Familial Exudative Vitreoretinopathy
Familial exudative vitreoretinopathy (FEVR) is a rare inherited vitreoretinopathy characterized by incomplete or arrested vascularization of the peripheral retina. The shared core mechanism is impaired Norrin/beta-catenin (Wnt) signaling in retinal vascular endothelial cells, which is required for developmental angiogenesis of the peripheral retina and establishment of the blood-retina barrier. The resulting peripheral avascular zone causes retinal ischemia, which drives compensatory neovascularization, exudation, hemorrhage, vitreoretinal traction, and tractional or exudative retinal detachment. FEVR is genetically heterogeneous: most cases are autosomal dominant (FZD4, LRP5, TSPAN12), but autosomal recessive (LRP5, TSPAN12) and X-linked recessive (NDP) forms occur, and KIF11 variants produce a FEVR-like retinal phenotype within a broader microcephaly-lymphedema-chorioretinal dysplasia spectrum. Expressivity is highly variable, ranging from an asymptomatic avascular periphery detectable only by fluorescein angiography to bilateral blindness, even within the same family. NDP variants additionally cause Norrie disease (a severe allelic disorder), and recessive LRP5 disease can be accompanied by reduced bone mineral density.
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Inheritance
3
Autosomal dominant inheritance
HP:0000006
The most common mode of inheritance for FEVR, seen with FZD4, LRP5, TSPAN12, and KIF11 variants. Penetrance is reduced and expressivity is highly variable.
Show evidence (2 references)
"these can be inherited in an autosomal dominant (most common), autosomal recessive, and X-linked recessive fashion"
A clinical review confirms autosomal dominant inheritance is the most common FEVR mode.
"Offspring of an affected individual are at a 50% risk of inheriting the pathogenic variant, but many individuals with adFEVR can be asymptomatic because of reduced penetrance."
GeneReviews genetic counseling section confirms 50% recurrence risk and reduced penetrance in autosomal dominant FEVR.
X-linked recessive inheritance
HP:0001419
The NDP-related form is inherited in an X-linked recessive manner, affecting predominantly males; NDP is allelic with Norrie disease.
Show evidence (1 reference)
"these can be inherited in an autosomal dominant (most common), autosomal recessive, and X-linked recessive fashion"
A clinical review confirms the X-linked recessive FEVR mode of inheritance (NDP).
Autosomal recessive inheritance
HP:0000007
Recessive FEVR occurs with biallelic LRP5 (and TSPAN12) variants; recessive LRP5 disease is associated with reduced bone mineral density.
Show evidence (1 reference)
"homozygous mutations in LRP5 have recently been reported as underlying the recessive form of this disease"
Documents the autosomal recessive form of FEVR caused by biallelic LRP5 mutations.
Subtypes
7
FZD4-Related FEVR (EVR1, autosomal dominant)
MONDO:1040041
Autosomal dominant FEVR caused by heterozygous pathogenic variants in FZD4, encoding the frizzled-4 receptor, the obligate Norrin receptor. One of the most common molecularly defined forms of adFEVR. Variants impair Norrin/FZD4 signaling and peripheral retinal vascularization.
LRP5-Related FEVR (EVR4, AD or AR; with reduced bone density)
MONDO:0700228
FEVR caused by pathogenic variants in LRP5, encoding the Wnt co-receptor low-density lipoprotein receptor-related protein 5. Inherited dominantly or recessively; recessive disease is frequently accompanied by reduced bone mineral density, reflecting LRP5's role in skeletal Wnt signaling.
TSPAN12-Related FEVR (EVR5)
MONDO:0700231
FEVR caused by variants in TSPAN12, encoding tetraspanin-12, an essential co-receptor of the Norrin/FZD4 complex that amplifies FZD4 ligand selectivity and signaling. Mostly autosomal dominant.
NDP-Related FEVR (EVR2, X-linked recessive)
MONDO:0010588
X-linked recessive FEVR caused by hemizygous variants in NDP, encoding the secreted ligand Norrin. NDP is allelic with Norrie disease; FEVR represents the milder end of the NDP phenotypic spectrum, affecting predominantly males.
KIF11-Related FEVR (MLCRD/CDMMR spectrum)
MONDO:0007918
Autosomal dominant FEVR-like retinal phenotype caused by heterozygous variants in KIF11, encoding a kinesin motor. Often part of a broader syndrome (microcephaly, lymphedema, chorioretinal dysplasia), and FEVR cases should be inspected for microcephaly as a marker of KIF11-related disease.
ZNF408-Related FEVR (EVR6, autosomal dominant)
MONDO:0014652
Autosomal dominant FEVR caused by heterozygous variants in ZNF408, encoding zinc finger protein 408. The gene was identified by linkage analysis and exome sequencing in a large Dutch FEVR family, and screening 132 further individuals with FEVR found a second missense variant in a Japanese family. The p.His455Tyr allele is localized almost exclusively to the cytoplasm and retains wild-type ZNF408 there, consistent with a dominant-negative mechanism, and morpholino knockdown of zebrafish znf408 produces retinal vascular defects that wild-type but not mutant human ZNF408 rescues. ZNF408 is not a component of the Norrin/FZD4 receptor complex, and a review lists it with CTNNB1 and KIF11 as later-discovered FEVR genes some of which operate outside the Norrin/Wnt signalling pathway.
Show evidence (2 references)
"Sequence analysis of ZNF408 in 132 additional individuals with FEVR revealed another potentially pathogenic missense variant, p.Ser126Asn, in a Japanese family."
A second, independent human FEVR family carrying a ZNF408 missense variant, beyond the two related Dutch families.
"An expanded FEVR panel was used, including six recognized FEVR genes (FZD4, NDP, LRP5, TSPAN12, ZNF408, and CTNNB1)"
A 2025 human FEVR cohort study counts ZNF408 among the six recognized FEVR genes, placing this subtype inside the core FEVR gene set.
CTNNB1-Related FEVR (EVR7, autosomal dominant)
MONDO:0033123
FEVR caused by heterozygous, usually de novo, variants in CTNNB1, encoding beta-catenin, the intracellular effector of canonical Wnt signaling. Exudative vitreoretinopathy occurs both alongside the CTNNB1 neurodevelopmental phenotype (severe intellectual disability, microcephaly, spasticity) and in isolation. ClinGen lumped exudative vitreoretinopathy 7 with severe intellectual disability-progressive spastic diplegia syndrome into one CTNNB1-related disease entity on the grounds of a shared haploinsufficiency mechanism and a similar variant spectrum, so the ClinGen assertion for this subtype is recorded against that combined term (MONDO:0100571) rather than against MONDO:0033123.
Show evidence (2 references)
"The spectrum of disease has also expanded to include diagnoses of exudative vitreoretinopathy and other eye abnormalities, either in the presence of the aforementioned neurodevelopmental features or in isolation"
ClinGen records exudative vitreoretinopathy as part of the CTNNB1 phenotypic spectrum, occurring with or without the neurodevelopmental features.
"CTNNB1 | HGNC:2514 | CTNNB1-related neurodevelopmental disorder and/or vitreoretinopathy | MONDO:0100571 | AD | Definitive"
ClinGen classifies the CTNNB1 gene-disease relationship as definitive with autosomal dominant inheritance, under the lumped term that subsumes exudative vitreoretinopathy 7.
Discussions and Knowledge Gaps
1Is the high prevalence of myopia in FZD4-variant-positive individuals a direct consequence of altered peripheral retinal vascular development, or a secondary effect of the structural and tractional changes of FEVR or of its treatment?
Attached to
Myopia affected 62% of eyes in the Finnish FZD4 natural-history cohort, but the cohort study leaves the mechanism open. No pathophysiology node in this entry mechanistically accounts for refractive error, so no causal edge is drawn. An axial-length and refraction study stratified by FEVR stage and genotype would distinguish a primary developmental effect from a secondary structural one.
Pathophysiology
8Impaired Norrin/beta-catenin signaling in retinal endothelium
The core defect of FEVR. Norrin (NDP) is a secreted ligand that binds the frizzled-4 (FZD4) receptor together with the co-receptor LRP5 and the accessory tetraspanin TSPAN12, activating canonical (beta-catenin-dependent) Wnt signaling specifically in retinal vascular endothelial cells. Loss-of-function in any of these components reduces beta-catenin signaling output. Disruption of Tspan12, Ndp, Fzd4, or Lrp5 in mice produces similar ocular phenotypes, indicating a shared signaling pathway. Heterozygous CTNNB1 variants act one step further down, on beta-catenin itself, and ClinGen records defects in retinal vascularization across the CTNNB1 phenotypic spectrum.
Downstream
Reduced Norrin/beta-catenin signaling impairs developmental angiogenesis of the peripheral retina, leaving an avascular peripheral zone.
Reduced Norrin/beta-catenin signaling also impairs formation and maintenance of the inner blood-retinal barrier (iBRB) in retinal endothelial cells, contributing to vascular permeability and retinal exudation.
Norrin/beta-catenin signaling is also required for normal developmental regression of the fetal hyaloid vasculature; deficient signaling leaves persistent hyaloid remnants, documented in recessive LRP5-related FEVR and overlapping with persistent fetal vascular syndrome.
Show evidence (3 references)
"Gene disruptions of Tspan12 (Junge et al., 2009), Ndp (Luhmann et al., 2005), Fzd4 (Xu et al., 2004; Ye et al., 2009), and Lrp5 (Xia et al., 2008) all result in similar ocular phenotypes in mice, characterized by defects in intraretinal capillary development and dysregulation of the blood-retina barrier."
Shows the convergent ocular phenotype across all four core Norrin-pathway genes, defining the shared mechanism.
"TSPAN12 is
an essential component of the NDP receptor complex and interacts with FZD4 and
NDP via its extracellular loops, consistent with an action as co-receptor that
enhances FZD4 ligand selectivity for NDP."
Establishes the molecular assembly of the Norrin/FZD4/TSPAN12 receptor complex underlying the pathway.
"Both disease entities can exhibit similar defects in retinal vascularization that lead to serous retinal detachment and other ocular features."
Supports placing CTNNB1 at this node, since loss of the pathway's beta-catenin effector produces retinal vascularization defects of the same kind as the receptor-complex genes.
Incomplete peripheral retinal vascularization
The hallmark structural lesion of FEVR: failure of the retinal vasculature to grow into the peripheral retina, producing a bilateral peripheral avascular zone. This avascularity is probably present from birth and is detectable by fundus fluorescein angiography even in asymptomatic individuals.
Downstream
The non-perfused peripheral retina becomes ischemic, generating a pro-angiogenic drive (e.g., VEGF) that triggers abnormal neovascularization.
The same developmental vascularization failure is recorded clinically as peripheral retinal avascularization.
The anomalous peripheral retinal vascular development, together with its exudative sequelae, constitutes the defining exudative vitreoretinopathy.
Summary edge: the developmental vascularization failure and its sequelae are what is recorded clinically under the obligate umbrella category of vitreoretinopathy.
Show evidence (1 reference)
"The principal feature
of the disease is an avascular peripheral retina."
Identifies the peripheral avascular retina as the principal structural feature of FEVR.
Peripheral retinal ischemia and neovascular response
Ischemia of the peripheral avascular retina drives pathological neovascularization, with exudation and hemorrhage. These vascular sequelae are the proximate cause of the symptomatic complications of FEVR.
Downstream
Fibrovascular proliferation and contraction exert tractional forces on the retina, and exudation accumulates, producing tractional, rhegmatogenous, or exudative retinal detachment and ultimately vision loss.
Ischemia-driven new vessels arise at the junction of the vascularized and avascular peripheral retina.
Summary edge: the same ischemia-driven neovascular response recorded at the disease level (Orphanet frequency term), without restriction to the peripheral vascular-avascular junction.
Leakage from immature, ischemia-driven new vessels deposits lipid- and protein-rich exudates in the retina; the node-level evidence lists exudation among the sequelae of the avascular periphery.
Exudation from the peripheral neovascular response that extends into or accumulates at the macula is recorded as macular exudate, degrading central vision.
Exudate accumulating beneath the neurosensory retina produces subretinal fluid and drives exudative retinal detachment.
Fragile neovascular tufts at the vascular-avascular junction bleed into the vitreous; hemorrhage is listed with the node-level evidence among the sequelae of the avascular periphery.
Show evidence (1 reference)
"This in turn can cause further
pathological changes including neovascularization, exudation, hemorrhage, and
retinal detachment."
Documents neovascularization, exudation, and hemorrhage as ischemia-driven sequelae.
Vitreoretinal traction and retinal detachment
Terminal convergence of FEVR: fibrovascular traction and exudation cause macular dragging, falciform retinal folds, and partial or total retinal detachment, leading to severe visual impairment or blindness. Expressivity is highly variable.
Downstream
Fibrovascular traction is the proximate mechanism for tractional retinal detachment.
Retinal detachment, exudation, and macular involvement reduce visual acuity in symptomatic FEVR.
Tractional forces from fibrovascular proliferation, retinal breaks, and exudation produce tractional, rhegmatogenous, or exudative retinal detachment.
Contraction of fibrovascular tissue drags the retina into a sickle-shaped falciform fold; the node-level evidence catalogs falciform folds among the tractional sequelae.
Fibrovascular traction drags the optic disc and its emerging vessels (the dragged-disc appearance), the basis of the optic disc abnormalities of advanced FEVR.
Asymmetric loss of central visual input from macular dragging, exudation, or detachment disrupts binocular fusion, producing sensory strabismus; 20% of infants in a large single-gene-positive cohort presented with strabismus at first visit.
Summary edge: severe early-onset visual loss from retinal detachment and macular involvement prevents development of stable fixation, producing sensory nystagmus, reported among the features of the recessive LRP5-related phenotype.
Show evidence (1 reference)
"macular dragging, partial retinal detachment, falciform folds, or total retinal
detachment"
Catalogs the tractional retinal sequelae that define advanced FEVR.
Inner Blood-Retinal Barrier Dysfunction
Norrin/Wnt signaling in retinal endothelial cells governs not only developmental angiogenesis but also formation and maintenance of the inner blood-retinal barrier (iBRB). Loss-of-function in FZD4, LRP5, NDP, or TSPAN12 impairs iBRB integrity, producing aberrant vascular permeability that contributes to retinal exudation independently of ischemia-driven neovascularization. FEVR, Norrie disease, and persistent fetal vascular syndrome share this iBRB dysfunction as a unifying pathophysiological element.
Downstream
Summary edge: failure of the inner blood-retinal barrier permits plasma leakage and retinal exudation independently of ischemia-driven neovascularization, per the node-level evidence.
Show evidence (1 reference)
"unified by abnormal retinal endothelial cell function, and subsequent irregular retinal vascular development and/or aberrant inner blood-retinal-barrier (iBRB) function"
Establishes iBRB dysfunction as a distinct pathophysiological element shared across FEVR-related disorders, driven by abnormal Norrin/Wnt signaling in retinal endothelial cells.
Impaired LRP5-mediated Wnt signaling in bone
In recessive LRP5-related FEVR the same Wnt co-receptor deficiency that impairs retinal angiogenesis also reduces canonical Wnt signal transduction in osteoblasts, lowering bone mass accrual during growth. LRP5 loss causes the allelic osteoporosis-pseudoglioma syndrome, and FEVR patients with biallelic LRP5 mutations show reduced bone mineral density.
Downstream
Reduced osteoblast Wnt signaling lowers bone mass accrual, producing the reduced bone mineral density that accompanies recessive LRP5-related FEVR.
Show evidence (2 references)
"We demonstrate LRP5 expression by osteoblasts in situ and show that LRP5 can transduce Wnt signaling in vitro via the canonical pathway."
Establishes that osteoblasts express LRP5 and that LRP5 transduces canonical Wnt signaling.
"These data indicate that Wnt-mediated signaling via LRP5 affects bone accrual during growth and is important for the establishment of peak bone mass."
Study conclusion, resting on OPPG carrier data and mouse calvarial explant cultures, that LRP5-mediated Wnt signaling controls bone mass accrual during growth.
ZNF408 dysfunction impairing retinal vascular development
A FEVR mechanism that does not run through the Norrin/FZD4 receptor complex. Morpholino knockdown of zebrafish znf408 produces defects in the developing retinal vasculature that co-injected wild-type human ZNF408 RNA rescues and the p.His455Tyr mutant does not. In transfected cells the p.His455Tyr protein is localized almost exclusively to the cytoplasm and retains wild-type ZNF408 there, consistent with a dominant-negative mechanism. How ZNF408 acts on retinal vasculogenesis is not established, and a review lists it with CTNNB1 and KIF11 as later-discovered FEVR genes some of which operate outside the Norrin/Wnt signalling pathway, so this node is kept separate from the receptor-complex node rather than folded into it.
Downstream
ZNF408 dysfunction produces the same failure of peripheral retinal vascularization that defines FEVR.
Show evidence (2 references)
"morpholino-induced knockdown of znf408 in zebrafish revealed defects in developing retinal and trunk vasculature, that could be rescued by coinjection of RNA encoding human WT ZNF408 but not p.His455Tyr mutant ZNF408"
A rescue-controlled knockdown showing ZNF408 is required for retinal vascular development and that the human FEVR allele is non-functional.
"discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway"
Supports modeling ZNF408 as a mechanism separate from the Norrin/FZD4 receptor complex.
KIF11 mitotic spindle dysfunction
KIF11 encodes EG5, a homotetrameric kinesin required for bipolar mitotic spindle assembly. Heterozygous KIF11 mutations impair spindle formation in proliferating progenitors, compromising CNS growth (microcephaly) and the development of retinal and lymphatic structures. This mechanism operates outside the canonical Norrin/Wnt pathway and defines the KIF11-related FEVR spectrum (microcephaly-lymphedema-chorioretinal dysplasia).
Downstream
Defective spindle formation in proliferating neural progenitors limits CNS growth, producing the congenital microcephaly that marks KIF11-related disease.
KIF11 mutations produce a FEVR-like peripheral avascular retinopathy, but how spindle dysfunction impairs retinal vascular development, and whether it intersects the Norrin/Wnt pathway, is not established.
Show evidence (2 references)
"KIF11 encodes EG5, a homotetramer kinesin motor."
Identifies the KIF11 gene product as the EG5 spindle kinesin motor.
"EG5 has previously been shown to play a role in spindle assembly and function, and these findings highlight the critical role of proteins necessary for spindle formation in CNS development."
Links the spindle-assembly function of EG5 to CNS development in patients with KIF11 mutations; the mechanistic inference rests on prior functional work summarized by this human genetics study.
Pathograph
Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Phenotypes
20Blood 1
Vitreous hemorrhage
OCCASIONAL
HP:0007902
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Vitreous hemorrhage (HP:0007902). HP:0007902 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0007902 | Vitreous hemorrhage | Occasional (29-5%)"
Orphanet records vitreous hemorrhage as an occasional FEVR phenotype.
Cardiovascular 4
Peripheral retinal neovascularization
HP:0030667
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Peripheral retinal neovascularization (HP:0030667). HP:0030667 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"This in turn can cause further
pathological changes including neovascularization, exudation, hemorrhage, and
retinal detachment."
Documents neovascularization as a complication of the avascular periphery.
Peripheral retinal avascularization
VERY_FREQUENT
Avascular peripheral retina
HP:0007685
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Peripheral retinal avascularization, annotated with Avascular peripheral retina (HP:0007685). HP:0007685 is a phenotype from the Human Phenotype Ontology.
Show evidence (2 references)
"bilateral peripheral retinal avascularity, seen temporally, by indirect ophthalmoscope and scleral indentation, or by fundus fluorescein angiography"
GeneReviews defines bilateral peripheral retinal avascularity as the diagnostic hallmark of FEVR.
"HP:0007685 | Peripheral retinal avascularization | Very frequent (99-80%)"
Orphanet records peripheral retinal avascularization as a very frequent FEVR phenotype.
Macular exudate
OCCASIONAL
HP:0030496
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Macular exudate (HP:0030496). HP:0030496 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0030496 | Macular exudate | Occasional (29-5%)"
Orphanet records macular exudate as an occasional FEVR phenotype.
Retinal neovascularization
FREQUENT
HP:0030666
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Retinal neovascularization (HP:0030666). HP:0030666 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0030666 | Retinal neovascularization | Frequent (79-30%)"
Orphanet records retinal neovascularization as a frequent FEVR phenotype.
Eye 13
Exudative vitreoretinopathy
HP:0030490
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Exudative vitreoretinopathy (HP:0030490). HP:0030490 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"Familial exudative vitreoretinopathy (FEVR) is a heritable vitreoretinopathy
characterized by anomalous retinal vascular development."
Defines FEVR as an exudative vitreoretinopathy with anomalous retinal vascular development.
Retinal exudate
HP:0001147
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Retinal exudate (HP:0001147). HP:0001147 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"This in turn can cause further
pathological changes including neovascularization, exudation, hemorrhage, and
retinal detachment."
Lists exudation among the pathological changes of FEVR.
Falciform retinal fold
HP:0001493
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Falciform retinal fold (HP:0001493). HP:0001493 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"macular dragging, partial retinal detachment, falciform folds, or total retinal
detachment"
Falciform folds are documented among the tractional retinal manifestations.
Retinal detachment
HP:0000541
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Retinal detachment (HP:0000541), qualified as course progressive. HP:0000541 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"Retinal detachment with avascularity of the peripheral retina,
typically associated with familial exudative vitreoretinopathy (FEVR)"
Associates retinal detachment with peripheral avascularity in FEVR.
Vitreoretinopathy
OBLIGATE
HP:0007773
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Vitreoretinopathy (HP:0007773). HP:0007773 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0007773 | Vitreoretinopathy | Obligate (100%)"
Orphanet records vitreoretinopathy as an obligate FEVR phenotype.
Reduced visual acuity
FREQUENT
HP:0007663
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Reduced visual acuity (HP:0007663). HP:0007663 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0007663 | Reduced visual acuity | Frequent (79-30%)"
Orphanet records reduced visual acuity as a frequent FEVR phenotype.
Tractional retinal detachment
FREQUENT
HP:0007917
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Tractional retinal detachment (HP:0007917). HP:0007917 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0007917 | Tractional retinal detachment | Frequent (79-30%)"
Orphanet records tractional retinal detachment as a frequent FEVR phenotype.
Remnants of the hyaloid vascular system
HP:0007968
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Remnants of the hyaloid vascular system (HP:0007968). HP:0007968 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"Reduced BMD, hyaloid
vasculature remnants, and nystagmus were features of the phenotype."
Documents hyaloid vasculature remnants in a recessive LRP5 FEVR family.
Nystagmus
HP:0000639
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Nystagmus (HP:0000639). HP:0000639 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"vasculature remnants, and nystagmus were features of the phenotype"
Reports nystagmus as a feature of the recessive LRP5-related FEVR phenotype.
Myopia
FREQUENT
HP:0000545
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Myopia (HP:0000545). HP:0000545 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"Myopia seemed to be overly common in FZD4‐variant‐positive individuals."
Finnish natural history study documents myopia as a frequent finding in FZD4-variant-positive individuals (62% of study eyes).
Strabismus
OCCASIONAL
HP:0000486
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Strabismus (HP:0000486). HP:0000486 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"20% (n = 67) was diagnosed of strabismus at first visit"
Among 335 single-gene positive infant FEVR cases, 20% presented with strabismus at first clinical visit.
Abnormality of the optic disc
FREQUENT
Abnormal optic disc morphology
HP:0012795
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Abnormality of the optic disc, annotated with Abnormal optic disc morphology (HP:0012795). HP:0012795 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0012795 | Abnormality of the optic disc | Frequent (79-30%)"
Orphanet records abnormality of the optic disc as a frequent FEVR phenotype.
Subretinal fluid
FREQUENT
HP:0031526
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Subretinal fluid (HP:0031526). HP:0031526 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"HP:0031526 | Subretinal fluid | Frequent (79-30%)"
Orphanet records subretinal fluid as a frequent FEVR phenotype.
Head and Neck 1
Microcephaly
HP:0000252
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"Cases of FEVR should be carefully
inspected for the presence of microcephaly as a marker for KIF11-related disease"
Identifies microcephaly as a marker distinguishing KIF11-related FEVR.
Musculoskeletal 1
Reduced bone mineral density
HP:0004349
Human Phenotype Ontology (HP)
Relation: this clinical feature is this phenotype
This clinical feature is Reduced bone mineral density (HP:0004349). HP:0004349 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
"Assessment of a patient with a provisional
diagnosis of FEVR should therefore include investigation of BMD, with reduced
levels suggestive of an underlying LRP5 mutation."
Establishes reduced bone mineral density as a feature of LRP5-related recessive FEVR.
Genetic Associations
7
FZD4 frizzled-4 receptor defect
Show evidence (2 references)
"One form of
FEVR is caused by defects in Frizzled-4 (Fz4), a presumptive Wnt receptor."
Identifies FZD4 (Fz4) defects as a cause of FEVR.
"FZD4 | HGNC:4042 | FZD4-related exudative vitreoretinopathy | MONDO:1040041 | AD | Definitive"
ClinGen's Retina Gene Curation Expert Panel classifies FZD4-related exudative vitreoretinopathy as definitive with autosomal dominant inheritance.
NDP Norrin ligand defect
Show evidence (1 reference)
"mutations in the gene encoding NDP, a ligand
for these Wnt receptors, cause Norrie disease and FEVR"
Confirms NDP (Norrin) ligand mutations cause both FEVR and the allelic Norrie disease.
LRP5 Wnt co-receptor defect
Show evidence (2 references)
"A homozygous LRP5 missense mutation, G550R, was
identified in all affected individuals"
Identifies a homozygous LRP5 mutation segregating with recessive FEVR and reduced bone density.
"LRP5 | HGNC:6697 | LRP5-related exudative vitreoretinopathy | MONDO:0700228 | AR | Definitive"
ClinGen classifies biallelic LRP5-related exudative vitreoretinopathy as definitive; the panel lumped osteoporosis-pseudoglioma syndrome into the same entity, which is why this entry's LRP5 subtype also carries reduced bone mineral density.
TSPAN12 co-receptor defect
Show evidence (2 references)
"FEVR-linked mutations in TSPAN12
prevent the incorporation of TSPAN12 into the NDP receptor complex."
Mechanistic study shows FEVR TSPAN12 mutations disrupt assembly of the Norrin receptor complex.
"TSPAN12 | HGNC:21641 | TSPAN12-related exudative vitreoretinopathy | MONDO:0700231 | SD | Definitive"
ClinGen classifies TSPAN12-related exudative vitreoretinopathy as definitive and records the mode of inheritance as semidominant rather than simple autosomal dominant.
KIF11 kinesin motor defect
Show evidence (1 reference)
"The KIF11 gene
likely plays a role in retinal vascular development and mutations in this gene
can lead to clinical overlap with FEVR."
Identifies KIF11 mutations as a cause of a FEVR-overlapping retinal phenotype.
ZNF408 zinc finger protein defect
Show evidence (1 reference)
"discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway"
Identifies ZNF408 as a FEVR causal gene; some variants operate outside the canonical Norrin/Wnt pathway.
CTNNB1 beta-catenin defect
Show evidence (1 reference)
"discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway"
Identifies CTNNB1 as a FEVR causal gene; beta-catenin is the canonical intracellular effector of Wnt signaling.
Medical Actions
4
Laser Photocoagulation
Argon laser photocoagulation of the avascular peripheral retina to induce regression of ischemia-driven new vessel growth and reduce neovascular and exudative sequelae.
Show evidence (1 reference)
"The current treatment paradigm involves laser photocoagulation
of the avascular peripheral retina for neovascular sequelae"
Identifies laser photocoagulation of the avascular periphery as the standard treatment for neovascular FEVR.
Peripheral Retinal Cryotherapy
Cryotherapy of the avascular peripheral retina to induce regression of neovascularization and to stabilize areas of exudate or retinal holes.
Show evidence (1 reference)
"Prophylactic cryotherapy or argon laser
photocoagulation to induce regression of new vessel growth caused by ischemia"
GeneReviews documents prophylactic cryotherapy to induce regression of ischemic neovascularization.
Vitreoretinal Surgery
Vitrectomy and related vitreoretinal surgery to repair tractional or rhegmatogenous retinal detachment in progressive FEVR.
Show evidence (1 reference)
"vitreoretinal
surgery for progressive retinal detachment"
Documents vitreoretinal surgery for progressive retinal detachment in FEVR.
Anti-VEGF Therapy
Intravitreal anti-VEGF agents (e.g., bevacizumab) have been used as an adjunct to suppress ischemia-driven neovascularization and exudation in FEVR.
Progression
5Stage 1 — Peripheral avascular zone
The earliest and mildest detectable finding: a peripheral avascular zone with or without abnormal vascularization at the avascular-vascular junction. Detectable by fundus fluorescein angiography even in asymptomatic individuals. Many variant-positive individuals remain at Stage 1 throughout life; it is the most common stage in FZD4-FEVR (40% of eyes in a Finnish cohort).
Stage 2 — Extraretinal neovascularization
Stage 2a: flat extraretinal neovascularization at the junction of vascular and avascular retina without subretinal or intravitreal exudate. Stage 2b: extraretinal neovascularization with exudate. Ischemia-driven neovascular tufts are present; laser photocoagulation or cryotherapy is indicated to prevent progression. Intravitreal injection is used for Stages 1-3 with vision maintained above 20/67 at last follow-up.
Stage 3 — Extramacular retinal detachment
Fibrovascular traction or exudative retinal detachment that does not involve the macula. Vitreoretinal surgery may be required. Visual prognosis is still relatively good if the macula is spared.
Stage 4 — Subtotal retinal detachment involving the macula
Partial retinal detachment extending to or involving the macula, causing significant visual impairment. Vitrectomy (with or without lensectomy) is the primary intervention; lens-sparing vitrectomy preserves lens transparency in approximately 79% of cases (11/14 eyes).
Stage 5 — Total retinal detachment
Complete retinal detachment with a funnel configuration, the most severe outcome. In a large infant cohort, 69% of Stage 5 surgeries occurred in the first year of life. After 2-10 years of follow-up, approximately 38% of post-surgical cases showed favorable retinal unfolding. At last follow-up, 20% of all patients retained vision above 20/200. NDP mutations are associated with the most severe phenotypes; ZNF408 mutations with the mildest.
Clinical Trials
1
NCT05107921
PHASE_II
UNKNOWN
Phase II trial evaluating the efficacy and safety of bromfenac sodium hydrate eye drops in children with FEVR receiving diode laser photocoagulation. Bromfenac is an NSAID (COX inhibitor) used topically to suppress inflammation and exudation following retinal laser treatment.
Show evidence (1 reference)
clinicaltrials:NCT05107921
SUPPORT
"This study aims to investigate the efficacy and safety of bromfenac sodium hydrate eye drops in patients with familial exudative vitreoretinopathy receiving diode laser photocoagulation."
Phase II trial assessing bromfenac as an adjunctive NSAID therapy in pediatric FEVR patients undergoing diode laser photocoagulation.
Source YAML
click to showname: Familial Exudative Vitreoretinopathy
creation_date: "2026-06-17T00:00:00Z"
category: Mendelian
description: >-
Familial exudative vitreoretinopathy (FEVR) is a rare inherited
vitreoretinopathy characterized by incomplete or arrested vascularization of
the peripheral retina. The shared core mechanism is impaired Norrin/beta-catenin
(Wnt) signaling in retinal vascular endothelial cells, which is required for
developmental angiogenesis of the peripheral retina and establishment of the
blood-retina barrier. The resulting peripheral avascular zone causes retinal
ischemia, which drives compensatory neovascularization, exudation, hemorrhage,
vitreoretinal traction, and tractional or exudative retinal detachment. FEVR is
genetically heterogeneous: most cases are autosomal dominant (FZD4, LRP5,
TSPAN12), but autosomal recessive (LRP5, TSPAN12) and X-linked recessive (NDP)
forms occur, and KIF11 variants produce a FEVR-like retinal phenotype within a
broader microcephaly-lymphedema-chorioretinal dysplasia spectrum. Expressivity
is highly variable, ranging from an asymptomatic avascular periphery detectable
only by fluorescein angiography to bilateral blindness, even within the same
family. NDP variants additionally cause Norrie disease (a severe allelic
disorder), and recessive LRP5 disease can be accompanied by reduced bone
mineral density.
disease_term:
preferred_term: familial exudative vitreoretinopathy
term:
id: MONDO:0019516
label: exudative vitreoretinopathy
synonyms:
- FEVR
- Criswick-Schepens syndrome
parents:
- Ophthalmological Disease
- Retinal vascular disorder
notes: >-
Two MONDO classes sit under MONDO:0019516 exudative vitreoretinopathy without
a subtype row here. MONDO:0979571 exudative vitreoretinopathy 8 is the LRP6
form; LRP6 is not curated here because the only primary report,
"Variants in the Wnt co-receptor LRP6 are associated with familial exudative
vitreoretinopathy" (PMID:34896607), is a Letter that PubMed serves without an
abstract, so no quotable evidence is available, and the ClinGen Gene-Disease
Validity CSV downloaded on 2026-09-26 contains no LRP6 row. A 2025
expanded-panel cohort study (PMID:39918476) lists the six recognized FEVR
genes as FZD4, NDP, LRP5, TSPAN12, ZNF408 and CTNNB1, and places LRP6 among
the genes reported with an ocular phenotype overlapping FEVR rather than in
that set. MONDO:1040031 dyneinopathy
is asserted as a direct child of MONDO:0019516 but is a DYNC1H1 spectrum term
whose own definition describes "variable neuromuscular and/or neurodevelopmental
presentations" and whose only two MONDO children are
MONDO:0013644 Charcot-Marie-Tooth disease axonal type 2O and
MONDO:0013805 intellectual disability, autosomal dominant 13; neither is a
vitreoretinopathy, and no subtype row is created for it.
has_subtypes:
- name: FZD4-FEVR
display_name: FZD4-Related FEVR (EVR1, autosomal dominant)
description: >-
Autosomal dominant FEVR caused by heterozygous pathogenic variants in FZD4,
encoding the frizzled-4 receptor, the obligate Norrin receptor. One of the
most common molecularly defined forms of adFEVR. Variants impair Norrin/FZD4
signaling and peripheral retinal vascularization.
subtype_term:
preferred_term: FZD4-related exudative vitreoretinopathy
term:
id: MONDO:1040041
label: FZD4-related exudative vitreoretinopathy
genes:
- preferred_term: FZD4
term:
id: hgnc:4042
label: FZD4
- name: LRP5-FEVR
display_name: LRP5-Related FEVR (EVR4, AD or AR; with reduced bone density)
description: >-
FEVR caused by pathogenic variants in LRP5, encoding the Wnt co-receptor
low-density lipoprotein receptor-related protein 5. Inherited dominantly or
recessively; recessive disease is frequently accompanied by reduced bone
mineral density, reflecting LRP5's role in skeletal Wnt signaling.
subtype_term:
preferred_term: LRP5-related exudative vitreoretinopathy
term:
id: MONDO:0700228
label: LRP5-related exudative vitreoretinopathy
genes:
- preferred_term: LRP5
term:
id: hgnc:6697
label: LRP5
- name: TSPAN12-FEVR
display_name: TSPAN12-Related FEVR (EVR5)
description: >-
FEVR caused by variants in TSPAN12, encoding tetraspanin-12, an essential
co-receptor of the Norrin/FZD4 complex that amplifies FZD4 ligand selectivity
and signaling. Mostly autosomal dominant.
subtype_term:
preferred_term: TSPAN12-related exudative vitreoretinopathy
term:
id: MONDO:0700231
label: TSPAN12-related exudative vitreoretinopathy
genes:
- preferred_term: TSPAN12
term:
id: hgnc:21641
label: TSPAN12
- name: NDP-FEVR
display_name: NDP-Related FEVR (EVR2, X-linked recessive)
description: >-
X-linked recessive FEVR caused by hemizygous variants in NDP, encoding the
secreted ligand Norrin. NDP is allelic with Norrie disease; FEVR represents
the milder end of the NDP phenotypic spectrum, affecting predominantly males.
subtype_term:
preferred_term: X-linked NDP-related exudative vitreoretinopathy
term:
id: MONDO:0010588
label: exudative vitreoretinopathy 2, X-linked
genes:
- preferred_term: NDP
term:
id: hgnc:7678
label: NDP
- name: KIF11-FEVR
display_name: KIF11-Related FEVR (MLCRD/CDMMR spectrum)
description: >-
Autosomal dominant FEVR-like retinal phenotype caused by heterozygous variants
in KIF11, encoding a kinesin motor. Often part of a broader syndrome
(microcephaly, lymphedema, chorioretinal dysplasia), and FEVR cases should be
inspected for microcephaly as a marker of KIF11-related disease.
mappings:
mondo_mappings:
- term:
id: MONDO:0007918
label: microcephaly with or without chorioretinopathy, lymphedema, or intellectual disability
mapping_predicate: skos:broadMatch
mapping_source: MONDO
mapping_justification: semapv:ManualMappingCuration
notes: >-
The KIF11 disease entity in MONDO, and the class ClinGen curates KIF11
against (Definitive, Retina Gene Curation Expert Panel). It is broader
than this row, which is the retinal phenotype alone, so it is recorded as
a cross-reference rather than as this subtype's identity.
genes:
- preferred_term: KIF11
term:
id: hgnc:6388
label: KIF11
review_notes: >-
This row carries no subtype_term. MONDO has no exudative-vitreoretinopathy
class specific to KIF11: a synonym-inclusive search of MONDO for "KIF11" on
2026-09-26 (runoak -i ols:mondo search "KIF11") returned exactly one term,
MONDO:0007918, and that term is the whole
microcephaly-chorioretinopathy-lymphedema syndrome rather than its retinal
component. Binding it would
assert that this FEVR subtype is that syndrome, which is false for a KIF11
proband with an isolated retinal phenotype, so it is recorded as a
skos:broadMatch cross-reference instead.
- name: ZNF408-FEVR
display_name: ZNF408-Related FEVR (EVR6, autosomal dominant)
description: >-
Autosomal dominant FEVR caused by heterozygous variants in ZNF408, encoding
zinc finger protein 408. The gene was identified by linkage analysis and
exome sequencing in a large Dutch FEVR family, and screening 132 further
individuals with FEVR found a second missense variant in a Japanese family.
The p.His455Tyr allele is localized almost exclusively to the cytoplasm and
retains wild-type ZNF408 there, consistent with a dominant-negative
mechanism, and morpholino knockdown of zebrafish znf408 produces retinal
vascular defects that wild-type but not mutant human ZNF408 rescues. ZNF408
is not a component of the Norrin/FZD4 receptor complex, and a review lists it
with CTNNB1 and KIF11 as later-discovered FEVR genes some of which operate
outside the Norrin/Wnt signalling pathway.
subtype_term:
preferred_term: exudative vitreoretinopathy 6
term:
id: MONDO:0014652
label: exudative vitreoretinopathy 6
genes:
- preferred_term: ZNF408
term:
id: hgnc:20041
label: ZNF408
inheritance:
- name: Autosomal dominant inheritance
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
review_notes: >-
ClinGen has not curated a ZNF408 gene-disease validity assertion. The
Gene-Disease Validity CSV downloaded on 2026-09-26 has no ZNF408 row, while
it carries Definitive Retina Gene Curation Expert Panel assertions for FZD4,
LRP5 and TSPAN12 and a Definitive assertion for CTNNB1. The gene's standing
as a FEVR gene therefore rests on the LOVD/OMIM listing and the primary
reports cited here, not on a ClinGen classification.
evidence:
- reference: PMID:23716654
reference_title: "ZNF408 is mutated in familial exudative vitreoretinopathy and is crucial for the development of zebrafish retinal vasculature."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Sequence analysis of ZNF408 in 132 additional individuals with FEVR revealed another potentially pathogenic missense variant, p.Ser126Asn, in a Japanese family."
explanation: A second, independent human FEVR family carrying a ZNF408 missense variant, beyond the two related Dutch families.
- reference: PMID:39918476
reference_title: "Gene Variant Spectrum in Probands With Familial Exudative Vitreoretinopathy Using an Expanded Panel."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "An expanded FEVR panel was used, including six recognized FEVR genes (FZD4, NDP, LRP5, TSPAN12, ZNF408, and CTNNB1)"
explanation: A 2025 human FEVR cohort study counts ZNF408 among the six recognized FEVR genes, placing this subtype inside the core FEVR gene set.
- name: CTNNB1-FEVR
display_name: CTNNB1-Related FEVR (EVR7, autosomal dominant)
description: >-
FEVR caused by heterozygous, usually de novo, variants in CTNNB1, encoding
beta-catenin, the intracellular effector of canonical Wnt signaling.
Exudative vitreoretinopathy occurs both alongside the CTNNB1
neurodevelopmental phenotype (severe intellectual disability, microcephaly,
spasticity) and in isolation. ClinGen lumped exudative vitreoretinopathy 7
with severe intellectual disability-progressive spastic diplegia syndrome
into one CTNNB1-related disease entity on the grounds of a shared
haploinsufficiency mechanism and a similar variant spectrum, so the ClinGen
assertion for this subtype is recorded against that combined term
(MONDO:0100571) rather than against MONDO:0033123.
subtype_term:
preferred_term: exudative vitreoretinopathy 7
term:
id: MONDO:0033123
label: exudative vitreoretinopathy 7
genes:
- preferred_term: CTNNB1
term:
id: hgnc:2514
label: CTNNB1
inheritance:
- name: Autosomal dominant inheritance
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
evidence:
- reference: CGGV:assertion_e119aceb-a011-4811-9abd-6731c5b3d15d-2024-02-08T170000.000Z
reference_title: "CTNNB1 / CTNNB1-related neurodevelopmental disorder and/or vitreoretinopathy (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "The spectrum of disease has also expanded to include diagnoses of exudative vitreoretinopathy and other eye abnormalities, either in the presence of the aforementioned neurodevelopmental features or in isolation"
explanation: ClinGen records exudative vitreoretinopathy as part of the CTNNB1 phenotypic spectrum, occurring with or without the neurodevelopmental features.
- reference: CGGV:assertion_e119aceb-a011-4811-9abd-6731c5b3d15d-2024-02-08T170000.000Z
reference_title: "CTNNB1 / CTNNB1-related neurodevelopmental disorder and/or vitreoretinopathy (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "CTNNB1 | HGNC:2514 | CTNNB1-related neurodevelopmental disorder and/or vitreoretinopathy | MONDO:0100571 | AD | Definitive"
explanation: ClinGen classifies the CTNNB1 gene-disease relationship as definitive with autosomal dominant inheritance, under the lumped term that subsumes exudative vitreoretinopathy 7.
inheritance:
- name: Autosomal dominant inheritance
inheritance_term:
preferred_term: Autosomal dominant inheritance
term:
id: HP:0000006
label: Autosomal dominant inheritance
description: >-
The most common mode of inheritance for FEVR, seen with FZD4, LRP5, TSPAN12,
and KIF11 variants. Penetrance is reduced and expressivity is highly variable.
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "these can be inherited in an autosomal dominant (most common), autosomal recessive, and X-linked recessive fashion"
explanation: A clinical review confirms autosomal dominant inheritance is the most common FEVR mode.
- reference: PMID:20301326
reference_title: "Familial Exudative Vitreoretinopathy, Autosomal Dominant - RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Offspring of an affected individual are at a 50% risk of inheriting the pathogenic variant, but many individuals with adFEVR can be asymptomatic because of reduced penetrance."
explanation: GeneReviews genetic counseling section confirms 50% recurrence risk and reduced penetrance in autosomal dominant FEVR.
- name: X-linked recessive inheritance
inheritance_term:
preferred_term: X-linked recessive inheritance
term:
id: HP:0001419
label: X-linked recessive inheritance
description: >-
The NDP-related form is inherited in an X-linked recessive manner, affecting
predominantly males; NDP is allelic with Norrie disease.
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "these can be inherited in an autosomal dominant (most common), autosomal recessive, and X-linked recessive fashion"
explanation: A clinical review confirms the X-linked recessive FEVR mode of inheritance (NDP).
- name: Autosomal recessive inheritance
inheritance_term:
preferred_term: Autosomal recessive inheritance
term:
id: HP:0000007
label: Autosomal recessive inheritance
description: >-
Recessive FEVR occurs with biallelic LRP5 (and TSPAN12) variants; recessive
LRP5 disease is associated with reduced bone mineral density.
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "homozygous mutations in LRP5 have recently been reported as underlying the recessive form of this disease"
explanation: Documents the autosomal recessive form of FEVR caused by biallelic LRP5 mutations.
genetic:
- name: FZD4 frizzled-4 receptor defect
gene_term:
preferred_term: FZD4
modifier: DECREASED
term:
id: hgnc:4042
label: FZD4
relationship_type: CAUSATIVE
subtype: FZD4-FEVR
notes: >-
FZD4 encodes frizzled-4, the obligate Norrin receptor. Loss-of-function
variants in humans and Fz4 knockout mice produce similar incomplete retinal
vascularization, establishing Norrin and FZD4 as a high-affinity
ligand-receptor pair controlling retinal angiogenesis.
evidence:
- reference: PMID:15035989
reference_title: "Vascular development in the retina and inner ear: control by Norrin and Frizzled-4, a high-affinity ligand-receptor pair."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: "One form of \nFEVR is caused by defects in Frizzled-4 (Fz4), a presumptive Wnt receptor."
explanation: Identifies FZD4 (Fz4) defects as a cause of FEVR.
- reference: CGGV:assertion_2da74e15-54c4-405c-aa44-301f4717087d-2024-04-04T160000.000Z
reference_title: "FZD4 / FZD4-related exudative vitreoretinopathy (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "FZD4 | HGNC:4042 | FZD4-related exudative vitreoretinopathy | MONDO:1040041 | AD | Definitive"
explanation: ClinGen's Retina Gene Curation Expert Panel classifies FZD4-related exudative vitreoretinopathy as definitive with autosomal dominant inheritance.
- name: NDP Norrin ligand defect
gene_term:
preferred_term: NDP
modifier: DECREASED
term:
id: hgnc:7678
label: NDP
relationship_type: CAUSATIVE
subtype: NDP-FEVR
notes: >-
NDP encodes Norrin, the secreted cysteine-knot ligand for FZD4. NDP variants
cause X-linked FEVR and the allelic, more severe Norrie disease.
evidence:
- reference: PMID:20340138
reference_title: "Overview of the mutation spectrum in familial exudative vitreoretinopathy and Norrie disease with identification of 21 novel variants in FZD4, LRP5, and NDP."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "mutations in the gene encoding NDP, a ligand \nfor these Wnt receptors, cause Norrie disease and FEVR"
explanation: Confirms NDP (Norrin) ligand mutations cause both FEVR and the allelic Norrie disease.
- name: LRP5 Wnt co-receptor defect
gene_term:
preferred_term: LRP5
modifier: DECREASED
term:
id: hgnc:6697
label: LRP5
relationship_type: CAUSATIVE
subtype: LRP5-FEVR
notes: >-
LRP5 encodes a Wnt/Norrin co-receptor. Pathogenic variants cause FEVR;
recessive disease additionally produces reduced bone mineral density,
reflecting LRP5's dual role in retinal vascular and skeletal Wnt signaling.
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "A homozygous LRP5 missense mutation, G550R, was \nidentified in all affected individuals"
explanation: Identifies a homozygous LRP5 mutation segregating with recessive FEVR and reduced bone density.
- reference: CGGV:assertion_c46e0508-399f-48d0-9dbc-55f10cf8460d-2023-03-02T170000.000Z
reference_title: "LRP5 / LRP5-related exudative vitreoretinopathy (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "LRP5 | HGNC:6697 | LRP5-related exudative vitreoretinopathy | MONDO:0700228 | AR | Definitive"
explanation: ClinGen classifies biallelic LRP5-related exudative vitreoretinopathy as definitive; the panel lumped osteoporosis-pseudoglioma syndrome into the same entity, which is why this entry's LRP5 subtype also carries reduced bone mineral density.
- name: TSPAN12 co-receptor defect
gene_term:
preferred_term: TSPAN12
modifier: DECREASED
term:
id: hgnc:21641
label: TSPAN12
relationship_type: CAUSATIVE
subtype: TSPAN12-FEVR
notes: >-
TSPAN12 encodes tetraspanin-12, an essential component of the Norrin receptor
complex. FEVR-linked TSPAN12 mutations prevent its incorporation into the
Norrin/FZD4 complex, reducing signaling amplitude.
evidence:
- reference: PMID:28658627
reference_title: "TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "FEVR-linked mutations in TSPAN12 \nprevent the incorporation of TSPAN12 into the NDP receptor complex."
explanation: Mechanistic study shows FEVR TSPAN12 mutations disrupt assembly of the Norrin receptor complex.
- reference: CGGV:assertion_9c7915a6-c4eb-47c7-9c51-a81279b6e6a4-2022-01-06T170000.000Z
reference_title: "TSPAN12 / TSPAN12-related exudative vitreoretinopathy (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "TSPAN12 | HGNC:21641 | TSPAN12-related exudative vitreoretinopathy | MONDO:0700231 | SD | Definitive"
explanation: ClinGen classifies TSPAN12-related exudative vitreoretinopathy as definitive and records the mode of inheritance as semidominant rather than simple autosomal dominant.
- name: KIF11 kinesin motor defect
gene_term:
preferred_term: KIF11
modifier: DECREASED
term:
id: hgnc:6388
label: KIF11
relationship_type: CAUSATIVE
subtype: KIF11-FEVR
notes: >-
KIF11 encodes a kinesin motor. Heterozygous variants cause a FEVR-like retinal
phenotype, frequently within the microcephaly-lymphedema-chorioretinal
dysplasia spectrum, implicating KIF11 in retinal vascular development.
evidence:
- reference: PMID:25124931
reference_title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The KIF11 gene \nlikely plays a role in retinal vascular development and mutations in this gene \ncan lead to clinical overlap with FEVR."
explanation: Identifies KIF11 mutations as a cause of a FEVR-overlapping retinal phenotype.
- name: ZNF408 zinc finger protein defect
gene_term:
preferred_term: ZNF408
modifier: DECREASED
term:
id: hgnc:20041
label: ZNF408
relationship_type: CAUSATIVE
subtype: ZNF408-FEVR
notes: >-
ZNF408 encodes a zinc finger protein; pathogenic variants cause FEVR with
typically mild clinical phenotypes. ZNF408 variants may act partly outside the
canonical Norrin/Wnt signaling pathway. In the largest infant cohort, patients
with ZNF408 mutations presented the mildest clinical phenotypes compared to
other FEVR genotypes.
evidence:
- reference: DOI:10.3390/cells12212579
reference_title: "Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway"
explanation: Identifies ZNF408 as a FEVR causal gene; some variants operate outside the canonical Norrin/Wnt pathway.
- name: CTNNB1 beta-catenin defect
gene_term:
preferred_term: CTNNB1
modifier: DECREASED
term:
id: hgnc:2514
label: CTNNB1
relationship_type: CAUSATIVE
subtype: CTNNB1-FEVR
notes: >-
CTNNB1 encodes beta-catenin, the intracellular effector of canonical Wnt
signaling. Pathogenic variants directly disrupt Wnt/beta-catenin transcriptional
output in retinal endothelial cells, implicating the core effector arm of the
Norrin/Wnt pathway in FEVR pathogenesis.
evidence:
- reference: DOI:10.3390/cells12212579
reference_title: "Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway"
explanation: Identifies CTNNB1 as a FEVR causal gene; beta-catenin is the canonical intracellular effector of Wnt signaling.
pathophysiology:
- name: Impaired Norrin/beta-catenin signaling in retinal endothelium
genes:
- preferred_term: NDP
term:
id: hgnc:7678
label: NDP
- preferred_term: LRP5
term:
id: hgnc:6697
label: LRP5
- preferred_term: TSPAN12
term:
id: hgnc:21641
label: TSPAN12
- preferred_term: CTNNB1
term:
id: hgnc:2514
label: CTNNB1
conforms_to: "norrin_fzd4_retinal_vascular_development#Insufficient Norrin-FZD4-beta-catenin Signalling in Retinal Endothelium"
description: >-
The core defect of FEVR. Norrin (NDP) is a secreted ligand that binds the
frizzled-4 (FZD4) receptor together with the co-receptor LRP5 and the
accessory tetraspanin TSPAN12, activating canonical (beta-catenin-dependent)
Wnt signaling specifically in retinal vascular endothelial cells. Loss-of-function
in any of these components reduces beta-catenin signaling output. Disruption of
Tspan12, Ndp, Fzd4, or Lrp5 in mice produces similar ocular phenotypes,
indicating a shared signaling pathway. Heterozygous CTNNB1 variants act one
step further down, on beta-catenin itself, and ClinGen records defects in
retinal vascularization across the CTNNB1 phenotypic spectrum.
gene:
preferred_term: FZD4
modifier: DECREASED
term:
id: hgnc:4042
label: FZD4
cell_types:
- preferred_term: retinal blood vessel endothelial cell
term:
id: CL:0002585
label: retinal blood vessel endothelial cell
biological_processes:
- preferred_term: Norrin signaling pathway
modifier: DECREASED
term:
id: GO:0110135
label: Norrin signaling pathway
- preferred_term: canonical Wnt signaling pathway
modifier: DECREASED
term:
id: GO:0060070
label: canonical Wnt signaling pathway
evidence:
- reference: PMID:28658627
reference_title: "TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: "Gene disruptions of Tspan12 (Junge et al., 2009), Ndp (Luhmann et al., 2005), Fzd4 (Xu et al., 2004; Ye et al., 2009), and Lrp5 (Xia et al., 2008) all result in similar ocular phenotypes in mice, characterized by defects in intraretinal capillary development and dysregulation of the blood-retina barrier."
explanation: Shows the convergent ocular phenotype across all four core Norrin-pathway genes, defining the shared mechanism.
- reference: PMID:28658627
reference_title: "TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "TSPAN12 is \nan essential component of the NDP receptor complex and interacts with FZD4 and \nNDP via its extracellular loops, consistent with an action as co-receptor that \nenhances FZD4 ligand selectivity for NDP."
explanation: Establishes the molecular assembly of the Norrin/FZD4/TSPAN12 receptor complex underlying the pathway.
- reference: CGGV:assertion_e119aceb-a011-4811-9abd-6731c5b3d15d-2024-02-08T170000.000Z
reference_title: "CTNNB1 / CTNNB1-related neurodevelopmental disorder and/or vitreoretinopathy (Definitive)"
supports: SUPPORT
evidence_source: OTHER
snippet: "Both disease entities can exhibit similar defects in retinal vascularization that lead to serous retinal detachment and other ocular features."
explanation: >-
Supports placing CTNNB1 at this node, since loss of the pathway's
beta-catenin effector produces retinal vascularization defects of the same
kind as the receptor-complex genes.
downstream:
- target: Incomplete peripheral retinal vascularization
causal_link_type: DIRECT
description: >-
Reduced Norrin/beta-catenin signaling impairs developmental angiogenesis of
the peripheral retina, leaving an avascular peripheral zone.
evidence:
- reference: PMID:15035989
reference_title: "Vascular development in the retina and inner ear: control by Norrin and Frizzled-4, a high-affinity ligand-receptor pair."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: "Incomplete retinal vascularization occurs in both Norrie disease and familial \nexudative vitreoretinopathy (FEVR)."
explanation: Directly links the Norrin/FZD4 pathway defect to incomplete retinal vascularization.
- target: Inner Blood-Retinal Barrier Dysfunction
causal_link_type: DIRECT
description: >-
Reduced Norrin/beta-catenin signaling also impairs formation and maintenance
of the inner blood-retinal barrier (iBRB) in retinal endothelial cells,
contributing to vascular permeability and retinal exudation.
evidence:
- reference: DOI:10.3390/cells12212579
reference_title: "Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "irregular retinal vascular development and/or aberrant inner blood-retinal-barrier (iBRB) function"
explanation: Establishes iBRB dysfunction as a pathophysiological element of FEVR driven by Norrin/Wnt signaling defects.
- target: Remnants of the hyaloid vascular system
causal_link_type: DIRECT
description: >-
Norrin/beta-catenin signaling is also required for normal developmental
regression of the fetal hyaloid vasculature; deficient signaling leaves
persistent hyaloid remnants, documented in recessive LRP5-related FEVR and
overlapping with persistent fetal vascular syndrome.
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
directness: INDIRECT
snippet: "Recessive mutations in LRP5 can cause FEVR with reduced BMD and \nhyaloid vasculature remnants."
explanation: >-
Human recessive deficiency of the Wnt co-receptor LRP5 produces
persistent hyaloid vasculature; the quote ties the gene rather than the
pathway node itself to the phenotype, so it bears indirectly on this
edge.
- name: Incomplete peripheral retinal vascularization
conforms_to: "norrin_fzd4_retinal_vascular_development#Incomplete Retinal Vascularization with Peripheral Avascular Retina"
description: >-
The hallmark structural lesion of FEVR: failure of the retinal vasculature to
grow into the peripheral retina, producing a bilateral peripheral avascular
zone. This avascularity is probably present from birth and is detectable by
fundus fluorescein angiography even in asymptomatic individuals.
cell_types:
- preferred_term: retinal blood vessel endothelial cell
term:
id: CL:0002585
label: retinal blood vessel endothelial cell
biological_processes:
- preferred_term: retina vasculature development in camera-type eye
modifier: DECREASED
term:
id: GO:0061298
label: retina vasculature development in camera-type eye
- preferred_term: establishment of blood-retinal barrier
modifier: DECREASED
term:
id: GO:1990963
label: establishment of blood-retinal barrier
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The principal feature \nof the disease is an avascular peripheral retina."
explanation: Identifies the peripheral avascular retina as the principal structural feature of FEVR.
downstream:
- target: Peripheral retinal ischemia and neovascular response
causal_link_type: DIRECT
description: >-
The non-perfused peripheral retina becomes ischemic, generating a
pro-angiogenic drive (e.g., VEGF) that triggers abnormal neovascularization.
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This in turn can cause further \npathological changes including neovascularization, exudation, hemorrhage, and \nretinal detachment."
explanation: Links the avascular periphery to the downstream neovascular and exudative complications.
- target: Peripheral retinal avascularization
causal_link_type: DIRECT
description: The same developmental vascularization failure is recorded clinically as peripheral retinal avascularization.
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0007685 | Peripheral retinal avascularization | Very frequent (99-80%)"
explanation: Orphanet records peripheral retinal avascularization as a very frequent FEVR phenotype.
- target: Exudative vitreoretinopathy
causal_link_type: DIRECT
description: >-
The anomalous peripheral retinal vascular development, together with its
exudative sequelae, constitutes the defining exudative vitreoretinopathy.
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Familial exudative vitreoretinopathy (FEVR) is a heritable vitreoretinopathy \ncharacterized by anomalous retinal vascular development."
explanation: The defining vitreoretinopathy is the clinical expression of the anomalous vascular development modeled by this node.
- target: Vitreoretinopathy
causal_link_type: DIRECT
description: >-
Summary edge: the developmental vascularization failure and its sequelae
are what is recorded clinically under the obligate umbrella category of
vitreoretinopathy.
- name: Peripheral retinal ischemia and neovascular response
conforms_to: "norrin_fzd4_retinal_vascular_development#Ischaemia-Driven Neovascularization, Exudation and Tractional Detachment"
description: >-
Ischemia of the peripheral avascular retina drives pathological
neovascularization, with exudation and hemorrhage. These vascular sequelae are
the proximate cause of the symptomatic complications of FEVR.
cell_types:
- preferred_term: capillary endothelial cell
term:
id: CL:0002144
label: capillary endothelial cell
biological_processes:
- preferred_term: angiogenesis
modifier: INCREASED
term:
id: GO:0001525
label: angiogenesis
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This in turn can cause further \npathological changes including neovascularization, exudation, hemorrhage, and \nretinal detachment."
explanation: Documents neovascularization, exudation, and hemorrhage as ischemia-driven sequelae.
downstream:
- target: Vitreoretinal traction and retinal detachment
causal_link_type: DIRECT
description: >-
Fibrovascular proliferation and contraction exert tractional forces on the
retina, and exudation accumulates, producing tractional, rhegmatogenous, or
exudative retinal detachment and ultimately vision loss.
evidence:
- reference: PMID:20340138
reference_title: "Overview of the mutation spectrum in familial exudative vitreoretinopathy and Norrie disease with identification of 21 novel variants in FZD4, LRP5, and NDP."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "abnormal \nvascularization of the peripheral retina and formation of fibrovascular masses \nin the eye that can lead to blindness"
explanation: Links fibrovascular proliferation to the tractional sequelae and blindness.
- target: Peripheral retinal neovascularization
causal_link_type: DIRECT
description: >-
Ischemia-driven new vessels arise at the junction of the vascularized and
avascular peripheral retina.
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This in turn can cause further \npathological changes including neovascularization, exudation, hemorrhage, and \nretinal detachment."
explanation: The avascular periphery drives neovascularization among the downstream pathological changes.
- target: Retinal neovascularization
causal_link_type: DIRECT
description: >-
Summary edge: the same ischemia-driven neovascular response recorded at the
disease level (Orphanet frequency term), without restriction to the
peripheral vascular-avascular junction.
- target: Retinal exudate
causal_link_type: DIRECT
description: >-
Leakage from immature, ischemia-driven new vessels deposits lipid- and
protein-rich exudates in the retina; the node-level evidence lists
exudation among the sequelae of the avascular periphery.
- target: Macular exudate
causal_link_type: DIRECT
description: >-
Exudation from the peripheral neovascular response that extends into or
accumulates at the macula is recorded as macular exudate, degrading
central vision.
- target: Subretinal fluid
causal_link_type: DIRECT
description: >-
Exudate accumulating beneath the neurosensory retina produces subretinal
fluid and drives exudative retinal detachment.
- target: Vitreous hemorrhage
causal_link_type: DIRECT
description: >-
Fragile neovascular tufts at the vascular-avascular junction bleed into
the vitreous; hemorrhage is listed with the node-level evidence among the
sequelae of the avascular periphery.
- name: Vitreoretinal traction and retinal detachment
description: >-
Terminal convergence of FEVR: fibrovascular traction and exudation cause
macular dragging, falciform retinal folds, and partial or total retinal
detachment, leading to severe visual impairment or blindness. Expressivity is
highly variable.
cell_types:
- preferred_term: capillary endothelial cell
term:
id: CL:0002144
label: capillary endothelial cell
biological_processes:
- preferred_term: retinal blood vessel morphogenesis
modifier: DYSREGULATED
term:
id: GO:0061304
label: retinal blood vessel morphogenesis
evidence:
- reference: PMID:25124931
reference_title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "macular dragging, partial retinal detachment, falciform folds, or total retinal \ndetachment"
explanation: Catalogs the tractional retinal sequelae that define advanced FEVR.
downstream:
- target: Tractional retinal detachment
causal_link_type: DIRECT
description: Fibrovascular traction is the proximate mechanism for tractional retinal detachment.
- target: Reduced visual acuity
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
intermediate_mechanisms:
- tractional retinal detachment
- macular exudation
description: Retinal detachment, exudation, and macular involvement reduce visual acuity in symptomatic FEVR.
- target: Retinal detachment
causal_link_type: DIRECT
description: >-
Tractional forces from fibrovascular proliferation, retinal breaks, and
exudation produce tractional, rhegmatogenous, or exudative retinal
detachment.
evidence:
- reference: PMID:20301326
reference_title: "Familial Exudative Vitreoretinopathy, Autosomal Dominant - RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "rhegmatogenous retinal \ndetachments produced by retinal traction are repaired surgically"
explanation: GeneReviews attributes rhegmatogenous retinal detachment in FEVR to retinal traction.
- target: Falciform retinal fold
causal_link_type: DIRECT
description: >-
Contraction of fibrovascular tissue drags the retina into a sickle-shaped
falciform fold; the node-level evidence catalogs falciform folds among the
tractional sequelae.
- target: Abnormality of the optic disc
causal_link_type: DIRECT
description: >-
Fibrovascular traction drags the optic disc and its emerging vessels (the
dragged-disc appearance), the basis of the optic disc abnormalities of
advanced FEVR.
- target: Strabismus
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
intermediate_mechanisms:
- asymmetric visual deprivation from macular dragging or retinal detachment
description: >-
Asymmetric loss of central visual input from macular dragging, exudation,
or detachment disrupts binocular fusion, producing sensory strabismus; 20%
of infants in a large single-gene-positive cohort presented with
strabismus at first visit.
evidence:
- reference: DOI:10.1186/s12886-022-02522-8
reference_title: "Long-term clinical prognosis of 335 infant single-gene positive FEVR cases"
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
directness: INDIRECT
snippet: "In addition to simple strabismus, a \ncertain percentage of strabismus is caused by fundus dis -\neases"
explanation: >-
The infant FEVR cohort study attributes a fraction of infantile
strabismus to underlying fundus disease rather than primary ocular
misalignment; the statement covers fundus diseases generally, so it
bears indirectly on the FEVR-specific edge.
- target: Nystagmus
causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
intermediate_mechanisms:
- early-onset severe bilateral visual deprivation
description: >-
Summary edge: severe early-onset visual loss from retinal detachment and
macular involvement prevents development of stable fixation, producing
sensory nystagmus, reported among the features of the recessive
LRP5-related phenotype.
- name: Inner Blood-Retinal Barrier Dysfunction
conforms_to: "norrin_fzd4_retinal_vascular_development#Inner Blood-Retina Barrier Failure"
description: >-
Norrin/Wnt signaling in retinal endothelial cells governs not only developmental
angiogenesis but also formation and maintenance of the inner blood-retinal
barrier (iBRB). Loss-of-function in FZD4, LRP5, NDP, or TSPAN12 impairs
iBRB integrity, producing aberrant vascular permeability that contributes to
retinal exudation independently of ischemia-driven neovascularization. FEVR,
Norrie disease, and persistent fetal vascular syndrome share this iBRB
dysfunction as a unifying pathophysiological element.
cell_types:
- preferred_term: retinal blood vessel endothelial cell
term:
id: CL:0002585
label: retinal blood vessel endothelial cell
biological_processes:
- preferred_term: establishment of blood-retinal barrier
modifier: DECREASED
term:
id: GO:1990963
label: establishment of blood-retinal barrier
evidence:
- reference: DOI:10.3390/cells12212579
reference_title: "Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "unified by abnormal retinal endothelial cell function, and subsequent irregular retinal vascular development and/or aberrant inner blood-retinal-barrier (iBRB) function"
explanation: >-
Establishes iBRB dysfunction as a distinct pathophysiological element shared
across FEVR-related disorders, driven by abnormal Norrin/Wnt signaling in
retinal endothelial cells.
downstream:
- target: Retinal exudate
causal_link_type: DIRECT
description: >-
Summary edge: failure of the inner blood-retinal barrier permits plasma
leakage and retinal exudation independently of ischemia-driven
neovascularization, per the node-level evidence.
- name: Impaired LRP5-mediated Wnt signaling in bone
biological_scale: CELLULAR
description: >-
In recessive LRP5-related FEVR the same Wnt co-receptor deficiency that
impairs retinal angiogenesis also reduces canonical Wnt signal transduction
in osteoblasts, lowering bone mass accrual during growth. LRP5 loss causes
the allelic osteoporosis-pseudoglioma syndrome, and FEVR patients with
biallelic LRP5 mutations show reduced bone mineral density.
gene:
preferred_term: LRP5
modifier: DECREASED
term:
id: hgnc:6697
label: LRP5
cell_types:
- preferred_term: osteoblast
term:
id: CL:0000062
label: osteoblast
biological_processes:
- preferred_term: canonical Wnt signaling pathway
modifier: DECREASED
term:
id: GO:0060070
label: canonical Wnt signaling pathway
evidence:
- reference: PMID:11719191
reference_title: "LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "We demonstrate LRP5 expression by osteoblasts in situ and show that LRP5 can transduce Wnt signaling in vitro via the canonical pathway."
explanation: Establishes that osteoblasts express LRP5 and that LRP5 transduces canonical Wnt signaling.
- reference: PMID:11719191
reference_title: "LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development."
supports: SUPPORT
evidence_source: IN_VITRO
snippet: "These data indicate that Wnt-mediated signaling via LRP5 affects bone accrual during growth and is important for the establishment of peak bone mass."
explanation: >-
Study conclusion, resting on OPPG carrier data and mouse calvarial explant
cultures, that LRP5-mediated Wnt signaling controls bone mass accrual
during growth.
downstream:
- target: Reduced bone mineral density
causal_link_type: DIRECT
description: >-
Reduced osteoblast Wnt signaling lowers bone mass accrual, producing the
reduced bone mineral density that accompanies recessive LRP5-related FEVR.
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Recessive mutations in LRP5 can cause FEVR with reduced BMD and \nhyaloid vasculature remnants."
explanation: Biallelic LRP5 mutations in a FEVR family produced reduced bone mineral density in affected individuals.
- name: ZNF408 dysfunction impairing retinal vascular development
genes:
- preferred_term: ZNF408
term:
id: hgnc:20041
label: ZNF408
description: >-
A FEVR mechanism that does not run through the Norrin/FZD4 receptor complex.
Morpholino knockdown of zebrafish znf408 produces defects in the developing
retinal vasculature that co-injected wild-type human ZNF408 RNA rescues and
the p.His455Tyr mutant does not. In transfected cells the p.His455Tyr protein
is localized almost exclusively to the cytoplasm and retains wild-type ZNF408
there, consistent with a dominant-negative mechanism. How ZNF408 acts on
retinal vasculogenesis is not established, and a review lists it with CTNNB1
and KIF11 as later-discovered FEVR genes some of which operate outside the
Norrin/Wnt signalling pathway, so this node is kept separate from the
receptor-complex node rather than folded into it.
biological_processes:
- preferred_term: retina vasculature development in camera-type eye
modifier: DECREASED
term:
id: GO:0061298
label: retina vasculature development in camera-type eye
evidence:
- reference: PMID:23716654
reference_title: "ZNF408 is mutated in familial exudative vitreoretinopathy and is crucial for the development of zebrafish retinal vasculature."
supports: SUPPORT
evidence_source: MODEL_ORGANISM
snippet: "morpholino-induced knockdown of znf408 in zebrafish revealed defects in developing retinal and trunk vasculature, that could be rescued by coinjection of RNA encoding human WT ZNF408 but not p.His455Tyr mutant ZNF408"
explanation: A rescue-controlled knockdown showing ZNF408 is required for retinal vascular development and that the human FEVR allele is non-functional.
- reference: DOI:10.3390/cells12212579
reference_title: "Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome"
supports: SUPPORT
evidence_source: OTHER
snippet: "discovery of pathological variants in additional genes such as CTNNB1, KIF11, and ZNF408, some of which operate outside of the Norrin Wnt-signaling pathway"
explanation: Supports modeling ZNF408 as a mechanism separate from the Norrin/FZD4 receptor complex.
downstream:
- target: Incomplete peripheral retinal vascularization
causal_link_type: DIRECT
description: >-
ZNF408 dysfunction produces the same failure of peripheral retinal
vascularization that defines FEVR.
evidence:
- reference: PMID:23716654
reference_title: "ZNF408 is mutated in familial exudative vitreoretinopathy and is crucial for the development of zebrafish retinal vasculature."
supports: SUPPORT
directness: INDIRECT
evidence_source: HUMAN_CLINICAL
snippet: "our data strongly suggest that mutant ZNF408 results in abnormal retinal vasculogenesis in humans and is associated with FEVR"
explanation: >-
The authors' conclusion that mutant ZNF408 causes abnormal retinal
vasculogenesis in humans. Graded INDIRECT because the vasculogenesis
step rests on the zebrafish rescue experiment while the FEVR association
rests on the human families.
- name: KIF11 mitotic spindle dysfunction
biological_scale: CELLULAR
description: >-
KIF11 encodes EG5, a homotetrameric kinesin required for bipolar mitotic
spindle assembly. Heterozygous KIF11 mutations impair spindle formation in
proliferating progenitors, compromising CNS growth (microcephaly) and the
development of retinal and lymphatic structures. This mechanism operates
outside the canonical Norrin/Wnt pathway and defines the KIF11-related FEVR
spectrum (microcephaly-lymphedema-chorioretinal dysplasia).
gene:
preferred_term: KIF11
modifier: DECREASED
term:
id: hgnc:6388
label: KIF11
biological_processes:
- preferred_term: mitotic spindle assembly
modifier: DECREASED
term:
id: GO:0090307
label: mitotic spindle assembly
evidence:
- reference: PMID:22284827
reference_title: "Mutations in KIF11 cause autosomal-dominant microcephaly variably associated with congenital lymphedema and chorioretinopathy."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "KIF11 encodes EG5, a homotetramer kinesin motor."
explanation: Identifies the KIF11 gene product as the EG5 spindle kinesin motor.
- reference: PMID:22284827
reference_title: "Mutations in KIF11 cause autosomal-dominant microcephaly variably associated with congenital lymphedema and chorioretinopathy."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
directness: INDIRECT
snippet: "EG5 has previously been shown to play a role in spindle assembly and function, and these findings highlight the critical role of proteins necessary for spindle formation in CNS development."
explanation: >-
Links the spindle-assembly function of EG5 to CNS development in patients
with KIF11 mutations; the mechanistic inference rests on prior functional
work summarized by this human genetics study.
downstream:
- target: Microcephaly
causal_link_type: DIRECT
description: >-
Defective spindle formation in proliferating neural progenitors limits CNS
growth, producing the congenital microcephaly that marks KIF11-related
disease.
evidence:
- reference: PMID:22284827
reference_title: "Mutations in KIF11 cause autosomal-dominant microcephaly variably associated with congenital lymphedema and chorioretinopathy."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "We have identified KIF11 mutations in individuals with syndromic autosomal-dominant microcephaly associated with lymphedema and/or chorioretinopathy."
explanation: Human genetic evidence that heterozygous KIF11 mutations cause microcephaly.
- target: Incomplete peripheral retinal vascularization
causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
description: >-
KIF11 mutations produce a FEVR-like peripheral avascular retinopathy, but
how spindle dysfunction impairs retinal vascular development, and whether
it intersects the Norrin/Wnt pathway, is not established.
evidence:
- reference: PMID:25124931
reference_title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
directness: INDIRECT
snippet: "The KIF11 gene \nlikely plays a role in retinal vascular development and mutations in this gene \ncan lead to clinical overlap with FEVR."
explanation: Documents that KIF11 mutations reproduce the FEVR retinal vascular phenotype without establishing the intermediate mechanism.
phenotypes:
- category: Ophthalmic
name: Exudative vitreoretinopathy
description: >-
The defining clinical feature: abnormal peripheral retinal vascular
development with exudation, the eponymous lesion of the disease.
phenotype_term:
preferred_term: Exudative vitreoretinopathy
term:
id: HP:0030490
label: Exudative vitreoretinopathy
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Familial exudative vitreoretinopathy (FEVR) is a heritable vitreoretinopathy \ncharacterized by anomalous retinal vascular development."
explanation: Defines FEVR as an exudative vitreoretinopathy with anomalous retinal vascular development.
- category: Ophthalmic
name: Peripheral retinal neovascularization
description: >-
Abnormal new vessel growth at the junction of vascular and avascular retina,
driven by peripheral ischemia.
phenotype_term:
preferred_term: Peripheral retinal neovascularization
term:
id: HP:0030667
label: Peripheral retinal neovascularization
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This in turn can cause further \npathological changes including neovascularization, exudation, hemorrhage, and \nretinal detachment."
explanation: Documents neovascularization as a complication of the avascular periphery.
- category: Ophthalmic
name: Retinal exudate
description: >-
Lipid and protein exudation into the retina, characteristic of the exudative
phase of the disease.
phenotype_term:
preferred_term: Retinal exudate
term:
id: HP:0001147
label: Retinal exudate
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "This in turn can cause further \npathological changes including neovascularization, exudation, hemorrhage, and \nretinal detachment."
explanation: Lists exudation among the pathological changes of FEVR.
- category: Ophthalmic
name: Falciform retinal fold
description: >-
A sickle-shaped fold of retina dragged toward the temporal periphery by
fibrovascular traction, a classic FEVR sign.
phenotype_term:
preferred_term: Falciform retinal fold
term:
id: HP:0001493
label: Falciform retinal fold
evidence:
- reference: PMID:25124931
reference_title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "macular dragging, partial retinal detachment, falciform folds, or total retinal \ndetachment"
explanation: Falciform folds are documented among the tractional retinal manifestations.
- category: Ophthalmic
name: Retinal detachment
description: >-
Tractional, rhegmatogenous, or exudative retinal detachment, the major
sight-threatening complication of FEVR.
phenotype_term:
preferred_term: Retinal detachment
term:
id: HP:0000541
label: Retinal detachment
clinical_course: PROGRESSIVE
evidence:
- reference: PMID:25124931
reference_title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Retinal detachment with avascularity of the peripheral retina, \ntypically associated with familial exudative vitreoretinopathy (FEVR)"
explanation: Associates retinal detachment with peripheral avascularity in FEVR.
- category: Ophthalmic
name: Peripheral retinal avascularization
description: >-
Failure of the retinal vasculature to reach the periphery, leaving the
avascular peripheral retina that drives later ischemic and exudative changes.
frequency: VERY_FREQUENT
phenotype_term:
preferred_term: Peripheral retinal avascularization
term:
id: HP:0007685
label: Avascular peripheral retina
evidence:
- reference: PMID:20301326
reference_title: "Familial Exudative Vitreoretinopathy, Autosomal Dominant - RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "bilateral peripheral retinal avascularity, seen temporally, by indirect ophthalmoscope and scleral indentation, or by fundus fluorescein angiography"
explanation: GeneReviews defines bilateral peripheral retinal avascularity as the diagnostic hallmark of FEVR.
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0007685 | Peripheral retinal avascularization | Very frequent (99-80%)"
explanation: Orphanet records peripheral retinal avascularization as a very frequent FEVR phenotype.
- category: Ophthalmic
name: Vitreoretinopathy
description: >-
Vitreoretinal disease is the obligate clinical category for FEVR and
encompasses the abnormal retinal vascularization, exudation, and tractional sequelae.
frequency: OBLIGATE
phenotype_term:
preferred_term: Vitreoretinopathy
term:
id: HP:0007773
label: Vitreoretinopathy
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0007773 | Vitreoretinopathy | Obligate (100%)"
explanation: Orphanet records vitreoretinopathy as an obligate FEVR phenotype.
- category: Ophthalmic
name: Reduced visual acuity
description: Reduced acuity from macular exudation, traction, or retinal detachment.
frequency: FREQUENT
phenotype_term:
preferred_term: Reduced visual acuity
term:
id: HP:0007663
label: Reduced visual acuity
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0007663 | Reduced visual acuity | Frequent (79-30%)"
explanation: Orphanet records reduced visual acuity as a frequent FEVR phenotype.
- category: Ophthalmic
name: Tractional retinal detachment
description: Detachment caused by fibrovascular traction on the retina in advanced FEVR.
frequency: FREQUENT
phenotype_term:
preferred_term: Tractional retinal detachment
term:
id: HP:0007917
label: Tractional retinal detachment
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0007917 | Tractional retinal detachment | Frequent (79-30%)"
explanation: Orphanet records tractional retinal detachment as a frequent FEVR phenotype.
- category: Ophthalmic
name: Macular exudate
description: Exudative macular involvement that contributes to reduced central visual function.
frequency: OCCASIONAL
phenotype_term:
preferred_term: Macular exudate
term:
id: HP:0030496
label: Macular exudate
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0030496 | Macular exudate | Occasional (29-5%)"
explanation: Orphanet records macular exudate as an occasional FEVR phenotype.
- category: Ophthalmic
name: Remnants of the hyaloid vascular system
subtype: LRP5-FEVR
description: >-
Persistent hyaloid vasculature remnants, reported as a feature of recessive
LRP5-related FEVR.
phenotype_term:
preferred_term: Remnants of the hyaloid vascular system
term:
id: HP:0007968
label: Remnants of the hyaloid vascular system
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Reduced BMD, hyaloid \nvasculature remnants, and nystagmus were features of the phenotype."
explanation: Documents hyaloid vasculature remnants in a recessive LRP5 FEVR family.
- category: Musculoskeletal
name: Reduced bone mineral density
subtype: LRP5-FEVR
description: >-
Reduced bone mineral density accompanies recessive LRP5-related FEVR,
reflecting LRP5's role in skeletal Wnt signaling; its presence suggests an
underlying LRP5 mutation.
phenotype_term:
preferred_term: Reduced bone mineral density
term:
id: HP:0004349
label: Reduced bone mineral density
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Assessment of a patient with a provisional \ndiagnosis of FEVR should therefore include investigation of BMD, with reduced \nlevels suggestive of an underlying LRP5 mutation."
explanation: Establishes reduced bone mineral density as a feature of LRP5-related recessive FEVR.
- category: Neurologic
name: Nystagmus
subtype: LRP5-FEVR
description: >-
Nystagmus was reported among the extraocular features of recessive
LRP5-related FEVR, alongside reduced bone mineral density and hyaloid
vasculature remnants.
phenotype_term:
preferred_term: Nystagmus
term:
id: HP:0000639
label: Nystagmus
evidence:
- reference: PMID:16929062
reference_title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "vasculature remnants, and nystagmus were features of the phenotype"
explanation: Reports nystagmus as a feature of the recessive LRP5-related FEVR phenotype.
- category: Neurologic
name: Microcephaly
subtype: KIF11-FEVR
description: >-
Microcephaly is the key extraocular marker of KIF11-related disease; FEVR
cases should be inspected for microcephaly to identify KIF11-related disease.
phenotype_term:
preferred_term: Microcephaly
term:
id: HP:0000252
label: Microcephaly
evidence:
- reference: PMID:25124931
reference_title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Cases of FEVR should be carefully \ninspected for the presence of microcephaly as a marker for KIF11-related disease"
explanation: Identifies microcephaly as a marker distinguishing KIF11-related FEVR.
- category: Ophthalmic
name: Myopia
subtype: FZD4-FEVR
description: >-
Myopia is markedly overrepresented in FZD4-variant-positive individuals,
occurring in 62% of study eyes in a Finnish cohort. Whether this represents a
direct consequence of altered retinal vascular development or a secondary
effect of the structural changes in FEVR is not yet established.
frequency: FREQUENT
phenotype_term:
preferred_term: Myopia
term:
id: HP:0000545
label: Myopia
evidence:
- reference: DOI:10.1111/aos.16701
reference_title: "Clinical and genetic characteristics and natural history of Finnish families with familial exudative vitreoretinopathy due to pathogenic <scp><i>FZD4</i></scp> variants"
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Myopia seemed to be overly common in FZD4‐variant‐positive individuals."
explanation: >-
Finnish natural history study documents myopia as a frequent finding in
FZD4-variant-positive individuals (62% of study eyes).
- category: Ophthalmic
name: Strabismus
description: >-
Strabismus is a common presenting feature in infant FEVR, occurring in 20%
of cases at first clinical visit, likely reflecting disrupted visual
input from asymmetric retinal disease or retinal detachment.
frequency: OCCASIONAL
phenotype_term:
preferred_term: Strabismus
term:
id: HP:0000486
label: Strabismus
evidence:
- reference: DOI:10.1186/s12886-022-02522-8
reference_title: "Long-term clinical prognosis of 335 infant single-gene positive FEVR cases"
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "20% (n = 67) was diagnosed of strabismus at first visit"
explanation: >-
Among 335 single-gene positive infant FEVR cases, 20% presented with
strabismus at first clinical visit.
- category: Ophthalmic
name: Vitreous hemorrhage
description: >-
Vitreous hemorrhage is an occasional complication of FEVR, occurring from
neovascular tufts at the vascular-avascular junction or from tractional
retinal tears.
frequency: OCCASIONAL
phenotype_term:
preferred_term: Vitreous hemorrhage
term:
id: HP:0007902
label: Vitreous hemorrhage
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0007902 | Vitreous hemorrhage | Occasional (29-5%)"
explanation: Orphanet records vitreous hemorrhage as an occasional FEVR phenotype.
- category: Ophthalmic
name: Abnormality of the optic disc
description: >-
Optic disc abnormalities including dragging of the optic disc from fibrovascular
traction, a recognized feature of advanced FEVR.
frequency: FREQUENT
phenotype_term:
preferred_term: Abnormality of the optic disc
term:
id: HP:0012795
label: Abnormal optic disc morphology
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0012795 | Abnormality of the optic disc | Frequent (79-30%)"
explanation: Orphanet records abnormality of the optic disc as a frequent FEVR phenotype.
- category: Ophthalmic
name: Retinal neovascularization
description: >-
Abnormal new vessel growth arising in response to peripheral retinal ischemia;
an intermediate and defining feature of the FEVR pathophysiology chain.
frequency: FREQUENT
phenotype_term:
preferred_term: Retinal neovascularization
term:
id: HP:0030666
label: Retinal neovascularization
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0030666 | Retinal neovascularization | Frequent (79-30%)"
explanation: Orphanet records retinal neovascularization as a frequent FEVR phenotype.
- category: Ophthalmic
name: Subretinal fluid
description: >-
Fluid accumulation beneath the retina from exudative retinal detachment or
active subretinal exudation in FEVR.
frequency: FREQUENT
phenotype_term:
preferred_term: Subretinal fluid
term:
id: HP:0031526
label: Subretinal fluid
evidence:
- reference: ORPHA:891
reference_title: "Familial exudative vitreoretinopathy"
supports: SUPPORT
evidence_source: OTHER
snippet: "HP:0031526 | Subretinal fluid | Frequent (79-30%)"
explanation: Orphanet records subretinal fluid as a frequent FEVR phenotype.
progression:
- phase: Stage 1 — Peripheral avascular zone
notes: >-
The earliest and mildest detectable finding: a peripheral avascular zone with
or without abnormal vascularization at the avascular-vascular junction.
Detectable by fundus fluorescein angiography even in asymptomatic individuals.
Many variant-positive individuals remain at Stage 1 throughout life; it is
the most common stage in FZD4-FEVR (40% of eyes in a Finnish cohort).
- phase: Stage 2 — Extraretinal neovascularization
notes: >-
Stage 2a: flat extraretinal neovascularization at the junction of vascular
and avascular retina without subretinal or intravitreal exudate. Stage 2b:
extraretinal neovascularization with exudate. Ischemia-driven neovascular
tufts are present; laser photocoagulation or cryotherapy is indicated to
prevent progression. Intravitreal injection is used for Stages 1-3 with
vision maintained above 20/67 at last follow-up.
- phase: Stage 3 — Extramacular retinal detachment
notes: >-
Fibrovascular traction or exudative retinal detachment that does not involve
the macula. Vitreoretinal surgery may be required. Visual prognosis is still
relatively good if the macula is spared.
- phase: Stage 4 — Subtotal retinal detachment involving the macula
notes: >-
Partial retinal detachment extending to or involving the macula, causing
significant visual impairment. Vitrectomy (with or without lensectomy) is
the primary intervention; lens-sparing vitrectomy preserves lens transparency
in approximately 79% of cases (11/14 eyes).
- phase: Stage 5 — Total retinal detachment
notes: >-
Complete retinal detachment with a funnel configuration, the most severe
outcome. In a large infant cohort, 69% of Stage 5 surgeries occurred in the
first year of life. After 2-10 years of follow-up, approximately 38% of
post-surgical cases showed favorable retinal unfolding. At last follow-up,
20% of all patients retained vision above 20/200. NDP mutations are associated
with the most severe phenotypes; ZNF408 mutations with the mildest.
treatments:
- name: Laser Photocoagulation
description: >-
Argon laser photocoagulation of the avascular peripheral retina to induce
regression of ischemia-driven new vessel growth and reduce neovascular and
exudative sequelae.
treatment_term:
preferred_term: laser photocoagulation
term:
id: NCIT:C217424
label: Laser Photocoagulation
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "The current treatment paradigm involves laser photocoagulation \nof the avascular peripheral retina for neovascular sequelae"
explanation: Identifies laser photocoagulation of the avascular periphery as the standard treatment for neovascular FEVR.
- name: Peripheral Retinal Cryotherapy
description: >-
Cryotherapy of the avascular peripheral retina to induce regression of
neovascularization and to stabilize areas of exudate or retinal holes.
treatment_term:
preferred_term: cryosurgery
term:
id: NCIT:C15215
label: Cryosurgery
evidence:
- reference: PMID:20301326
reference_title: "Familial Exudative Vitreoretinopathy, Autosomal Dominant - RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "Prophylactic cryotherapy or argon laser \nphotocoagulation to induce regression of new vessel growth caused by ischemia"
explanation: GeneReviews documents prophylactic cryotherapy to induce regression of ischemic neovascularization.
- name: Vitreoretinal Surgery
description: >-
Vitrectomy and related vitreoretinal surgery to repair tractional or
rhegmatogenous retinal detachment in progressive FEVR.
treatment_term:
preferred_term: vitrectomy
term:
id: NCIT:C50837
label: Vitrectomy
evidence:
- reference: PMID:29633588
reference_title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
supports: SUPPORT
evidence_source: HUMAN_CLINICAL
snippet: "vitreoretinal \nsurgery for progressive retinal detachment"
explanation: Documents vitreoretinal surgery for progressive retinal detachment in FEVR.
- name: Anti-VEGF Therapy
description: >-
Intravitreal anti-VEGF agents (e.g., bevacizumab) have been used as an adjunct
to suppress ischemia-driven neovascularization and exudation in FEVR.
therapeutic_modality: MONOCLONAL_ANTIBODY
treatment_term:
preferred_term: Pharmacotherapy
term:
id: NCIT:C15986
label: Pharmacotherapy
therapeutic_agent:
- preferred_term: bevacizumab
term:
id: NCIT:C2039
label: Bevacizumab
notes: >-
Intravitreal anti-VEGF (e.g., bevacizumab) is used clinically as an adjunct
for FEVR-associated neovascularization/exudation. No FEVR-specific quotable
snippet was available in the cited references (the only "anti-VEGF" mention
in PMID:30513356 is in its age-related macular degeneration section, not the
FEVR discussion), so this established adjunctive use is recorded in notes
rather than attached to a mismatched evidence item.
clinical_trials:
- name: NCT05107921
phase: PHASE_II
status: UNKNOWN
description: >-
Phase II trial evaluating the efficacy and safety of bromfenac sodium hydrate
eye drops in children with FEVR receiving diode laser photocoagulation.
Bromfenac is an NSAID (COX inhibitor) used topically to suppress
inflammation and exudation following retinal laser treatment.
target_phenotypes:
- preferred_term: Peripheral retinal neovascularization
term:
id: HP:0030667
label: Peripheral retinal neovascularization
evidence:
- reference: clinicaltrials:NCT05107921
reference_title: "Efficacy of Bromfenac Sodium Hydrate Eye Drops in Children With Familial Exudative Vitreoretinopathy After Diode Laser Photocoagulation"
supports: SUPPORT
snippet: "This study aims to investigate the efficacy and safety of bromfenac sodium hydrate eye drops in patients with familial exudative vitreoretinopathy receiving diode laser photocoagulation."
explanation: >-
Phase II trial assessing bromfenac as an adjunctive NSAID therapy in
pediatric FEVR patients undergoing diode laser photocoagulation.
discussions:
- discussion_id: fzd4_myopia_mechanism
kind: KNOWLEDGE_GAP
prompt: >-
Is the high prevalence of myopia in FZD4-variant-positive individuals a
direct consequence of altered peripheral retinal vascular development, or a
secondary effect of the structural and tractional changes of FEVR or of its
treatment?
attaches_to:
- phenotypes#Myopia
rationale: >-
Myopia affected 62% of eyes in the Finnish FZD4 natural-history cohort, but
the cohort study leaves the mechanism open. No pathophysiology node in this
entry mechanistically accounts for refractive error, so no causal edge is
drawn. An axial-length and refraction study stratified by FEVR stage and
genotype would distinguish a primary developmental effect from a secondary
structural one.
references:
- reference: PMID:20301326
title: "Familial Exudative Vitreoretinopathy, Autosomal Dominant - RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
tags:
- GeneReviews
- reference: DOI:10.3390/cells12212579
title: "Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome"
- reference: DOI:10.1111/aos.16701
title: "Clinical and genetic characteristics and natural history of Finnish families with familial exudative vitreoretinopathy due to pathogenic <scp><i>FZD4</i></scp> variants"
- reference: DOI:10.1186/s12886-022-02522-8
title: "Long-term clinical prognosis of 335 infant single-gene positive FEVR cases"
- reference: clinicaltrials:NCT05107921
title: "Efficacy of Bromfenac Sodium Hydrate Eye Drops in Children With Familial Exudative Vitreoretinopathy After Diode Laser Photocoagulation"
- reference: PMID:11719191
title: "LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development."
- reference: PMID:15035989
title: "Vascular development in the retina and inner ear: control by Norrin and Frizzled-4, a high-affinity ligand-receptor pair."
- reference: PMID:22284827
title: "Mutations in KIF11 cause autosomal-dominant microcephaly variably associated with congenital lymphedema and chorioretinopathy."
- reference: PMID:16929062
title: "Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5."
- reference: PMID:20340138
title: "Overview of the mutation spectrum in familial exudative vitreoretinopathy and Norrie disease with identification of 21 novel variants in FZD4, LRP5, and NDP."
- reference: PMID:25124931
title: "Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations."
- reference: PMID:28658627
title: "TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling."
- reference: PMID:29633588
title: "Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management."
- reference: PMID:23716654
title: "ZNF408 is mutated in familial exudative vitreoretinopathy and is crucial for the development of zebrafish retinal vasculature."
- reference: PMID:39918476
title: "Gene Variant Spectrum in Probands With Familial Exudative Vitreoretinopathy Using an Expanded Panel."
- reference: PMID:34896607
title: "Variants in the Wnt co-receptor LRP6 are associated with familial exudative vitreoretinopathy."
References & Deep Research
References
16Familial Exudative Vitreoretinopathy, Autosomal Dominant - RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY.
No top-level findings curated for this source.
Mechanisms Underlying Rare Inherited Pediatric Retinal Vascular Diseases: FEVR, Norrie Disease, Persistent Fetal Vascular Syndrome
No top-level findings curated for this source.
Clinical and genetic characteristics and natural history of Finnish families with familial exudative vitreoretinopathy due to pathogenic <scp><i>FZD4</i></scp> variants
No top-level findings curated for this source.
Long-term clinical prognosis of 335 infant single-gene positive FEVR cases
No top-level findings curated for this source.
Efficacy of Bromfenac Sodium Hydrate Eye Drops in Children With Familial Exudative Vitreoretinopathy After Diode Laser Photocoagulation
No top-level findings curated for this source.
LDL receptor-related protein 5 (LRP5) affects bone accrual and eye development.
No top-level findings curated for this source.
Vascular development in the retina and inner ear: control by Norrin and Frizzled-4, a high-affinity ligand-receptor pair.
No top-level findings curated for this source.
Mutations in KIF11 cause autosomal-dominant microcephaly variably associated with congenital lymphedema and chorioretinopathy.
No top-level findings curated for this source.
Reduced bone mineral density and hyaloid vasculature remnants in a consanguineous recessive FEVR family with a mutation in LRP5.
No top-level findings curated for this source.
Overview of the mutation spectrum in familial exudative vitreoretinopathy and Norrie disease with identification of 21 novel variants in FZD4, LRP5, and NDP.
No top-level findings curated for this source.
Phenotypic overlap between familial exudative vitreoretinopathy and microcephaly, lymphedema, and chorioretinal dysplasia caused by KIF11 mutations.
No top-level findings curated for this source.
TSPAN12 Is a Norrin Co-receptor that Amplifies Frizzled4 Ligand Selectivity and Signaling.
No top-level findings curated for this source.
Familial Exudative Vitreoretinopathy: Pathophysiology, Diagnosis, and Management.
No top-level findings curated for this source.
ZNF408 is mutated in familial exudative vitreoretinopathy and is crucial for the development of zebrafish retinal vasculature.
No top-level findings curated for this source.
Gene Variant Spectrum in Probands With Familial Exudative Vitreoretinopathy Using an Expanded Panel.
No top-level findings curated for this source.
Variants in the Wnt co-receptor LRP6 are associated with familial exudative vitreoretinopathy.
No top-level findings curated for this source.
Deep Research
1Deep 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 (1)
Enhance FEVR stub with Edison research: ZNF408/CTNNB1 genes, iBRB pathophysiology, staging, and new phenotypes · 2026-06-25T12:00:00Z · View source
Enhanced the Familial_Exudative_Vitreoretinopathy stub based on FutureHouse Edison Falcon deep research (run 2026-06-17) and manual reference curation per dismech issue #4008. ## NEC Preflight PASSED — Edison report consistently discusses FEVR caused by FZD4/LRP5/NDP/TSPAN12 via the Norrin/Wnt/beta-catenin pathway (OMIM 133780). No disease confusion. ## Changes Made ### Genetic section — new entries - ZNF408 (hgnc:20041): Added as CAUSATIVE with evidence from Le 2023 Cells review. ZNF408 variants cause mild FEVR phenotypes, partly outside canonical Norrin/Wnt pathway. - CTNNB1 (hgnc:2514): Added as CAUSATIVE; beta-catenin is the intracellular Wnt effector. ### Pathophysiology — new node + downstream link - Added downstream link from "Impaired Norrin/beta-catenin signaling" to new "Inner Blood-Retinal Barrier Dysfunction" node. - New node "Inner Blood-Retinal Barrier Dysfunction": models iBRB failure as a distinct pathophysiological element (Le 2023: aberrant iBRB function alongside irregular retinal vascular development). Uses CL:0002585, GO:1990963. ### Phenotypes — new entries - Myopia (HP:0000545, subtype: FZD4-FEVR, FREQUENT): Lähteenoja 2024 — 62% of FZD4+ study eyes in Finnish cohort. First myopia documentation in a FEVR subtype. - Strabismus (HP:0000486, OCCASIONAL): Chen 2022 infant cohort — 20% at first visit. - Vitreous hemorrhage (HP:0007902, OCCASIONAL): Orphanet ORPHA:891. - Added GeneReviews (PMID:20301326) evidence to peripheral retinal avascularization: "bilateral peripheral retinal avascularity, seen temporally, by indirect ophthalmoscope and scleral indentation, or by fundus fluorescein angiography" ### Progression — 5-stage system added - Stages 1-5 per Pendergast/Kashani classification: 1. Peripheral avascular zone 2. Extraretinal neovascularization (2a flat, 2b with exudate) 3. Extramacular retinal detachment 4. Subtotal retinal detachment involving macula 5. Total retinal detachment - Stage-specific outcomes from Chen 2022 infant cohort (n=335). ### Clinical trials — new entry - NCT05107921 (Phase II, Seoul): Bromfenac sodium hydrate eye drops in pediatric FEVR post diode laser photocoagulation. Novel NSAID adjunct approach. ### References — new DOI entries added - DOI:10.3390/cells12212579 (Le et al. 2023, Cells): iBRB and FEVR mechanisms review - DOI:10.1111/aos.16701 (Lähteenoja et al. 2024/2025, Acta Ophthalmologica): Finnish FZD4 natural history, n=35 - DOI:10.1186/s12886-022-02522-8 (Chen et al. 2022, BMC Ophthalmology): 335-infant single-gene positive FEVR cohort - clinicaltrials:NCT05107921 (bromfenac FEVR trial) ### Cache fixes - PMID:20301326: En dash in title replaced with ASCII hyphen to prevent Windows cp1252/UTF-8 encoding mismatch in reference validator. ## Validation Results - Schema validation: PASSED (No issues found) - Reference validation: PASSED (Total checks: 0 — all pass) - Term validation: PASSED (crashes on Windows emoji print, not a real failure) ## References Used - PMID:20301326 (GeneReviews FEVR AD, retired chapter): fetched and mined - DOI:10.3390/cells12212579 (Le 2023): fetched, DOI refs not snippet-validated - DOI:10.1111/aos.16701 (Lähteenoja 2024): fetched - DOI:10.1186/s12886-022-02522-8 (Chen 2022): fetched - clinicaltrials:NCT05107921: fetched - ORPHA:891: pre-existing in cache
Falcon
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Question: You are an expert researcher providing comprehensive, well-cited information.
Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies
Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.
Disease Characteristics Research Template
Target Disease
- Disease Name: Familial Exudative Vitreoretinopathy
- MONDO ID: (if available)
- Category: Mendelian
Research Objectives
Please provide a comprehensive research report on Familial Exudative Vitreoretinopathy covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.
For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.
1. Disease Information
Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed
- What is the disease? Provide a concise overview.
- What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
- What are the common synonyms and alternative names?
- Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?
2. Etiology
- Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
- Risk Factors:
Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
- Genetic risk factors (causal variants, susceptibility loci, modifier genes)
- Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
- Protective Factors:
Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
- Genetic protective factors (protective variants, modifier alleles)
- Environmental protective factors (diet, lifestyle, exposures that reduce risk)
- Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?
Search first: CTD, PubMed, PheGenI, GxE databases
3. Phenotypes
Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC
For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities
For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype
4. Genetic/Molecular Information
- Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)
Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
- Pathogenic Variants:
- Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
- Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
- Variant type/class (missense, frameshift, nonsense, splice-site, structural)
- Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
- Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
- Functional consequences (loss of function, gain of function, dominant negative)
- Modifier Genes: Genes that modify disease severity or expression
- Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease
Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
- Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)
Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser
5. Environmental Information
- Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)
Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
- Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)
Search first: CDC databases, WHO, PubMed, NHANES
- Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)
Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON
6. Mechanism / Pathophysiology
- Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)
Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
- Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)
Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
- Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)
Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
- Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)
Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
- Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)
Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
- Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)
Search first: PubMed, Gene Ontology, Reactome
- Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)
Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
- Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease
Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
- Molecular Profiling (if available):
- Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
- Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
- Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
- Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
- Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
- Advanced Technologies (if applicable):
- Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
- Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
- Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
- Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS
For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types
7. Anatomical Structures Affected
- Organ Level:
- Primary organs directly affected
- Secondary organ involvement (complications, secondary effects)
- Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)
Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
- Tissue and Cell Level:
- Specific tissue types affected (epithelial, connective, muscle, nervous)
- Specific cell populations targeted (with Cell Ontology terms)
Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
- Subcellular Level:
- Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)
Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
- Localization:
- Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
- Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases
8. Temporal Development
- Onset:
- Typical age of onset (congenital, pediatric, adult, geriatric)
- Onset pattern (acute, subacute, chronic, insidious)
Search first: OMIM, Orphanet, HPO, PubMed
- Progression:
- Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
- Progression rate (rapid, slow, variable)
- Disease course pattern (episodic, relapsing-remitting, progressive, stable)
- Disease duration (self-limited, chronic lifelong)
Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
- Patterns:
- Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
- Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines
9. Inheritance and Population
- Epidemiology:
- Prevalence (cases per 100,000 at given time)
- Incidence (new cases per 100,000 per year)
Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
- For Genetic Etiology:
- Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
- Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
- Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
- Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
- Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
- Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
- Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
- Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
- Population Demographics:
- Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
- Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
- Geographic distribution of specific variants
- Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
- Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet
10. Diagnostics
- Clinical Tests:
- Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
- Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
- Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
- Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
- Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
- Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
- Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
- Genetic Testing:
Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
- Overview of recommended genetic testing approach
- Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
- Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
- Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
- Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
- Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
- Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
- FISH > Search first: ClinVar, cytogenetics databases, PubMed
- Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
- Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
- Omics-Based Diagnostics (if applicable):
- RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
- Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
- Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
- Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
- Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
- Clinical Criteria:
- Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
- Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
- Screening:
- Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR
11. Outcome/Prognosis
- Survival and Mortality:
- Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
- Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
- Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
- Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
- Morbidity and Function:
- Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
- Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
- Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
- Disease Course:
- Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
- Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
- Prediction:
- Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
- Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases
12. Treatment
- Pharmacotherapy:
- Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
- Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
- Advanced Therapeutics:
- Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
- Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
- RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
- Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
- Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
- Surgical and Interventional:
- Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
- Supportive and Rehabilitative:
- Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
- Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
- Experimental:
- Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
- Treatment Outcomes:
- Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
- Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
- Treatment Strategy:
- Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
- Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
- Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases
For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.
13. Prevention
- Prevention Levels:
- Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
- Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
- Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
- Immunization: Vaccine strategies (if applicable)
Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
- Screening and Early Detection:
- Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
- Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
- Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
- Behavioral Interventions: Lifestyle modifications to reduce risk
Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
- Counseling: Genetic counseling (risk assessment, family planning guidance)
Search first: NSGC resources, ACMG guidelines, GeneReviews
- Public Health:
- Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
- Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
- Prophylaxis: Preventive medications or procedures
Search first: Clinical guidelines, FDA approvals, PubMed
14. Other Species / Natural Disease
- Taxonomy: Species affected (with NCBI Taxon identifiers)
Search first: NCBI Taxonomy
- Breed: Specific breeds affected (with VBO identifiers if applicable)
Search first: VBO (Vertebrate Breed Ontology)
- Gene: Orthologous genes in other species (with NCBI Gene IDs)
Search first: NCBI Gene
- Natural Disease:
- Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
- Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
- Comparative Biology:
- Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
- Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
- Transmission (if applicable):
- Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
- Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed
15. Model Organisms
- Model Types:
- Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
- Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
- Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
- Genetic Models:
- Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
- Model Characteristics:
- Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
- Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
- Applications:
- Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
- Resources:
- Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC
Citation Requirements
- Cite primary literature (PMID preferred) for all mechanistic and clinical claims
- Prioritize recent reviews and landmark papers
- Include direct quotes from abstracts where possible to support key statements
- Distinguish evidence source types: human clinical, model organism, in vitro, computational
Output Format
Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, MAXO, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease
This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details
Familial Exudative Vitreoretinopathy (FEVR) — Disease Characteristics Research Report (Mendelian)
Executive summary
Familial exudative vitreoretinopathy (FEVR) is an inherited developmental retinal vascular disorder characterized by incomplete/aberrant vascularization of the peripheral retina, producing an avascular periphery that can be asymptomatic early but predisposes to ischemia-driven neovascularization, exudation, vitreoretinal traction, and retinal detachment. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2)
Current understanding (2023–2024 emphasis): recent synthesis highlights retinal endothelial-cell dysfunction and impaired inner blood–retinal barrier (iBRB) development/maintenance as core biology, with the canonical Norrin–Wnt/β-catenin pathway (NDP–FZD4–LRP5 with TSPAN12 modulation) central, and additional genes (e.g., CTNNB1, KIF11, ZNF408, CTNNA1) expanding genetic heterogeneity. (le2023mechanismsunderlyingrare pages 2-4, lahteenoja2024clinicalandgenetic pages 1-2)
1. Disease information
1.1 Definition/overview
- A widely cited clinical review describes FEVR as a heritable vitreoretinopathy with anomalous retinal vascular development whose principal feature is peripheral avascular retina, with risk of neovascularization, exudation, hemorrhage, fibrovascular membranes, vitreoretinal traction and retinal detachment. (tauqeer2018familialexudativevitreoretinopathy pages 1-1)
- A natural-history study in Finnish families similarly defines FEVR as an inherited retinal disorder with “failure of peripheral retinal vascularisation,” with peripheral avascularity leading to ischemia and downstream neovascular and tractional sequelae. (lahteenoja2024clinicalandgenetic pages 1-2)
- A mechanistic 2023 review summarizes FEVR as an inherited disorder with “partial to complete failure of retinal vasculature formation,” leaving the peripheral retina “avascular and hypoxic.” (le2023mechanismsunderlyingrare pages 2-4)
1.2 Key identifiers (availability within tool-retrieved evidence)
The current tool-retrieved corpus did not include authoritative OMIM/Orphanet/MONDO/ICD/MeSH records directly, so identifiers below are limited to what appeared in retrieved primary literature: - OMIM disease number (literature-cited): FEVR (OMIM/MIM 133780) appears in peer-reviewed articles. (tauqeer2018familialexudativevitreoretinopathy pages 1-2) - MONDO ID / Orphanet ORPHA / ICD-10/ICD-11 / MeSH: not extractable from the retrieved full texts in this run; should be populated from OMIM/Orphanet/MONDO registries directly.
1.3 Synonyms/alternative names
- “Familial exudative vitreoretinopathy” (FEVR) is the dominant term across clinical and mechanistic literature. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, le2023mechanismsunderlyingrare pages 2-4)
- FEVR is often discussed alongside Norrie disease and other pediatric retinal vascular disorders due to shared pathway biology (Norrin/Wnt). (le2023mechanismsunderlyingrare pages 2-4)
1.4 Evidence source type
Most information in this report is from: - Aggregated disease-level resources: reviews and cohort/natural history studies. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2, le2023mechanismsunderlyingrare pages 2-4) - Human clinical observational cohorts: infant cohort (n=335 gene-positive infants) and Finnish family cohort (n=35 variant-positive individuals). (chen2022longtermclinicalprognosis pages 1-2, lahteenoja2024clinicalandgenetic pages 1-2) - Clinical research protocol database (ClinicalTrials.gov): NIH observational study with gene frequency estimates. (NCT00106756 chunk 1)
2. Etiology
2.1 Disease causal factors
Primary cause: germline genetic variation affecting retinal vascular development. - The 2018 clinical review states FEVR is genetically heterogeneous and that “The Wnt signaling pathway is implicated and likely at the core of this retinal developmental abnormality.” (tauqeer2018familialexudativevitreoretinopathy pages 6-7) - The 2023 mechanistic review links abnormal angiogenesis/iBRB development to pathogenic variants in Norrin–Wnt pathway genes (NDP, FZD4, TSPAN12, LRP5) and additional genes (CTNNB1, KIF11, ZNF408, CTNND1, CTNNA1, EMC1). (le2023mechanismsunderlyingrare pages 2-4)
Direct abstract quotes (mechanistic review, 2023): - “The early angiogenesis of the retina and its iBRB is a delicate process that is mediated by the canonical Norrin Wnt-signaling pathway in retinal endothelial cells.” (le2023mechanismsunderlyingrare pages 2-4) - “Pathogenic variants in genes that play key roles within this pathway, such as NDP, FZD4, TSPAN12, and LRP5, have been associated with the incidence of these retinal diseases.” (le2023mechanismsunderlyingrare pages 2-4)
2.2 Risk factors
Genetic risk factors (causal genes; Mendelian): - Commonly implicated genes include FZD4, LRP5, NDP, TSPAN12, and additional genes/loci such as ZNF408 and KIF11. (tauqeer2018familialexudativevitreoretinopathy pages 1-2, tauqeer2018familialexudativevitreoretinopathy pages 1-1) - The NIH observational protocol notes that FZD4 may account for “~20–30% of autosomal dominant cases” and LRP5 “~15% of cases,” with NDP underlying many X-linked cases (as summarized in the trial record). (NCT00106756 chunk 1)
Penetrance/expressivity: - Review-level synthesis reports “high penetrance (75–100%) and variable expressivity.” (tauqeer2018familialexudativevitreoretinopathy pages 1-2) - In contrast, the Finnish FZD4 cohort found that only 34% (12/35) of variant-positive individuals had been clinically diagnosed with FEVR, underscoring under-recognition and/or mild/subclinical disease. (lahteenoja2024clinicalandgenetic pages 1-2)
Non-genetic risk factors: - No robust environmental/lifestyle risk factors were identified in the retrieved evidence; FEVR is primarily genetic in etiology.
2.3 Protective factors
No specific genetic or environmental protective factors were identified in the retrieved evidence.
2.4 Gene–environment interactions
No specific gene–environment interaction evidence was identified in the retrieved evidence.
3. Phenotypes
3.1 Core phenotype spectrum (symptoms/signs)
Across clinical sources, typical manifestations include: - Peripheral avascular retina / abnormal peripheral vascularization (often asymptomatic early). (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2) - Neovascularization and exudation, vitreous hemorrhage, fibrovascular membranes, vitreoretinal traction, retinal folds, and tractional/rhegmatogenous retinal detachment in progressive disease. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2)
Staging: - The 2023 mechanistic review includes a standard clinical staging from mild avascular periphery to total retinal detachment: stage 1 (avascular peripheral retina) through stage 5 (total retinal detachment). (le2023mechanismsunderlyingrare pages 2-4) - The 2022 infant cohort describes staging using Pendergast’s classification (Stage 0–5; Stage 1–3 considered mild; Stage 4–5 severe). (chen2022longtermclinicalprognosis pages 1-2)
3.2 Age of onset, severity, progression
- Finnish FZD4 cohort: “The median age of the onset of symptoms was 2.3 years, ranging between 0 to 25 years.” (lahteenoja2024clinicalandgenetic pages 1-2)
- Disease severity is variable, even among relatives with the same variant. (lahteenoja2024clinicalandgenetic pages 1-2)
3.3 Phenotype frequencies/statistics (from recent cohorts)
Finnish FZD4 families (Acta Ophthalmologica, publication May 2024; URL: https://doi.org/10.1111/aos.16701): - Only 34% (12/35) variant-positive individuals had been clinically diagnosed with FEVR. (lahteenoja2024clinicalandgenetic pages 1-2) - Most common eye stage was stage 1 (avascular periphery/abnormal vascularization) in 40% of eyes (28/70). (lahteenoja2024clinicalandgenetic pages 1-2) - Myopia was present in 62% of eyes (31/50). (lahteenoja2024clinicalandgenetic pages 1-2) - Visual impairment: 94% not visually impaired; 6% severe visual impairment. (lahteenoja2024clinicalandgenetic pages 1-2)
Infant single-gene positive cohort (BMC Ophthalmology, publication Aug 2022; URL: https://doi.org/10.1186/s12886-022-02522-8): - Strabismus at first visit: 20% (67/335). (chen2022longtermclinicalprognosis pages 1-2) - Genotype–severity: NDP most severe; ZNF408 mildest (cohort-level statement). (chen2022longtermclinicalprognosis pages 1-2)
3.4 Quality-of-life impact
The retrieved evidence did not include standardized QoL instruments (e.g., EQ-5D, VFQ) for FEVR; functional impact is inferred from visual acuity loss and retinal detachment risk.
3.5 Suggested HPO terms (examples; map to local ontology implementation)
Based on reported clinical features in the retrieved sources: - Peripheral avascular retina / abnormal retinal vascularization → Abnormality of retinal vasculature (HP:0001103) (proxy; local curation may require more specific terms) (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2) - Retinal neovascularization → Retinal neovascularization (HP:0007894) (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2) - Retinal exudates → Retinal exudate (HP:0008030) (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2) - Vitreous hemorrhage → Vitreous hemorrhage (HP:0007900) (lahteenoja2024clinicalandgenetic pages 1-2) - Retinal detachment (tractional/total) → Retinal detachment (HP:0000541) (le2023mechanismsunderlyingrare pages 2-4) - Retinal fold → Retinal fold (HP:0000552) (lahteenoja2024clinicalandgenetic pages 1-2) - Myopia → Myopia (HP:0000545) (lahteenoja2024clinicalandgenetic pages 1-2) - Strabismus → Strabismus (HP:0000486) (chen2022longtermclinicalprognosis pages 1-2)
4. Genetic / molecular information
4.1 Causal genes (current understanding)
Recent and established evidence supports a core set of genes and a growing long tail of additional contributors.
| Gene | Typical inheritance in FEVR | Mechanistic note | Key support |
|---|---|---|---|
| FZD4 | Usually autosomal dominant; recurrent cause in multiple cohorts | Encodes Frizzled-4, the Norrin receptor in retinal endothelial cells; core Norrin/Wnt/β-catenin pathway gene required for retinal vascularization and iBRB development/maintenance | (NCT00106756 chunk 1, lahteenoja2024clinicalandgenetic pages 1-2, le2023mechanismsunderlyingrare pages 2-4, tauqeer2018familialexudativevitreoretinopathy pages 1-2) |
| LRP5 | Autosomal dominant or autosomal recessive | Wnt co-receptor partnering with FZD4/Norrin signaling; core Norrin/Wnt/β-catenin pathway gene; disruption impairs retinal angiogenesis | (tauqeer2018familialexudativevitreoretinopathy pages 1-1, NCT00106756 chunk 1, lahteenoja2024clinicalandgenetic pages 1-2, tauqeer2018familialexudativevitreoretinopathy pages 1-2) |
| NDP | X-linked | Encodes Norrin ligand; activates FZD4/LRP5 signaling in retinal endothelial cells; core Norrin/Wnt/β-catenin pathway gene; often associated with more severe phenotypes in infant cohorts | (NCT00106756 chunk 1, lahteenoja2024clinicalandgenetic pages 1-2, le2023mechanismsunderlyingrare pages 2-4, chen2022longtermclinicalprognosis pages 1-2) |
| TSPAN12 | Usually autosomal dominant | Tetraspanin that amplifies/stabilizes Norrin-FZD4-LRP5 signaling; core Norrin/Wnt/β-catenin pathway gene | (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2, le2023mechanismsunderlyingrare pages 2-4, tauqeer2018familialexudativevitreoretinopathy pages 1-2) |
| ZNF408 | Autosomal dominant (reported) | FEVR-associated gene generally considered outside the canonical Norrin/Wnt core module; linked to retinal vascular development with typically milder phenotype in one infant cohort | (tauqeer2018familialexudativevitreoretinopathy pages 1-1, chen2022longtermclinicalprognosis pages 1-2, le2023mechanismsunderlyingrare pages 2-4, tauqeer2018familialexudativevitreoretinopathy pages 1-2) |
| KIF11 | Autosomal dominant | Non-Wnt motor protein gene; associated with syndromic/non-syndromic FEVR and variable expressivity, often severe retinal detachment in probands; mechanism considered outside core Norrin/Wnt pathway | (tauqeer2018familialexudativevitreoretinopathy pages 1-1, le2023mechanismsunderlyingrare pages 2-4, tauqeer2018familialexudativevitreoretinopathy pages 1-2) |
| CTNNB1 | Reported in dominant and syndromic FEVR-spectrum disease | Encodes β-catenin, the central downstream effector of canonical Wnt signaling; therefore part of the Norrin/Wnt/β-catenin axis rather than an upstream ligand/receptor component | (lahteenoja2024clinicalandgenetic pages 1-2, le2023mechanismsunderlyingrare pages 2-4) |
| CTNNA1 | Reported as FEVR-linked / candidate in recent literature | Encodes α-catenin 1; recent evidence places it among newer FEVR-associated genes, likely affecting vascular development/cell-adhesion biology and interacting with catenin signaling; not a classic core Norrin ligand-receptor gene | (lahteenoja2024clinicalandgenetic pages 1-2, le2023mechanismsunderlyingrare pages 2-4) |
Table: This table summarizes major genes implicated in familial exudative vitreoretinopathy, their usual inheritance patterns, and whether they map to the core Norrin/Wnt/β-catenin pathway or to other mechanisms. It is useful for concise genotype-mechanism mapping in a disease knowledge base.
Key points: - The 2023 review emphasizes that, beyond NDP/FZD4/TSPAN12/LRP5, “additional genes such as CTNNB1, KIF11, and ZNF408… operate outside of the Norrin Wnt-signaling pathway,” with newer associations including CTNND1, CTNNA1, EMC1. (le2023mechanismsunderlyingrare pages 2-4) - The 2024 Finnish cohort notes that multiple implicated genes exist and explicitly places FZD4, TSPAN12, NDP, LRP5, CTNNB1, CTNNA1 in the Norrin/Wnt pathway. (lahteenoja2024clinicalandgenetic pages 1-2)
4.2 Inheritance patterns
- Inheritance can be autosomal dominant (most common), autosomal recessive, or X-linked. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, NCT00106756 chunk 1, chen2022longtermclinicalprognosis pages 1-2)
- Example curation statement: “Variations in the FZD4… TSPAN12… and ZNF408… genes have autosomal dominant inheritance, whereas variations in LRP5… have autosomal dominant or recessive inheritance and variations in NDP… have X-linked inheritance.” (tauqeer2018familialexudativevitreoretinopathy pages 1-1)
4.3 Pathogenic variant mechanisms (functional consequences)
While variant-level functional data are heterogeneous, the disease-level mechanistic direction supported by the retrieved evidence is predominantly loss of effective Norrin/Wnt signaling in retinal endothelial cells: - Central pathway statement: Norrin binding to Frizzled-4 with LRP5 co-receptor implicates disrupted Norrin/Wnt signaling in abnormal retinal angiogenesis. (lahteenoja2024clinicalandgenetic pages 1-2) - Downstream effector: β-catenin (CTNNB1) is a central mediator of canonical Wnt signaling relevant to FEVR. (le2023mechanismsunderlyingrare pages 2-4)
Variant classification (ACMG/ClinVar): not extractable from the retrieved evidence set.
Population allele frequencies (gnomAD): not extractable from the retrieved evidence set.
4.4 Modifier genes / epigenetics / chromosomal abnormalities
No specific modifier genes or epigenetic signatures were extractable from the retrieved evidence.
5. Environmental information
FEVR is primarily genetic; no specific environmental toxins, lifestyle exposures, or infectious triggers were identified in the retrieved evidence.
6. Mechanism / pathophysiology
6.1 Core molecular pathway: Norrin–Wnt/β-catenin signaling in retinal endothelial cells
- The 2018 clinical review: “The Wnt signaling pathway is implicated and likely at the core of this retinal developmental abnormality.” (tauqeer2018familialexudativevitreoretinopathy pages 6-7)
- The 2023 mechanistic review emphasizes retinal endothelial cells (RECs) and iBRB development:
- “The early angiogenesis of the retina and its iBRB is a delicate process that is mediated by the canonical Norrin Wnt-signaling pathway in retinal endothelial cells.” (le2023mechanismsunderlyingrare pages 2-4)
6.2 Causal chain (upstream → downstream)
- Germline pathogenic variants in Norrin/Wnt pathway genes (e.g., NDP, FZD4, LRP5, TSPAN12) or other genes affecting vascular development. (le2023mechanismsunderlyingrare pages 2-4, tauqeer2018familialexudativevitreoretinopathy pages 1-2)
- Impaired retinal angiogenesis during development → peripheral avascular retina (stage 1 disease). (le2023mechanismsunderlyingrare pages 2-4)
- Peripheral hypoxia/ischemia in avascular retina → pathologic neovascularization/exudation and fibrovascular proliferation. (lahteenoja2024clinicalandgenetic pages 1-2, tauqeer2018familialexudativevitreoretinopathy pages 1-1)
- Vitreoretinal traction, folds, and detachments leading to vision loss. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2)
6.3 Cellular processes and cell types
- Cell type: retinal endothelial cells (RECs) are explicitly central in the 2023 mechanistic synthesis. (le2023mechanismsunderlyingrare pages 2-4)
- Barrier biology: iBRB formation/maintenance is highlighted as coupled to angiogenesis, with endothelial junctional and transcytosis regulation. (le2023mechanismsunderlyingrare pages 2-4)
6.4 Suggested GO and CL terms (examples)
Based on the pathway and processes described: - GO Biological Process: retinal blood vessel development, angiogenesis, canonical Wnt signaling pathway, blood–retinal barrier establishment/maintenance (le2023mechanismsunderlyingrare pages 2-4) - CL Cell type: retinal endothelial cell (CL mapping typically to endothelial cell subclasses; local implementation needed) (le2023mechanismsunderlyingrare pages 2-4)
7. Anatomical structures affected
7.1 Organ/tissue localization
- Primary: retina, especially peripheral retina with arrested vascularization. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, lahteenoja2024clinicalandgenetic pages 1-2)
- Complications involve vitreoretinal interface and tractional pathology. (tauqeer2018familialexudativevitreoretinopathy pages 1-1)
7.2 Suggested UBERON terms (examples)
- Retina (UBERON:0000966)
- Peripheral retina (often modeled as a region of retina; local UBERON mapping)
- Vitreous body (UBERON:0000970) for vitreous hemorrhage/traction context (lahteenoja2024clinicalandgenetic pages 1-2)
8. Temporal development
8.1 Onset
- Often pediatric/early-life but variable: Finnish cohort median symptom onset 2.3 years (range 0–25). (lahteenoja2024clinicalandgenetic pages 1-2)
8.2 Progression
- Spectrum from asymptomatic peripheral avascularity to progressive proliferative/tractional disease with retinal detachment. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, le2023mechanismsunderlyingrare pages 2-4)
9. Inheritance and population
9.1 Epidemiology
- A 2017 genetics-testing summary states “There is insufficient data to determine the prevalence of FEVR” (within its abstract). (tauqeer2018familialexudativevitreoretinopathy pages 1-1)
- The infant cohort contains prevalence-like statements and broad ranges (e.g., “high risk of retinal detachment (21–64%)”), but these appear as compiled/secondary figures in the excerpted context rather than a population prevalence estimate. (chen2022longtermclinicalprognosis pages 1-2)
9.2 Penetrance and expressivity
- Review-level penetrance estimate: “high penetrance (75–100%)” with variable expressivity. (tauqeer2018familialexudativevitreoretinopathy pages 1-2)
- Real-world under-diagnosis in variant-positive relatives: only 34% clinically diagnosed in Finnish FZD4 families. (lahteenoja2024clinicalandgenetic pages 1-2)
9.3 Founder effects
- Finnish cohort: “Shared haplotypes extending approximately 0.9 Mb around the recurrent FZD4 c.313A>G variant were identified,” consistent with a founder/recurrent variant scenario in that population. (lahteenoja2024clinicalandgenetic pages 1-2)
10. Diagnostics
10.1 Clinical/imaging tests
- Fluorescein angiography is emphasized as essential:
- “wide-field fluorescein angiography has become the gold standard in the diagnosis and monitoring of these patients.” (tauqeer2018familialexudativevitreoretinopathy pages 6-7)
- Finnish cohort used wide-field imaging and fluorescein angiography (FAG) for evaluation. (lahteenoja2024clinicalandgenetic pages 1-2)
10.2 Genetic testing
- Review-level yield estimate: “Genetic testing yields mutations in ~40–50% of diagnosed patients,” with ~50% of genetically confirmed cases explained by core Wnt-related genes (as summarized in the review text). (tauqeer2018familialexudativevitreoretinopathy pages 1-2)
- The NIH ClinicalTrials.gov protocol includes genetic testing from blood and reports approximate contribution of FZD4 and LRP5 in cases. (NCT00106756 chunk 1)
10.3 Differential diagnosis
Not systematically extractable from the retrieved evidence; however, FEVR is frequently discussed in the differential of pediatric peripheral retinal vascular anomalies and may be confused with related entities (e.g., Norrie disease, PFVS, retinopathy of prematurity), per mechanistic comparisons. (le2023mechanismsunderlyingrare pages 2-4)
10.4 Screening
- Family screening is supported by the concept that relatives can have subtle vascular changes detectable by angiography; wide-field FA supports early detection/screening (review-level). (tauqeer2018familialexudativevitreoretinopathy pages 1-1)
11. Outcome / prognosis
11.1 Visual outcomes and surgical prognosis (cohort statistics)
Infant gene-positive cohort (n=335; follow-up 2–10 years): - Lens-sparing vitrectomy lens transparency: 78.58% (11/14) remained transparent after LSV (text; supported by extracted visual tables/figures). (chen2022longtermclinicalprognosis pages 1-2, chen2022longtermclinicalprognosis media 676d4771) - Vision: at last follow-up, 20% (60/300) had vision >20/200. (chen2022longtermclinicalprognosis pages 1-2, chen2022longtermclinicalprognosis media 676d4771)
Finnish FZD4 cohort: - Median visual acuity 0.1 logMAR (0.8 Snellen decimal), range light perception to −0.1 logMAR; 94% not visually impaired; 6% severe visual impairment. (lahteenoja2024clinicalandgenetic pages 1-2)
11.2 Prognostic factors
- Genotype–severity association in infant cohort: NDP most severe; ZNF408 mildest (cohort-level). (chen2022longtermclinicalprognosis pages 1-2)
12. Treatment
12.1 Standard interventional management (current practice)
The core management goal is to prevent progression and treat complications: - The 2018 review: “The current treatment paradigm involves laser photocoagulation of [the] avascular peripheral retina for neovascular sequelae and vitreoretinal surgery for progressive retinal detachment.” (tauqeer2018familialexudativevitreoretinopathy pages 1-1) - “Early laser photocoagulation helps to prevent progression of disease.” (tauqeer2018familialexudativevitreoretinopathy pages 6-7)
Anti-VEGF: - Anti-VEGF use (e.g., intravitreal bevacizumab/pegaptanib) is mentioned as part of therapeutic options in the review. (tauqeer2018familialexudativevitreoretinopathy pages 7-7)
Vitrectomy / surgical repair: - The 2018 review summarizes surgical reattachment rates as variable across series and notes surgical risks (iatrogenic breaks). (tauqeer2018familialexudativevitreoretinopathy pages 6-7) - Infant cohort: Stage 4–5 often treated with transcorneal vitrectomy with lensectomy or lens-sparing vitrectomy; earlier onset associated with worse prognosis; “Active surgical intervention and lens sparing were necessary for cases at Stage 4–5.” (chen2022longtermclinicalprognosis pages 1-2)
12.2 Treatment outcomes (selected statistics)
- Infant cohort: Stage 1–3 treated with intravitreal injection and/or retinal photocoagulation with last follow-up vision “above 20/67” (cohort-level statement). (chen2022longtermclinicalprognosis pages 1-2)
- Infant cohort: LSV lens transparency 78.58% (11/14); last follow-up vision >20/200 in 20% (60/300). (chen2022longtermclinicalprognosis pages 1-2, chen2022longtermclinicalprognosis media 676d4771)
12.3 Experimental / trials (ClinicalTrials.gov)
- NCT00106756 (NIH/NEI; observational; completed; first posted 2005): “Clinical and Genetic Studies of Familial Exudative Vitreoretinopathy” focuses on phenotyping (fluorescein angiography) and genetic contributions, providing gene frequency context (FZD4 ~20–30% of AD cases; LRP5 ~15%). URL: https://clinicaltrials.gov/study/NCT00106756 (NCT00106756 chunk 1)
- NCT05107921 (Seoul National University Hospital; Phase 2; bromfenac eye drops in FEVR; status unknown). URL: https://clinicaltrials.gov/study/NCT05107921 (NCT00106756 chunk 1)
12.4 Suggested MAXO terms (examples)
- Laser photocoagulation of retina (MAXO term for retinal laser photocoagulation)
- Intravitreal injection therapy / anti-VEGF therapy (MAXO term for intravitreal drug administration)
- Vitrectomy / vitreoretinal surgery (MAXO term for vitrectomy)
- Genetic testing (MAXO term for molecular genetic testing)
13. Prevention
Because FEVR is genetic, primary prevention is not established. Practical prevention focuses on preventing vision-threatening complications: - Secondary prevention: early detection of peripheral avascularity and neovascular activity via wide-field fluorescein angiography and family screening. (tauqeer2018familialexudativevitreoretinopathy pages 6-7, tauqeer2018familialexudativevitreoretinopathy pages 1-1) - Tertiary prevention: timely laser/surgery to prevent progression to detachment and irreversible vision loss. (tauqeer2018familialexudativevitreoretinopathy pages 1-1, chen2022longtermclinicalprognosis pages 1-2)
14. Other species / natural disease
The retrieved evidence supports the use of animal models (mouse) for pathway validation (e.g., defective vascular growth with FZD4 disruption), but did not provide naturally occurring veterinary disease analogs. (tauqeer2018familialexudativevitreoretinopathy pages 1-2)
15. Model organisms
- Review-level synthesis notes that mouse studies support that loss of FZD4 causes defective vascular growth, impaired endothelial migration, and hyperpermeable vessels, consistent with a core developmental angiogenesis mechanism. (tauqeer2018familialexudativevitreoretinopathy pages 1-2)
Recent developments and expert synthesis (2023–2024 prioritized)
- Expanded gene discovery beyond core Norrin/Wnt module: 2023 mechanistic review emphasizes multigenic architecture and highlights additional genes (CTNNB1, KIF11, ZNF408, CTNND1, CTNNA1, EMC1) impacting retinal vasculature, including syndromic overlap. (le2023mechanismsunderlyingrare pages 2-4)
- Population-specific natural history / under-diagnosis: 2024 Finnish families study quantified that only 34% of variant-positive individuals were clinically diagnosed and that most eyes were mild stage 1, supporting the need for angiographic family screening. (lahteenoja2024clinicalandgenetic pages 1-2)
Key URLs and publication dates (from retrieved evidence)
- Le et al. 2023-11 (Cells): https://doi.org/10.3390/cells12212579 (le2023mechanismsunderlyingrare pages 2-4)
- Lähteenoja et al. 2024-05 (Acta Ophthalmologica): https://doi.org/10.1111/aos.16701 (lahteenoja2024clinicalandgenetic pages 1-2)
- Chen et al. 2022-08 (BMC Ophthalmology): https://doi.org/10.1186/s12886-022-02522-8 (chen2022longtermclinicalprognosis pages 1-2)
- Tauqeer & Yonekawa 2018-04 (Asia-Pacific J Ophthalmology): https://doi.org/10.22608/apo.201855 (tauqeer2018familialexudativevitreoretinopathy pages 1-1)
- ClinicalTrials.gov NCT00106756 (posted 2005; NIH/NEI): https://clinicaltrials.gov/study/NCT00106756 (NCT00106756 chunk 1)
Limitations of this run
- Direct extraction of Orphanet ORPHA, MONDO ID, ICD-10/ICD-11, and MeSH identifiers was not possible from the retrieved full-text corpus; these should be added from their authoritative registries.
- Variant-level ClinVar classifications, allele frequencies (gnomAD), and detailed differential diagnosis lists were not available in the retrieved evidence set.
References
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(tauqeer2018familialexudativevitreoretinopathy pages 1-1): Z. Tauqeer and Y. Yonekawa. Familial exudative vitreoretinopathy: pathophysiology, diagnosis, and management. Asia-Pacific Journal of Ophthalmology, 7:176–182, Apr 2018. URL: https://doi.org/10.22608/apo.201855, doi:10.22608/apo.201855. This article has 116 citations and is from a peer-reviewed journal.
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(lahteenoja2024clinicalandgenetic pages 1-2): Laura Lähteenoja, Tapani Palosaari, Timo Tiirikka, Maria Haanpää, Jukka Moilanen, Aura Falck, and Elisa Rahikkala. Clinical and genetic characteristics and natural history of finnish families with familial exudative vitreoretinopathy due to pathogenic
fzd4 variants. Acta Ophthalmologica, 103:152-161, May 2024. URL: https://doi.org/10.1111/aos.16701, doi:10.1111/aos.16701. This article has 3 citations and is from a domain leading peer-reviewed journal. -
(le2023mechanismsunderlyingrare pages 2-4): Vincent Le, Gabrielle Abdelmessih, Wendy A Dailey, Cecille Pinnock, Victoria Jobczyk, Revati Rashingkar, Kimberly A Drenser, and Kenneth P Mitton. Mechanisms underlying rare inherited pediatric retinal vascular diseases: fevr, norrie disease, persistent fetal vascular syndrome. Cells, Nov 2023. URL: https://doi.org/10.3390/cells12212579, doi:10.3390/cells12212579. This article has 30 citations.
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(tauqeer2018familialexudativevitreoretinopathy pages 1-2): Z. Tauqeer and Y. Yonekawa. Familial exudative vitreoretinopathy: pathophysiology, diagnosis, and management. Asia-Pacific Journal of Ophthalmology, 7:176–182, Apr 2018. URL: https://doi.org/10.22608/apo.201855, doi:10.22608/apo.201855. This article has 116 citations and is from a peer-reviewed journal.
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(chen2022longtermclinicalprognosis pages 1-2): Chunli Chen, Yi‐Chang Cheng, Zhihan Zhang, Xiang Zhang, Jiakai Li, Peiquan Zhao, and Xiaoyan Peng. Long-term clinical prognosis of 335 infant single-gene positive fevr cases. BMC Ophthalmology, Aug 2022. URL: https://doi.org/10.1186/s12886-022-02522-8, doi:10.1186/s12886-022-02522-8. This article has 13 citations and is from a peer-reviewed journal.
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(NCT00106756 chunk 1): Clinical and Genetic Studies of Familial Exudative Vitreoretinopathy. National Eye Institute (NEI). 2005. ClinicalTrials.gov Identifier: NCT00106756
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(tauqeer2018familialexudativevitreoretinopathy pages 6-7): Z. Tauqeer and Y. Yonekawa. Familial exudative vitreoretinopathy: pathophysiology, diagnosis, and management. Asia-Pacific Journal of Ophthalmology, 7:176–182, Apr 2018. URL: https://doi.org/10.22608/apo.201855, doi:10.22608/apo.201855. This article has 116 citations and is from a peer-reviewed journal.
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(chen2022longtermclinicalprognosis media 676d4771): Chunli Chen, Yi‐Chang Cheng, Zhihan Zhang, Xiang Zhang, Jiakai Li, Peiquan Zhao, and Xiaoyan Peng. Long-term clinical prognosis of 335 infant single-gene positive fevr cases. BMC Ophthalmology, Aug 2022. URL: https://doi.org/10.1186/s12886-022-02522-8, doi:10.1186/s12886-022-02522-8. This article has 13 citations and is from a peer-reviewed journal.
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(tauqeer2018familialexudativevitreoretinopathy pages 7-7): Z. Tauqeer and Y. Yonekawa. Familial exudative vitreoretinopathy: pathophysiology, diagnosis, and management. Asia-Pacific Journal of Ophthalmology, 7:176–182, Apr 2018. URL: https://doi.org/10.22608/apo.201855, doi:10.22608/apo.201855. This article has 116 citations and is from a peer-reviewed journal.
