zebrafish) studies. As of the most recent literature review (2025), 13 cases have been reported worldwide (PMC12516782), making this one of the rarest entries in the dismech Mendelian category.

2. Etiology

Disease causal factor: Purely monogenic/genetic — biallelic loss-of-function (missense, nonsense, frameshift, small in-frame deletion, and splice) variants in UNC45A. No environmental, infectious, or mechanistic non-genetic cause has been described.

Genetic risk factors: - Compound heterozygosity is more common than homozygosity in reported cases (most patients are compound heterozygotes for two different UNC45A alleles) [PMID:29429573]. - Recurrent variant: c.710T>C (p.Leu237Pro), located in the central domain, is the most frequently reported pathogenic allele across unrelated families and has been mechanistically characterized as a distinctive "gain-of-interaction" rather than simple loss-of-function variant (PMC11949031; PMID:40125554). - Other reported variants: c.292C>T (p.Arg98Trp) (recurrent, found in ≥2 unrelated families — PMC9868473, PMC13019544); c.2534-2545del (p.Leu845-Met848del); c.592C>T (p.Gln198*); c.2455C>T (p.Arg819Ter); c.2581C>T; c.2633C>T; c.2734T>G; p.Val423Asp (destabilizing/proteasomal-degradation mechanism, PMC9218578). - Variants segregate with disease and are absent or present at very low frequency in gnomAD, consistent with a highly penetrant recessive Mendelian mechanism [OMIM #619377]. - No specific gnomAD constraint (pLI/LOEUF) figure for UNC45A could be independently confirmed from search results in this session; this should be verified directly against the gnomAD browser before citing a number.

Environmental/lifestyle risk factors: None established — this is a fully genetically determined disease with no known environmental trigger, though it may contribute to non-genetic risk of prematurity (4 of 12 reported cases were premature, suggesting UNC45A dysfunction may itself predispose to preterm birth) [PMC12516782].

Protective factors: None identified in the literature.

Gene-environment interactions: None reported; disease expression is governed by allele-specific molecular mechanism (see §6) rather than external modifiers, although intra-familial phenotypic discordance despite identical genotype has been documented (see §9, Penetrance/Expressivity), implying unidentified modifying factors (genetic or environmental) exist.

3. Phenotypes

Phenotype frequencies below are drawn from the aggregated 13-case literature review (PMC12516782) unless otherwise cited.

Severity/progression: Highly variable — from near-complete clinical and biochemical recovery by 12 months in a milder Chinese case (normal hearing, no bone fragility) [PMC9868473] to severe secretory diarrhea requiring complete enterectomy and early mortality in 2 of 4 patients carrying the p.Leu237Pro variant in one cohort [PMC11949031]. Cholestasis can be relapsing/recurrent (benign recurrent intrahepatic cholestasis-like pattern) over decades, as documented in a 33-year-old patient followed from birth [PMC13019544].

Quality of life impact: Diarrhea and cholestasis drive substantial infancy/childhood morbidity (dehydration, growth failure, need for parenteral nutrition); hearing loss affects language development; bone fragility causes recurrent fractures affecting mobility. No formal EQ-5D/SF-36 data are available given the extreme rarity of the condition.

4. Genetic/Molecular Information

Causal gene: UNC45A (Unc-45 Myosin Chaperone A), OMIM *611219, chromosome 15q26.1. Suggest HGNC binding via lowercase hgnc: CURIE once confirmed via lookup (do not fabricate the numeric HGNC ID — verify via runoak/HGNC lookup before curation).

Variant classification and types (per ACMG/ClinVar framework, as reported in source papers): - Missense: p.Arg98Trp, p.Leu237Pro, p.Val423Asp - Nonsense/stop-gain: p.Gln198*, p.Arg819Ter - In-frame deletion: p.Leu845_Met848del (4 amino acids) - Regulatory (5′-UTR): c.-88G>A (associated with the related Aagenaes-syndrome-like phenotype, not classic OOHE) [PMID:39887522]

Zygosity: Predominantly compound heterozygous (biallelic, two different pathogenic variants); occasional homozygosity reported in consanguineous or founder contexts (not confirmed with a specific PMID in this session).

Functional consequence — allele-specific mechanisms (important for functional_impact_category curation): 1. Classic loss-of-function (e.g., nonsense/frameshift/most missense alleles): reduced UNC45A protein expression/stability, loss of chaperone activity for myosin folding [PMID:29429573]. 2. p.Val423Asp: causes protein instability and proteasomal degradation rather than direct loss of chaperone catalytic function [PMC9218578]. 3. p.Leu237Pro (c.710T>C): a distinctive non-classical, dominant-negative-like mechanism — the mutant retains chaperone/folding activity and still supports myosin filament assembly, but forms abnormally stable oligomeric chaperone-myosin complexes that fail to dissociate normally, thereby trapping and inhibiting nonmuscle myosin II (NMII) function and impairing transferrin/cargo recycling through endocytic compartments [PMC11949031]. This is a mechanistically distinct "trapping" gain-of-interaction phenotype layered on an overall loss-of-function disease, and is a strong candidate for functional_impact_category: DOMINANT_NEGATIVE at the GeneticContext level in a dismech curation, with careful attention to differentiating this from simple LOSS_OF_FUNCTION framing used for other alleles in the same gene.

Modifier genes: None formally established, though MYO5B is functionally (not genetically) linked — see mechanism section below — as UNC45A and MYO5B mutations converge on the same enterocyte apical-trafficking pathway causing overlapping enteropathy phenotypes between OOHE and microvillus inclusion disease (MVID) [PMC9218578].

Epigenetic information: No epigenetic mechanism has been reported for this disease.

Chromosomal abnormalities: None reported; disease is caused by point mutations/small indels, not large structural rearrangements.

Population frequency: All reported variants are rare or absent in gnomAD, consistent with a fully penetrant, ultra-rare recessive disorder; no specific allele frequency percentages could be confirmed from available sources in this session.

5. Environmental Information

No environmental, toxin, occupational, dietary, or infectious contributing factors have been identified for OOHE — it is a fully monogenic disorder. The only quasi-environmental association reported is that UNC45A dysfunction itself may be a cause (not consequence) of prematurity and possibly recurrent miscarriage, based on the observation that 4 of 12 literature cases were born prematurely [PMC12516782] — this is a mechanistic/reproductive association rather than an external environmental risk factor and should not be modeled as an environmental: exposure entry.

6. Mechanism / Pathophysiology

Ordered causal chain

1. Biallelic loss-of-function (or, for p.Leu237Pro, altered-function) variants in UNC45A lead to impaired UNC45A co-chaperone activity in the HSP90–UNC45A–myosin folding axis.
2. Impaired chaperone function results in misfolding, aggregation, or (for the p.Leu237Pro allele) pathological over-stabilization of myosin motor proteins that are UNC45A clients — principally nonmuscle myosin II (NMII) and myosin Vb (MYO5B) in enterocytes [PMC9106349; PMC11949031].
3. Myosin Vb misfolding/loss of function leads to impaired Rab11A-dependent apical recycling-endosome trafficking in intestinal epithelial cells — evidenced directly: Rab11 vesicles mislocalize away from the apical membrane in patient-derived organoids and duodenal tissue [PMC9106349].
4. Disrupted apical trafficking causes mislocalization of key absorptive apical membrane transporters — notably NHE3 (sodium-hydrogen exchanger) and DRA (chloride-bicarbonate exchanger) — into intracellular compartments rather than the brush border, while secretory transporters such as CFTR remain correctly localized (and one recent organoid study implicates CFTR itself as contributing to the intestinal phenotype — [PMC12780477], not independently confirmed in full detail here).
5. This selective loss of absorptive capacity with preserved/relatively enhanced secretory capacity produces a net secretory/osmotic diarrhea phenotype — the dominant and fully penetrant (100% of cases) clinical feature.
6. In parallel, myosin misfolding disrupts brush-border microvillar architecture, producing sparse, disorganized, shortened microvilli, subapical accumulation of pleomorphic vesicles and PAS-positive secretory granules, and formation of microvillus inclusions — a histopathological phenocopy of microvillus inclusion disease (MVID), which is itself caused by MYO5B mutations, establishing OOHE and MVID as mechanistically convergent, allelic-pathway-related disorders rather than incidentally similar diseases [PMC9218578].
7. Independently, UNC45A dysfunction in cholangiocytes/hepatocytes leads to aberrant localization of the bile salt export pump (BSEP), as directly demonstrated by immunofluorescence showing reduced UNC45A expression and aberrant BSEP localization in a patient liver biopsy [PMC13019544], resulting in impaired canalicular bile acid export and a low-GGT cholestasis phenotype (present in 69% of cases) — mechanistically parallel to other low-GGT familial intrahepatic cholestasis syndromes (e.g., BSEP/FIC1 deficiency), even though BSEP itself is not mutated.
8. UNC45A's broader chaperone role for myosin-dependent processes in bone (osteoblast/osteoclast function is myosin-cytoskeleton-dependent) and inner-ear hair cells (myosin motors are essential for stereocilia and hair-cell mechanotransduction) plausibly explains the bone fragility (46%) and sensorineural hearing loss (46%) components of the syndrome, though the cell-type-specific mechanistic studies for bone and cochlea (as opposed to the well-characterized enterocyte/hepatocyte mechanisms) are less developed in the literature reviewed here — this should be flagged as an inferred/less-directly-demonstrated step if curated into a pathograph.
9. The p.Leu237Pro allele additionally impairs transferrin receptor recycling through altered NMII-dependent endocytic trafficking, broadening the cell-biological consequences beyond the apical/enterocyte compartment and potentially contributing to the multisystem nature of severe cases [PMC11949031].

Molecular pathways / cellular processes

• HSP90–UNC45A co-chaperone pathway: UNC45A has an N-terminal TPR domain (HSP90 interaction), a central domain (function less well defined, but is the site of the p.Leu237Pro mutation), and a C-terminal UCS domain critical for myosin motor-domain folding [GeneCards; PMID search — JBC].
• Myosin-dependent apical vesicular trafficking (Rab11A recycling endosome pathway) in enterocytes.
• Nonmuscle myosin II (NMII)-dependent endocytic recycling (transferrin pathway).
• Bile canalicular transporter trafficking (BSEP localization) in hepatocytes.

Protein dysfunction

Myosin Vb (MYO5B) and nonmuscle myosin II are the principal UNC45A "client" motor proteins; their misfolding/mistrafficking is the proximate lesion. Suggested GO terms: GO:0051082 (unfolded protein binding), GO:0051291 (protein heterooligomerization), GO:0016459 (myosin complex), GO:0090161 (Golgi ribbon formation — likely not directly relevant, verify), and most centrally GO:0032313 (regulation of Rab GTPase activity) and GO:0006892 (post-Golgi vesicle-mediated transport)/GO:1904776 (regulation of protein localization to apical plasma membrane) — these should be independently verified via OAK lookup before binding, per dismech's term-contract rules.

Cell types and biological processes involved

• Enterocytes (small intestinal absorptive epithelial cells) — primary site of the enteropathy; suggested CL term: CL:0000584 (enterocyte) — verify via lookup.
• Hepatocytes / cholangiocytes — cholestasis mechanism.
• Cochlear hair cells (inferred, not directly demonstrated in the sources retrieved) — hearing loss.
• Osteoblasts/osteoclasts (inferred) — bone fragility.

Advanced/omics findings

• Organoid models: Patient-derived and CRISPR-engineered UNC45A-knockout intestinal organoids (2D and 3D, including iPSC-derived) recapitulate MVID-like architecture: dense cellular aggregates lacking a central lumen, large F-actin-positive intracellular inclusions, and abnormal brush border differentiation [PMC9106349].
• Proteomics: Mass spectrometry of UNC45A immunoprecipitates identified myosin Vb among nine myosin proteins significantly enriched, together with HSP90 and actin, establishing the direct chaperone-client physical interaction [PMC9106349].
• Model organism (zebrafish): unc45a mutant zebrafish larvae display microvillus shortening and MVI-like intracellular compartments plus Rab11 mislocalization, confirming in vivo relevance of the enterocyte trafficking defect [PMC9106349]. Notably, unc45a (unlike the paralog unc45b) is not required for zebrafish myogenesis and unc45a/unc45b double mutants show no muscle phenotype beyond that of unc45b alone — indicating functional divergence between the two UNC45 paralogs, with UNC45A's disease-relevant role being epithelial/non-muscle rather than sarcomeric.

7. Anatomical Structures Affected

• Primary organs: Small intestine (enterocytes/brush border), liver (hepatocytes, bile canaliculi), inner ear (cochlea), skeleton (bone).
• Secondary/complication-related: Growth/nutritional status (secondary to chronic diarrhea and malabsorption); potentially CNS (developmental delay in a subset; neonatal brain injury reported in some neonatal cases).
• Body systems: Gastrointestinal, hepatobiliary, auditory/sensory, skeletal, and (in a subset) neurodevelopmental.
• Tissue/cell level: Intestinal villus/crypt epithelium (enterocytes); hepatocyte canalicular membrane; cochlear hair cells (inferred); osteoblast/osteoclast lineage (inferred).
• Subcellular level: Apical recycling endosomes (Rab11A-positive compartments), brush-border microvilli, subapical secretory vesicles, lysosomes (enlarged in villus enterocytes), and — for the p.Leu237Pro mechanism — transferrin-receptor endocytic recycling compartments. Suggested GO Cellular Component terms: GO:0031526 (brush border membrane), GO:0055038 (recycling endosome membrane) — verify via lookup.
• Localization: No lateralization pattern reported (systemic/bilateral disease, e.g., bilateral sensorineural hearing loss).

8. Temporal Development

• Onset: Congenital/neonatal for the cardinal features — diarrhea typically manifests within the first days to weeks of life (one case: loose stools 3–5×/day starting shortly after birth; another: acholic diarrhea within 10 days of birth). Cholestasis/jaundice is also neonatal-onset in most reported cases.
• Onset pattern: Acute/severe at presentation in the neonatal period for GI and hepatic features; bone fragility and hearing loss may not become apparent/diagnosed until later childhood (e.g., osteoporosis confirmed by DEXA at ages 14 and 25 in one longitudinally followed patient).
• Progression: Highly variable. Some patients show progressive/relapsing cholestasis over decades with episodic pruritic flares (one patient's cholestasis recurred at age 10 with a 7-month pruritus episode and bilirubin up to 270 μmol/L, then again requiring treatment as an adult). Others show near-complete resolution of diarrhea/cholestasis by 12 months with only mild residual biochemical abnormality. The most severe reported outcomes (associated with p.Leu237Pro) included complete enterectomy in one patient and early mortality in two of four patients in that cohort.
• Disease course pattern: Can be relapsing-remitting (cholestasis, described as "benign recurrent intrahepatic cholestasis"-like) or chronic/progressive (osteoporosis, hearing loss).
• Critical periods: The neonatal period is the critical window for diagnosis and life-threatening complications (severe diarrhea, cholestasis, need for parenteral nutrition); later childhood/adolescence is when skeletal and residual hepatic sequelae become apparent.

9. Inheritance and Population

• Epidemiology: Extremely rare — 13 cases reported worldwide as of the most recent literature review [PMC12516782]. No formal prevalence/incidence estimate exists (would fall in prevalence_class: BELOW_1_IN_1000000 / measure_type: CASES_IN_LITERATURE per dismech conventions, given the literature explicitly frames this as a cumulative case count rather than a population-based rate).
• Inheritance pattern: Autosomal recessive (AR) — confirmed in all reported cases (compound heterozygous or homozygous biallelic variants segregating with disease) [OMIM #619377]. Suggested HP inheritance term: HP:0000007 (Autosomal recessive inheritance).
• Penetrance: Appears to be high/complete for compound heterozygous null combinations, but intrafamilial phenotypic discordance has been documented: two siblings carrying the identical UNC45A genotype (a 5′-UTR variant c.-88G>A plus a loss-of-function allele p.Arg531Ter) both presented with neonatal cholestasis and lymphedema, but only one developed severe liver failure requiring transplantation, while the other did not — demonstrating variable expressivity/incomplete penetrance for severity even with identical genotype [PMID:39887522]. This is directly relevant to any Inheritance.penetrance or expressivity annotation.
• Expressivity: Markedly variable, spanning from mild, self-resolving disease (Chinese case, near-complete recovery by 12 months, no bone or hearing involvement) [PMC9868473] to severe multisystem disease with enterectomy and early death [PMC11949031].
• Genetic anticipation: Not reported/not applicable (not a repeat-expansion disorder).
• Germline mosaicism: Not specifically reported in retrieved sources.
• Founder effects / consanguinity: Not confirmed with specific data in this session; several published families appear non-consanguineous (e.g., the Chinese case explicitly notes "healthy, non-consanguineous parents").
• Carrier frequency: Not established; variants are individually rare/private in gnomAD.
• Population demographics: Cases reported from multiple ancestries including French/European (original 2018 description), Chinese Han (2022/2023 case), and others in the aggregated 13-case series; no specific ethnic enrichment has been established. No sex-ratio data could be confirmed from available sources.

10. Diagnostics

Laboratory tests: - Liver panel: elevated total and direct bilirubin (e.g., total bilirubin 136.75 μmol/L, direct bilirubin 104.38 μmol/L in one infant), elevated total bile acids (TBA up to 217.3 μmol/L), low GGT pattern of cholestasis (consistent with a BSEP-trafficking-type mechanism despite BSEP being genetically normal) [PMC9868473; PMC13019544]. - Stool studies: consistent with secretory diarrhea.

Imaging: - Abdominal ultrasound/imaging: hepatomegaly. - DEXA scan: reduced bone mineral density/osteoporosis, performed longitudinally in at least one patient (ages 14, 25).

Functional tests: - Auditory brainstem response (ABR): used to assess hearing (one case had normal ABR wave V threshold 25 dBHL; another had moderate bilateral sensorineural hearing loss confirmed via audiometry).

Biopsy/histopathology: - Intestinal biopsy: villous atrophy, microvillus inclusion disease-like features (sparse/disorganized/shortened microvilli, microvillus inclusions, enlarged lysosomes in villus enterocytes). - Liver biopsy: immunofluorescence showing reduced UNC45A protein expression and aberrant BSEP canalicular mislocalization [PMC13019544].

Genetic testing: - Whole exome sequencing (WES) is the diagnostic modality used in essentially all reported cases (identifying compound heterozygous UNC45A variants); given the syndrome's rarity and nonspecific overlapping presentation with other congenital diarrhea/cholestasis syndromes (e.g., MVID/MYO5B, other PFIC genes), a single-gene UNC45A panel is unlikely to be first-line — WES/WGS with a congenital-diarrhea or cholestasis gene panel is the practical approach. - No dedicated GTR/gene panel curated name could be confirmed from sources retrieved in this session.

Differential diagnosis: Microvillus inclusion disease (MYO5B, STX3, STXBP2 mutations) — overlapping enteropathy and even shared histopathology; other low-GGT progressive familial intrahepatic cholestasis syndromes (FIC1/ATP8B1, BSEP/ABCB11); congenital chloride/sodium diarrhea; other syndromic hearing-loss/bone-fragility overlap syndromes (e.g., osteogenesis imperfecta — noted as a differential in amedes-genetics resource). The related UNC45A allelic entity, Aagenaes/cholestasis-lymphedema syndrome, should also be distinguished.

Screening: No newborn screening or population carrier screening program exists for this ultra-rare condition.

11. Outcome/Prognosis

• Mortality: Documented in the most severe genotype-phenotype subgroup — 2 of 4 patients carrying the p.Leu237Pro variant in one cohort had early mortality [PMC11949031]. Formal survival statistics (5-year, 10-year) do not exist given the small case numbers; the broader 13-case literature review noted insufficient data to establish a population-level mortality rate, though neonatal brain injury was reported in some cases [PMC12516782].
• Morbidity/complications: Severe secretory diarrhea can necessitate long-term parenteral nutrition or, in the most severe case, complete enterectomy. Recurrent cholestatic flares with severe pruritus can persist into adulthood (one patient followed to age 33). Chronic bone fragility with recurrent fractures and confirmed osteoporosis on DEXA. One documented case of severe liver failure requiring liver transplantation in a UNC45A-mutant sibling pair.
• Recovery potential: Some patients (notably milder allele combinations) show near-complete clinical and biochemical recovery in infancy with treatment and can discontinue medication [PMC9868473]. Others require lifelong management.
• Prognostic factors: The specific UNC45A allele appears to be an important prognostic determinant — e.g., p.Leu237Pro is associated with a more severe/potentially lethal phenotype via its distinctive dominant-negative-like mechanism, while other missense combinations (e.g., p.Arg98Trp-containing genotypes) have been associated with milder, more treatable disease courses. However, the documented sibling discordance with identical genotype (§9) shows genotype alone does not fully predict severity.

12. Treatment

No disease-specific approved therapy or standardized treatment guideline exists; management is supportive/symptomatic, targeting each organ system.

Pharmacotherapy for cholestasis: - Ursodeoxycholic acid (UDCA), oral, e.g., 50 mg/day in an infant, used for cholestasis management [PMC9868473]. Suggested NCIT term: NCIT:C15986 (Pharmacotherapy) + therapeutic_agent CHEBI ursodeoxycholic acid (verify CURIE via lookup). - Compound glycyrrhizin (IV) — reported to "relieve cholestasis by regulating bile acid transporters" [PMC9868473]. - Ademetionine 1,4-butanedisulfonate (S-adenosylmethionine) — hepatoprotective adjunct used alongside UDCA. - Odevixibat — an ileal bile acid transporter (IBAT) inhibitor, used via compassionate use in a 31-year-old patient at 38.5 μg/kg/day; over 2.5 years of follow-up the patient experienced no further episodes of pruritus or weight loss, with sustained low bilirubin/bile acid levels — the first reported targeted pharmacologic intervention for recurrent UNC45A-associated cholestasis and notable because IBAT inhibitors are otherwise approved/studied for other genetic cholestatic diseases (e.g., PFIC, Alagille syndrome) [PMC13019544]. This represents a genuine therapeutic_modality: SMALL_MOLECULE candidate treatment worth curating with an NCIT/CHEBI binding for odevixibat if available. - Fat-soluble vitamin supplementation (A, D, E, K) — standard supportive care for cholestasis-associated malabsorption.

Nutritional/supportive management for diarrhea: - Combination of parenteral nutrition and enteral nutrition, individualized; some patients improve with oral formula feeding and gain weight over time [PMC12516782]. - In the most severe case, complete enterectomy was performed [PMC11949031] — an NCIT surgical-procedure term (NCIT:C15329 Surgical Procedure) would apply, with preferred_term specifying enterectomy.

Hearing loss management: - Hearing aids — reported for moderate bilateral sensorineural hearing loss [PMC13019544]. Suggested NCIT device pattern per dismech convention: bind the clinical action term with a qualifiers device sub-binding rather than binding the device term directly to treatment_term (per the dismech Treatment Terms guidance on devices). - No cochlear implantation has been specifically reported for this syndrome in the sources retrieved (unlike some other syndromic hearing-loss entries in the KB).

Bone fragility management: - No bisphosphonate use for OOHE specifically was confirmed in this session's searches (a bisphosphonate result returned was for an unrelated condition, MPS IVA) — do not assume bisphosphonate use without a direct primary-source citation; this is a plausible but currently unconfirmed treatment avenue for curation purposes.

Liver transplantation: - Reported as a rescue intervention in at least one sibling with severe liver failure, though specific to the related/overlapping Aagenaes-like phenotype rather than confirmed in classic OOHE cohorts [context from sibling-discordance search; PMID:39887522 general topic].

Experimental/investigational: No registered clinical trials specific to UNC45A/OOHE were identified in this session's searches; odevixibat use above was compassionate/off-label rather than a formal trial.

Treatment outcomes: Response to UDCA + supportive hepatoprotective regimen was associated with "complete clinical and biochemical recovery" at 12 months in a milder case [PMC9868473]. Odevixibat's 2.5-year efficacy signal (no pruritus/weight-loss recurrence) in a single adult patient is the strongest treatment-response data currently available, though it derives from a single case and should be treated as preliminary.

13. Prevention

No primary, secondary, or tertiary prevention strategies exist beyond standard genetic counseling for known carrier couples (given full autosomal recessive inheritance) and, where a familial pathogenic variant is known, prenatal or preimplantation genetic testing could theoretically be offered — no specific literature on this practice for UNC45A/OOHE was identified in this session. No immunization, screening program, or public-health intervention is applicable to this monogenic disorder.

14. Other Species / Natural Disease

No naturally occurring UNC45A-deficient disease has been reported in non-human species (companion animals, livestock, or wildlife) in the sources retrieved — OMIA and veterinary literature searches were not performed in this session and should be checked separately before asserting a negative finding definitively.

Orthologous gene: UNC45A has zebrafish (unc45a) and Drosophila, C. elegans orthologs (the UNC-45/CRO1/She4p — "UCS" — protein family is deeply conserved from yeast to human); vertebrates have duplicated into two paralogs, UNC45A (general/non-muscle) and UNC45B (striated-muscle-specific).

Comparative biology: The UCS-domain myosin-chaperone function is evolutionarily ancient and highly conserved (from the yeast She4 protein through C. elegans UNC-45 to human UNC45A/B), supporting strong translational validity of model-organism mechanistic findings, though the disease-specific epithelial/hepatocyte trafficking phenotype appears to be a vertebrate/mammalian-relevant elaboration rather than a universally conserved disease mechanism.

15. Model Organisms

• Zebrafish (Danio rerio): unc45a loss-of-function/mutant larvae recapitulate key enterocyte phenotypes — microvillus shortening, MVI-like (microvillus-inclusion-like) intracellular compartments, and Rab11 mislocalization — providing solid in vivo confirmation of the apical-trafficking mechanism [PMC9106349]. Notably, unc45a mutants do not show a muscle phenotype (unlike unc45b mutants), so zebrafish unc45a models are specifically useful for the epithelial/enteric arm of the disease, not for bone or hearing phenotypes, which remain less modeled.
• Human iPSC-derived and CRISPR-engineered intestinal organoids (2D/3D): UNC45A-knockout Caco-2 cells and patient-derived organoids are the best-characterized disease models, recapitulating MVID-like architecture (dense aggregates lacking central lumen, F-actin-positive inclusions, mislocalized apical transporters NHE3/DRA, disorganized brush border) [PMC9106349]. A more recent study used primary human intestinal organoids from patients carrying biallelic UNC45A variants to implicate CFTR in the pathogenesis of the intestinal phenotype [PMC12780477] — this paper's full methodological/quantitative detail could not be extracted in this session due to access restrictions and should be independently verified before citing specific findings.
• Cell lines: Caco-2 (intestinal epithelial) cells with CRISPR UNC45A knockout, plus MG132 proteasome-inhibitor treatment used to demonstrate myosin Vb aggregate formation upon UNC45A loss.
• Model limitations: No mouse model of UNC45A-related disease was identified in this session's searches (searches focused on zebrafish and organoid systems); bone- and cochlea-specific animal or cellular models of OOHE were not identified, representing a translational gap between the well-modeled enteric/hepatic mechanism and the less-mechanistically-explained skeletal/auditory phenotypes.
• Research applications: Organoid and zebrafish models are primarily used to dissect the myosin-chaperone-trafficking mechanism in enterocytes and to test candidate therapeutics (e.g., relevance to the CFTR-implicating organoid study, which may point toward CFTR-modulating drugs as a novel therapeutic avenue, though this requires direct verification of that paper's content).

Notes on Evidence Gaps and Curation Caveats

Consistent with dismech's evidence-discipline requirements, the following should be independently verified via primary-source fetch and exact-quote extraction before being curated into a KB entry, since access restrictions in this session prevented full-text confirmation of several details: 1. The original 2018 Esteve et al. AJHG paper (PMID:29429573) abstract could not be directly fetched (ScienceDirect/PubMed blocked) — its exact founding cohort size, ages, and full phenotype table should be re-confirmed directly. 2. The OMIM entry and clinical synopsis (#619377) returned 403 errors and were reconstructed from MedGen/search-snippet cross-references only — the full OMIM clinical synopsis categories should be fetched directly (e.g., via an authenticated OMIM API key) before use as a curation source. 3. The CFTR-organoid paper (PMC12780477) content could not be extracted past a bot-check page; only its title/topic is confirmed. 4. No confirmed Orphanet (ORPHA) code was found for this entry in this session. 5. gnomAD constraint metrics (pLI/LOEUF) for UNC45A were not independently confirmed and should be pulled directly from the gnomAD browser.

Sources

• OMIM #619377 — Osteootohepatoenteric Syndrome
• OMIM Clinical Synopsis #619377
• OMIM *611219 — UNC45A
• MedGen C5543557 — Osteootohepatoenteric syndrome
• MalaCards — Osteootohepatoenteric Syndrome
• Esteve et al. 2018 — Loss-of-Function Mutations in UNC45A Cause a Syndrome Associating Cholestasis, Diarrhea, Impaired Hearing, and Bone Fragility, AJHG, PMID:29429573
• Esteve et al. bioRxiv preprint (2018)
• Case report: Osteo-oto-hepato-enteric syndrome caused by UNC45A deficiency (Chinese neonate), PMID:36699472, PMC9868473
• UNC45A deficiency causes microvillus inclusion disease–like phenotype by impairing myosin VB–dependent apical trafficking, PMC9106349
• A Functional Relationship Between UNC45A and MYO5B Connects Two Rare Diseases With Shared Enteropathy, PMC9218578
• Altered chaperone–nonmuscle myosin II interactions drive pathogenicity of the UNC45A c.710T>C variant in osteo-oto-hepato-enteric syndrome, JCI Insight, PMID:40125554, PMC11949031
• Odevixibat treatment for recurrent cholestasis in a patient with biallelic UNC45A variants causing osteo-oto-hepato-enteric syndrome, PMC13019544
• A Case Report and Literature Review on Osteo‐Oto‐Hepato‐Enteric Syndrome in Premature Infants Caused by UNC45A Deficiency, PMC12516782
• A New UNC45A 5'UTR Variant in Patients with Aagenaes Syndrome, PMID:39887522
• Primary human intestinal organoids with biallelic UNC45A variants suggest role of CFTR in pathogenesis of UNC45A‐related intestinal disorder, PMC12780477
• GeneCards — UNC45A
• Lack of Developmental Redundancy between Unc45 Proteins in Zebrafish Muscle Development, PMC3492250
• thegencc.org — UNC45A gene-disease submission

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Quotes not found in the cited source

Searched the abstract, any retrieved full text, and the title. A quote drawn from a part of the paper that was not retrieved will appear here too, so check before treating one as invented:

Every one of these was searched against an abstract alone, with no full text retrieved - marked abstract only below. Where full text can be fetched, re-running with it will settle them; where the source publishes only a summary to PubMed, as GeneReviews chapters do, it will not, and the quote has to be checked by hand against the chapter itself.

• PMC:PMC9868473 (abstract only): "relieve cholestasis by regulating bile acid transporters"
• closest text in source: "Laboratory tests revealed highly elevated levels of total serum bilirubin (TB), direct bilirubin (DB), and total bile acid (TBA)"

Term Validation

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

Obsolete terms

These terms are real but deprecated. Citing one is not a fabrication; it does mean the report is naming something the ontology has retired:

• GO:0051082 (obsolete unfolded protein binding) (1 mention)
• GO:0032313 (GO_0032313) (1 mention) - replaced by GO:0043087

28 of 30 terms resolved to a current term; the rest could not be looked up either way.