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Mappings

MONDO

MONDO:0019354 Stickler syndrome Not Yet Curated

Orphanet cross-references its Stickler syndrome record to the broader MONDO grouping class. This entry curates the COL11A1-related type 2 subtype specifically (MONDO:0011493), so the mapping to the group term is broad.

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Definitions

1

Orphanet disease definition

Orphanet defines Stickler syndrome as a group of connective tissue disorders with ophthalmic, auditory, orofacial and articular manifestations. It has no separate record for type 2, so the quoted definition is the group's; the clause that separates the two main forms is the vitreous phenotype, evidenced below from the primary literature.

CASE_DEFINITION

Show evidence (2 references)

ORPHA:828 SUPPORT Other

"A rare group of genetic connective tissue disorders characterized by ophthalmic, auditory, orofacial and articular manifestations"

Orphanet's definition of the Stickler syndrome group, of which the COL11A1-related type 2 curated here is one of the two main clinical forms. Orphanet's sentence goes on to distinguish the forms by vitreous phenotype, but that clause carries a ligature character in the cached record and is not quotable as a clean substring, so the point is evidenced from PMID:20513134 below instead.

PMID:20513134 SUPPORT Human Clinical

"Mutations in COL2A1 usually result in a congenital membranous vitreous anomaly. In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance."

Supplies the type-2-defining half of the definition: the vitreous phenotype that separates COL11A1 from COL2A1 disease.

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Inheritance

1

Autosomal dominant HP:0000006

Classic STL2 segregates as an autosomal dominant trait, with a single heterozygous COL11A1 variant sufficient to produce the full syndrome including the vitreoretinal features. Expressivity is highly variable both within and among families; locus and allelic heterogeneity account for part of the interfamilial variability.

Autosomal dominant inheritance Expressivity: VARIABLE

Show evidence (3 references)

PMID:8872475 SUPPORT Human Clinical

"Stickler syndrome (hereditary arthro-ophthalmopathy) is the commonest inherited cause of retinal detachment and one of the commonest autosomal dominant connective tissue dysplasias"

The defining COL11A1 linkage study describes Stickler syndrome as an autosomal dominant connective tissue dysplasia.

PMID:20301479 SUPPORT Human Clinical

"Stickler syndrome caused by pathogenic variants in COL2A1, COL11A1, or COL11A2 is inherited in an autosomal dominant manner"

GeneReviews states the inheritance mode for the COL11A1-related form curated here.

PMID:20301479 SUPPORT Human Clinical

"Variable phenotypic expression of Stickler syndrome occurs both within and among families; interfamilial variability is in part explained by locus and allelic heterogeneity"

Supports the variable-expressivity statement recorded above.

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Discussions and Knowledge Gaps

1

Why do cho/+ mice, heterozygous for a Col11a1 functional null, develop the joint phenotype of COL11A1 disease but show no hearing loss at all, when human COL11A1 heterozygotes have frequent sensorineural hearing loss?

HUMAN MODEL MISMATCH OPEN cho_heterozygote_auditory_mismatch

Attached to

pathophysiology#Cochlear Extracellular Matrix Abnormality animal_models#cho/+ heterozygous Col11a1 mouse

The mismatch is mechanistically load-bearing rather than a modelling nuisance. The mouse heterozygote tests halved Col11a1 dosage; human STL2 alleles are missense and splice changes whose product still enters the heterotrimer. That the joint phenotype survives the switch to a null allele while the auditory phenotype does not is the study's argument that the human cochlear lesion needs dominant-negative mutant chains and is not a dosage effect. The cho/cho homozygote is not the exception it looks like: it does have marked ABR hearing loss and a disorganized organ of Corti, but that is a recessive, perinatally lethal genotype modelling the fibrochondrogenesis end of the COL11A1 spectrum rather than dominant STL2. So no current mouse model addresses the auditory arm of STL2 at the right gene dosage; a knock-in of a human triple-helical missense allele would be the test.

Show evidence (3 references)

PMID:12527136 SUPPORT Model Organism

"To determine if Col11a1 haploinsufficiency causes hearing loss in cho/+ mice, auditory brainstem response (ABR) thresholds were measured at 2, 4, 6, 8 and 10 months of age. There was no difference in ABR thresholds for click and tone burst stimuli between cho/+ and +/+ mice at all ages."

The negative auditory result in the heterozygous mouse that constitutes the mismatch.

PMID:12527136 SUPPORT Model Organism

"We conclude that Stickler syndrome and Marshall syndrome mutations in COL11A1 cause hearing loss via dominant negative effects upon wild-type fibrillar collagen polypeptides in the extracellular matrices of the cochlea"

The authors' resolution of the mismatch, and the reason it is mechanistically informative rather than merely a failed model.

PMID:1952599 SUPPORT Model Organism

"These mice show marked hearing loss when tested by auditory brain-stem responses. The temporal bone shows underdevelopment of the organs of Corti in the lower turn of the cochlea."

The homozygote does have a cochlear phenotype, so the mismatch is specific to the heterozygote and to gene dosage rather than to the mouse cochlea being insensitive to Col11a1 loss.

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Pathophysiology

9

COL11A1 Triple-Helical Domain Variant

A heterozygous COL11A1 variant - classically a glycine substitution within the Gly-X-Y repeat of the triple-helical domain, or a splice-site change causing in-frame skipping of a triple-helical exon - yields a structurally abnormal pro-alpha1(XI) chain. The chain is still competent to enter the type XI heterotrimer, which is what makes the lesion dominant negative rather than a simple loss of one allele's product.

Genetic context COL11A1 hgnc:2186 allele_type: SNV variant_origin: GERMLINE zygosity: HETEROZYGOUS functional_impact_category: DOMINANT_NEGATIVE

Heterozygous germline COL11A1 variants acting through incorporation of the mutant chain into the collagen XI heterotrimer.

Downstream

Impaired Type XI Collagen Regulation of Fibrillogenesis The mutant alpha1(XI) chain is incorporated into wild-type-containing fibrillar collagen assemblies and disrupts their function.

Show evidence (3 references)

PMID:8872475 SUPPORT Human Clinical

"characterise the mutation as a Glycine to Valine substitution at position 97 of the triple helical domain caused by a single base G-->T mutation"

The founding STL2 family carries a glycine substitution in the triple-helical domain of alpha1(XI), the variant class described by this node.

PMID:8872475 SUPPORT Human Clinical

"a family with the full Type 2 Stickler syndrome including vitreous and retinal abnormalities is linked to the COL11A1 gene"

Establishes COL11A1 as the locus for the full type 2 syndrome, vitreoretinal features included.

PMID:10486316 SUPPORT Human Clinical

"Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene"

Shows that where in COL11A1 the variant falls, and what kind it is, determines whether the phenotype reads as Marshall or as Stickler - the reason this node is specified by variant class and not by gene alone.

Impaired Type XI Collagen Regulation of Fibrillogenesis

Type XI collagen co-assembles with type II collagen and controls fibril nucleation, diameter and spacing. With a mutant alpha1(XI) chain in the heterotrimer, that control is lost and the resulting heterotypic fibrils are abnormally sized, sparse and disorganized wherever the type II/XI network is load-bearing.

collagen fibril organization GO:0030199 ↓ DECREASED extracellular matrix organization GO:0030198 ↓ DECREASED

Downstream

Beaded Vitreous Anomaly In the vitreous the same loss of fibril regulation presents as the beaded lamellar phenotype, which tracks the causal gene closely enough to be used clinically to predict it.

Disorganized Cartilage Collagen Matrix

Cochlear Extracellular Matrix Abnormality The cochlear extracellular matrices carry the same fibrillar collagen, and it is the mutant chains within them - not reduced dosage - that the mouse work implicates.

Middle Ear Collagen Abnormality A separate, smaller branch: the fibrous layer of the tympanic membrane is also collagenous, and abnormality there is hypermobility rather than cochlear dysfunction.

High myopia The refractive error of STL2 is congenital or early in onset and is attributed to the same structural collagen defect in the developing eye. Left uncited: no source found states the step from collagen XI dysregulation to axial elongation, as opposed to listing myopia among the syndrome's features.

Show evidence (3 references)

PMID:7859283 SUPPORT Model Organism

"The data demonstrate that collagen XI is essential for normal formation of cartilage collagen fibrils and the cohesive properties of cartilage"

The cho mouse establishes that collagen XI is required for normal fibril formation, the function lost at this node.

PMID:32950601 SUPPORT Model Organism

"Reducing Col11a1 and, therefore collagen XI content, resulted in abnormal fibril structure, loss of normal fibril diameter control with a significant shift to small diameters and disrupted parallel alignment of fibrils"

Directly demonstrates the loss of fibril-diameter control described by this node. Reported in tendon rather than vitreous or cartilage, so it supports the general regulatory role rather than the tissue-specific consequence.

PMID:8872475 SUPPORT Human Clinical

"Type XI collagen is a quantitatively minor fibrillar collagen related to type V collagen and associated with the more abundant type II collagen fibrils"

Supports the co-assembly of collagen XI with the abundant type II fibrils that this node's regulatory claim depends on.

Beaded Vitreous Anomaly

In the vitreous the disordered type II/XI network presents as sparse, irregularly thickened and beaded lamellae, in contrast to the membranous vitreous of COL2A1-related type 1 disease. This is the sign the diagnosis is made on at the slit lamp.

vitreous humor UBERON:0001797

Downstream

Vitreoretinal Traction and Retinal Tear The abnormal gel is the substrate on which peripheral tractional tears form.

Beaded vitreous appearance

Show evidence (2 references)

PMID:20513134 SUPPORT Human Clinical

"In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance"

States the beaded vitreous phenotype of COL11A1 disease and its contrast with the COL2A1 membranous phenotype.

PMID:10573014 SUPPORT Human Clinical

"These data confirm that mutations in COL11A1 cause Stickler syndrome with the type2 vitreous phenotype and also reveal further locus heterogeneity"

Independent linkage confirmation that COL11A1 variants produce the type 2 vitreous phenotype.

Vitreoretinal Traction and Retinal Tear

The abnormal vitreous gel retains adherence at the vitreous base while losing its normal internal architecture, so that ordinary vitreous movement or minor trauma transmits traction to the peripheral retina and produces giant retinal tears.

Downstream

Retinal detachment

Show evidence (3 references)

PMID:36583093 SUPPORT Human Clinical

"Both syndromic and non-syndromic eyes suffer RRD predominately from the same pathogenesis, vitreous tractional tears in the peripheral retina."

Names the mechanism this node describes - peripheral tractional tearing driven by the vitreous - rather than merely associating the syndrome with detachment.

PMID:36583093 SUPPORT Human Clinical

"Stickler syndrome, a rare inherited disease, carries a lifetime risk of rhegmatogenous retinal detachment (RRD) of up to 65%, higher than any other predisposing condition known."

Quantifies the lifetime detachment risk this node leads to. Scoped to Stickler syndrome as a whole; no type-2 figure is asserted from it.

PMID:24793526 SUPPORT INDIRECT Human Clinical

"a standardized retinal prophylactic treatment developed to prevent retinal detachment arising from giant retinal tears in type 1 Stickler syndrome"

Names giant retinal tear as the route to detachment that prophylaxis targets. Scoped to type 1, so it reaches this node's claim by extension from the shared vitreoretinal mechanism.

Disorganized Cartilage Collagen Matrix

In cartilage the same fibril dysregulation gives thick, sparse fibrils and disturbed spatial organization and hypertrophic maturation of chondrocytes, affecting both the craniofacial cartilages laid down in development and the articular cartilage that has to bear load for a lifetime.

chondrocyte CL:0000138

Downstream

Craniofacial Cartilage Malformation

Articular Cartilage Degeneration

Show evidence (2 references)

PMID:19638309 SUPPORT Model Organism

"Col11a1 depletion affected the spatial organization of chondrocytes, the shaping of cartilage elements, and the maturation of chondrocytes to hypertrophy"

Describes the disorganized cartilage this node asserts, at the level of chondrocyte organization and maturation.

PMID:7859283 SUPPORT Model Organism

"the normal differentiation and spatial organization of growth plate chondrocytes is critially dependent on the presence of type XI collagen in cartilage extracellular matrix"

The cho mouse links loss of cartilage collagen XI to disordered growth plate chondrocyte organization.

Craniofacial Cartilage Malformation

Defective cartilage matrix during craniofacial morphogenesis underlies the midfacial hypoplasia and the failure of palatal shelf fusion seen as cleft palate or Pierre Robin sequence.

Animal models

col11a1a morpholino knockdown zebrafish Zebrafish recapitulates Knockdown embryos develop craniofacial cartilage defects with disordered chondrocyte organization and abnormally thick, sparse cartilage matrix fibrils, which the authors note resemble human Stickler/Marshall chondrodysplasia.

Downstream

Midface retrusion

Cleft palate

Show evidence (1 reference)

PMID:19638309 SUPPORT Model Organism

"Collagen XI alpha1-deficient zebrafish embryos developed defects in craniofacial cartilage formation and in notochord morphology"

Demonstrates that loss of collagen XI produces craniofacial cartilage malformation, the claim of this node. The authors note the defects resemble human Stickler/Marshall chondrodysplasia.

Articular Cartilage Degeneration

Articular cartilage built on abnormally thick fibrils degenerates early, with matrix metalloproteinase induction, proteoglycan loss and reduced tensile stiffness preceding the clinical arthropathy.

Animal models

cho/+ heterozygous Col11a1 mouse Mouse recapitulates cho/+ mice develop increased articular cartilage fibril diameter and osteoarthritis-like degeneration of knee and temporomandibular joints from three months of age.

Downstream

Premature osteoarthritis

Show evidence (2 references)

PMID:13130470 SUPPORT Model Organism

"The diameter of collagen fibrils in articular cartilage of knee joints from heterozygous cho/+ mice was increased relative to that in control cartilage, and histologic analysis showed OA-like degenerative changes in knee and TM joints, starting at age 3 months"

Ties increased fibril diameter from reduced collagen XI directly to early degenerative change in articular cartilage.

PMID:13130470 SUPPORT Model Organism

"Heterozygosity for a loss-of-function mutation in Col11a1 results in the development of OA in the knee and TM joints of cho/+ mice"

A single abnormal Col11a1 allele is sufficient for early osteoarthritis in the mouse joint.

Middle Ear Collagen Abnormality

The fibrous layer of the tympanic membrane is collagenous too. Abnormal collagen there gives a hypermobile tympanic membrane, found in about a quarter of ears in type 2 disease and less often than in type 1. This is a distinct route to hearing impairment from the cochlear node, and it is not the only route to a conductive loss: palatal clefting with middle ear effusion accounts for much of the conductive component across Stickler syndrome.

Downstream

Conductive hearing impairment Inferential, and deliberately marked as such. The source attributes middle-ear collagen abnormality to the hypermobile tympanic membrane, and separately counts a conductive loss in 3% of ears; it does not join the two. The intermediate - abnormal tympanic membrane mechanics degrading sound conduction - is the standard otologic account rather than something this cohort demonstrated. A palatal defect with middle ear effusion is a competing and probably commoner route to conductive loss in Stickler syndrome, which is why this edge is not drawn DIRECT.

Show evidence (1 reference)

PMID:32901364 SUPPORT Human Clinical

"The proportion of hypermobile tympanic membranes (24%) was less than previously documented in type 1 Stickler Syndrome. When present, this appears to arise as a direct result of collagen abnormalities in the middle ear."

Attributes tympanic membrane hypermobility in genetically confirmed STL2 patients to middle ear collagen abnormality, which is this node's claim, and quantifies it against type 1.

Cochlear Extracellular Matrix Abnormality

Col11a1 is expressed in the developing cochlea and contributes collagen to the basilar and tectorial membranes. A dominant-negative alpha1(XI) chain in those specialized matrices degrades sound transduction across the whole frequency range, giving a cochlear - not retrocochlear - hearing loss.

cochlea UBERON:0001844

Animal models

cho/+ heterozygous Col11a1 mouse Mouse fails to recapitulate Auditory brainstem response thresholds in cho/+ mice are indistinguishable from wild-type littermates through ten months of age, despite the same animals developing the joint phenotype. Human COL11A1 heterozygotes have frequent sensorineural hearing loss.

Downstream

Sensorineural hearing impairment

Show evidence (3 references)

PMID:15141750 SUPPORT Model Organism

"The expression patterns suggest essential roles for Col11a1 and Col11a2 in the basilar or tectorial membranes"

Localizes Col11a1 expression to the cochlear structures this node implicates.

PMID:32901364 SUPPORT Human Clinical

"it is likely that hearing loss in type 2 Stickler Syndrome arises in the auditory periphery, without significant central processing deficits"

Localizes the lesion in genetically confirmed STL2 patients to the cochlea rather than to central auditory processing.

PMID:32901364 SUPPORT Human Clinical

"The impact on hearing thresholds can be seen across the frequency range, suggesting a contribution of defective collagen throughout the cochlea"

The pan-frequency threshold shift is the authors' argument for defective collagen distributed through the cochlea, which is this node's claim.

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Pathograph

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

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Phenotypes

11

Ear 2

Sensorineural hearing impairment FREQUENT HP:0000407

Show evidence (2 references)

PMID:32901364 SUPPORT Human Clinical

"Hearing impairment was identified in at least one ear for 69% of individuals. Analysis against age-matched normative data showed that reduced hearing sensitivity was present across all test frequencies. Sensorineural hearing loss was most common (77% of ears)"

In 65 genetically confirmed STL2 patients, 69% of individuals had hearing impairment and sensorineural loss predominated - the basis for the FREQUENT band recorded here.

PMID:23110709 SUPPORT Human Clinical

"Overall, mutations in COL11A1 (82.5%) and COL11A2 (94.1%) seem to be more frequently associated with hearing impairment than mutations in COL2A1 (52.2%)"

A gene-scoped literature review puts hearing impairment at 82.5% of COL11A1 patients, higher than the 69% measured in the single genetically confirmed cohort above; the lower, directly measured figure is the one the band follows.

Conductive hearing impairment HP:0000405

Show evidence (2 references)

PMID:32901364 SUPPORT Human Clinical

"Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively. The proportion of hypermobile tympanic membranes (24%) was less than previously documented in type 1 Stickler Syndrome. When present, this appears to arise as a..."

The 3% figure is the conductive share of ears. The middle-ear collagen attribution in the final sentence is made for the hypermobile tympanic membranes, not for the conductive loss. No frequency band is set because the reported denominator is ears, not individuals.

PMID:23110709 SUPPORT Human Clinical

"Conductive (14.1%) and mixed (18.1%) hearing loss was primarily found in young patients or patients with a palatal defect"

Across the Stickler literature the conductive component tracks young age and palatal defect, which is the effusion route rather than an intrinsic middle-ear collagen defect. Recorded here because it is the counterpoint to the single-cohort attribution above, and it is scoped to Stickler syndrome as a whole rather than to type 2.

Eye 3

High myopia HP:0011003

A cross-study prevalence of 83% is reported, but over a review population pooling STL1 and STL2, so no frequency band is claimed for type 2 here.

Show evidence (1 reference)

PMID:10486316 SUPPORT Human Clinical

"Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit"

Names high myopia as a defining feature of the COL11A1-associated Stickler/Marshall spectrum.

Retinal detachment HP:0000541

The pooled 45% detachment rate in PMID:32316871 covers STL1 and STL2 together, so it is not adopted as a type 2 frequency band.

Show evidence (2 references)

PMID:32316871 SUPPORT Human Clinical

"Generally, the first detachment occurred in the second decade of life in STL1 patients and later in STL2."

Reports retinal detachment in STL2 specifically and its later onset relative to STL1.

PMID:8872475 SUPPORT Human Clinical

"Stickler syndrome (hereditary arthro-ophthalmopathy) is the commonest inherited cause of retinal detachment"

Supports retinal detachment as the central ocular morbidity of the syndrome.

Cataract FREQUENT HP:0000518

Not attached to a pathophysiology node. No source found states how collagen XI dysregulation produces lens opacity, and drawing the edge on the strength of the two occurring in the same disease would assert a mechanism nobody has shown.

Show evidence (1 reference)

PMID:32316871 SUPPORT Human Clinical

"Cataracts were more common in STL2 patients, 59% versus 36% in STL1."

A type-2-scoped figure of 59%, which falls in the FREQUENT band (30-79%) recorded here.

Head and Neck 3

Micrognathia HP:0000347

Show evidence (1 reference)

PMID:20301479 SUPPORT Human Clinical

"mandibular advancement procedure to correct malocclusion for those with persistent micrognathia"

GeneReviews management guidance presupposes persistent micrognathia as a feature of the syndrome.

Cleft palate HP:0000175

Show evidence (1 reference)

PMID:20301479 SUPPORT Human Clinical

"midfacial underdevelopment and cleft palate (either alone or as part of the Pierre Robin sequence)"

GeneReviews lists cleft palate, alone or as part of Pierre Robin sequence, among the clinical characteristics of Stickler syndrome.

Midface retrusion HP:0011800

Show evidence (1 reference)

PMID:10486316 SUPPORT Human Clinical

"Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit"

Names midfacial hypoplasia as a defining feature of the COL11A1 Stickler/Marshall spectrum.

Musculoskeletal 1

Premature osteoarthritis HP:0003088

Show evidence (2 references)

PMID:32901364 SUPPORT Human Clinical

"The condition is characterised by classic ocular abnormalities, auditory dysfunction, osteoarthropathy and oro-facial dysplasia."

Names osteoarthropathy as one of the four defining features of type 2 Stickler syndrome specifically.

PMID:20301479 SUPPORT Human Clinical

"midfacial underdevelopment and cleft palate (either alone or as part of the Pierre Robin sequence); and early-onset degenerative joint disease"

GeneReviews lists early-onset degenerative joint disease among the clinical characteristics of Stickler syndrome. The quote carries the neighbouring craniofacial clause because the source states the features as one list.

Other 2

Beaded vitreous appearance HP:0031154

Show evidence (1 reference)

PMID:20513134 SUPPORT Human Clinical

"In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance"

Directly describes the beaded vitreous of COL11A1-related disease.

Mixed hearing impairment HP:0000410

Show evidence (1 reference)

PMID:32901364 SUPPORT Human Clinical

"Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively."

Reports the mixed-loss share of ears in 65 genetically confirmed STL2 patients. No frequency band is set because the denominator is ears.

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Genetic Associations

1

COL11A1

Gene: COL11A1 hgnc:2186 relationship_type: CAUSATIVE variant_origin: GERMLINE

Autosomal dominant

Show evidence (2 references)

PMID:8872475 SUPPORT Human Clinical

"only mutations in COL11A1 will give the full syndrome including the vitreo-retinal features"

Establishes COL11A1 as the causal locus for the full type 2 phenotype including the ocular features, separating it from COL11A2.

PMID:12527136 SUPPORT Model Organism

"Heterozygosity for mutations in the fibrillar collagen gene COL11A1 causes sensorineural hearing loss in patients with Stickler syndrome or Marshall syndrome"

States the heterozygous COL11A1 gene-disease relationship curated here.

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Medical Actions

8

Prophylactic Retinal Cryotherapy

Action: retinal cryotherapy Ontology label: Cryotherapy NCIT:C40030

360-degree contiguous cryotherapy at the retina-pars plana junction, to forestall giant retinal tear and detachment before it happens. The controlled evidence comes from type 1 cohorts, so use in STL2 is extrapolated from the shared vitreoretinal mechanism rather than demonstrated.

Mechanism Target:

Vitreoretinal Traction and Retinal Tear — Prophylactic chorioretinal adhesion at the vitreous base blocks the progression from vitreoretinal traction to detachment.

Show evidence (2 references)

PMID:24793526 SUPPORT INDIRECT Human Clinical

"all analyses indicate that the Cambridge prophylactic cryotherapy protocol is safe and markedly reduces the risk of retinal detachment"

The controlled cohort establishing prophylactic cryotherapy efficacy was conducted in 487 type 1 Stickler syndrome patients, so it supports use in type 2 only by extension from the shared vitreoretinal mechanism.

PMID:21466760 SUPPORT INDIRECT Human Clinical

"Only 360° cryotherapy and focal and circumferential laser treatment have been evaluated for the type 1 Stickler syndrome population, and then only by a single retrospective, controlled, cohort study in each case."

A systematic review making the scope limitation explicit: the prophylaxis evidence base is type 1 and retrospective, which is why this treatment carries INDIRECT directness for type 2.

Prophylactic 360-Degree Laser Retinopexy

Action: laser retinopexy Ontology label: Laser Therapy NCIT:C15466

Circumferential laser retinopexy posterior to the ora serrata, the other arm of retinal-detachment prophylaxis. As with cryotherapy the reported series are in Stickler syndrome broadly rather than type 2 specifically.

Mechanism Target:

Vitreoretinal Traction and Retinal Tear — Laser-induced chorioretinal adhesion at the vitreous base interrupts the progression from a traction tear to detachment.

Show evidence (2 references)

PMID:36583093 SUPPORT INDIRECT Human Clinical

"extraordinary publications in 2021-2022, each reporting successful prevention of RRD in Stickler syndrome, using 360-degree (encircling) laser retinopexy"

Reports successful prevention of rhegmatogenous retinal detachment with 360-degree laser retinopexy in Stickler syndrome. Scoped to Stickler syndrome as a whole rather than to type 2, hence INDIRECT.

PMID:20301479 SUPPORT Human Clinical

"laser therapy for prevention of retinal detachment"

GeneReviews names laser therapy for retinal detachment prevention among the treatments of manifestations.

Ophthalmic Surveillance, Refractive Correction and Patient Education

Action: ophthalmic surveillance and patient education Ontology label: Supportive Care NCIT:C15747

Annual review by a vitreoretinal specialist, spectacle correction of the refractive error, and teaching patients the symptoms of a detachment so they present within the window in which vision can be saved. Repair of an established detachment is not curated as a separate treatment here - see the entry `notes`.

Target Phenotypes: Retinal detachment HP:0000541 High myopia HP:0011003

Show evidence (2 references)

PMID:20301479 SUPPORT Human Clinical

"education on risks and symptoms of retinal detachment; correction of refractive errors with spectacles"

The GeneReviews treatment-of-manifestations items this record covers: detachment education and spectacle correction.

PMID:20301479 SUPPORT Human Clinical

"Surveillance: Annual examination by a vitreoretinal specialist; audiologic evaluations annually"

The GeneReviews surveillance schedule underpinning the annual vitreoretinal review recorded here.

Avoidance of Contact Sports

Action: activity restriction to prevent traumatic retinal detachment Ontology label: Supportive Care NCIT:C15747

Standing advice to avoid contact sports and other activities carrying a risk of ocular or head trauma, because the abnormal vitreous converts minor trauma into a retinal detachment. This is the syndrome's circumstances-to-avoid warning.

Mechanism Target:

Vitreoretinal Traction and Retinal Tear — Removing the mechanical trigger that precipitates tears in an already abnormal vitreoretinal interface.

Show evidence (1 reference)

PMID:20301479 SUPPORT Human Clinical

"Agents/circumstances to avoid: Activities such as contact sports that may lead to traumatic retinal detachment."

The GeneReviews agents-and-circumstances-to-avoid recommendation this entry records.

Hearing Amplification and Audiologic Surveillance

Action: hearing amplification Ontology label: Supportive Care NCIT:C15747

Annual audiologic evaluation with hearing aid fitting for the sensorineural loss, plus prompt treatment of otitis media and consideration of myringotomy tubes where a conductive component is present. Surveillance matters disproportionately here because many of these patients are also visually impaired.

Target Phenotypes: Sensorineural hearing impairment HP:0000407

Show evidence (2 references)

PMID:20301479 SUPPORT Human Clinical

"standard treatment of sensorineural and conductive hearing loss; prompt treatment of otitis media; consider myringotomy tubes for recurrent otitis media"

GeneReviews management guidance for the auditory features treated here.

PMID:23110709 SUPPORT Human Clinical

"Regular auditory follow-up is strongly advised, particularly because many Stickler patients are visually impaired"

Supports the surveillance component and its rationale in a dual-sensory-impairment population.

Craniofacial and Cleft Palate Surgical Management

Action: craniofacial surgical management Ontology label: Surgical Procedure NCIT:C15329

Care in a comprehensive craniofacial clinic, with tracheostomy where needed for neonatal Pierre Robin airway obstruction, mandibular advancement for persistent micrognathia, and feeding and nutritional support.

Target Phenotypes: Cleft palate HP:0000175

Show evidence (1 reference)

PMID:20301479 SUPPORT Human Clinical

"Management in a comprehensive craniofacial clinic when possible; tracheostomy as needed in infants with Pierre Robin sequence; mandibular advancement procedure to correct malocclusion for those with persistent micrognathia"

The GeneReviews craniofacial management recommendations recorded by this treatment.

Symptomatic Management of Arthropathy

Action: symptomatic management of arthropathy Ontology label: Supportive Care NCIT:C15747

Symptomatic treatment of the joint disease with orthopedic input, plus clinical, radiographic and orthopedic assessment as needed. There is no disease-modifying therapy for the underlying collagen defect.

Target Phenotypes: Premature osteoarthritis HP:0003088

Show evidence (2 references)

PMID:20301479 SUPPORT Human Clinical

"symptomatic treatment for arthropathy; treatment of osteoarticular manifestations per orthopedist"

The GeneReviews management recommendation for the joint features that this record covers.

PMID:20301479 SUPPORT Human Clinical

"clinical, radiographic, and/or orthopedic assessment as needed"

The GeneReviews surveillance item for the musculoskeletal features.

Genetic Counseling and Cascade Testing

Action: Genetic Counseling NCIT:C15240

Counseling for the 50% transmission risk, and identification of at-risk relatives so that ophthalmic surveillance and prophylaxis can begin before a first detachment rather than after one.

Show evidence (2 references)

PMID:20301479 SUPPORT Human Clinical

"It is appropriate to determine which family members at risk have Stickler syndrome and thus warrant ongoing surveillance and possible treatment to prevent retinal detachment."

GeneReviews evaluation-of-relatives-at-risk guidance, which is the rationale for cascade testing recorded here.

PMID:20301479 SUPPORT Human Clinical

"Each child of an individual with autosomal dominant Stickler syndrome has a 50% chance of inheriting the pathogenic variant."

The transmission risk this counseling record is built around.

🌍

Environmental Factors

1

Ocular or head trauma, including contact sports

Left without an `exposure_term`. ECTO was searched for trauma, injury, mechanical and physical exposure terms and for sport; it has `ECTO:6000002` exposure to exercise and `ECTO:6000031` exposure to strenuous exercise, neither of which means blunt ocular or head trauma. No term beats a wrong one, so none is bound.

Trauma is not a cause of STL2 - the disease is fully monogenic - but it is the trigger that converts an already abnormal vitreoretinal interface into a detachment. This is the interaction behind the syndrome's one standing activity restriction.

Show evidence (1 reference)

PMID:20301479 SUPPORT Human Clinical

"Agents/circumstances to avoid: Activities such as contact sports that may lead to traumatic retinal detachment."

The GeneReviews circumstances-to-avoid item establishing trauma as the relevant environmental exposure in this disease.

Mechanism Target:

TRIGGERS Vitreoretinal Traction and Retinal Tear — Impact transmitted to an abnormal vitreous gel produces the tractional tear that the intrinsic mechanism has already made the eye vulnerable to.

Show evidence (1 reference)

PMID:20301479 SUPPORT Human Clinical

"Activities such as contact sports that may lead to traumatic retinal detachment."

GeneReviews names contact sports as the activity that may lead to traumatic retinal detachment, which is the exposure-to-mechanism link asserted here.

🔬

Diagnosis

1

Molecular genetic testing on a Stickler syndrome gene panel

The diagnosis rests on the clinical phenotype - the beaded vitreous is the single most useful clue toward COL11A1 - confirmed by a heterozygous pathogenic variant. Because the syndrome is locus heterogeneous, a multi-gene panel rather than single-gene COL11A1 sequencing is the standard first-tier test.

The yield figure is for Stickler syndrome panels overall, not for STL2 specifically; the same series found ocular signs and family history were the commonest indications for ordering one.

Show evidence (2 references)

PMID:20301479 SUPPORT Human Clinical

"The diagnosis of Stickler syndrome can be established in a proband with characteristic clinical features and/or a heterozygous pathogenic variant in COL2A1, COL11A1, or COL11A2"

GeneReviews' diagnostic statement, which names COL11A1 among the genes whose heterozygous variants establish the diagnosis.

PMID:41856555 SUPPORT Human Clinical

"The diagnostic yield of Stickler syndrome panels was 50%, with a higher rate among cases reporting a family history"

Quantifies the real-world yield of the panel approach in a diagnostic laboratory series. The abstract does not state the denominator for the 50%, and it is not the 7798 panels ordered - those yielded 214 cases with a pathogenic or likely pathogenic variant in total.

📊

Prevalence

1

Worldwide

Birth Prevalence Unknown

No band or rate is asserted. Orphanet's birth-prevalence rows are scoped to the whole Stickler syndrome group, of which COL11A1-related type 2 is the minority form, and those rows disagree with each other by two orders of magnitude - from 1-9 per 1,000,000 in France to 1-5 per 10,000 worldwide. No type-2-specific population estimate was found, so the record carries the association and the reason a number was declined. The share of Stickler patients who carry a COL11A1 variant is recorded instead as a case fraction under `genetic`.

Show evidence (1 reference)

ORPHA:828 SUPPORT Other

"1-5 / 10 000 | Worldwide | Prevalence at birth | PMID:20301479"

Cited for the association only. This is Orphanet's worldwide birth-prevalence class for the Stickler syndrome group as a whole, so no band is adopted for type 2: the row is scoped more broadly than this entry, and Orphanet's own record carries four other rows spanning a 500-fold range.

🔀

Differential Diagnoses

3

Conditions with similar clinical presentations that must be differentiated from Stickler Syndrome Type 2:

Stickler Syndrome Type 1

Overlapping Features The commoner COL2A1-related form. Separated at the slit lamp by a membranous rather than beaded vitreous, and clinically by less frequent hearing impairment.

Distinguishing Features

Membranous rather than beaded vitreous phenotype
COL2A1 haploinsufficiency rather than dominant-negative COL11A1
Hearing impairment in about half of COL2A1 patients (52.2%) versus 82.5% of COL11A1 patients in the same review

Show evidence (2 references)

PMID:20513134 SUPPORT Human Clinical

"Mutations in COL2A1 usually result in a congenital membranous vitreous anomaly. In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance."

States the vitreous phenotype that distinguishes the two forms.

PMID:23110709 SUPPORT Human Clinical

"Overall, mutations in COL11A1 (82.5%) and COL11A2 (94.1%) seem to be more frequently associated with hearing impairment than mutations in COL2A1 (52.2%)"

Quantifies the auditory difference between the COL11A1 and COL2A1 forms.

Marshall Syndrome

Overlapping Features An allelic COL11A1 disorder overlapping STL2, associated in particular with splicing variants of the 54-bp exons in the C-terminal region of the gene.

Distinguishing Features

Retracted midface with flat nasal bridge, short nose, anteverted nostrils and long philtrum
Short stature and abnormal cranial ossification
Retinal detachment reported less often than in Stickler syndrome
Overlapping cases carrying features of both syndromes are well described

Show evidence (2 references)

PMID:10486316 SUPPORT Human Clinical

"Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene"

Identifies the COL11A1 variant class that separates the Marshall phenotype from classic Stickler syndrome.

PMID:10486316 SUPPORT Human Clinical

"Some patients, however, presented with phenotypes of both Marshall and Stickler syndromes."

Records the overlap that makes this the principal differential rather than a cleanly separable entity.

Otospondylomegaepiphyseal Dysplasia

Overlapping Features The COL11A2-related type XI collagenopathy, presenting with hearing loss and skeletal dysplasia but without the ocular disease. The accepted explanation is that the alpha2(V) chain substitutes for alpha2(XI) in vitreous, so a COL11A2 lesion is covered for there and not elsewhere.

Distinguishing Features

Absence of the vitreous and retinal features
Caused by COL11A2 rather than COL11A1

Show evidence (3 references)

PMID:8872475 SUPPORT Human Clinical

"A mutation in COL11A2, the gene for alpha 2 (XI) procollagen, has recently been found in a family described as having Stickler syndrome, although there was no ocular involvement."

Records the absence of ocular involvement in COL11A2-related disease, the feature that distinguishes it from STL2.

PMID:10486316 SUPPORT Human Clinical

"chain substitutes for the α2(XI) chain in the vitreous (Mayne et al.1993), thus explaining the lack of the ocular symptoms in patients with the COL11A2 gene mutations"

Gives the mechanistic reason COL11A2 disease spares the eye, which is what makes the ocular features a reliable discriminator.

PMID:33348901 SUPPORT Human Clinical

"Type 2 SS and the SS variant otospondylomegaepiphyseal dysplasia (OSMED) are caused by deleterious variants in COL11A1 and COL11A2, respectively."

States the gene assignment that separates the two entities.

🐁

Animal Models

2

cho/+ heterozygous Col11a1 mouse

The spontaneous chondrodysplasia (cho) allele is a functional null of Col11a1. Homozygotes die perinatally; heterozygotes are viable and are the standard genetic model for the joint arm of COL11A1 disease. Because the allele is a null rather than a dominant-negative missense change, the heterozygote models haploinsufficiency and not the human STL2 lesion - which is why it splits so sharply between the joint and ear phenotypes.

Species

Mouse

Genotype

Col11a1 cho/+ (heterozygous functional null)

Publication

PMID:13130470

Pathograph links

Articular Cartilage Degeneration recapitulates fidelity: moderate cho/+ mice develop increased articular cartilage fibril diameter and osteoarthritis-like degeneration of knee and temporomandibular joints from three months of age.

Limitations: The cho allele is a functional null, so the heterozygote reproduces the joint phenotype through halved collagen XI dosage rather than through the dominant-negative incorporation that operates in human STL2.

Readouts

Articular cartilage collagen fibril diameter

Direction: INCREASED

Interpretation: Structural correlate of loss of collagen XI fibril-diameter control in the joint.

Show evidence (1 reference)

PMID:13130470 SUPPORT Model Organism

"The diameter of collagen fibrils in articular cartilage of knee joints from heterozygous cho/+ mice was increased relative to that in control cartilage"

Reports the fibril-diameter measurement behind this readout.

Show evidence (1 reference)

PMID:13130470 SUPPORT Model Organism

"Heterozygosity for a loss-of-function mutation in Col11a1 results in the development of OA in the knee and TM joints of cho/+ mice"

Supports treating cho/+ as informative for the articular cartilage degeneration node.

Cochlear Extracellular Matrix Abnormality fails to recapitulate fidelity: low Auditory brainstem response thresholds in cho/+ mice are indistinguishable from wild-type littermates through ten months of age, despite the same animals developing the joint phenotype. Human COL11A1 heterozygotes have frequent sensorineural hearing loss.

Limitations: The negative result is specific to a null allele on a C57BL/6 background. The authors read it as evidence that the human auditory phenotype requires dominant-negative mutant chains rather than reduced dosage, so the model's failure is mechanistically informative but it cannot be used to study the human cochlear lesion.

Readouts

Auditory brainstem response threshold

Direction: UNCHANGED

Interpretation: No hearing loss detectable in the heterozygote at any age tested - a negative result against the human phenotype.

Show evidence (1 reference)

PMID:12527136 SUPPORT Model Organism

"There was no difference in ABR thresholds for click and tone burst stimuli between cho/+ and +/+ mice at all ages"

Reports the ABR measurement behind this readout.

Show evidence (1 reference)

PMID:12527136 SUPPORT Model Organism

"our results indicate that Col11a1 haploinsufficiency does not cause significant hearing loss on the C57BL/6 strain background"

Substantiates the failure of this model to reproduce the human cochlear phenotype.

Show evidence (1 reference)

PMID:12527136 SUPPORT Model Organism

"Chondrodysplasia (cho) is a functional null allele of Col11a1 that causes lethal chondrodysplasia in cho/cho newborn mice, and osteoarthritis in cho/+ heterozygotes."

Establishes the identity and phenotype of the cho/+ model recorded here: a Col11a1 functional null whose heterozygote develops osteoarthritis.

col11a1a morpholino knockdown zebrafish

Morpholino knockdown of the zebrafish COL11A1 ortholog, expressed at 48 hours post fertilisation in craniofacial skeleton, pectoral fin endoskeleton and otic vesicles.

Species

Zebrafish

Genotype

col11a1a morpholino knockdown

Publication

PMID:19638309

Pathograph links

Craniofacial Cartilage Malformation recapitulates fidelity: moderate Knockdown embryos develop craniofacial cartilage defects with disordered chondrocyte organization and abnormally thick, sparse cartilage matrix fibrils, which the authors note resemble human Stickler/Marshall chondrodysplasia.

Limitations: A transient morpholino knockdown in a teleost with two COL11A1 orthologs, modelling loss of collagen XI rather than the human dominant-negative allele; no ocular or auditory phenotype was assessed.

Show evidence (1 reference)

PMID:19638309 SUPPORT Model Organism

"the defects observed in cartilage formation resemble those observed in human chondrodysplasia such as the Stickler/Marshall syndrome"

The authors' own assessment that this model is informative for the human craniofacial cartilage phenotype.

Show evidence (1 reference)

PMID:19638309 SUPPORT Model Organism

"Zebrafish represent a novel reliable vertebrate model for collagen XI collagenopathies."

The authors' assessment that this model system is informative for the collagen XI collagenopathies, of which STL2 is one.

{ }

Source YAML

click to show

name: Stickler Syndrome Type 2
creation_date: "2026-09-04T00:00:00Z"
category: Mendelian
description: >
  Stickler syndrome type 2 (STL2) is the COL11A1-related form of Stickler
  syndrome, an autosomal dominant hereditary arthro-ophthalmopathy. Type XI
  collagen is a quantitatively minor fibrillar collagen that nucleates and
  limits the lateral growth of the type II collagen fibrils of vitreous,
  cartilage and cochlear extracellular matrix; a heterozygous COL11A1 variant
  in the triple-helical domain is incorporated into the heterotrimer and
  poisons that regulatory function. STL2 is separated from the commoner COL2A1
  form (type 1) at the slit lamp: the vitreous lamellae are irregular and
  beaded rather than membranous. Clinically it combines congenital high myopia
  and a lifelong risk of giant retinal tear and rhegmatogenous retinal
  detachment with predominantly cochlear sensorineural hearing loss, midfacial
  hypoplasia and cleft palate, and early degenerative joint disease. Hearing
  loss is both more frequent and more prominent than in type 1.
disease_term:
  preferred_term: Stickler syndrome type 2
  term:
    id: MONDO:0011493
    label: Stickler syndrome type 2
synonyms:
- STL2
- COL11A1-related Stickler syndrome
- beaded vitreous Stickler syndrome
- hereditary arthro-ophthalmopathy, type 2
parents:
- Stickler Syndrome
references:
- reference: PMID:20301479
  title: "Stickler Syndrome."
  tags:
  - GeneReviews
definitions:
- name: Orphanet disease definition
  definition_type: CASE_DEFINITION
  description: >
    Orphanet defines Stickler syndrome as a group of connective tissue
    disorders with ophthalmic, auditory, orofacial and articular
    manifestations. It has no separate record for type 2, so the quoted
    definition is the group's; the clause that separates the two main forms
    is the vitreous phenotype, evidenced below from the primary literature.
  evidence:
  - reference: ORPHA:828
    reference_title: "Stickler syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "A rare group of genetic connective tissue disorders characterized by ophthalmic, auditory, orofacial and articular manifestations"
    explanation: >
      Orphanet's definition of the Stickler syndrome group, of which the
      COL11A1-related type 2 curated here is one of the two main clinical
      forms. Orphanet's sentence goes on to distinguish the forms by vitreous
      phenotype, but that clause carries a ligature character in the cached
      record and is not quotable as a clean substring, so the point is
      evidenced from PMID:20513134 below instead.
  - reference: PMID:20513134
    reference_title: "Stickler syndrome and the vitreous phenotype: mutations in COL2A1 and COL11A1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in COL2A1 usually result in a congenital membranous vitreous anomaly. In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance."
    explanation: >
      Supplies the type-2-defining half of the definition: the vitreous
      phenotype that separates COL11A1 from COL2A1 disease.
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0019354
      label: Stickler syndrome
    mapping_predicate: skos:broadMatch
    mapping_source: ORPHA:828
    mapping_justification: >
      Orphanet cross-references its Stickler syndrome record to the broader
      MONDO grouping class. This entry curates the COL11A1-related type 2
      subtype specifically (MONDO:0011493), so the mapping to the group term
      is broad.
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  expressivity: VARIABLE
  description: >
    Classic STL2 segregates as an autosomal dominant trait, with a single
    heterozygous COL11A1 variant sufficient to produce the full syndrome
    including the vitreoretinal features. Expressivity is highly variable
    both within and among families; locus and allelic heterogeneity account
    for part of the interfamilial variability.
  evidence:
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stickler syndrome (hereditary arthro-ophthalmopathy) is the commonest inherited cause of retinal detachment and one of the commonest autosomal dominant connective tissue dysplasias"
    explanation: >
      The defining COL11A1 linkage study describes Stickler syndrome as an
      autosomal dominant connective tissue dysplasia.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stickler syndrome caused by pathogenic variants in COL2A1, COL11A1, or COL11A2 is inherited in an autosomal dominant manner"
    explanation: >
      GeneReviews states the inheritance mode for the COL11A1-related form
      curated here.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Variable phenotypic expression of Stickler syndrome occurs both within and among families; interfamilial variability is in part explained by locus and allelic heterogeneity"
    explanation: Supports the variable-expressivity statement recorded above.
prevalence:
- population: Worldwide
  measure_type: BIRTH_PREVALENCE
  prevalence_class: UNKNOWN
  notes: >
    No band or rate is asserted. Orphanet's birth-prevalence rows are scoped
    to the whole Stickler syndrome group, of which COL11A1-related type 2 is
    the minority form, and those rows disagree with each other by two orders
    of magnitude - from 1-9 per 1,000,000 in France to 1-5 per 10,000
    worldwide. No type-2-specific population estimate was found, so the
    record carries the association and the reason a number was declined.
    The share of Stickler patients who carry a COL11A1 variant is recorded
    instead as a case fraction under `genetic`.
  evidence:
  - reference: ORPHA:828
    reference_title: "Stickler syndrome"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "1-5 / 10 000 | Worldwide | Prevalence at birth | PMID:20301479"
    explanation: >
      Cited for the association only. This is Orphanet's worldwide
      birth-prevalence class for the Stickler syndrome group as a whole, so
      no band is adopted for type 2: the row is scoped more broadly than this
      entry, and Orphanet's own record carries four other rows spanning a
      500-fold range.
pathophysiology:
- name: COL11A1 Triple-Helical Domain Variant
  description: >
    A heterozygous COL11A1 variant - classically a glycine substitution within
    the Gly-X-Y repeat of the triple-helical domain, or a splice-site change
    causing in-frame skipping of a triple-helical exon - yields a structurally
    abnormal pro-alpha1(XI) chain. The chain is still competent to enter the
    type XI heterotrimer, which is what makes the lesion dominant negative
    rather than a simple loss of one allele's product.
  biological_scale: MOLECULAR
  genetic_context:
    gene:
      preferred_term: COL11A1
      term:
        id: hgnc:2186
        label: COL11A1
    allele_type: SNV
    variant_origin: GERMLINE
    zygosity: HETEROZYGOUS
    functional_impact_category: DOMINANT_NEGATIVE
    description: >
      Heterozygous germline COL11A1 variants acting through incorporation of
      the mutant chain into the collagen XI heterotrimer.
  downstream:
  - target: Impaired Type XI Collagen Regulation of Fibrillogenesis
    causal_link_type: DIRECT
    description: >
      The mutant alpha1(XI) chain is incorporated into wild-type-containing
      fibrillar collagen assemblies and disrupts their function.
    evidence:
    - reference: PMID:12527136
      reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We conclude that Stickler syndrome and Marshall syndrome mutations in COL11A1 cause hearing loss via dominant negative effects upon wild-type fibrillar collagen polypeptides in the extracellular matrices of the cochlea"
      explanation: >
        States the causal step from the COL11A1 variant to poisoning of
        wild-type fibrillar collagen, which is the edge asserted here. The
        authors reach it because halving Col11a1 dosage in the mouse does not
        reproduce the human phenotype.
  evidence:
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "characterise the mutation as a Glycine to Valine substitution at position 97 of the triple helical domain caused by a single base G-->T mutation"
    explanation: >
      The founding STL2 family carries a glycine substitution in the
      triple-helical domain of alpha1(XI), the variant class described by
      this node.
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a family with the full Type 2 Stickler syndrome including vitreous and retinal abnormalities is linked to the COL11A1 gene"
    explanation: >
      Establishes COL11A1 as the locus for the full type 2 syndrome,
      vitreoretinal features included.
  - reference: PMID:10486316
    reference_title: "Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene"
    explanation: >
      Shows that where in COL11A1 the variant falls, and what kind it is,
      determines whether the phenotype reads as Marshall or as Stickler -
      the reason this node is specified by variant class and not by gene
      alone.
- name: Impaired Type XI Collagen Regulation of Fibrillogenesis
  description: >
    Type XI collagen co-assembles with type II collagen and controls fibril
    nucleation, diameter and spacing. With a mutant alpha1(XI) chain in the
    heterotrimer, that control is lost and the resulting heterotypic fibrils
    are abnormally sized, sparse and disorganized wherever the type II/XI
    network is load-bearing.
  biological_scale: MOLECULAR
  biological_processes:
  - preferred_term: collagen fibril organization
    term:
      id: GO:0030199
      label: collagen fibril organization
    modifier: DECREASED
  - preferred_term: extracellular matrix organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: DECREASED
  downstream:
  - target: Beaded Vitreous Anomaly
    causal_link_type: DIRECT
    description: >
      In the vitreous the same loss of fibril regulation presents as the
      beaded lamellar phenotype, which tracks the causal gene closely enough
      to be used clinically to predict it.
    evidence:
    - reference: PMID:20513134
      reference_title: "Stickler syndrome and the vitreous phenotype: mutations in COL2A1 and COL11A1."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Although the systemic phenotype is highly variable, the vitreous phenotype has been used successfully to differentiate between patients with mutations in these different genes."
      explanation: >
        Establishes that the vitreous phenotype is determined by which
        collagen gene is mutated - the step from the molecular lesion to the
        vitreous appearance that this edge asserts.
  - target: Disorganized Cartilage Collagen Matrix
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:19638309
      reference_title: "Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Knockdown of col11a1 in embryos stimulated the expression of the marker of chondrocyte differentiation col2a1, resulting in the deposit of abnormally thick and sparse fibrils in the cartilage extracellular matrix"
      explanation: >
        Removing collagen XI is sufficient to produce an abnormal cartilage
        fibril matrix, which is the step this edge asserts.
  - target: Cochlear Extracellular Matrix Abnormality
    causal_link_type: DIRECT
    description: >
      The cochlear extracellular matrices carry the same fibrillar collagen,
      and it is the mutant chains within them - not reduced dosage - that the
      mouse work implicates.
    evidence:
    - reference: PMID:12527136
      reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We conclude that Stickler syndrome and Marshall syndrome mutations in COL11A1 cause hearing loss via dominant negative effects upon wild-type fibrillar collagen polypeptides in the extracellular matrices of the cochlea"
      explanation: >
        States the step from poisoned fibrillar collagen to the cochlear
        extracellular matrices that this edge asserts.
  - target: Middle Ear Collagen Abnormality
    causal_link_type: DIRECT
    description: >
      A separate, smaller branch: the fibrous layer of the tympanic membrane
      is also collagenous, and abnormality there is hypermobility rather than
      cochlear dysfunction.
  - target: High myopia
    description: >
      The refractive error of STL2 is congenital or early in onset and is
      attributed to the same structural collagen defect in the developing
      eye. Left uncited: no source found states the step from collagen XI
      dysregulation to axial elongation, as opposed to listing myopia among
      the syndrome's features.
  evidence:
  - reference: PMID:7859283
    reference_title: "A fibrillar collagen gene, Col11a1, is essential for skeletal morphogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The data demonstrate that collagen XI is essential for normal formation of cartilage collagen fibrils and the cohesive properties of cartilage"
    explanation: >
      The cho mouse establishes that collagen XI is required for normal
      fibril formation, the function lost at this node.
  - reference: PMID:32950601
    reference_title: "Collagen XI regulates the acquisition of collagen fibril structure, organization and functional properties in tendon."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Reducing Col11a1 and, therefore collagen XI content, resulted in abnormal fibril structure, loss of normal fibril diameter control with a significant shift to small diameters and disrupted parallel alignment of fibrils"
    explanation: >
      Directly demonstrates the loss of fibril-diameter control described by
      this node. Reported in tendon rather than vitreous or cartilage, so it
      supports the general regulatory role rather than the tissue-specific
      consequence.
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Type XI collagen is a quantitatively minor fibrillar collagen related to type V collagen and associated with the more abundant type II collagen fibrils"
    explanation: >
      Supports the co-assembly of collagen XI with the abundant type II
      fibrils that this node's regulatory claim depends on.
- name: Beaded Vitreous Anomaly
  description: >
    In the vitreous the disordered type II/XI network presents as sparse,
    irregularly thickened and beaded lamellae, in contrast to the membranous
    vitreous of COL2A1-related type 1 disease. This is the sign the diagnosis
    is made on at the slit lamp.
  biological_scale: TISSUE
  locations:
  - preferred_term: vitreous humor
    term:
      id: UBERON:0001797
      label: vitreous humor
  downstream:
  - target: Vitreoretinal Traction and Retinal Tear
    causal_link_type: DIRECT
    description: >
      The abnormal gel is the substrate on which peripheral tractional tears
      form.
    evidence:
    - reference: PMID:36583093
      reference_title: "Preventing Retinal Detachment: Where are We? Implications from Stickler Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Both syndromic and non-syndromic eyes suffer RRD predominately from the same pathogenesis, vitreous tractional tears in the peripheral retina."
      explanation: >
        Names vitreous tractional tearing of the peripheral retina as the
        pathogenesis of detachment in Stickler syndrome, which is the step
        this edge asserts.
  - target: Beaded vitreous appearance
  evidence:
  - reference: PMID:20513134
    reference_title: "Stickler syndrome and the vitreous phenotype: mutations in COL2A1 and COL11A1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance"
    explanation: >
      States the beaded vitreous phenotype of COL11A1 disease and its
      contrast with the COL2A1 membranous phenotype.
  - reference: PMID:10573014
    reference_title: "Stickler syndrome: further mutations in COL11A1 and evidence for additional locus heterogeneity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "These data confirm that mutations in COL11A1 cause Stickler syndrome with the type2 vitreous phenotype and also reveal further locus heterogeneity"
    explanation: >
      Independent linkage confirmation that COL11A1 variants produce the type
      2 vitreous phenotype.
- name: Vitreoretinal Traction and Retinal Tear
  description: >
    The abnormal vitreous gel retains adherence at the vitreous base while
    losing its normal internal architecture, so that ordinary vitreous
    movement or minor trauma transmits traction to the peripheral retina and
    produces giant retinal tears.
  biological_scale: TISSUE
  downstream:
  - target: Retinal detachment
  evidence:
  - reference: PMID:36583093
    reference_title: "Preventing Retinal Detachment: Where are We? Implications from Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both syndromic and non-syndromic eyes suffer RRD predominately from the same pathogenesis, vitreous tractional tears in the peripheral retina."
    explanation: >
      Names the mechanism this node describes - peripheral tractional tearing
      driven by the vitreous - rather than merely associating the syndrome
      with detachment.
  - reference: PMID:36583093
    reference_title: "Preventing Retinal Detachment: Where are We? Implications from Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stickler syndrome, a rare inherited disease, carries a lifetime risk of rhegmatogenous retinal detachment (RRD) of up to 65%, higher than any other predisposing condition known."
    explanation: >
      Quantifies the lifetime detachment risk this node leads to. Scoped to
      Stickler syndrome as a whole; no type-2 figure is asserted from it.
  - reference: PMID:24793526
    reference_title: "Prevention of retinal detachment in Stickler syndrome: the Cambridge prophylactic cryotherapy protocol."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "a standardized retinal prophylactic treatment developed to prevent retinal detachment arising from giant retinal tears in type 1 Stickler syndrome"
    explanation: >
      Names giant retinal tear as the route to detachment that prophylaxis
      targets. Scoped to type 1, so it reaches this node's claim by extension
      from the shared vitreoretinal mechanism.
- name: Disorganized Cartilage Collagen Matrix
  description: >
    In cartilage the same fibril dysregulation gives thick, sparse fibrils and
    disturbed spatial organization and hypertrophic maturation of
    chondrocytes, affecting both the craniofacial cartilages laid down in
    development and the articular cartilage that has to bear load for a
    lifetime.
  biological_scale: TISSUE
  cell_types:
  - preferred_term: chondrocyte
    term:
      id: CL:0000138
      label: chondrocyte
  downstream:
  - target: Craniofacial Cartilage Malformation
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:36278545
      reference_title: "The Shape of the Jaw-Zebrafish Col11a1a Regulates Meckel's Cartilage Morphogenesis and Mineralization."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "zebrafish col11a1a knockdown impairs the cellular organization of Meckel's cartilage in the developing jaw and alters the bone formation that occurs adjacent to the Meckel's cartilage"
      explanation: >
        Ties disordered cartilage cellular organization directly to
        malformation of a craniofacial cartilage and the bone formed against
        it.
  - target: Articular Cartilage Degeneration
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:13130470
      reference_title: "Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho)."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "The diameter of collagen fibrils in articular cartilage of knee joints from heterozygous cho/+ mice was increased relative to that in control cartilage, and histologic analysis showed OA-like degenerative changes in knee and TM joints, starting at age 3 months"
      explanation: >
        Reports the abnormal cartilage fibrils and the degeneration in the
        same joints, which is the step this edge asserts.
  evidence:
  - reference: PMID:19638309
    reference_title: "Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Col11a1 depletion affected the spatial organization of chondrocytes, the shaping of cartilage elements, and the maturation of chondrocytes to hypertrophy"
    explanation: >
      Describes the disorganized cartilage this node asserts, at the level of
      chondrocyte organization and maturation.
  - reference: PMID:7859283
    reference_title: "A fibrillar collagen gene, Col11a1, is essential for skeletal morphogenesis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the normal differentiation and spatial organization of growth plate chondrocytes is critially dependent on the presence of type XI collagen in cartilage extracellular matrix"
    explanation: >
      The cho mouse links loss of cartilage collagen XI to disordered growth
      plate chondrocyte organization.
- name: Craniofacial Cartilage Malformation
  description: >
    Defective cartilage matrix during craniofacial morphogenesis underlies the
    midfacial hypoplasia and the failure of palatal shelf fusion seen as cleft
    palate or Pierre Robin sequence.
  biological_scale: TISSUE
  downstream:
  - target: Midface retrusion
  - target: Cleft palate
  evidence:
  - reference: PMID:19638309
    reference_title: "Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Collagen XI alpha1-deficient zebrafish embryos developed defects in craniofacial cartilage formation and in notochord morphology"
    explanation: >
      Demonstrates that loss of collagen XI produces craniofacial cartilage
      malformation, the claim of this node. The authors note the defects
      resemble human Stickler/Marshall chondrodysplasia.
- name: Articular Cartilage Degeneration
  description: >
    Articular cartilage built on abnormally thick fibrils degenerates early,
    with matrix metalloproteinase induction, proteoglycan loss and reduced
    tensile stiffness preceding the clinical arthropathy.
  biological_scale: TISSUE
  downstream:
  - target: Premature osteoarthritis
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:13130470
      reference_title: "Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho)."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Morphologic and biochemical evidence of OA appears to precede significant mechanical changes, suggesting that the cho mutation leads to OA through a mechanism that does not initially involve mechanical factors."
      explanation: >
        Orders the steps: the matrix change comes first and the osteoarthritis
        follows, which is the direction this edge asserts.
  evidence:
  - reference: PMID:13130470
    reference_title: "Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho)."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The diameter of collagen fibrils in articular cartilage of knee joints from heterozygous cho/+ mice was increased relative to that in control cartilage, and histologic analysis showed OA-like degenerative changes in knee and TM joints, starting at age 3 months"
    explanation: >
      Ties increased fibril diameter from reduced collagen XI directly to
      early degenerative change in articular cartilage.
  - reference: PMID:13130470
    reference_title: "Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho)."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Heterozygosity for a loss-of-function mutation in Col11a1 results in the development of OA in the knee and TM joints of cho/+ mice"
    explanation: >
      A single abnormal Col11a1 allele is sufficient for early osteoarthritis
      in the mouse joint.
- name: Middle Ear Collagen Abnormality
  description: >
    The fibrous layer of the tympanic membrane is collagenous too. Abnormal
    collagen there gives a hypermobile tympanic membrane, found in about a
    quarter of ears in type 2 disease and less often than in type 1. This is
    a distinct route to hearing impairment from the cochlear node, and it is
    not the only route to a conductive loss: palatal clefting with middle ear
    effusion accounts for much of the conductive component across Stickler
    syndrome.
  biological_scale: TISSUE
  downstream:
  - target: Conductive hearing impairment
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    description: >
      Inferential, and deliberately marked as such. The source attributes
      middle-ear collagen abnormality to the hypermobile tympanic membrane,
      and separately counts a conductive loss in 3% of ears; it does not
      join the two. The intermediate - abnormal tympanic membrane mechanics
      degrading sound conduction - is the standard otologic account rather
      than something this cohort demonstrated. A palatal defect with middle
      ear effusion is a competing and probably commoner route to conductive
      loss in Stickler syndrome, which is why this edge is not drawn DIRECT.
    evidence:
    - reference: PMID:32901364
      reference_title: Auditory dysfunction in type 2 Stickler Syndrome.
      supports: SUPPORT
      directness: INDIRECT
      evidence_source: HUMAN_CLINICAL
      snippet: "Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively."
      explanation: >
        Establishes that a conductive component exists in this cohort. It
        reaches the edge only through the inference named in the
        description: the source counts the conductive loss and attributes
        middle-ear collagen to tympanic hypermobility, without linking them.
  evidence:
  - reference: PMID:32901364
    reference_title: Auditory dysfunction in type 2 Stickler Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The proportion of hypermobile tympanic membranes (24%) was less than previously documented in type 1 Stickler Syndrome. When present, this appears to arise as a direct result of collagen abnormalities in the middle ear."
    explanation: >
      Attributes tympanic membrane hypermobility in genetically confirmed
      STL2 patients to middle ear collagen abnormality, which is this node's
      claim, and quantifies it against type 1.
- name: Cochlear Extracellular Matrix Abnormality
  description: >
    Col11a1 is expressed in the developing cochlea and contributes collagen to
    the basilar and tectorial membranes. A dominant-negative alpha1(XI) chain
    in those specialized matrices degrades sound transduction across the whole
    frequency range, giving a cochlear - not retrocochlear - hearing loss.
  biological_scale: TISSUE
  locations:
  - preferred_term: cochlea
    term:
      id: UBERON:0001844
      label: cochlea
  downstream:
  - target: Sensorineural hearing impairment
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:12527136
      reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Heterozygosity for mutations in the fibrillar collagen gene COL11A1 causes sensorineural hearing loss in patients with Stickler syndrome or Marshall syndrome."
      explanation: >
        States the causal step from the COL11A1 collagen lesion to
        sensorineural hearing loss in patients.
  evidence:
  - reference: PMID:15141750
    reference_title: "Col11a1 and Col11a2 mRNA expression in the developing mouse cochlea: implications for the correlation of hearing loss phenotype with mutant type XI collagen genotype."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The expression patterns suggest essential roles for Col11a1 and Col11a2 in the basilar or tectorial membranes"
    explanation: >
      Localizes Col11a1 expression to the cochlear structures this node
      implicates.
  - reference: PMID:32901364
    reference_title: "Auditory dysfunction in type 2 Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "it is likely that hearing loss in type 2 Stickler Syndrome arises in the auditory periphery, without significant central processing deficits"
    explanation: >
      Localizes the lesion in genetically confirmed STL2 patients to the
      cochlea rather than to central auditory processing.
  - reference: PMID:32901364
    reference_title: "Auditory dysfunction in type 2 Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The impact on hearing thresholds can be seen across the frequency range, suggesting a contribution of defective collagen throughout the cochlea"
    explanation: >
      The pan-frequency threshold shift is the authors' argument for defective
      collagen distributed through the cochlea, which is this node's claim.
phenotypes:
- category: Ophthalmologic
  name: Beaded vitreous appearance
  description: >
    Sparse, irregularly thickened and beaded vitreous lamellae throughout the
    vitreous cavity - the type 2 vitreous phenotype, and the sign that
    separates COL11A1 from COL2A1 disease clinically.
  phenotype_term:
    preferred_term: Beaded vitreous appearance
    term:
      id: HP:0031154
      label: Beaded vitreous appearance
  diagnostic: true
  evidence:
  - reference: PMID:20513134
    reference_title: "Stickler syndrome and the vitreous phenotype: mutations in COL2A1 and COL11A1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance"
    explanation: Directly describes the beaded vitreous of COL11A1-related disease.
- category: Ophthalmologic
  name: High myopia
  description: >
    Congenital or early-onset myopia, usually moderate to high, is among the
    presenting features of the type XI collagenopathies.
  phenotype_term:
    preferred_term: High myopia
    term:
      id: HP:0011003
      label: High myopia
  evidence:
  - reference: PMID:10486316
    reference_title: "Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit"
    explanation: >
      Names high myopia as a defining feature of the COL11A1-associated
      Stickler/Marshall spectrum.
  notes: >
    A cross-study prevalence of 83% is reported, but over a review population
    pooling STL1 and STL2, so no frequency band is claimed for type 2 here.
- category: Ophthalmologic
  name: Retinal detachment
  description: >
    Rhegmatogenous retinal detachment, classically from a giant retinal tear.
    Detachment tends to occur later in STL2 than in STL1, but the risk is
    lifelong and persists into and beyond middle age.
  phenotype_term:
    preferred_term: Retinal detachment
    term:
      id: HP:0000541
      label: Retinal detachment
  evidence:
  - reference: PMID:32316871
    reference_title: "Ocular complications and prophylactic strategies in Stickler syndrome: a systematic literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Generally, the first detachment occurred in the second decade of life in STL1 patients and later in STL2."
    explanation: >
      Reports retinal detachment in STL2 specifically and its later onset
      relative to STL1.
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stickler syndrome (hereditary arthro-ophthalmopathy) is the commonest inherited cause of retinal detachment"
    explanation: Supports retinal detachment as the central ocular morbidity of the syndrome.
  notes: >
    The pooled 45% detachment rate in PMID:32316871 covers STL1 and STL2
    together, so it is not adopted as a type 2 frequency band.
- category: Ophthalmologic
  name: Cataract
  description: >
    Cataract, reported more often in COL11A1-related than in COL2A1-related
    disease.
  phenotype_term:
    preferred_term: Cataract
    term:
      id: HP:0000518
      label: Cataract
  frequency: FREQUENT
  evidence:
  - reference: PMID:32316871
    reference_title: "Ocular complications and prophylactic strategies in Stickler syndrome: a systematic literature review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cataracts were more common in STL2 patients, 59% versus 36% in STL1."
    explanation: >
      A type-2-scoped figure of 59%, which falls in the FREQUENT band
      (30-79%) recorded here.
  notes: >
    Not attached to a pathophysiology node. No source found states how
    collagen XI dysregulation produces lens opacity, and drawing the edge on
    the strength of the two occurring in the same disease would assert a
    mechanism nobody has shown.
- category: Auditory
  name: Sensorineural hearing impairment
  description: >
    Bilateral cochlear hearing loss affecting all test frequencies rather than
    the high frequencies alone. It is the predominant type of hearing
    impairment in STL2 and is more consistently present than in type 1
    disease.
  phenotype_term:
    preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  frequency: FREQUENT
  evidence:
  - reference: PMID:32901364
    reference_title: "Auditory dysfunction in type 2 Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hearing impairment was identified in at least one ear for 69% of individuals. Analysis against age-matched normative data showed that reduced hearing sensitivity was present across all test frequencies. Sensorineural hearing loss was most common (77% of ears)"
    explanation: >
      In 65 genetically confirmed STL2 patients, 69% of individuals had
      hearing impairment and sensorineural loss predominated - the basis for
      the FREQUENT band recorded here.
  - reference: PMID:23110709
    reference_title: "Hearing impairment in Stickler syndrome: a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, mutations in COL11A1 (82.5%) and COL11A2 (94.1%) seem to be more frequently associated with hearing impairment than mutations in COL2A1 (52.2%)"
    explanation: >
      A gene-scoped literature review puts hearing impairment at 82.5% of
      COL11A1 patients, higher than the 69% measured in the single
      genetically confirmed cohort above; the lower, directly measured figure
      is the one the band follows.
- category: Auditory
  name: Conductive hearing impairment
  description: >
    A conductive component is present in a small minority of ears (3%).
    Separately, hypermobile tympanic membranes are found in 24% of ears -
    less often than has been documented in type 1 disease - and, when
    present, are attributed to collagen abnormality in the middle ear itself.
    The two observations are distinct: the source makes the collagen
    attribution for the hypermobile tympanic membrane, not for the conductive
    loss, and a palatal defect with middle ear effusion is a well-described
    route to conductive loss in Stickler syndrome.
  phenotype_term:
    preferred_term: Conductive hearing impairment
    term:
      id: HP:0000405
      label: Conductive hearing impairment
  evidence:
  - reference: PMID:32901364
    reference_title: "Auditory dysfunction in type 2 Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively. The proportion of hypermobile tympanic membranes (24%) was less than previously documented in type 1 Stickler Syndrome. When present, this appears to arise as a direct result of collagen abnormalities in the middle ear."
    explanation: >
      The 3% figure is the conductive share of ears. The middle-ear collagen
      attribution in the final sentence is made for the hypermobile tympanic
      membranes, not for the conductive loss. No frequency band is set
      because the reported denominator is ears, not individuals.
  - reference: PMID:23110709
    reference_title: "Hearing impairment in Stickler syndrome: a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Conductive (14.1%) and mixed (18.1%) hearing loss was primarily found in young patients or patients with a palatal defect"
    explanation: >
      Across the Stickler literature the conductive component tracks young
      age and palatal defect, which is the effusion route rather than an
      intrinsic middle-ear collagen defect. Recorded here because it is the
      counterpoint to the single-cohort attribution above, and it is scoped
      to Stickler syndrome as a whole rather than to type 2.
- category: Auditory
  name: Mixed hearing impairment
  description: >
    A mixed sensorineural and conductive loss, reported in 7% of ears in the
    genetically confirmed type 2 cohort.
  phenotype_term:
    preferred_term: Mixed hearing impairment
    term:
      id: HP:0000410
      label: Mixed hearing impairment
  evidence:
  - reference: PMID:32901364
    reference_title: Auditory dysfunction in type 2 Stickler Syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Sensorineural hearing loss was most common (77% of ears), with conductive (3%), mixed (7%) and no hearing loss (13%), respectively."
    explanation: >
      Reports the mixed-loss share of ears in 65 genetically confirmed STL2
      patients. No frequency band is set because the denominator is ears.
- category: Craniofacial
  name: Micrognathia
  description: >
    Micrognathia, which may persist and require mandibular advancement, and
    which underlies the Pierre Robin presentation in affected neonates.
  phenotype_term:
    preferred_term: Micrognathia
    term:
      id: HP:0000347
      label: Micrognathia
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "mandibular advancement procedure to correct malocclusion for those with persistent micrognathia"
    explanation: >
      GeneReviews management guidance presupposes persistent micrognathia as
      a feature of the syndrome.
- category: Craniofacial
  name: Cleft palate
  description: >
    Cleft palate, occurring in isolation or within the Pierre Robin sequence,
    with the associated neonatal airway and feeding risk.
  phenotype_term:
    preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "midfacial underdevelopment and cleft palate (either alone or as part of the Pierre Robin sequence)"
    explanation: >
      GeneReviews lists cleft palate, alone or as part of Pierre Robin
      sequence, among the clinical characteristics of Stickler syndrome.
- category: Craniofacial
  name: Midface retrusion
  description: >
    Midfacial hypoplasia with a flat facial profile, described as more
    pronounced in COL11A1-related than in COL2A1-related disease.
  phenotype_term:
    preferred_term: Midface retrusion
    term:
      id: HP:0011800
      label: Midface retrusion
  evidence:
  - reference: PMID:10486316
    reference_title: "Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit"
    explanation: >
      Names midfacial hypoplasia as a defining feature of the COL11A1
      Stickler/Marshall spectrum.
- category: Musculoskeletal
  name: Premature osteoarthritis
  description: >
    Early-onset degenerative joint disease, described in the STL2 literature
    as osteoarthropathy, affecting large weight-bearing joints well before the
    usual age.
  phenotype_term:
    preferred_term: Premature osteoarthritis
    term:
      id: HP:0003088
      label: Premature osteoarthritis
  evidence:
  - reference: PMID:32901364
    reference_title: "Auditory dysfunction in type 2 Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The condition is characterised by classic ocular abnormalities, auditory dysfunction, osteoarthropathy and oro-facial dysplasia."
    explanation: >
      Names osteoarthropathy as one of the four defining features of type 2
      Stickler syndrome specifically.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "midfacial underdevelopment and cleft palate (either alone or as part of the Pierre Robin sequence); and early-onset degenerative joint disease"
    explanation: >
      GeneReviews lists early-onset degenerative joint disease among the
      clinical characteristics of Stickler syndrome. The quote carries the
      neighbouring craniofacial clause because the source states the
      features as one list.
genetic:
- name: COL11A1
  gene_term:
    preferred_term: COL11A1
    term:
      id: hgnc:2186
      label: COL11A1
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  inheritance:
  - name: Autosomal dominant
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
  features: >
    Encodes the pro-alpha1 chain of type XI collagen. Pathogenic variants in
    the triple-helical domain - glycine substitutions and splice changes
    causing in-frame exon skipping - classically act through
    dominant-negative incorporation into the collagen XI heterotrimer, which
    distinguishes the mechanism from the haploinsufficiency typical of
    COL2A1-related type 1 disease. Nonsense and frameshift COL11A1 alleles
    may instead act by haploinsufficiency; that branch is not separately
    evidenced in this entry.
  evidence:
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "only mutations in COL11A1 will give the full syndrome including the vitreo-retinal features"
    explanation: >
      Establishes COL11A1 as the causal locus for the full type 2 phenotype
      including the ocular features, separating it from COL11A2.
  - reference: PMID:12527136
    reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Heterozygosity for mutations in the fibrillar collagen gene COL11A1 causes sensorineural hearing loss in patients with Stickler syndrome or Marshall syndrome"
    explanation: >
      States the heterozygous COL11A1 gene-disease relationship curated here.
  case_fractions:
  - population: Stickler syndrome patients (all types, literature estimate)
    case_fraction_low: 10.0
    case_fraction_high: 20.0
    notes: >
      The share of Stickler syndrome patients carrying a COL11A1 variant, as
      stated in a case report's introduction rather than measured in a
      cohort. Treat it as the field's working figure, not a measurement.
    evidence:
    - reference: PMID:32558342
      reference_title: "Variable clinical expression of Stickler Syndrome: A case report of a novel COL11A1 mutation."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "a heterozygous mutation in COL11A1 gene is identified in about 10 to 20% of Stickler Syndrome patients"
      explanation: >
        Gives the COL11A1 share of Stickler syndrome cases recorded by this
        case fraction.
  notes: >
    Biallelic loss-of-function COL11A1 variants cause fibrochondrogenesis
    rather than STL2, and other COL11A1 variants cause Marshall syndrome and
    non-syndromic hearing loss; the allelic series is not curated in this
    entry.
environmental:
- name: Ocular or head trauma, including contact sports
  description: >
    Trauma is not a cause of STL2 - the disease is fully monogenic - but it is
    the trigger that converts an already abnormal vitreoretinal interface into
    a detachment. This is the interaction behind the syndrome's one standing
    activity restriction.
  effect: Precipitates retinal tear and detachment in an eye already at risk
  influences_mechanisms:
  - target: Vitreoretinal Traction and Retinal Tear
    environmental_effect: TRIGGERS
    causal_link_type: DIRECT
    description: >
      Impact transmitted to an abnormal vitreous gel produces the tractional
      tear that the intrinsic mechanism has already made the eye vulnerable
      to.
    evidence:
    - reference: PMID:20301479
      reference_title: "Stickler Syndrome."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Activities such as contact sports that may lead to traumatic retinal detachment."
      explanation: >
        GeneReviews names contact sports as the activity that may lead to
        traumatic retinal detachment, which is the exposure-to-mechanism link
        asserted here.
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Agents/circumstances to avoid: Activities such as contact sports that may lead to traumatic retinal detachment."
    explanation: >
      The GeneReviews circumstances-to-avoid item establishing trauma as the
      relevant environmental exposure in this disease.
  notes: >
    Left without an `exposure_term`. ECTO was searched for trauma, injury,
    mechanical and physical exposure terms and for sport; it has
    `ECTO:6000002` exposure to exercise and `ECTO:6000031` exposure to
    strenuous exercise, neither of which means blunt ocular or head trauma.
    No term beats a wrong one, so none is bound.
animal_models:
- name: cho/+ heterozygous Col11a1 mouse
  species: Mouse
  genotype: Col11a1 cho/+ (heterozygous functional null)
  publication: PMID:13130470
  description: >
    The spontaneous chondrodysplasia (cho) allele is a functional null of
    Col11a1. Homozygotes die perinatally; heterozygotes are viable and are the
    standard genetic model for the joint arm of COL11A1 disease. Because the
    allele is a null rather than a dominant-negative missense change, the
    heterozygote models haploinsufficiency and not the human STL2 lesion -
    which is why it splits so sharply between the joint and ear phenotypes.
  modeled_mechanisms:
  - target: Articular Cartilage Degeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >
      cho/+ mice develop increased articular cartilage fibril diameter and
      osteoarthritis-like degeneration of knee and temporomandibular joints
      from three months of age.
    limitations: >
      The cho allele is a functional null, so the heterozygote reproduces the
      joint phenotype through halved collagen XI dosage rather than through
      the dominant-negative incorporation that operates in human STL2.
    readouts:
    - name: Articular cartilage collagen fibril diameter
      target: Articular Cartilage Degeneration
      direction: INCREASED
      interpretation: >
        Structural correlate of loss of collagen XI fibril-diameter control
        in the joint.
      evidence:
      - reference: PMID:13130470
        reference_title: "Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho)."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "The diameter of collagen fibrils in articular cartilage of knee joints from heterozygous cho/+ mice was increased relative to that in control cartilage"
        explanation: Reports the fibril-diameter measurement behind this readout.
    evidence:
    - reference: PMID:13130470
      reference_title: "Osteoarthritis-like changes and decreased mechanical function of articular cartilage in the joints of mice with the chondrodysplasia gene (cho)."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "Heterozygosity for a loss-of-function mutation in Col11a1 results in the development of OA in the knee and TM joints of cho/+ mice"
      explanation: >
        Supports treating cho/+ as informative for the articular cartilage
        degeneration node.
  - target: Cochlear Extracellular Matrix Abnormality
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >
      Auditory brainstem response thresholds in cho/+ mice are
      indistinguishable from wild-type littermates through ten months of age,
      despite the same animals developing the joint phenotype. Human COL11A1
      heterozygotes have frequent sensorineural hearing loss.
    limitations: >
      The negative result is specific to a null allele on a C57BL/6
      background. The authors read it as evidence that the human auditory
      phenotype requires dominant-negative mutant chains rather than reduced
      dosage, so the model's failure is mechanistically informative but it
      cannot be used to study the human cochlear lesion.
    readouts:
    - name: Auditory brainstem response threshold
      target: Cochlear Extracellular Matrix Abnormality
      direction: UNCHANGED
      interpretation: >
        No hearing loss detectable in the heterozygote at any age tested - a
        negative result against the human phenotype.
      evidence:
      - reference: PMID:12527136
        reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
        supports: SUPPORT
        evidence_source: MODEL_ORGANISM
        snippet: "There was no difference in ABR thresholds for click and tone burst stimuli between cho/+ and +/+ mice at all ages"
        explanation: Reports the ABR measurement behind this readout.
    evidence:
    - reference: PMID:12527136
      reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "our results indicate that Col11a1 haploinsufficiency does not cause significant hearing loss on the C57BL/6 strain background"
      explanation: >
        Substantiates the failure of this model to reproduce the human
        cochlear phenotype.
  evidence:
  - reference: PMID:12527136
    reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Chondrodysplasia (cho) is a functional null allele of Col11a1 that causes lethal chondrodysplasia in cho/cho newborn mice, and osteoarthritis in cho/+ heterozygotes."
    explanation: >
      Establishes the identity and phenotype of the cho/+ model recorded
      here: a Col11a1 functional null whose heterozygote develops
      osteoarthritis.
- name: col11a1a morpholino knockdown zebrafish
  species: Zebrafish
  genotype: col11a1a morpholino knockdown
  publication: PMID:19638309
  description: >
    Morpholino knockdown of the zebrafish COL11A1 ortholog, expressed at 48
    hours post fertilisation in craniofacial skeleton, pectoral fin
    endoskeleton and otic vesicles.
  modeled_mechanisms:
  - target: Craniofacial Cartilage Malformation
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >
      Knockdown embryos develop craniofacial cartilage defects with
      disordered chondrocyte organization and abnormally thick, sparse
      cartilage matrix fibrils, which the authors note resemble human
      Stickler/Marshall chondrodysplasia.
    limitations: >
      A transient morpholino knockdown in a teleost with two COL11A1
      orthologs, modelling loss of collagen XI rather than the human
      dominant-negative allele; no ocular or auditory phenotype was assessed.
    evidence:
    - reference: PMID:19638309
      reference_title: "Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "the defects observed in cartilage formation resemble those observed in human chondrodysplasia such as the Stickler/Marshall syndrome"
      explanation: >
        The authors' own assessment that this model is informative for the
        human craniofacial cartilage phenotype.
  evidence:
  - reference: PMID:19638309
    reference_title: "Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Zebrafish represent a novel reliable vertebrate model for collagen XI collagenopathies."
    explanation: >
      The authors' assessment that this model system is informative for the
      collagen XI collagenopathies, of which STL2 is one.
treatments:
- name: Prophylactic Retinal Cryotherapy
  description: >
    360-degree contiguous cryotherapy at the retina-pars plana junction, to
    forestall giant retinal tear and detachment before it happens. The
    controlled evidence comes from type 1 cohorts, so use in STL2 is
    extrapolated from the shared vitreoretinal mechanism rather than
    demonstrated.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: retinal cryotherapy
    term:
      id: NCIT:C40030
      label: Cryotherapy
  target_mechanisms:
  - target: Vitreoretinal Traction and Retinal Tear
    description: >
      Prophylactic chorioretinal adhesion at the vitreous base blocks the
      progression from vitreoretinal traction to detachment.
  evidence:
  - reference: PMID:24793526
    reference_title: "Prevention of retinal detachment in Stickler syndrome: the Cambridge prophylactic cryotherapy protocol."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "all analyses indicate that the Cambridge prophylactic cryotherapy protocol is safe and markedly reduces the risk of retinal detachment"
    explanation: >
      The controlled cohort establishing prophylactic cryotherapy efficacy was
      conducted in 487 type 1 Stickler syndrome patients, so it supports use
      in type 2 only by extension from the shared vitreoretinal mechanism.
  - reference: PMID:21466760
    reference_title: "The clinical effectiveness and safety of prophylactic retinal interventions to reduce the risk of retinal detachment and subsequent vision loss in adults and children with Stickler syndrome: a systematic review."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "Only 360° cryotherapy and focal and circumferential laser treatment have been evaluated for the type 1 Stickler syndrome population, and then only by a single retrospective, controlled, cohort study in each case."
    explanation: >
      A systematic review making the scope limitation explicit: the
      prophylaxis evidence base is type 1 and retrospective, which is why
      this treatment carries INDIRECT directness for type 2.
  notes: >
    The same review flags a high risk of bias in both underlying studies and
    the absence of randomised data. Determining the retinal detachment risk
    of type 2 patients specifically was named as a service priority.
- name: Prophylactic 360-Degree Laser Retinopexy
  description: >
    Circumferential laser retinopexy posterior to the ora serrata, the other
    arm of retinal-detachment prophylaxis. As with cryotherapy the reported
    series are in Stickler syndrome broadly rather than type 2 specifically.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: laser retinopexy
    term:
      id: NCIT:C15466
      label: Laser Therapy
  target_mechanisms:
  - target: Vitreoretinal Traction and Retinal Tear
    description: >
      Laser-induced chorioretinal adhesion at the vitreous base interrupts
      the progression from a traction tear to detachment.
  evidence:
  - reference: PMID:36583093
    reference_title: "Preventing Retinal Detachment: Where are We? Implications from Stickler Syndrome."
    supports: SUPPORT
    directness: INDIRECT
    evidence_source: HUMAN_CLINICAL
    snippet: "extraordinary publications in 2021-2022, each reporting successful prevention of RRD in Stickler syndrome, using 360-degree (encircling) laser retinopexy"
    explanation: >
      Reports successful prevention of rhegmatogenous retinal detachment with
      360-degree laser retinopexy in Stickler syndrome. Scoped to Stickler
      syndrome as a whole rather than to type 2, hence INDIRECT.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "laser therapy for prevention of retinal detachment"
    explanation: >
      GeneReviews names laser therapy for retinal detachment prevention among
      the treatments of manifestations.
- name: Ophthalmic Surveillance, Refractive Correction and Patient Education
  description: >
    Annual review by a vitreoretinal specialist, spectacle correction of the
    refractive error, and teaching patients the symptoms of a detachment so
    they present within the window in which vision can be saved. Repair of an
    established detachment is not curated as a separate treatment here - see
    the entry `notes`.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: ophthalmic surveillance and patient education
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Retinal detachment
    term:
      id: HP:0000541
      label: Retinal detachment
  - preferred_term: High myopia
    term:
      id: HP:0011003
      label: High myopia
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "education on risks and symptoms of retinal detachment; correction of refractive errors with spectacles"
    explanation: >
      The GeneReviews treatment-of-manifestations items this record covers:
      detachment education and spectacle correction.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Surveillance: Annual examination by a vitreoretinal specialist; audiologic evaluations annually"
    explanation: >
      The GeneReviews surveillance schedule underpinning the annual
      vitreoretinal review recorded here.
- name: Avoidance of Contact Sports
  description: >
    Standing advice to avoid contact sports and other activities carrying a
    risk of ocular or head trauma, because the abnormal vitreous converts
    minor trauma into a retinal detachment. This is the syndrome's
    circumstances-to-avoid warning.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: activity restriction to prevent traumatic retinal detachment
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_mechanisms:
  - target: Vitreoretinal Traction and Retinal Tear
    description: >
      Removing the mechanical trigger that precipitates tears in an already
      abnormal vitreoretinal interface.
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Agents/circumstances to avoid: Activities such as contact sports that may lead to traumatic retinal detachment."
    explanation: >
      The GeneReviews agents-and-circumstances-to-avoid recommendation this
      entry records.
- name: Hearing Amplification and Audiologic Surveillance
  description: >
    Annual audiologic evaluation with hearing aid fitting for the
    sensorineural loss, plus prompt treatment of otitis media and
    consideration of myringotomy tubes where a conductive component is
    present. Surveillance matters disproportionately here because many of
    these patients are also visually impaired.
  therapeutic_modality: DEVICE
  treatment_term:
    preferred_term: hearing amplification
    term:
      id: NCIT:C15747
      label: Supportive Care
    qualifiers:
    - predicate:
        preferred_term: medical device
        term:
          id: NCIT:C16830
          label: Medical Device
      value:
        preferred_term: hearing aid
        term:
          id: NCIT:C183182
          label: Hearing Aid
  target_phenotypes:
  - preferred_term: Sensorineural hearing impairment
    term:
      id: HP:0000407
      label: Sensorineural hearing impairment
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "standard treatment of sensorineural and conductive hearing loss; prompt treatment of otitis media; consider myringotomy tubes for recurrent otitis media"
    explanation: >
      GeneReviews management guidance for the auditory features treated here.
  - reference: PMID:23110709
    reference_title: "Hearing impairment in Stickler syndrome: a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Regular auditory follow-up is strongly advised, particularly because many Stickler patients are visually impaired"
    explanation: >
      Supports the surveillance component and its rationale in a
      dual-sensory-impairment population.
- name: Craniofacial and Cleft Palate Surgical Management
  description: >
    Care in a comprehensive craniofacial clinic, with tracheostomy where
    needed for neonatal Pierre Robin airway obstruction, mandibular
    advancement for persistent micrognathia, and feeding and nutritional
    support.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: craniofacial surgical management
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_phenotypes:
  - preferred_term: Cleft palate
    term:
      id: HP:0000175
      label: Cleft palate
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Management in a comprehensive craniofacial clinic when possible; tracheostomy as needed in infants with Pierre Robin sequence; mandibular advancement procedure to correct malocclusion for those with persistent micrognathia"
    explanation: >
      The GeneReviews craniofacial management recommendations recorded by
      this treatment.
- name: Symptomatic Management of Arthropathy
  description: >
    Symptomatic treatment of the joint disease with orthopedic input, plus
    clinical, radiographic and orthopedic assessment as needed. There is no
    disease-modifying therapy for the underlying collagen defect.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: symptomatic management of arthropathy
    term:
      id: NCIT:C15747
      label: Supportive Care
  target_phenotypes:
  - preferred_term: Premature osteoarthritis
    term:
      id: HP:0003088
      label: Premature osteoarthritis
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "symptomatic treatment for arthropathy; treatment of osteoarticular manifestations per orthopedist"
    explanation: >
      The GeneReviews management recommendation for the joint features that
      this record covers.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "clinical, radiographic, and/or orthopedic assessment as needed"
    explanation: The GeneReviews surveillance item for the musculoskeletal features.
- name: Genetic Counseling and Cascade Testing
  description: >
    Counseling for the 50% transmission risk, and identification of at-risk
    relatives so that ophthalmic surveillance and prophylaxis can begin before
    a first detachment rather than after one.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is appropriate to determine which family members at risk have Stickler syndrome and thus warrant ongoing surveillance and possible treatment to prevent retinal detachment."
    explanation: >
      GeneReviews evaluation-of-relatives-at-risk guidance, which is the
      rationale for cascade testing recorded here.
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Each child of an individual with autosomal dominant Stickler syndrome has a 50% chance of inheriting the pathogenic variant."
    explanation: The transmission risk this counseling record is built around.
diagnosis:
- name: Molecular genetic testing on a Stickler syndrome gene panel
  description: >
    The diagnosis rests on the clinical phenotype - the beaded vitreous is the
    single most useful clue toward COL11A1 - confirmed by a heterozygous
    pathogenic variant. Because the syndrome is locus heterogeneous, a
    multi-gene panel rather than single-gene COL11A1 sequencing is the
    standard first-tier test.
  evidence:
  - reference: PMID:20301479
    reference_title: "Stickler Syndrome."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of Stickler syndrome can be established in a proband with characteristic clinical features and/or a heterozygous pathogenic variant in COL2A1, COL11A1, or COL11A2"
    explanation: >
      GeneReviews' diagnostic statement, which names COL11A1 among the genes
      whose heterozygous variants establish the diagnosis.
  - reference: PMID:41856555
    reference_title: "Diagnostic genetic testing indications and findings in type II, IX and XI collagenopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnostic yield of Stickler syndrome panels was 50%, with a higher rate among cases reporting a family history"
    explanation: >
      Quantifies the real-world yield of the panel approach in a diagnostic
      laboratory series. The abstract does not state the denominator for the
      50%, and it is not the 7798 panels ordered - those yielded 214 cases
      with a pathogenic or likely pathogenic variant in total.
  notes: >
    The yield figure is for Stickler syndrome panels overall, not for STL2
    specifically; the same series found ocular signs and family history were
    the commonest indications for ordering one.
differential_diagnoses:
- name: Stickler Syndrome Type 1
  description: >
    The commoner COL2A1-related form. Separated at the slit lamp by a
    membranous rather than beaded vitreous, and clinically by less frequent
    hearing impairment.
  distinguishing_features:
  - Membranous rather than beaded vitreous phenotype
  - COL2A1 haploinsufficiency rather than dominant-negative COL11A1
  - Hearing impairment in about half of COL2A1 patients (52.2%) versus 82.5% of COL11A1 patients in the same review
  evidence:
  - reference: PMID:20513134
    reference_title: "Stickler syndrome and the vitreous phenotype: mutations in COL2A1 and COL11A1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in COL2A1 usually result in a congenital membranous vitreous anomaly. In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance."
    explanation: States the vitreous phenotype that distinguishes the two forms.
  - reference: PMID:23110709
    reference_title: "Hearing impairment in Stickler syndrome: a systematic review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Overall, mutations in COL11A1 (82.5%) and COL11A2 (94.1%) seem to be more frequently associated with hearing impairment than mutations in COL2A1 (52.2%)"
    explanation: Quantifies the auditory difference between the COL11A1 and COL2A1 forms.
- name: Marshall Syndrome
  description: >
    An allelic COL11A1 disorder overlapping STL2, associated in particular
    with splicing variants of the 54-bp exons in the C-terminal region of the
    gene.
  distinguishing_features:
  - Retracted midface with flat nasal bridge, short nose, anteverted nostrils and long philtrum
  - Short stature and abnormal cranial ossification
  - Retinal detachment reported less often than in Stickler syndrome
  - Overlapping cases carrying features of both syndromes are well described
  evidence:
  - reference: PMID:10486316
    reference_title: "Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene"
    explanation: >
      Identifies the COL11A1 variant class that separates the Marshall
      phenotype from classic Stickler syndrome.
  - reference: PMID:10486316
    reference_title: "Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Some patients, however, presented with phenotypes of both Marshall and Stickler syndromes."
    explanation: >
      Records the overlap that makes this the principal differential rather
      than a cleanly separable entity.
- name: Otospondylomegaepiphyseal Dysplasia
  description: >
    The COL11A2-related type XI collagenopathy, presenting with hearing loss
    and skeletal dysplasia but without the ocular disease. The accepted
    explanation is that the alpha2(V) chain substitutes for alpha2(XI) in
    vitreous, so a COL11A2 lesion is covered for there and not elsewhere.
  distinguishing_features:
  - Absence of the vitreous and retinal features
  - Caused by COL11A2 rather than COL11A1
  evidence:
  - reference: PMID:8872475
    reference_title: "A family with Stickler syndrome type 2 has a mutation in the COL11A1 gene resulting in the substitution of glycine 97 by valine in alpha 1 (XI) collagen."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A mutation in COL11A2, the gene for alpha 2 (XI) procollagen, has recently been found in a family described as having Stickler syndrome, although there was no ocular involvement."
    explanation: >
      Records the absence of ocular involvement in COL11A2-related disease,
      the feature that distinguishes it from STL2.
  - reference: PMID:10486316
    reference_title: "Splicing mutations of 54-bp exons in the COL11A1 gene cause Marshall syndrome, but other mutations cause overlapping Marshall/Stickler phenotypes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "chain substitutes for the α2(XI) chain in the vitreous (Mayne et al.1993), thus explaining the lack of the ocular symptoms in patients with the COL11A2 gene mutations"
    explanation: >
      Gives the mechanistic reason COL11A2 disease spares the eye, which is
      what makes the ocular features a reliable discriminator.
  - reference: PMID:33348901
    reference_title: "Exon-Trapping Assay Improves Clinical Interpretation of COL11A1 and COL11A2 Intronic Variants in Stickler Syndrome Type 2 and Otospondylomegaepiphyseal Dysplasia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Type 2 SS and the SS variant otospondylomegaepiphyseal dysplasia (OSMED) are caused by deleterious variants in COL11A1 and COL11A2, respectively."
    explanation: States the gene assignment that separates the two entities.
discussions:
- discussion_id: cho_heterozygote_auditory_mismatch
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  prompt: >
    Why do cho/+ mice, heterozygous for a Col11a1 functional null, develop the
    joint phenotype of COL11A1 disease but show no hearing loss at all, when
    human COL11A1 heterozygotes have frequent sensorineural hearing loss?
  attaches_to:
  - pathophysiology#Cochlear Extracellular Matrix Abnormality
  - animal_models#cho/+ heterozygous Col11a1 mouse
  rationale: >
    The mismatch is mechanistically load-bearing rather than a modelling
    nuisance. The mouse heterozygote tests halved Col11a1 dosage; human STL2
    alleles are missense and splice changes whose product still enters the
    heterotrimer. That the joint phenotype survives the switch to a null
    allele while the auditory phenotype does not is the study's argument that
    the human cochlear lesion needs dominant-negative mutant chains and is
    not a dosage effect. The cho/cho homozygote is not the exception it looks
    like: it does have marked ABR hearing loss and a disorganized organ of
    Corti, but that is a recessive, perinatally lethal genotype modelling the
    fibrochondrogenesis end of the COL11A1 spectrum rather than dominant
    STL2. So no current mouse model addresses the auditory arm of STL2 at the
    right gene dosage; a knock-in of a human triple-helical missense allele
    would be the test.
  evidence:
  - reference: PMID:12527136
    reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "To determine if Col11a1 haploinsufficiency causes hearing loss in cho/+ mice, auditory brainstem response (ABR) thresholds were measured at 2, 4, 6, 8 and 10 months of age. There was no difference in ABR thresholds for click and tone burst stimuli between cho/+ and +/+ mice at all ages."
    explanation: >
      The negative auditory result in the heterozygous mouse that constitutes
      the mismatch.
  - reference: PMID:12527136
    reference_title: "Auditory function associated with Col11a1 haploinsufficiency in chondrodysplasia (cho) mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We conclude that Stickler syndrome and Marshall syndrome mutations in COL11A1 cause hearing loss via dominant negative effects upon wild-type fibrillar collagen polypeptides in the extracellular matrices of the cochlea"
    explanation: >
      The authors' resolution of the mismatch, and the reason it is
      mechanistically informative rather than merely a failed model.
  - reference: PMID:1952599
    reference_title: "Ultrastructural changes of cochlea in mice with hereditary chondrodysplasia (cho/cho)."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These mice show marked hearing loss when tested by auditory brain-stem responses. The temporal bone shows underdevelopment of the organs of Corti in the lower turn of the cochlea."
    explanation: >
      The homozygote does have a cochlear phenotype, so the mismatch is
      specific to the heterozygote and to gene dosage rather than to the
      mouse cochlea being insensitive to Col11a1 loss.
notes: >
  Curated from a claude_code deep-research report
  (research/Stickler_Syndrome_Type_2-deep-research-claude_code.md) with the
  GeneReviews Stickler syndrome chapter (PMID:20301479) as the phenotype
  baseline. Two areas were deliberately left out. First, the rare biallelic
  COL11A1 form reported with unusually severe hearing loss: it is a distinct
  inheritance mode and belongs in its own record rather than as a footnote
  here. Second, a prevalence figure specific to type 2: none was found, so
  the `prevalence` record carries `prevalence_class: UNKNOWN` and states why
  a number was declined rather than adopting Orphanet's group-scoped band.
  The report's "10-20% of Stickler cases" figure is a case fraction rather
  than a population rate, and is recorded as one under
  `genetic.case_fractions`, sourced to PMID:32558342.

  No datasets are recorded. `just discover-datasets` returns only GENE_ONLY
  matches on COL11A1 - GEO series about collagen XI in ovarian cancer and in
  cutaneous squamous cell carcinoma invasion. Those accessions resolve
  perfectly and are about a different disease entirely, which is the Named
  Entity Confusion case the dataset-curation guidance warns about; none is
  admitted here.

  Lattice retinal degeneration is not recorded, and the omission is
  deliberate. The deep-research report puts paravascular lattice retinopathy
  at 38% and places it inside the vitreous-traction-to-detachment chain, so
  it belongs here on the merits; `HP:0007992` is the right term, and the
  report's proposed `HP:0000875` is *Episodic hypertension* and was rejected.
  What is missing is a quotable source. The 38% traces to Poulson et al.,
  "Clinical features of type 2 Stickler syndrome" (PMID:15286167,
  DOI:10.1136/jmg.2004.018382), which has no abstract in PubMed, whose BMJ
  full text returns HTTP 403, and whose PMC copy (PMC1735871) no `just
  fetch-reference` prefix reaches. Every other cached source that mentions
  lattice is scoped elsewhere: PMID:21466760 discusses it in type 1 Stickler
  cohorts, PMID:36583093 in the general rhegmatogenous-detachment population,
  and the one recent case report pairing lattice with Stickler (PMID:41997526)
  is COL2A1, so type 1. Adding the phenotype on any of those would import a
  claim across the scope boundary this entry is otherwise careful about.
  Revisit if the Poulson text becomes fetchable.

  Repair of an established detachment - scleral buckling, vitrectomy - is not
  curated as a treatment. It is part of management, but no quotable sentence
  about it was found in any cached source and the GeneReviews abstract does
  not mention it; attaching a prophylaxis quote to a surgical-repair record
  would be a claim-evidence mismatch. Prophylaxis, surveillance and education
  are curated instead.

📚

References & Deep Research

References

1

PMID:20301479

Stickler Syndrome.

No top-level findings curated for this source.

Deep Research

1

Claude Code ▸

Stickler Syndrome Type 2 (COL11A1-Related Stickler Syndrome): Comprehensive Research Report

claude-haiku-4-5-20251001, claude-sonnet-5 26 citations 2026-09-04T00:06:37.807998

Stickler Syndrome Type 2 (COL11A1-Related Stickler Syndrome): Comprehensive Research Report

1. Disease Information

Overview. Stickler syndrome type 2 (STL2) is a rare, autosomal dominant connective tissue disorder caused by heterozygous pathogenic variants in COL11A1, the gene encoding the α1(XI) chain of type XI collagen. It belongs to the "Stickler syndrome" family of collagenopathies (types I–V), all of which share a core tetrad of ocular, auditory, skeletal, and orofacial abnormalities but differ by causal gene and vitreous phenotype. Type 2 is distinguished clinically from type 1 (COL2A1-related) by its characteristic "beaded" (as opposed to "membranous"/type 1) vitreous anomaly, more pronounced midfacial hypoplasia, and substantially more prevalent and severe hearing loss (OMIM #604841; GeneReviews – Stickler Syndrome).

Key identifiers: - OMIM: #604841 (STICKLER SYNDROME, TYPE II; STL2) - Orphanet: ORPHA828 (Stickler syndrome, umbrella entry) / ORPHA90654 (type 2 specific entry cited in the literature) - Gene/Locus: COL11A1, chromosome 1p21.1 - MeSH/ICD-11: Grouped under hereditary connective tissue disorders / arthro-ophthalmopathy - Suggested MONDO mapping: A MONDO ID specific to STL2 should be confirmed via the MONDO browser at curation time (not resolved in this search pass).

Synonyms: Hereditary arthro-ophthalmopathy, type 2; STL2; beaded vitreous Stickler syndrome; Stickler syndrome, COL11A1-related. Note the close nosological relationship to Marshall syndrome and otospondylomegaepiphyseal dysplasia (OSMED), both also caused by COL11A1/COL11A2 variants, discussed further under Etiology.

Evidence basis: Most published data derive from aggregated clinical cohorts (case series of genetically confirmed COL11A1 probands and families), disease-level curated resources (OMIM, GeneReviews, Orphanet), and ClinVar variant submissions, rather than large-scale population EHR studies — consistent with STL2's rarity.

Sources: OMIM #604841, GeneReviews Stickler Syndrome (NBK1302), Orphanet – Stickler syndrome

2. Etiology

Disease causal factors. STL2 is a purely genetic, monogenic disorder. It is caused by heterozygous (dominant) pathogenic variants in COL11A1 that disrupt the assembly or function of type XI collagen heterotrimers in cartilage and vitreous extracellular matrix. There is no known environmental, infectious, or purely mechanistic (non-genetic) causal pathway for classic STL2; environmental/behavioral factors instead modulate secondary complications (e.g., ocular trauma precipitating retinal detachment) rather than causing the underlying disease.

Genetic risk factors: - Causal variants: Predominantly splice-site variants and missense substitutions in glycine residues of the collagen triple-helical Gly-X-Y repeat domain; also in-frame exonic deletions and, less commonly, nonsense/frameshift variants leading to premature stop codons. COL11A1 intron 50 has been identified as a mutational hot spot (GeneReviews NBK1302). - Splicing mutations affecting the 54-bp exons in the C-terminal (fibronectin-like) region of COL11A1 are specifically associated with the Marshall syndrome phenotype, whereas other COL11A1 variant types produce classic Stickler or overlapping Marshall/Stickler phenotypes — "of 10 mutation-positive patients, four were diagnosed with Marshall syndrome, but the remaining 6 showed an overlapping Marshall/Stickler phenotype" (Griffith et al., Am J Hum Genet, PMID:10486316). - Recessive/biallelic COL11A1 variants: a distinct, non-classical mode has been reported — inherited and de novo biallelic COL11A1 pathogenic variants causing a recessive form of type 2 Stickler syndrome with unusually severe hearing loss, distinct from the fibrochondrogenesis phenotype normally caused by biallelic loss-of-function COL11A1 variants (Nixon et al., 2020, PMC7507023; PMID via Mol Genet Genomic Med). - Population frequency of causal alleles: COL11A1 variants are individually ultra-rare; gnomAD population allele frequencies for reported pathogenic variants are typically <0.003%, consistent with a rare dominant disorder under purifying selection (ClinVar records). - Modifier/susceptibility factors: No confirmed modifier genes for STL2 severity have been established in the literature reviewed; phenotypic variability appears substantially attributable to variant type/location (dominant-negative vs. haploinsufficient mechanisms) rather than a distinct modifier locus.

Environmental risk factors: None causal for disease onset. However, contact sports and activities with head/ocular trauma risk are recognized risk factors for retinal detachment in already-affected individuals, and this underlies the standard counseling to avoid such activities (GeneReviews NBK1302).

Protective factors: No genetic or environmental protective factors specific to STL2 are documented in the literature surveyed. Prophylactic ophthalmologic intervention (see Prevention/Treatment) functions as a secondary-prevention strategy rather than a true "protective factor" against the underlying mutation.

Gene-environment interaction: The principal interaction described in the literature is mechanical/traumatic: the structurally weakened, "beaded" vitreous and peripheral retinal lattice degeneration confer markedly increased risk of retinal tear/detachment upon minor ocular trauma, amplifying an otherwise sporadic environmental exposure into a major morbidity in this genetic background.

3. Phenotypes

STL2 phenotypes span four organ systems, with characteristic frequency data drawn primarily from GeneReviews and cohort studies of genetically confirmed COL11A1 probands.

Ocular phenotypes

Feature	Frequency/Notes	Suggested HPO term
Myopia (typically congenital or early-onset, often high/progressive)	80–85% (up to 87% in one 31-patient, 6-pedigree series)	HP:0000545 (Myopia); HP:0011003 (Extreme myopia)
"Beaded"/type 2 congenital vitreous anomaly	Present in ~100% of confirmed COL11A1 cases in the defining cohort (31/31 individuals across 6 pedigrees)	Vitreous anomaly (no precise HPO 1:1 term; often captured under HP:0007957 Corneal/vitreous phenotype categories — verify at curation)
Retinal detachment	<40% (lower than COL2A1-related type 1)	HP:0000541 (Retinal detachment)
Paravascular lattice retinopathy	38% in the same 31-patient cohort	related to HP:0000875 (lattice degeneration, if available)
Cataract (often early-onset)	Reported but less quantified specifically for type 2	HP:0000518 (Cataract)

Onset is typically congenital/early childhood (myopia and vitreous anomaly present from birth or early infancy); progression of myopia can continue through childhood; retinal detachment risk is lifelong, including risk in adults >50 years old.

Auditory phenotypes

Overall prevalence of hearing impairment: 69–75-80% of individuals with type 2 Stickler syndrome have hearing loss in at least one ear (four-frequency average >20 dBHL) (Alexander et al. 2020, PMID:32901364).
Type: Predominantly sensorineural (77% of affected ears), with smaller proportions mixed (7%) or purely conductive (3%).
Severity: Most commonly mild in the better ear (46% of the cohort, 30/65 patients); reduced sensitivity is present across the full frequency spectrum (250 Hz–8 kHz), not confined to high frequencies as previously assumed.
Progression: Cross-sectional data (ages 3–70, mean 29.2) show "no significant progression of hearing loss beyond that expected of ageing (presbyacusis)" — i.e., largely stable/congenital rather than strongly progressive within an individual.
Mechanism: Cochlear/peripheral in origin (not central), possibly related to microstructural collagen irregularities in tympanic membrane fibrous layer and cochlear ECM; intrinsic tympanic membrane hypermobility (24% Ad-type tympanograms) is less frequent than in type 1 disease, suggesting a distinct intrinsic mechanism rather than sequelae of recurrent otitis media.
Suggested HPO terms: HP:0000407 (Sensorineural hearing impairment), HP:0000405 (Conductive hearing impairment), HP:0000410 (Mixed hearing impairment).

Orofacial phenotypes

Midfacial hypoplasia/flat facies: More pronounced in COL11A1-related than COL2A1-related disease. HPO: HP:0000272 (Flat face) / HP:0011800 (Midface retrusion).
Cleft palate (isolated or as part of Pierre Robin sequence): ~60% of COL11A1-related cases. HPO: HP:0000175 (Cleft palate); Pierre Robin sequence itself: HP:0000278 (Retrognathia) + HP:0000047 or the composite Pierre Robin term.
Micrognathia: HP:0000347.

Skeletal phenotypes

Early-onset degenerative joint disease/osteoarthritis, present in roughly 25% of affected individuals in the GeneReviews summary; joint hypermobility also reported. HPO: HP:0002829 (Arthralgia) / HP:0002758 (Osteoarthritis, early onset).

Quality of life impact

No STL2-specific EQ-5D/SF-36 data were identified in this search; qualitatively, the combination of progressive visual impairment risk (retinal detachment), hearing loss requiring amplification, orofacial surgical needs in infancy (Pierre Robin sequence can cause airway obstruction/feeding difficulty), and early degenerative joint disease collectively affect childhood development, education, and adult occupational/social function, per general Stickler syndrome literature (GeneReviews, NORD).

Sources: GeneReviews NBK1302, Alexander et al. 2020 — Auditory dysfunction in type 2 Stickler Syndrome, PMC8165062, OMIM #604841

4. Genetic/Molecular Information

Causal gene: COL11A1 (HGNC:2186; NCBI Gene 1301; OMIM *120280), chromosome 1p21.1, encoding pro-α1(XI) collagen chain, one of three chains (α1(XI), α2(XI), α3(XI)/COL2A1-derived) forming the heterotrimeric type XI collagen molecule.

Variant classes reported (per ClinVar and literature): - Missense variants substituting glycine residues in the Gly-X-Y triple-helical repeat (classic collagenopathy mechanism), e.g., p.Gly97Val reported in an early founding STL2 family (PMID:8872475). - Splice-site variants (donor/acceptor), frequently clustering around intron 50 and other introns; several verified functionally via minigene/exon-trapping assays (PMC7766184; Frontiers in Genetics 2025). - In-frame exonic deletions. - Nonsense variants causing premature stop codons (e.g., p.Glu1466Ter, p.Arg1362*). - Rare biallelic (compound heterozygous or homozygous) variants causing a recessive severe-hearing-loss phenotype rather than classic dominant STL2 or the more severe fibrochondrogenesis (Nixon et al. 2020).

Population frequency/gnomAD: Individual pathogenic COL11A1 variants are essentially absent or present at extremely low frequency (≤0.003%) in gnomAD control populations, consistent with a fully penetrant, rare autosomal dominant disorder under negative selection.

Somatic vs. germline: STL2 is exclusively a germline disorder; no somatic mosaicism-driven or acquired oncologic mechanism is implicated. Germline mosaicism in a parent is a recognized (though not separately quantified in this search) consideration for recurrence-risk counseling in apparently de novo cases, consistent with other autosomal dominant collagenopathies.

Functional consequence — molecular mechanism: "Pathogenic variants of type XI collagen more usually exert dominant negative effects," in contrast to COL2A1-related Stickler syndrome (type 1), which typically acts via haploinsufficiency. Dominant-negative variants (splice-site, in-frame deletion, glycine substitution) allow mutant α1(XI) chains to be incorporated into heterotrimers with wild-type chains, disrupting collagen fibril assembly ("fibrillogenesis") and secretion, producing a poison-peptide effect on the overall collagen network in vitreous and cartilage matrix. Loss-of-function/nonsense variants may instead act via haploinsufficiency in some cases.

Modifier genes: None specifically validated for STL2 in the sources reviewed.

Epigenetics: No disease-specific epigenetic (DNA methylation/histone) mechanism has been described for STL2 in the literature surveyed.

Chromosomal abnormalities: STL2 is caused by point/small-indel/splice variants rather than large chromosomal rearrangements; no recurrent CNV or translocation mechanism is reported.

Relationship to allelic disorders: COL11A1 variants also cause: - Marshall syndrome (particularly with splicing mutations of the 54-bp exons in the C-terminal region), overlapping clinically with STL2 but with more pronounced short nose/flat nasal bridge and midfacial hypoplasia. - Fibrochondrogenesis (severe skeletal dysplasia) from biallelic loss-of-function variants. - Nonsyndromic autosomal dominant sensorineural hearing loss, DFNA37, caused by a splice-altering COL11A1 variant, demonstrating allelic heterogeneity of clinical outcome depending on variant location/type (Nat Genet Med 2018).

Sources: GeneReviews NBK1302, OMIM #604841, ClinVar variant records, Griffith et al. Am J Hum Genet PMID:10486316, Alazami/Novel & recurrent COL11A1/COL2A1 mutations, Hum Genome Var 2017

5. Environmental Information

STL2 has no primary environmental, lifestyle, or infectious causal factor — it is a fully penetrant monogenic disorder. Environmental relevance is confined to: - Trauma: Contact sports, high-impact activity, and ocular trauma are recognized precipitants of retinal detachment in the structurally abnormal, "beaded" vitreous — this is the principal reason clinical guidance recommends avoidance of contact sports in affected individuals. - Noise exposure: No STL2-specific data on noise-induced hearing loss interaction were found in this search, though as with any baseline sensorineural hearing loss, cumulative noise exposure could theoretically compound existing deficits (inferred, not directly evidenced in the literature reviewed). - Infectious agents: Not causally implicated in STL2 pathogenesis itself; however, recurrent otitis media is a differential/comorbid contributor to conductive hearing loss components in Stickler syndrome broadly (more prominent in type 1 than reported for type 2, per the tympanometry data above).

No CTD (Comparative Toxicogenomics Database), TOXNET, or NHANES-level environmental exposure data specific to COL11A1/STL2 were located.

6. Mechanism / Pathophysiology

Ordered causal chain (from molecular lesion to clinical phenotype)

A heterozygous pathogenic variant (most often a glycine substitution or splice-altering mutation) in COL11A1 leads to an abnormal pro-α1(XI) collagen chain.
The abnormal chain is incorporated into the heterotrimeric type XI procollagen molecule alongside wild-type α2(XI) and α1(II)-lineage chains, which results in a dominant-negative poisoning of collagen triple-helix assembly (for splice/glycine/in-frame-deletion variants), or in reduced total functional protein (haploinsufficiency, more typical of nonsense/frameshift variants) — this specific dominant-negative-vs-haploinsufficiency branch point is a documented distinction rather than an inference.
Defective or reduced type XI collagen leads to disrupted regulation of lateral growth of co-assembled type II collagen fibrils, since type XI collagen normally acts as a nucleator/regulator controlling fibril diameter in cartilage and vitreous matrices where it constitutes 10–25% of vitreous collagen and 5–10% of cartilage collagen.
In the vitreous, this dysregulated fibrillogenesis results in short, irregular-diameter, thickened fibrils that aggregate into the diagnostic "beaded" lamellar vitreous phenotype (as opposed to the "membranous"/optically empty type 1 vitreous phenotype seen with COL2A1 haploinsufficiency) — demonstrated ultrastructurally and inferred from genotype-phenotype correlation studies.
The abnormal vitreous scaffold, combined with weakened vitreoretinal adhesion, predisposes to peripheral retinal lattice degeneration and, upon vitreous traction or trauma, leads to retinal tears and rhegmatogenous retinal detachment (documented clinical outcome, though the exact biomechanical step from beaded vitreous to lattice degeneration is partly inferred from structural/ultrastructural correlation rather than direct causal proof).
Independently, disrupted collagen XI content impairs normal growth-plate cartilage chondrocyte organization and endochondral ossification (demonstrated in the cho/cho mouse and zebrafish col11a1a knockdown models — see Model Organisms), which results in the midfacial hypoplasia/flat facies and, when severe enough during palatal shelf fusion in utero, causes cleft palate/Pierre Robin sequence via a mechanistic branch distinct from the ocular pathway.
Disrupted cartilage collagen matrix also leads to early degenerative joint disease (osteoarthropathy) via abnormal articular cartilage mechanical properties — demonstrated in heterozygous cho/+ mice, which develop osteoarthritis, supporting a direct model-organism causal link.
In the cochlea, type XI collagen abnormalities affect basilar and tectorial membrane extracellular matrix microstructure (inferred from cochlear expression pattern studies and structural correlation, since the heterozygous mouse model paradoxically shows no auditory phenotype — a documented human/model discrepancy, see below), leading to sensorineural hearing impairment across the frequency spectrum via a peripheral (cochlear), not central, auditory pathway (directly demonstrated by psychoacoustic/central-processing testing in the human cohort study).
Tympanic membrane fibrous-layer collagen abnormality separately may contribute to a smaller conductive/mixed hearing-loss component in a minority of ears, distinguishable from otitis-media-related conductive loss by tympanometric intrinsic hypermobility patterns (a mechanistic hypothesis, not fully proven).

Category detail

Molecular pathways: Collagen fibrillogenesis/triple-helix assembly is the dominant pathway (not a classical signaling cascade like Wnt/MAPK/PI3K-AKT); relevant GO terms include collagen fibril organization (GO:0030199) and extracellular matrix organization (GO:0030198).
Cellular processes: Chondrocyte differentiation/hypertrophy dysregulation (documented in zebrafish col11a1a knockdown, which alters "spatial organization of chondrocytes, the shaping of cartilage elements, and the maturation of chondrocytes to hypertrophy" — PMC9590009); no strong evidence of apoptosis, autophagy dysregulation, or classical inflammatory/immune-mediated cell death being primary in STL2 (unlike some other connective tissue disorders).
Protein dysfunction: Dominant-negative incorporation of mutant α1(XI) chains into heterotrimers causing structurally abnormal, likely intracellularly retained or extracellularly malformed collagen fibrils — a gain-of-abnormal-function/dominant-negative mechanism rather than simple misfolding/aggregation of the UPR type.
Tissue damage mechanisms: Mechanical/structural fragility (abnormal fibril diameter and spacing) rather than oxidative stress, ischemia, or classical fibrosis; retinal detachment represents a biomechanical tissue-failure event superimposed on this structurally weak matrix.
Biochemical abnormalities: Reduced or absent normal-diameter type XI collagen fibrils in vitreous and cartilage ECM; no known enzyme deficiency or ion channel defect is implicated.
Molecular profiling: No large-scale transcriptomic/proteomic/metabolomic datasets specific to human STL2 tissue were identified in this search (vitreous and cartilage biopsy material from patients is understandably difficult to obtain); most mechanistic data derive from animal/zebrafish models and biochemical/ultrastructural studies of collagen fibrils.
Advanced technologies: No single-cell, spatial transcriptomic, or CRISPR functional-genomics screen data specific to COL11A1/STL2 were found in this search pass; the zebrafish morphant/knockout and cho mouse models remain the principal functional-genomics tools used.

Suggested ontology terms: - GO:0030199 (collagen fibril organization), GO:0030198 (extracellular matrix organization), GO:0001501 (skeletal system development), GO:0060004 (reflex — not relevant), GO:0071711 (basement membrane organization) — verify applicability at curation. - CL terms: chondrocyte (CL:0000138), retinal pigment epithelial cell (context-dependent), hair cell of the cochlea (CL:0000583) as a candidate cochlear cell type of interest. - UBERON: vitreous body (UBERON:0001797), cartilage (UBERON:0002418), cochlea (UBERON:0000955), secondary palate (UBERON:0001716).

Sources: GeneReviews NBK1302, GeneCards COL11A1, Alexander et al. 2020, PMC8165062, Col11a1a zebrafish studies, PMC7558312, PMC9590009, Auditory function in cho mice, ResearchGate summary

7. Anatomical Structures Affected

Organ level: - Primary: Eye (vitreous, retina, lens), ear (cochlea, tympanic membrane), craniofacial skeleton (palate, mandible, midface), and appendicular/axial joints (articular cartilage). - Secondary/complications: Airway (Pierre Robin sequence–related obstruction in infancy), potentially cardiovascular (mitral valve prolapse is reported in some Stickler syndrome cohorts generally, though not specifically quantified for STL2 in this search). - Body systems: Ophthalmologic, auditory/vestibular, musculoskeletal, craniofacial/orofacial.

Tissue and cell level: - Vitreous humor (specialized extracellular matrix, largely acellular but organized by hyalocytes). - Articular and growth-plate cartilage (chondrocytes, CL:0000138). - Cochlear basilar and tectorial membranes (specialized ECM structures within the organ of Corti). - Tympanic membrane fibrous layer. - Palatal shelf mesenchyme during embryonic development.

Subcellular level: - Extracellular matrix/collagen fibrils (GO Cellular Component: extracellular matrix, GO:0031012); rough endoplasmic reticulum (site of procollagen synthesis/triple-helix folding) may be secondarily implicated in dominant-negative variants causing intracellular retention, though this is inferred by analogy to other collagenopathies rather than directly demonstrated for STL2 in the sources reviewed.

Localization: - Ocular findings are typically bilateral. - Hearing loss is "bilateral and symmetrical" in the majority of cases per the Alexander et al. cohort. - Craniofacial features (midfacial hypoplasia, cleft palate) are midline/bilateral rather than lateralized. - Joint disease can be poly-articular, most classically affecting large weight-bearing joints (hips, knees) with early degenerative change.

Suggested UBERON terms: UBERON:0001797 (vitreous body), UBERON:0000966 (retina), UBERON:0002418 (cartilage tissue), UBERON:0000955 (cochlea, or more specific substructures), UBERON:0001716 (secondary palate), UBERON:0002481 (mandible).

8. Temporal Development

Onset: - Congenital/early-childhood onset is typical for the defining ocular anomaly (vitreous phenotype present from birth), congenital or early-onset myopia, and — when present — cleft palate/Pierre Robin sequence (present at birth). - Hearing loss is generally present from early life (the cohort study spanning ages 3–70 supports this) rather than adult-onset. - Onset pattern for the joint disease is insidious, with "early-onset degenerative joint disease" typically manifesting well before the general population's usual osteoarthritis age.

Progression: - Ocular: Myopia may progress in childhood; retinal detachment risk is lifelong and can occur even after age 50, meaning prophylaxis is recommended "for SS adults of any age," not just childhood. - Auditory: Statistically, hearing loss shows "no significant progression... beyond that expected of ageing (presbyacusis)" in cross-sectional data — i.e., relatively stable rather than strongly progressive within an individual, though this is based on cross-sectional rather than longitudinal cohort data and should be interpreted cautiously. - Skeletal: Progressive, degenerative joint disease with earlier-than-typical onset of osteoarthritic changes. - Disease course pattern: Chronic and lifelong rather than episodic/relapsing-remitting; there is no described spontaneous remission. - Critical periods: In utero/early embryonic period for craniofacial (palatal fusion) and skeletal patterning; neonatal period for airway management in Pierre Robin sequence; childhood/adolescence is the critical window for ongoing surveillance (retinal exams) given retinal detachment risk starting early and persisting lifelong.

No formal staging system (analogous to AJCC cancer staging) exists for Stickler syndrome; severity is instead tracked via organ-specific outcome measures (visual acuity, audiometric thresholds, joint imaging).

9. Inheritance and Population

Epidemiology: - Overall Stickler syndrome (all types combined) birth prevalence is estimated at 1/7,500 to 1/9,000 (Orphanet). - COL11A1-related Stickler syndrome (type 2) accounts for approximately 10–20% of all genetically confirmed Stickler syndrome cases (multiple concordant sources: GeneReviews, Orphanet, and case-series literature).

Inheritance pattern: Autosomal dominant (classic STL2). A distinct, rarer autosomal recessive/biallelic form has also been reported, causing a severe-hearing-loss variant phenotype rather than the lethal fibrochondrogenesis otherwise associated with biallelic COL11A1 loss-of-function (Nixon et al. 2020).

Penetrance: Reported as high/complete for the core phenotype in dominant carriers, though expressivity (see below) is markedly variable — a heterozygous pathogenic variant essentially always produces some disease manifestation, but the specific combination and severity of features differs.

Expressivity: Highly variable, "both within and among families" (GeneReviews), and echoed in case reports such as "Variable clinical expression of Stickler Syndrome: A case report of a novel COL11A1 mutation" (PMID:32558342).

Genetic anticipation: Not a recognized feature of STL2 (no repeat-expansion mechanism); not applicable.

Germline mosaicism: Not specifically quantified for COL11A1 in the sources reviewed, but standard genetic counseling principles for autosomal dominant collagenopathies with apparent de novo variants would still consider low-level parental germline mosaicism a residual recurrence-risk factor (inferred from general collagenopathy genetics, not directly sourced here).

Founder effects: No specific COL11A1 founder mutation/population was identified in this search (contrast with some other Mendelian disorders); further targeted search of population genetics databases would be needed to confirm absence versus simply not surfaced.

Consanguinity: Relevant specifically to the rare recessive/biallelic COL11A1 form (Nixon et al. 2020 cohort included both inherited-biallelic and de novo-biallelic cases), where recessive inheritance would be expected to have a higher incidence in consanguineous families, though this was not explicitly quantified in the search results.

Carrier frequency: Not applicable in the classic sense for a fully penetrant dominant disorder; for the recessive biallelic form, no specific carrier frequency was found (individual variants are each individually rare per gnomAD).

Population demographics: - No specific ethnic or geographic enrichment for COL11A1-related STL2 was identified in the sources reviewed (contrast to some Stickler-related genes/populations with founder effects); Stickler syndrome overall is described as pan-ethnic. - Sex ratio: No sex-linked or sex-skewed prevalence was identified for STL2 (autosomal dominant with no reported sex-influenced penetrance in the sources reviewed). - Age distribution: All-ages disorder from birth through late adulthood, as evidenced by cohort studies spanning ages 3–70.

Sources: Orphanet – Stickler syndrome, GeneReviews NBK1302, Nixon et al. 2020, PMC7507023, Brizola et al. 2020, PMID:32558342

10. Diagnostics

Clinical tests: - Ophthalmologic examination: Slit-lamp and dilated fundoscopic exam to characterize the vitreous phenotype (type 2 "beaded" vitreous is itself a key diagnostic clue distinguishing STL2 from type 1), assess myopia degree, and screen for lattice retinopathy/retinal thinning. - Audiologic evaluation: Pure-tone audiometry across the full frequency range (250 Hz–8 kHz, per the Alexander et al. protocol), tympanometry to assess middle-ear/tympanic membrane compliance, and central auditory processing assessment to localize the lesion to the cochlear/peripheral level. - Imaging: Skeletal radiographs for epiphyseal changes and joint assessment; craniofacial imaging as needed for orofacial anomalies; no disease-specific advanced imaging modality (MRI/CT/PET) is a primary diagnostic tool. - Biopsy/pathology: Not routinely used for diagnosis; the diagnosis rests on clinical phenotype plus molecular confirmation rather than histopathology.

Genetic testing: - No universal consensus clinical diagnostic criteria exist for Stickler syndrome; diagnosis is established by "characteristic clinical features and/or a heterozygous pathogenic variant in COL2A1, COL9A1, COL9A2, COL9A3, COL11A1, or COL11A2" (GeneReviews). - Recommended approach: Given locus heterogeneity, a multi-gene panel covering COL2A1, COL9A1/2/3, COL11A1, and COL11A2 is the standard first-tier test; single-gene COL11A1 sequencing may be prioritized when the vitreous phenotype and more severe hearing loss/midfacial hypoplasia point specifically toward type 2. - Exon-trapping/minigene splicing assays have been used to functionally reclassify intronic COL11A1 variants of uncertain significance as pathogenic splice-altering variants (PMC7766184; Frontiers 2025). - WES/WGS utility: appropriate when panel testing is negative or when phenotype is atypical/overlapping (e.g., Marshall/Stickler overlap), given demonstrated allelic heterogeneity across the COL11A1 locus. - Chromosomal microarray/karyotype/FISH: Not indicated, as STL2 is not caused by CNV or chromosomal rearrangement. - Mitochondrial DNA/repeat expansion testing: Not applicable.

Omics-based diagnostics: No routine transcriptomic, proteomic, metabolomic, or liquid-biopsy-based diagnostic modality exists for STL2; RNA-based splicing assays (minigene constructs) function as a research/confirmatory tool for variant interpretation rather than a first-line clinical diagnostic.

Clinical criteria: No DSM/ICD-based standardized diagnostic checklist was identified in this search; clinical suspicion is typically built from the combined ocular-auditory-orofacial-skeletal tetrad plus family history, confirmed molecularly.

Differential diagnosis: Marshall syndrome (COL11A1, overlapping phenotype distinguished mainly by more pronounced short nose/flat nasal bridge), OSMED (COL11A2, no ocular involvement since COL11A2 is not vitreous-expressed), Stickler syndrome type 1 (COL2A1, membranous vitreous, more severe retinal detachment risk, milder hearing loss), other type XI/type IX collagenopathies (types 4/5), Pierre Robin sequence of other etiologies, and other syndromic causes of high myopia/hearing loss combinations.

Screening: No population-based newborn screening program exists for Stickler syndrome (it is not detected by standard metabolic newborn screening panels). Cascade genetic testing of at-risk relatives once a proband's COL11A1 variant is identified is the standard practice, alongside genetic counseling for family planning.

Sources: GeneReviews NBK1302, PMC7766184, Frontiers in Genetics 2025

11. Outcome/Prognosis

Survival and mortality: Stickler syndrome, including type 2, is not generally associated with reduced life expectancy from the connective tissue disorder itself. The main mortality risk historically relates to airway compromise in neonates with severe Pierre Robin sequence if unmanaged, which is a manageable, not inevitable, risk with modern neonatal care. No specific STL2 survival/mortality registry statistics were identified in this search.

Morbidity and function: - The principal morbidity drivers are visual (risk of retinal detachment leading to potential blindness if untreated or detected late) and auditory (bilateral, often lifelong sensorineural hearing loss affecting communication/education). - Early-onset degenerative joint disease contributes to musculoskeletal morbidity and potential need for early joint interventions (e.g., earlier-than-typical arthroplasty in severe cases, inferred from "early-onset degenerative joint disease" framing, though not explicitly quantified with an intervention rate in the sources found). - No disease-specific EQ-5D/SF-36/PROMIS quality-of-life dataset was located for STL2 in this search.

Disease course/complications: - Retinal detachment is the single most vision-threatening complication; with prophylactic treatment protocols (see Prevention/Treatment), detachment risk and visual morbidity can be substantially reduced. - Recurrent otitis media may complicate the auditory picture (more so in type 1 than type 2, per tympanometric data), and dental/orthodontic complications commonly follow midfacial hypoplasia and cleft palate repair. - Recovery potential: With early, consistent surveillance and prophylactic ophthalmologic intervention plus hearing amplification, functional visual and auditory outcomes are considerably better than the natural history without intervention — this is the central rationale for the structured lifelong surveillance protocols described below.

Prognostic factors: Variant type (dominant-negative splice/glycine-substitution variants vs. simple haploinsufficiency variants) likely influences phenotypic severity, though a fully validated genotype-severity prediction model was not identified in this search. Early diagnosis (enabling early prophylactic retinal treatment) is itself a major modifiable prognostic factor for visual outcome.

12. Treatment

There is currently no disease-modifying or curative therapy for STL2; management is entirely surveillance-based and symptomatic/preventive, targeting the organ-specific complications.

Pharmacotherapy: No COL11A1-targeted pharmacologic therapy exists. Standard analgesic/anti-inflammatory management (e.g., NSAIDs) may be used symptomatically for joint pain from early osteoarthritis, following general osteoarthritis management guidelines rather than a Stickler-specific protocol (NCIT:C15986, Pharmacotherapy — general, non-specific).

Advanced therapeutics (investigational): - Gene therapy and antisense oligonucleotide (ASO) approaches have been explored as an emerging strategy in Stickler syndrome broadly, with early research reportedly focused on correcting COL2A1-related (type 1) pathology; comparable COL11A1-targeted approaches were not identified as being in active clinical trials in this search. This should be treated as an early-stage/preclinical research direction rather than a current treatment option (NCIT:C15238, Gene Therapy — investigational only). - No cell therapy, targeted small-molecule, or immunotherapy approach specific to STL2 was identified.

Surgical and interventional: - Prophylactic retinal treatment: 360° laser photocoagulation or cryotherapy at the vitreous base/ora serrata is the mainstay of retinal-detachment prevention. Two named historical protocols: - Cambridge cryotherapy protocol: a 360° transconjunctival contiguous single row of cryotherapy spots at the retina–pars plana junction. - Manchester laser protocol: 3–4 rows of laser posterior to the ora serrata, 360°; an "extended vitreous base laser" approach (360° from ora serrata to equator) has shown better visual outcomes in some series. - The 2025 American Academy of Ophthalmology Preferred Practice Pattern guidelines recommend 360° laser prophylaxis for genetically confirmed Stickler syndrome patients (AAO EyeNet; search-derived summary). - Fellow-eye prophylaxis is "strongly recommended" after repair of a retinal detachment in the first eye, and prophylaxis should be offered to adults of any age given detachment risk persisting past age 50 (systematic review/meta-analysis summary, PMC9793794). - Vitreoretinal surgery (scleral buckle, vitrectomy) for established retinal detachment/giant retinal tear repair (NCIT:C15329, Surgical Procedure). - Orofacial surgery: Cleft palate repair; management of Pierre Robin sequence airway obstruction, sometimes requiring mandibular distraction osteogenesis or tracheostomy in severe neonatal cases (NCIT:C16186, Orthopedic Surgical Procedure / NCIT:C15329 general surgical procedure, per specific intervention). - Orthopedic intervention: As needed for advanced joint disease (e.g., joint replacement in severe early-onset osteoarthritis cases), though no STL2-specific arthroplasty statistics were found.

Supportive and rehabilitative care: - Hearing amplification (hearing aids) for sensorineural/mixed hearing loss; cochlear implantation would be considered per general audiology criteria in severe cases, though STL2-specific cochlear implant outcome data were not identified in this search. - Speech therapy for children with cleft palate/orofacial involvement. - Physical/occupational therapy for joint symptom management (NCIT:C15302, Physical Therapy). - Genetic counseling for affected families (NCIT:C15240, Genetic Counseling).

Experimental treatments: No active COL11A1-specific interventional clinical trial (ClinicalTrials.gov NCT identifier) was surfaced in this search; broader Stickler syndrome gene-therapy/ASO research (largely COL2A1-focused) represents the closest investigational analog.

Treatment outcomes: Prophylactic 360° laser/cryotherapy protocols are reported to be effective in reducing giant retinal tear/detachment incidence in both treated and fellow eyes, per multiple single-institution case series (search results above); no randomized controlled trial data were identified, and evidence is predominantly retrospective/observational.

Treatment strategy: Management follows an organ-system-based surveillance algorithm: annual dilated ophthalmologic exam (vitreoretinal specialist) starting in early childhood, annual audiologic evaluation, craniofacial/orthodontic follow-up through growth, and periodic musculoskeletal assessment — rather than a single unifying pharmacologic algorithm.

Sources: GeneReviews NBK1302, AAO EyeNet – Diagnosis and Management of Stickler Syndrome, Cambridge cryotherapy protocol, PMID:24793526, Preventing Retinal Detachment review, PMC9793794

13. Prevention

Primary prevention: Not applicable in the classic sense (no vaccination or exposure-avoidance strategy prevents the underlying genetic mutation); the closest analog is reproductive/preconception genetic counseling and, where desired, preimplantation genetic diagnosis (PGD) for families with a known pathogenic COL11A1 variant.

Secondary prevention: The dominant secondary-prevention strategy in STL2 is prophylactic vitreoretinal treatment (360° laser or cryotherapy) to prevent retinal detachment before it occurs — this is a hallmark, well-documented preventive intervention specific to this disease group (see Treatment section above), rather than a population screening program.

Screening/early detection: - No population-based newborn or carrier screening program exists for STL2 specifically. - Once a proband is molecularly diagnosed, cascade testing of first-degree relatives is standard, enabling early identification of at-risk family members before symptom onset, so that prophylactic ophthalmologic surveillance can begin proactively rather than reactively. - Prenatal testing is possible for known familial variants but is a family/ethical decision rather than a standard public-health recommendation, given the generally treatable/manageable nature of the disease.

Behavioral interventions: Avoidance of contact sports and high-risk trauma activities is the principal behavioral/lifestyle preventive recommendation to reduce retinal detachment risk.

Genetic counseling: Central to STL2 management given autosomal dominant inheritance with ~50% transmission risk per pregnancy for an affected parent, variable expressivity complicating risk prediction of severity (though not presence) in offspring, and the rare recessive biallelic form requiring different counseling for carrier parents.

Public health/environmental interventions: Not applicable — STL2 has no environmental/toxicant etiology to target with public health measures.

Prophylaxis: Beyond the ophthalmologic laser/cryotherapy prophylaxis already discussed, no pharmacologic prophylactic regimen exists.

14. Other Species / Natural Disease

Taxonomy of affected species: - Mouse (Mus musculus, NCBITaxon:10090): the chondrodysplasia (cho) mouse carries a spontaneous functional-null Col11a1 allele. Homozygous (cho/cho) mice die perinatally with lethal chondrodysplasia; heterozygous (cho/+) mice survive and develop osteoarthritis, modeling the human joint phenotype. - Zebrafish (Danio rerio, NCBITaxon:7955): possess two COL11A1 orthologs, col11a1a and col11a1b; col11a1a is most similar to human COL11A1 and to the mouse cho locus. - No specific naturally occurring companion-animal (dog/cat/horse) Stickler-syndrome-like COL11A1 disease was identified in this search; a targeted OMIA search would be needed to confirm absence versus a gap in this search pass.

Orthologous genes: Mouse Col11a1 (MGI ortholog of human COL11A1); zebrafish col11a1a/col11a1b (duplicated due to teleost genome duplication).

Natural disease/veterinary relevance: No veterinary clinical case series of naturally occurring COL11A1-associated disease in companion animals or wildlife was found in this search.

Comparative biology: - Conservation of mechanism: The role of type XI collagen in regulating collagen fibril diameter during chondrogenesis and cartilage matrix organization is evolutionarily conserved from fish to mammals, as shown by concordant phenotypes (abnormal, thickened/sparse fibrils; disrupted chondrocyte maturation) across zebrafish knockdown and mouse cho models. - Divergence: A striking cross-species discrepancy exists for the auditory phenotype — heterozygous cho/+ mice have normal auditory brainstem responses up to 10 months despite skeletal and joint phenotypes, whereas human COL11A1 heterozygotes commonly have significant sensorineural hearing loss. This has led researchers to conclude that "the lack of an auditory phenotype in the heterozygous mouse suggests haploinsufficiency is not the pathogenic mechanism underlying COL11A1-related auditory defects in humans" — an important translational caveat when extrapolating from the mouse heterozygote model to human auditory pathology. - Homozygous cho/cho mice do show "marked hearing loss when tested by auditory brain-stem responses," but this recessive-lethal genotype models fibrochondrogenesis-like severity rather than classic dominant human STL2.

Transmission: Not applicable — not an infectious or zoonotic disease.

Sources: Auditory function in cho mice — ResearchGate/PubMed summary, Ultrastructural cochlear changes in cho/cho mice, PMID:1952599, Col11a1/Col11a2 cochlear expression, PMID:15141750

15. Model Organisms

Mouse models

cho (chondrodysplasia) mouse: A spontaneous functional-null allele of Col11a1.
Homozygous (cho/cho): Lethal perinatal chondrodysplasia; cochlear ultrastructural abnormalities and marked ABR-measured hearing loss — a good model of the severe end of the COL11A1 biallelic spectrum (informing understanding of fibrochondrogenesis/recessive severe phenotypes) but not representative of classic dominant human STL2 due to its recessive, embryonic-lethal-adjacent severity.
Heterozygous (cho/+): Viable; develops osteoarthritis (modeling the human joint phenotype reasonably well) but has normal hearing up to 10 months of age, a notable failure to recapitulate the human auditory phenotype, suggesting either a species-specific auditory mechanism or that haploinsufficiency alone (as opposed to dominant-negative mutant protein incorporation) is insufficient to produce the human ear phenotype. This makes cho/+ a model with fidelity: HIGH for skeletal/joint phenotype but fidelity: LOW (or a "fails to recapitulate" relationship) for the auditory phenotype specifically — an important limitation to flag for any pathophysiology modeling that uses this line to justify auditory mechanism claims.
Databases: MGI (Mouse Genome Informatics).

Zebrafish models

col11a1a knockdown (morpholino) and mutant zebrafish: Recapitulate craniofacial cartilage abnormalities (Meckel's cartilage malformation), otolith abnormalities, and altered body length; demonstrate disrupted chondrocyte spatial organization and delayed/abnormal maturation to hypertrophy, plus deposition of abnormally thick, sparse collagen fibrils in cartilage ECM — a reasonably faithful recapitulation of the skeletal/craniofacial arm of human COL11A1 disease at the cellular/matrix level.
This model has been proposed as a system to dissect "the mechanism that links the skeletal phenomena to hearing loss resulting from mutations in the Col11a1 gene," i.e., its main research application is investigating the skeletal-auditory mechanistic link, though direct zebrafish auditory/lateral-line phenotype data specific to col11a1a were not detailed in the sources retrieved in this search.
Databases: ZFIN.
A related zebrafish model of Col2a1a (the type II collagen partner gene) has separately been used to study neural crest-related early eye development defects in Stickler syndrome (PMC9589970), providing a complementary ocular-development model system within the same collagen-network disease family, though this specific model targets COL2A1 (type 1 disease) rather than COL11A1.

Cellular/in vitro models

No iPSC-derived or immortalized cell-line model specific to COL11A1/STL2 chondrocyte or vitreous biology was identified in this search; this appears to be a relative gap in the current modeling landscape and a plausible candidate for future research investment (inferred from absence of hits, not a positive finding).

Model limitations summary

The cho/+ mouse is the best-established genetic model overall but has a documented, well-characterized failure to recapitulate the human auditory phenotype, which is mechanistically informative (arguing against simple haploinsufficiency as the auditory mechanism) but limits its use for auditory-specific translational study.
Zebrafish col11a1a models better capture cartilage/craniofacial cellular mechanism (chondrocyte organization/hypertrophy, fibril ultrastructure) and are proposed, but not yet fully validated, as a bridge to understanding the skeletal-auditory phenotypic link.
No model to date fully recapitulates the ocular "beaded" vitreous phenotype or the retinal detachment risk specifically for COL11A1 (as opposed to the Col2a1a zebrafish model used for the COL2A1/type 1 ocular phenotype).

Sources: Auditory function in cho mice, Ultrastructural cochlear changes cho/cho mice, PMID:1952599, Col11a1a Expression Is Required for Zebrafish Development, PMC7558312, The Shape of the Jaw — Zebrafish Col11a1a, PMC9590009, Craniofacial cartilage morphogenesis requires zebrafish col11a1 activity, PMID:19638309

Summary of Key Ontology Term Suggestions for KB Curation

Category	Suggested term(s)
Disease	OMIM:604841; Orphanet ORPHA828 / ORPHA90654 (verify exact STL2-specific ORPHA code and MONDO ID at curation)
Causal gene	hgnc:2186 (COL11A1)
Phenotypes (HP)	HP:0000545 (Myopia), HP:0000541 (Retinal detachment), HP:0000407 (Sensorineural hearing impairment), HP:0000405 (Conductive hearing impairment), HP:0000410 (Mixed hearing impairment), HP:0000175 (Cleft palate), HP:0000347 (Micrognathia), HP:0000272 (Flat face)/HP:0011800 (Midface retrusion), HP:0002758-type early-onset osteoarthritis term (verify exact code), HP:0000518 (Cataract)
Biological process (GO)	GO:0030199 (collagen fibril organization), GO:0030198 (extracellular matrix organization), GO:0001501 (skeletal system development)
Cell types (CL)	CL:0000138 (chondrocyte); cochlear/organ of Corti cell types as applicable
Anatomy (UBERON)	UBERON:0001797 (vitreous body), UBERON:0002418 (cartilage tissue), UBERON:0000955 (cochlea), UBERON:0001716 (secondary palate)
Treatment (NCIT)	NCIT:C15329 (Surgical Procedure — vitreoretinal/cleft repair), NCIT:C15302 (Physical Therapy), NCIT:C15240 (Genetic Counseling); no specific pharmacotherapy NCIT term is disease-modifying
Organism models (NCBITaxon)	NCBITaxon:10090 (Mus musculus, cho allele); NCBITaxon:7955 (Danio rerio, col11a1a)

Note on evidence gaps: This search did not surface disease-specific quality-of-life instrument data (EQ-5D/SF-36), population-specific ethnic/geographic prevalence variation, a validated genotype-severity prediction model, active COL11A1-targeted clinical trials, veterinary/OMIA natural-disease cases, or single-cell/spatial-omics datasets for human STL2 tissue — these should be flagged as "not available" or researched further rather than inferred, per the report's citation requirements.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	17
Resolved	17
Unresolved (possible confabulation)	0
Unverifiable	0
Quoted claims checked	3
Quoted claims found in source	1
Quoted claims not found in source	2
References weighed for topical relevance	17
On topic	13
Off topic	0

Quotes not found in the cited source

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

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

PMID:10486316: "of 10 mutation-positive patients, four were diagnosed with Marshall syndrome, but the remaining 6 showed an overlapping Marshall/Stickler phenotype"
closest text in source: "The α2(V) chain substitutes for the α2(XI) chain in the vitreous (Mayne et al.1993), thus explaining the lack of the ocular symptoms in patients with the COL11A2 gene mutations Our results indicate that patients with a splicing mutation in a 54-bp exon or with a mutation causing a 54-bp deletion in the C-terminal half of the COL11A1 gene more frequently showed with findings related to Marshall syndrome, and the mutations in the COL2A1 gene leading to a premature translation-termination codon caused the more classic Stickler syndrome phenotype"
PMC:PMC9590009 (abstract only): "spatial organization of chondrocytes, the shaping of cartilage elements, and the maturation of chondrocytes to hypertrophy"
closest text in source: "Our results demonstrate that zebrafish col11a1a knockdown impairs the cellular organization of Meckel's cartilage in the developing jaw and alters the bone formation that occurs adjacent to the Meckel's cartilage"

Term Validation

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

Outcome	Count
Terms checked	41
Resolved	39
Unresolved (possible confabulation)	0
Obsolete	0
Unverifiable	2
Terms whose name was checked	24
Terms named correctly	16
Terms named as a different term	4
Terms whose name is worth a second look	4

Terms the report names something else

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

HP:0000875 (1 mention) - the report calls it "lattice degeneration, if available"; HP calls it Episodic hypertension
GO:0060004 (1 mention) - the report calls it "reflex — not relevant"; GO calls it reflex
UBERON:0000955 (3 mentions) - the report calls it "cochlea, or more specific substructures"; UBERON calls it brain
UBERON:0002481 (1 mention) - the report calls it "mandible"; UBERON calls it bone tissue

Terms whose name is worth a second look

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

HP:0000272 (2 mentions) - the report calls it "Flat face"; HP calls it Malar flattening, and lists "Flat cheekbone" among its other names
HP:0002758 (2 mentions) - the report calls it "Osteoarthritis, early onset"; HP calls it Osteoarthritis
CL:0000138 (3 mentions) - the report calls it "CL terms: chondrocyte", "chondrocyte"; CL calls it chondrocyte
UBERON:0001797 (3 mentions) - the report calls it "UBERON: vitreous body", "vitreous body"; UBERON calls it vitreous humor, and lists "humor vitreous" among its other names

Terms named inconsistently

The report gives these identifiers more than one name of its own:

CL:0000138 - called "CL terms: chondrocyte", "chondrocyte"
UBERON:0001797 - called "UBERON: vitreous body", "vitreous body"

Prefixes with no resolver

Terms carrying these prefixes were not checked either way, because no configured ontology covers them. An unrecognised prefix may name an ontology this run could not reach as easily as one that does not exist, so nothing here is evidence of fabrication: OMIM.

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Inheritance

Discussions and Knowledge Gaps

Pathophysiology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Environmental Factors

Diagnosis

Prevalence

Differential Diagnoses

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Stickler Syndrome Type 2 (COL11A1-Related Stickler Syndrome): Comprehensive Research Report

1. Disease Information

2. Etiology

3. Phenotypes

Ocular phenotypes

Auditory phenotypes

Orofacial phenotypes

Skeletal phenotypes

Quality of life impact

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

Ordered causal chain (from molecular lesion to clinical phenotype)

Category detail

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Mouse models

Zebrafish models

Cellular/in vitro models

Model limitations summary

Summary of Key Ontology Term Suggestions for KB Curation

Reference Validation

Quotes not found in the cited source

Term Validation

Terms the report names something else

Terms whose name is worth a second look

Terms named inconsistently

Prefixes with no resolver