Doyne Honeycomb Retinal Dystrophy (DHRD) / Malattia Leventinese — Comprehensive Disease Report

Disease: Doyne Honeycomb Retinal Dystrophy (DHRD) Synonym: Malattia Leventinese (ML); Autosomal dominant radial drusen; Autosomal dominant drusen MONDO: MONDO:0007471 · OMIM: #126600 · Gene: EFEMP1 (fibulin-3) at 2p16.1 · Inheritance: Autosomal dominant · Category: Mendelian

Evidence source note: This report synthesizes aggregated disease-level resources (OMIM, Orphanet, ClinVar, UniProt) and primary literature (PubMed). It is not derived from individual patient EHR data. Evidence types are flagged as human clinical, model organism (mouse), in vitro (iPSC-RPE/cell), or review. DHRD is rare, so much of the clinical literature consists of case series and single families; mechanistic depth comes from mouse and iPSC models.

Summary

Doyne Honeycomb Retinal Dystrophy (DHRD) and Malattia Leventinese (ML) are the same autosomal dominant macular dystrophy, caused by a single recurrent missense mutation in EFEMP1: c.1033C>T, p.Arg345Trp (R345W), which alters the secreted extracellular-matrix glycoprotein fibulin-3. This degree of genetic homogeneity is remarkable: essentially every molecularly confirmed case worldwide carries this one variant, which was mapped to chromosome 2p16-21 and found absent in 477 controls and 494 age-related macular degeneration (AMD) patients, establishing both specificity and the monogenic nature of the disease (PMID: 10369267).

Mechanistically, mutant fibulin-3 misfolds and is retained intracellularly within retinal pigment epithelium (RPE) cells rather than being efficiently secreted (PMID: 12242346). This triggers endoplasmic-reticulum (ER) stress, aberrant extracellular-matrix accumulation, and a downstream cascade of alternative-pathway complement activation, NLRP3-inflammasome inflammation, and impaired RPE cholesterol efflux and lysosomal function. The clinical consequence is the early-adult-onset accumulation of radial / honeycomb sub-RPE drusen between the RPE and Bruch's membrane, producing progressive, bilateral central vision loss, sometimes complicated by secondary choroidal neovascularization (CNV).

There is no approved disease-modifying therapy; management is supportive (low-vision aids, monitoring, genetic counseling), with intravitreal anti-VEGF reserved for neovascular complications (variable, sometimes absent response). However, the well-defined causal chain has yielded multiple preclinically validated therapeutic strategies — GSK3 inhibition, complement factor B inhibition, NLRP3/caspase-1 inhibition, and lysosome modulation (trehalose) — tested in the Efemp1 R345W knock-in mouse and patient-derived iPSC-RPE. Because DHRD reproduces the drusen biology of AMD from a single clean genetic lesion, it is widely regarded as a monogenic surrogate model for AMD.

Key Findings

F001 — A single recurrent EFEMP1 R345W mutation causes DHRD/ML

A single heterozygous missense variant — EFEMP1 c.1033C>T, p.Arg345Trp (R345W) — has been identified as the cause in essentially all molecularly confirmed cases of DHRD/ML, inherited in an autosomal dominant pattern. EFEMP1 encodes the secreted ECM glycoprotein fibulin-3 (F3). Recent case reports from previously unreported populations (the first Scandinavian case, PMID: 33689237; Indian cases, PMID: 41971199) continue to confirm R345W as the sole recurrent pathogenic variant.

"A single variant in EFEMP1: c.1033C>T (R345W) has been identified as the cause in all cases." — PMID: 33689237

"Malattia Leventinese is a rare autosomal dominant macular dystrophy caused by a single" — PMID: 41971199

F002 — Mutant fibulin-3 misfolds and is retained intracellularly, driving sub-RPE drusen

Marmorstein et al. (PMID: 12242346) showed that wild-type EFEMP1 is a secreted protein whereas mutant EFEMP1 (R345W) is misfolded, secreted inefficiently, and retained within cells. In ML eyes, EFEMP1 accumulates within RPE cells and between the RPE and drusen; notably, EFEMP1 is not a major component of the drusen itself. In AMD eyes, EFEMP1 accumulates beneath the RPE overlying drusen. Patient-derived iPSC-RPE models from ML patients show fibulin-3 and ApoE aggregation, increased ER stress, and enhanced apoptosis (PMID: 42484373).

"wild-type EFEMP1 is a secreted protein whereas mutant EFEMP1 is misfolded, secreted inefficiently, and retained within cells" — PMID: 12242346

"MAL iPSC-RPE exhibited fibulin-3 and apolipoprotein E (ApoE) aggregation, increased endoplasmic reticulum stress, and enhanced apoptosis" — PMID: 42484373

F003 — Alternative-pathway complement and NLRP3 inflammasome drive sub-RPE deposits

In Efemp1 R345W/R345W knock-in mice, aged eyes showed an ~2-fold elevation of complement breakdown products iC3b and Ba (P<0.05); deletion of complement factor B (Cfb) partially normalized dysregulated pathways, and an oral factor B inhibitor reduced sub-RPE deposits by 65% (P=0.029) (PMID: 35943778). Genetic removal of Nlrp3 and its downstream effector caspase-1 (Casp1) protected against R345W Efemp1-induced basal laminar deposit formation (PMID: 39464028; PMID: 41198612). RNA-seq of knock-in eyecups showed an increased unfolded-protein response, decreased neural-retina mitochondrial function by 3 months, and increased inflammatory pathways by 17 months.

"oral dosing of a small molecule FB inhibitor from 10 to 12 months of age reduced sub-RPE deposits by 65% (P = 0.029)" — PMID: 35943778

"Complement activation was increased in aged Efemp1ki/ki eyes with an approximately 2-fold elevation of complement breakdown products iC3b and Ba (P < 0.05)" — PMID: 35943778

"we directly tested the role of Nlrp3 and its downstream effector, caspase 1 (Casp1) in mediating early AMD-like pathology" — PMID: 39464028

F004 — DHRD/ML maps to 2p16-21; R345W absent in controls and AMD cohorts (specificity)

Stone et al. (1999, PMID: 10369267) mapped both ML and DHRD loci to chromosome 2p16-21 and identified a single non-conservative Arg345Trp mutation in EFEMP1 in all families studied. The change was absent in 477 control individuals and in 494 AMD patients, establishing disease specificity and distinguishing DHRD/ML genetically from common AMD.

"a single non-conservative mutation (Arg345Trp) in the gene EFEMP1 ... in all families studied. This change was not present in 477 control individuals or in 494 patients with age-related macular degeneration" — PMID: 10369267

F005 — Phenotype: early-onset radial/honeycomb sub-RPE drusen with variable expressivity, CNV, central vision loss

Clinical reports consistently describe early-onset (typically 2nd–4th decade) yellow-white drusen beneath the RPE, often radially distributed around the macula and nasal to the optic disc, which coalesce into a honeycomb pattern. Drusen show increased fundus autofluorescence. Complications include RPE changes and secondary CNV. Marked intra- and inter-familial phenotypic variability in visual loss and imaging findings occurs despite the identical genotype (PMID: 25111685; PMID: 33689237; PMID: 41971199).

"Intrafamilial patients with Malattia leventinese/Doyne honeycomb retinal dystrophy seem to be phenotypically variable in visual loss, ophthalmoscopic findings, autofluorescence imaging, and optical coherence tomography changes" — PMID: 25111685

"All cases exhibited early-onset central vision loss and small, radially distributed drusen, consistent with ML/DHRD" — PMID: 41971199

F006 — No approved disease-modifying therapy; supportive care with emerging preclinical targets

No approved therapy halts DHRD/ML progression; care is supportive (low-vision aids, monitoring, genetic counseling). Secondary CNV is treated with intravitreal anti-VEGF, though responses are variable and sometimes absent (PMID: 33689237). Nanosecond 2RT laser has been piloted and may stabilize some functional parameters without structural change (PMID: 38023612). Preclinical disease-modifying strategies target the causal pathway: GSK3 inhibition (CHIR99021) reduced R345W-associated basal laminar deposits (PMID: 39114980); an oral complement factor B inhibitor reduced sub-RPE deposits by 65% (PMID: 35943778); NLRP3/caspase-1 ablation prevented deposits (PMID: 39464028); and the lysosome modulator trehalose reduced drusen-like deposits in patient iPSC-RPE (PMID: 42484373).

"treatment of 8-month-old R345W+/+ knockin mice with CHIR (25 mg/kg i.p., 1 mo) was well tolerated and significantly reduced R345W F3-associated AMD-like basal laminar deposit number and size, thereby preventing the main pathological feature in these mice" — PMID: 39114980

"2RT treatment in DHRD may improve or stabilize some retinal function parameters without significant structural changes" — PMID: 38023612

"Secondary choroidal neovascularizations were identified on both eyes, and anti-vascular endothelial growth factor was administered, without effect" — PMID: 33689237

F007 — Disease models: Efemp1 R345W knock-in mouse and patient iPSC-RPE recapitulate sub-RPE/basal laminar deposits

The principal in vivo model is the Efemp1 p.R345W knock-in mouse (Efemp1ki/ki; R345W+/+), which develops microscopic basal laminar deposits (BLamDs) — an early feature of DHRD/ML and AMD — alongside increased unfolded-protein response, decreased neural-retina mitochondrial function by 3 months, increased inflammatory/complement pathways by 17 months, and a sex difference (females > males). A HiBiT luminescent tag knocked into the endogenous F3 locus enables high-throughput fibulin-3 detection for drug screening (PMID: 39114980). In vitro, patient-derived iPSC-RPE recapitulate fibulin-3/ApoE aggregation, ER stress, apoptosis, and (with photoreceptor outer-segment feeding) drusen-like deposits containing ApoE, complement, and collagen IV (PMID: 42484373); isogenic DHRD iPSC-RPE revealed impaired cholesterol efflux via CES1 downregulation (PMID: 33909993).

"Aged Efemp1 R345W/R345W knock-in mice (Efemp1ki/ki) develop microscopic deposits on the basal side of retinal pigment epithelial cells (RPE), an early feature in DHRD/ML and AMD" — PMID: 35943778

"Long-term culture with photoreceptor outer segments led to drusen-like deposits containing ApoE, complement components, and collagen IV accumulation" — PMID: 42484373

F008 — Lipid/cholesterol dysregulation and lysosomal dysfunction are downstream RPE pathologies

DHRD iPSC-RPE exhibit abnormal intracellular lipid-droplet accumulation and pericellular lipid-rich deposits, driven by downregulation of carboxylesterase 1 (CES1) — impairing conversion of cholesteryl ester to free cholesterol and thus cholesterol efflux (PMID: 33909993). CES1 knockdown or EFEMP1 overexpression reproduced lipid accumulation. Independently, ML iPSC-RPE show lysosomal dysfunction with reduced TFEB transcripts and altered lysosomal gene programs, plus increased hexosylceramide and bis(monoacylglycero)phosphate; trehalose restored lysosomal function and reduced drusen-like deposits, MMP2 activation, and apoptosis (PMID: 42484373).

"we detected significant downregulation of carboxylesterase 1 (CES1), an enzyme that converts cholesteryl ester to free cholesterol, an indispensable process in cholesterol export" — PMID: 33909993

"A key pathological feature was lysosomal dysfunction associated with altered regulation of lysosomal gene programs, including reduced transcription factor EB transcript levels" — PMID: 42484373

F009 — Diagnosis rests on multimodal retinal imaging plus EFEMP1 genetic confirmation

Multimodal imaging defines the diagnostic signature: large round drusen in the perimacular area and around the optic disc, and small non-round, radially distributed drusen temporal to the macula. Fundus autofluorescence (FAF) shows intense autofluorescence of large drusen; on fluorescein (FA)/indocyanine green (ICGA) angiography, large round drusen become hyperfluorescent late while small radial drusen decrease fluorescence; OCT shows hyperreflective material between RPE and Bruch's membrane causing focal dome-shaped or diffuse RPE elevation (PMID: 22814526). Best-corrected visual acuity ranged 20/25 to 20/200. Definitive diagnosis is molecular: detection of heterozygous EFEMP1 c.1033C>T (p.Arg345Trp) by single-gene testing, inherited retinal disease gene panels, or exome sequencing (PMID: 41971199).

"OCT showed the large round drusen as focal or diffuse deposition of hyperreflective material between the RPE and Bruch membrane within the macula, determining focal dome-shaped or diffuse RPE elevation" — PMID: 22814526

"The smallest drusen were not round, radially distributed, mostly localized temporally to the macula" — PMID: 22814526

F010 — DHRD/ML is a monogenic surrogate model for AMD; fibulin-3 regulates Bruch's-membrane ECM and MMP/TIMP3 balance

A 2026 review frames DHRD as "a monogenic disorder that serves as a surrogate model for AMD due to similar phenotypic manifestations," focusing on interactions between EFEMP1, matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases-3 (TIMP3), and complement factors, and states the EFEMP1 R345W mutation "causes rapid disease progression through impaired protein secretion, abnormal matrix accumulation, and complement dysregulation" (PMID: 42569289). In both DHRD/ML and AMD, drusen form as extracellular deposits between RPE and Bruch's membrane, and both share alternative-complement activation (factor H/factor B axis; PMID: 17659362).

"Doyne Honeycomb Retinal Dystrophy-a monogenic disorder that serves as a surrogate model for AMD due to similar phenotypic manifestations" — PMID: 42569289

Mechanistic Model / Interpretation

Ordered causal chain (initiating lesion → clinical manifestation)

1. A germline heterozygous EFEMP1 c.1033C>T (p.R345W) mutation produces a single amino-acid substitution (Arg→Trp) in secreted fibulin-3. (demonstrated — PMID: 10369267)
2. The R345W substitution causes fibulin-3 to misfold, so the protein is secreted inefficiently and retained intracellularly within the RPE. (demonstrated — PMID: 12242346)
3. Intracellular retention leads to ER stress (unfolded-protein response) and co-aggregation with ApoE, which results in enhanced RPE apoptosis. (demonstrated in iPSC-RPE and knock-in eyecups — PMID: 42484373)
4. Branch A — ECM dysregulation: abnormal fibulin-3 handling disturbs the MMP/TIMP3 balance and extracellular-matrix homeostasis of Bruch's membrane, promoting abnormal matrix accumulation. (mechanistic review — PMID: 42569289)
5. Branch B — Complement: sub-RPE changes activate the alternative complement pathway (↑iC3b, ↑Ba; factor B–dependent), which drives sub-RPE deposit accumulation. (demonstrated — PMID: 35943778)
6. Branch C — Inflammasome: NLRP3/caspase-1 activation contributes to basal laminar deposit formation. (demonstrated by genetic ablation — PMID: 39464028)
7. Branch D — Lipid/lysosome: CES1 downregulation impairs cholesterol efflux → lipid-droplet accumulation; reduced TFEB causes lysosomal dysfunction → impaired clearance. (demonstrated in iPSC-RPE — PMID: 33909993; PMID: 42484373)
8. Branches A–D converge to produce extracellular drusen between RPE and Bruch's membrane, in a characteristic radial/honeycomb macular and peripapillary pattern. (demonstrated — PMID: 22814526)
9. Progressive drusen, RPE atrophy, and (in a subset) secondary choroidal neovascularization result in bilateral early-adult-onset central vision loss, metamorphopsia, and scotomas. (demonstrated — PMID: 25111685; PMID: 33689237)

EFEMP1 R345W → fibulin-3 misfolding → intracellular retention / ER stress / ApoE co-aggregation → RPE apoptosis
                              │
    ┌─────────────────┬──────────────┼─────────────────┬───────────────────┐
    ▼                 ▼               ▼                 ▼                   ▼
       ECM / MMP-TIMP3   Alternative     NLRP3 / Casp1    CES1↓ cholesterol    TFEB↓ lysosomal
       dysregulation     complement      inflammasome     efflux impaired      dysfunction
    └─────────────────┴──────────────┴─────────────────┴───────────────────┘
                              ▼
      Sub-RPE / basal-laminar DRUSEN (radial → honeycomb)
                              ▼
RPE atrophy ± secondary CNV  →  bilateral central vision loss

Upstream vs downstream: The mutation and protein misfolding (steps 1–3) are strictly upstream and shared by every patient. Complement, inflammasome, ECM, and lipid/lysosome arms (steps 4–7) are downstream, partially parallel, and therapeutically tractable. Drusen and vision loss (steps 8–9) are the terminal, clinically observed outputs.

Cell types / processes: RPE (CL:0002586, retinal pigment epithelial cell) is the primary affected cell; photoreceptors are secondarily affected. Key GO biological processes: response to endoplasmic reticulum stress (GO:0034976), complement activation, alternative pathway (GO:0006957), NLRP3 inflammasome complex assembly (GO:0044546), cholesterol efflux (GO:0033344), autophagy/lysosome organization (GO:0007040), extracellular matrix organization (GO:0030198). Anatomy: macula lutea (UBERON:0002423), RPE (UBERON:0001782), Bruch's membrane (UBERON:0004864).

Section-by-Section Report

1. Disease Information

DHRD is a rare, autosomal dominant, bilateral macular dystrophy characterized by early-onset sub-RPE drusen forming a honeycomb pattern. It is identical in etiology to Malattia Leventinese, originally described in families from the Leventine valley of Switzerland. Identifiers: MONDO:0007471; OMIM #126600; gene EFEMP1 (OMIM *601548); ICD-10 H35.5 (hereditary retinal dystrophy); MeSH "Retinal Dystrophies"/"Macular Degeneration" (no DHRD-specific MeSH descriptor). Synonyms: Malattia Leventinese; Doyne honeycomb degeneration/choroiditis; autosomal dominant radial drusen; autosomal dominant drusen; dominant drusen. Information is derived from aggregated disease-level resources (OMIM, Orphanet) and from individual-patient case series/cohorts in the ophthalmic literature.

2. Etiology

Causal factor: purely genetic — a single heterozygous EFEMP1 R345W mutation (F001, F004). Genetic risk: R345W is both necessary and (with autosomal dominant inheritance) sufficient; no susceptibility loci or validated modifier genes are established, though phenotypic variability implies unidentified genetic/environmental modifiers. Environmental/lifestyle risk factors, protective factors, infectious agents, and gene–environment interactions are not established for this monogenic disease. Because DHRD overlaps mechanistically with AMD, it is plausible (but unproven for DHRD) that AMD-associated environmental factors (smoking, oxidative stress) modulate expressivity.

3. Phenotypes

Severity and progression are variable even within families sharing R345W (PMID: 25111685). Quality-of-life impact: progressive central vision loss impairs reading, driving, and facial recognition; formal EQ-5D/SF-36 data specific to DHRD are not available.

4. Genetic / Molecular Information

Causal gene: EFEMP1 (HGNC:3218; fibulin-3; 2p16.1; OMIM *601548). Pathogenic variant: c.1033C>T, p.Arg345Trp (R345W) — a missense variant, classified pathogenic (ClinVar), germline, functionally acting via a dominant gain-of-toxic-function misfolding mechanism rather than simple haploinsufficiency (F002). Allele frequency: effectively absent in population databases and in 477 controls / 494 AMD cases (PMID: 10369267). Modifier genes: none validated; variable expressivity suggests their existence. Epigenetic information: none specific to DHRD. Chromosomal abnormalities: none — this is a point mutation.

5. Environmental Information

No environmental, lifestyle, or infectious contributors are established for DHRD; it is a Mendelian point-mutation disorder. Any environmental influence is limited to possible (unproven) modulation of expressivity.

6. Mechanism / Pathophysiology

See the Mechanistic Model section above for the ordered causal chain and branch diagram. In brief: R345W → fibulin-3 misfolding/intracellular retention → ER stress + ApoE aggregation + RPE apoptosis → convergent downstream arms (alternative complement, NLRP3 inflammasome, ECM/MMP-TIMP3 dysregulation, CES1-dependent cholesterol-efflux failure, TFEB-dependent lysosomal dysfunction) → sub-RPE drusen → RPE atrophy ± CNV → central vision loss. Molecular profiling (knock-in RNA-seq) shows early unfolded-protein response and mitochondrial decline, with later inflammatory/complement upregulation (PMID: 35943778). Lipidomics of ML iPSC-RPE shows increased hexosylceramide and BMP (PMID: 42484373).

7. Anatomical Structures Affected

Organ: eye — specifically the macula (UBERON:0002423) and peripapillary retina. Tissue/cell: retinal pigment epithelium (UBERON:0001782; CL:0002586) is primary; photoreceptors secondary; drusen deposit at the RPE–Bruch's membrane interface (UBERON:0004864). Subcellular: endoplasmic reticulum (GO:0005783; misfolding/retention), lysosome (GO:0005764; dysfunction), mitochondria (GO:0005739; functional decline), extracellular matrix/basal lamina. Localization: bilateral, macular + peripapillary (nasal to optic disc).

8. Temporal Development

Onset: typically 2nd–4th decade (early adult); insidious/chronic. Drusen may be detectable before symptoms. Progression: early (sparse radial drusen) → intermediate (coalescence into honeycomb) → advanced (RPE atrophy, central vision loss) → complication stage (CNV in a subset). Rate is slow but progressive and variable; disease is chronic and lifelong. Patterns: no spontaneous remission; CNV episodes are episodic. A therapeutic "critical period" for deposit prevention (before irreversible RPE/photoreceptor loss) is suggested by preclinical studies that intervene at the deposit-formation stage.

9. Inheritance and Population

Inheritance: autosomal dominant, high/near-complete but age-dependent penetrance, with variable expressivity (F005). Epidemiology: rare; precise prevalence/incidence not well quantified. Founder clustering historically noted in the Swiss Leventine valley (ML), with cases now reported worldwide (Europe, China, India, Scandinavia). No genetic anticipation (not a repeat-expansion disorder). Germline mosaicism, consanguinity, and carrier-frequency considerations are not prominent given dominant inheritance and the single recurrent allele. Sex ratio: roughly equal in humans, though the mouse model shows a female-biased deposit burden. Age distribution skews toward adult diagnosis.

10. Diagnostics

Clinical/imaging (F009): fundoscopy (radial/honeycomb drusen), OCT (hyperreflective sub-RPE material, dome-shaped RPE elevation), FAF (intense drusen autofluorescence), FA/ICGA (late hyperfluorescence of large drusen). Functional: microperimetry, Preferential Hyperacuity Perimeter, visual acuity (20/25–20/200). Genetic testing is definitive: single-gene EFEMP1 testing, inherited retinal dystrophy gene panels (e.g., Illumina MiSeq), or WES/WGS detecting heterozygous c.1033C>T. Given the single recurrent variant, targeted single-variant testing is highly efficient. Differential diagnosis: AMD (later onset, no R345W), familial/cuticular drusen, Sorsby fundus dystrophy (TIMP3), autosomal dominant drusen of other etiologies, pattern dystrophies. Screening: cascade/predictive genetic testing of at-risk relatives.

11. Outcome / Prognosis

DHRD is not life-threatening; survival and mortality are unaffected. Morbidity is visual: progressive bilateral central vision loss causing significant disability for reading/driving, with preserved peripheral vision. CNV, when it occurs, accelerates central loss. Prognostic factors: extent/confluence of drusen, RPE atrophy, development of CNV; genotype is uniform (R345W) so does not stratify prognosis. No validated molecular prognostic biomarkers specific to DHRD. Recovery potential is limited once atrophy develops.

12. Treatment

No approved disease-modifying therapy (F006). Supportive: low-vision rehabilitation, Amsler-grid self-monitoring, genetic counseling. Neovascular complications: intravitreal anti-VEGF (bevacizumab/ranibizumab/aflibercept; NCIT: Anti-VEGF Therapy) — response variable, sometimes absent (PMID: 33689237). Interventional (experimental): nanosecond 2RT laser — functional stabilization without structural change (PMID: 38023612). Preclinically validated disease-modifying candidates:

No DHRD-specific pharmacogenomics, gene therapy, cell therapy, or RNA-based therapy has reached the clinic, though the single recurrent allele makes DHRD attractive for allele-specific gene editing/silencing. Suggested NCIT intervention terms: Anti-VEGF Therapy, Laser Therapy, Gene Therapy, Supportive Care.

13. Prevention

No primary prevention exists for a germline Mendelian disease. Secondary prevention: regular ophthalmic surveillance to detect CNV early for anti-VEGF. Genetic prevention/counseling: cascade testing of relatives, reproductive options (preimplantation genetic testing, prenatal diagnosis) given the single known variant and 50% transmission risk. Tertiary prevention: low-vision support and prompt CNV management to limit disability. No immunization or public-health/environmental interventions apply.

14. Other Species / Natural Disease

No naturally occurring R345W-driven DHRD/ML is documented in companion or wild animals (no OMIA entry for this specific disease). Orthologous gene: mouse Efemp1 (and orthologs across vertebrates) is highly conserved; the R345W knock-in demonstrates functional conservation of the mechanism. No zoonotic or cross-species transmission applies (non-infectious genetic disease).

15. Model Organisms

In vivo: the Efemp1 p.R345W knock-in mouse (Efemp1ki/ki; R345W+/+) is the principal model, recapitulating sub-RPE basal laminar deposits, unfolded-protein response, mitochondrial decline, and age-dependent complement/inflammation, with a female-biased deposit burden (F007). A HiBiT-tagged F3 locus mouse enables high-throughput fibulin-3 quantification for drug screening (PMID: 39114980). In vitro: patient-derived iPSC-RPE (and isogenic CRISPR-corrected controls) reproduce fibulin-3/ApoE aggregation, ER stress, apoptosis, CES1-dependent lipid accumulation, TFEB-linked lysosomal dysfunction, and (with outer-segment feeding) drusen-like deposits (PMID: 42484373; PMID: 33909993). Phenotype recapitulation: strong for early sub-RPE/basal-laminar deposit biology and molecular cascades. Limitations: mice do not form a true macula and develop only microscopic (not clinical honeycomb) drusen; long aging is required; iPSC-RPE lack full retinal architecture and chronic in-vivo context.

Evidence Base

Limitations and Knowledge Gaps

• Epidemiology is poorly quantified. No reliable prevalence/incidence figures for DHRD/ML exist; most data come from case series and families, not registries.
• Mechanism of dominance is incompletely resolved. Whether R345W fibulin-3 acts purely as a gain-of-toxic-misfolding, dominant-negative, or combined mechanism is not fully settled.
• Modifiers of expressivity are unknown. Identical genotype yields highly variable phenotype even within families; the responsible genetic/environmental modifiers are unidentified.
• Model limitations. Mice lack a macula and form only microscopic deposits; iPSC-RPE lack intact retinal architecture — neither fully reproduces clinical honeycomb drusen or long-term CNV.
• No human therapeutic trials of the preclinical targets. GSK3, factor B, NLRP3, and lysosome strategies are validated only in mouse/iPSC-RPE; human efficacy and safety are unknown.
• Quality-of-life data are absent. No DHRD-specific EQ-5D/SF-36/PROMIS outcomes have been reported.
• Causal-chain branch ordering is partly inferred. The relative timing/dominance of complement vs inflammasome vs lipid/lysosome arms is not fully established in humans.

Proposed Follow-up Experiments / Actions

1. Natural-history registry — establish a multicenter DHRD/ML cohort with standardized multimodal imaging to quantify prevalence, progression rate, CNV incidence, and vision-loss trajectories.
2. Modifier discovery — WGS + expression/epigenetic profiling across discordant R345W carriers (including unaffected relatives) to find genetic/environmental modifiers of expressivity.
3. Allele-specific gene therapy — because the disease is driven by one dominant allele, develop allele-specific CRISPR editing or ASO/siRNA silencing of mutant EFEMP1, validated in R345W knock-in mice and iPSC-RPE.
4. Translate preclinical pharmacology — advance the best-validated candidates (complement factor B inhibitor; GSK3 inhibitor; NLRP3 inhibitor; trehalose/lysosome modulators) toward IND-enabling studies and early-phase trials, using drusen volume (OCT/FAF) as a surrogate endpoint.
5. Biomarker development — define imaging (drusen volume kinetics) and molecular (complement breakdown products, lipid species) biomarkers for trial stratification and prognosis.
6. Improved models — generate macula-bearing or longer-lived models (e.g., non-human primate knock-in, retinal organoids with photoreceptor–RPE co-culture) to capture honeycomb-drusen and CNV phenotypes.
7. Cross-validate with AMD — directly test whether DHRD-derived therapeutic targets (factor B, NLRP3, GSK3) translate to polygenic AMD, leveraging DHRD as a clean monogenic surrogate.

Report compiled from 10 confirmed findings across 5 investigation iterations and 18 reviewed papers. All mechanistic and clinical claims are cited to primary literature or reviews with exact PMID references; citation snippets were verified against stored abstracts during the investigation.

Artifacts

• OpenScientist final report
• OpenScientist final report

Reference Validation

Checked with linkml-reference-validator 0.3.0.

All extracted references resolved successfully.

Term Validation

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

Terms the report names something else

These identifiers resolve, so nothing about them looks wrong, and the ontology calls them something unrelated to what the report calls them. That usually means the identifier is not the one the sentence needs:

• UBERON:0002423 (2 mentions) - the report calls it "macula"; UBERON calls it hepatobiliary system
• UBERON:0004864 (2 mentions) - the report calls it "RPE–Bruch's membrane interface"; UBERON calls it vasculature of retina
• HP:0011506 (1 mention) - the report calls it "Macular drusen"; HP calls it Choroidal neovascularization
• HP:0012508 (1 mention) - the report calls it "Symptom"; HP calls it Metamorphopsia
• HP:0007814 (1 mention) - the report calls it "Clinical sign"; HP calls it Retinal pigment epithelial mottling
• HP:0030500 (1 mention) - the report calls it "Clinical sign"; HP calls it Yellow/white macular lesion

Terms whose name is worth a second look

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

• GO:0007040 (1 mention) - the report calls it "autophagy/lysosome organization"; GO calls it lysosome organization