Martin P. Snead

Clinical and Molecular genetics of Stickler syndrome.

Stickler syndrome is an autosomal dominant disorder with characteristic ophthalmological and orofacial features, deafness, and arthritis. Abnormalities of vitreous gel architecture are a pathognomonic feature, usually associated with high myopia which is congenital and non-progressive. There is a substantial risk of retinal detachment. Less common ophthalmological features include paravascular pigmented lattice degeneration and cataracts. Non-ocular features show great variation in expression. Children with Stickler syndrome typically have a flat midface with depressed nasal bridge, short nose, anteverted nares, and micrognathia. These features can become less pronounced with age. Midline clefting, if present, ranges in severity from a cleft of the soft palate to Pierre-Robin sequence. There is joint hypermobility which declines with age. Osteoarthritis develops typically in the third or fourth decade. Mild spondyloepiphyseal dysplasia is often apparent radiologically. Sensorineural deafness with high tone loss may be asymptomatic or mild. Occasional findings include slender extremities and long fingers. Stature and intellect are usually normal. Mitral valve prolapse was reported to be a common finding in one series but not in our experience. The majority of families with Stickler syndrome have mutations in the COL2A1 gene and show the characteristic type 1 vitreous phenotype. The remainder with the type 2 vitreous phenotype have mutations in COL11A1 or other loci yet to be identified. Mutations in COL11A2 can give rise to a syndrome with the systemic features of Stickler syndrome but no ophthalmological abnormality.

COL2A1 exon 2 mutations: relevance to the Stickler and Wagner syndromes.

AIMS To compare the clinical and molecular genetic features of two phenotypically distinct subgroups of families with type 1 Stickler syndrome. BACKGROUND Stickler syndrome (hereditary arthro-ophthalmopathy, McKusick Nos 108300 and 184840) is a dominantly inherited disorder of collagen connective tissue, resulting in an abnormal vitreous, myopia, and a variable degree of orofacial abnormality, deafness, and arthropathy. Stickler syndrome is the commonest inherited cause of rhegmatogenous retinal detachment in childhood with a risk of giant retinal tear (GRT) which is commonly bilateral and a frequent cause of blindness. METHOD Pedigrees were identified from the vitreoretinal service database and subclassified according to vitreoretinal phenotype. Ophthalmic, skeletal, auditory, and orofacial features were assessed. Linkage analysis was carried out with markers for the candidate genes COL2A1, COL11A1, and COL11A2. The COL2A1 gene was amplified as five overlapping PCR products. Direct sequencing of individual exons identified mutations. RESULTS Eight families exhibiting the type 1 vitreous phenotype were studied. Seven were consistent for linkage to COL2A1, with lod scores ranging from 2.1 to 0.3. In most instances linkage to COL11A1 and COL11A2 could be excluded. One family was analysed without prior linkage analysis. Three of the families exhibited a predominantly ocular phenotype with minimal or absent systemic involvement and were found to have mutations in exon 2 of COL2A1. Five other pedigrees with an identical ocular phenotype plus orofacial, auditory, and articular involvement had mutations in others regions of the COL2A1 gene. None of the pedigrees exhibited the characteristic lenticular, retinal pigment epithelial, or choroidal changes seen in Wagner syndrome. CONCLUSIONS These data confirm that type 1 Stickler syndrome is caused by mutations in the gene encoding type II collagen (COL2A1). In addition, data are submitted showing that mutations involving exon 2 of COL2A1 are characterised by a predominantly ocular variant of this disorder, consistent with the major form of type II procollagen in non-ocular tissues having exon 2 spliced out. Such patients are all at high risk of retinal detachment. This has important implications for counselling patients with regard to the development of systemic complications. It also emphasises the importance and reliability of the ophthalmic examination in the differential diagnosis of this predominantly ocular form of Stickler syndrome from Wagners vitreoretinopathy.

Stickler syndrome: correlation between vitreoretinal phenotypes and linkage to COL 2A1.

Stickler syndrome is an autosomal dominantly inherited condition characterised by ocular, articular, facial, auditory and oral features. There is locus heterogeneity with about two thirds of families showing linkage to the gene encoding type II procollagen (COL 2A1). Clinical overlap with Marshalls, Wagners and other syndromes has caused considerable confusion but the importance of the congenital vitreous anomaly, as first described by Scott, has not previously been emphasised. This study examines the linkage of two vitreo-retinal phenotype subgroups of Stickler syndrome to COL 2A1. A total of 97 affected patients from 24 pedigrees were examined. This is the largest published series of Stickler syndrome patients to date and all have undergone full clinical and ophthalmological examination by a single investigator. A clinical classification is proposed based on vitreoretinal phenotype. All patients demonstrating the congenital vitreous anomaly have been designated Stickler syndrome type 1 and those without the congenital vitreous anomaly as Stickler syndrome type 2 patients. There were 69 affected patients from 20 unrelated type 1 pedigrees and 28 affected patients from 4 unrelated type 2 pedigrees. Using two markers at the COL 2A1 locus, Stickler syndrome type 1 pedigrees showed complete linkage to COL 2A1 with a maximum lod score of 12.33 at zero recombination. Linkage to COL 2A1 was excluded in the two type 2 pedigrees that were informative. From these data it appears that this clinical classification is a useful first step in resolving the genetic heterogeneity in this condition.

Pathological changes in the vitreoretinal junction 1: epiretinal membrane formation

Purpose/BackgroundEpiretinal membrane (ERM) formation is a common change resulting in disturbance of macular vision and predisposing to rhegmatogenous retinal detachment. Current treatment strategies rely chiefly on surgical removal of the membranes from the surface of the retina, allowing the retina to remodel and reattach. Improved knowledge of the pathological process behind the formation of these membranes, particularly knowledge of the cell types involved in their formation, is likely to increase our understanding of the way this group of diseases behave and to improve treatment.MethodsWe reviewed the histological findings of 109 surgically removed specimens and correlated these to age-related changes seen in a 32 cadaver eyes studied after corneal harvesting. The samples were studied using light microscopy and immunocytochemistry.ResultsIn all cases of idiopathic ERMs, including cellophane maculopathy, macular hole, and vitreomacular traction syndrome, laminocytes were the exclusive cell type present. In cases of macular pucker associated with retinal tears, the membranes contain variable cohesive groups of retinal pigment epithelial (RPE) cells in addition to laminocytes. In cases of proliferative diabetic retinopathy, membranes consist almost entirely of capillaries and hyaline stromal tissue, with or without haemosiderin pigment and RPE cells and in which laminocytes and ILM were not identified. In cadaver eyes PVD was seen in 17/32 (53%) of cases, and the vitreous was attached in 14/32 (43.7%) and in one case no vitreous was present. Isolated laminocytes were present on the retinal surface in 12/18 cases with detached vitreous and in 1/14 cases with attached vitreous. In all cases laminocytes were scanty and confined to the optic nerve head, macular or subjacent macular retina. Immunohistochemistry findings indicate that laminocytes are positive for glial fibrillary acidic protein (GFAP), cytokeratin marker AE1/AE3, type II collagen, and type IV collagen. In some cases novel basement membrane formation was seen. There was a tendency for increased positivity of GFAP and AE1/AE3 with increased cellularity, and where novel basement membrane formation was present.ConclusionLaminocytes are the fundamental cell type in idiopathic ERMs. These cells are frequently found in small and dispersed numbers in eyes containing a PVD. The presence of retinal pigment cells invariable indicates proliferative retinopathy and is only seen in association with a retinal detachment or tear. Diabetic membranes are composed of neovascular stromal tissue, which is most likely to be a response to retinal hypoxia.

Stickler syndrome, ocular-only variants and a key diagnostic role for the ophthalmologist

The entity described by Gunnar Stickler, which included hereditary arthro-ophthalmopathy associated with retinal detachment, has recently been recognised to consist of a number of subgroups, which might now more correctly be referred to as the Stickler syndromes. They are the most common clinical manifestation of the type II/XI collagenopathies and are the most common cause of inherited rhegmatogenous retinal detachment. This review article is intended to provide the ophthalmologist with an update on current research, subgroups, and their diagnosis together with a brief overview of allied conditions to be considered in the clinical differential diagnosis. We highlight the recently identified subgroups with a high risk of retinal detachment but with minimal or absent systemic involvement—a particularly important group for the ophthalmologist to identify.

Hyperconvolution of the inner limiting membrane in vitreomaculopathies

BackgroundThis study investigates the similarities and differences between epiretinal membranes in four clinically distinct types of vitreomaculopathy. We propose a hypothesis on the origin of the predominant cell type and its potential role in causing these conditions.MethodsEpiretinal membranes (ERMs) surgically removed from a prospective, consecutive series of vitrectomies for macular pucker associated with an untreated peripheral horseshoe tear (MP), cellophane maculopathy (CM), stage 4 macular hole (MH) and vitreomacular traction syndrome (VMT) were examined by light microscopy and by immunocytochemistry (ICC) using antibodies marking type IV collagen, type II collagen, glial fibrillary acidic protein (GFAP), and low- and high-molecular-weight cytokeratin (MNF116). These specimens were compared with post-mortem control eyes with and without physiological posterior vitreous detachment (PVD). Light microscopy was carried out on 5-μm-thick sections cut from formalin-fixed, paraffin-embedded tissue blocks. Appropriate autoclave or enzyme pre-digestion steps were deployed to retrieve antigens for ICC. No patient had undergone previous vitreoretinal surgery or peripheral retinopexy.ResultsFrom a series of 38 patients, (13 CM, 8 MP, 16 MH and 1 VMT) a total of 20 specimens contained sufficient tissue for histology and immunocytochemistry. All specimens contained portions of inner limiting membrane (ILM) coated by GFAP-positive cells. Specimens from patients with MP and CM exhibited hyperconvolution of the ILM, which was not found in the specimens from patients with MH or VMT or in the control eyes. Hyperconvolution was associated with increased glial cell density, GFAP staining intensity and duplication of ILM basement membrane. Three cases of ERMs from the MP group contained, in addition, cytokeratin-positive cells. In the control group; post-mortem eyes with PVDs showed patchy staining of the posterior hyaloid membrane for GFAP and type 4 collagen. Post-mortem eyes with attached gel showed weak positivity of the ILM for type 4 collagen, and a monolayer of GFAP-positive cells lined the vitreous aspect of the ILM.ConclusionsThese results indicate that glial cells are fundamentally important in the formation of ERMs found in this group of vitreomaculopathies. The hyperconvolution and duplication of the ILM in CM and MP were striking and distinctive features and suggest a mechanism by which these membranes exert tractional forces on the retina. Post-mortem control eyes contained a similar (but more dispersed) population of GFAP-positive cells in the region of the ILM, suggesting the primary aetiology for CM and MP may originate within the ILM. ERMs from MP cases may, in addition, contain cytokeratin-positive cells, of probable RPE origin.

Clinical characterisation and molecular analysis of Wagner syndrome.

Aim: To detail the clinical findings in a British family with molecularly characterised Wagner syndrome. Background: Only in the last year has the specific genetic defect in Wagner syndrome been identified, and the background literature of the molecular genetics is outlined. Clinical and laboratory findings in a second case of Wagner syndrome are included to highlight difficulties that can be encountered when identifying pathogenic mutations for disorders arising in complex genes. Methods: Mutation screening was performed using PCR and RT-PCR. Results: A heterozygous mutation was found converting the donor splice site of exon 8 of the chondroitin sulphate proteoglycan 2 (CSPG2). This is the same mutation that has been reported in the original Wagner pedigree. The main clinical features of Wagner syndrome are vitreous syneresis, thickening and incomplete separation of the posterior hyaloid membrane, chorioretinal changes accompanied by subnormal electroretinographic responses, an ectopic fovea and early-onset cataract. A clinical feature present in this family, but previously undescribed, is anterior uveitis without formation of synechiae. Wagner syndrome has a progressive course, resulting in loss of vision even in the absence of retinal detachment. Conclusion: On a background of considerable confusion regarding the distinction between Wagner syndrome and predominantly ocular Stickler syndrome, it is now apparent the that two conditions are both clinically and genetically distinct. This report summarises the clinical findings in Wagner syndrome and extends the phenotypic characteristics.

Clinical, histological and ultrastructural studies of the posterior hyaloid membrane

Aims To investigate the histological, immunohistochemical and ultrastructural features of the posterior hyaloid membrane (PHM) in its naturally separated state in patients without previous surgery and slit-lamp documentation of antemortem posterior vitreous detachment (PVD).Methods A prospective study was commenced in 1992 to recruit patients with physiological PVD from an unselected group of general medical inpatients and ascertain the prevalence of PVD. Postmortem specimens subsequently available were studied to analyse the clinicopathological correlation and processed using standard techniques for histology, immunohistochemistry and electron microscopy.Results Eighty-five patients were examined with ages ranging from 68 to 98 yrs (mean 83.4 yrs). The posterior hyaloid membrane had clearly separated from the retina in 66% of eyes. Twenty-nine eyes from 15 patients were subsequently studied pathologically. The posterior hyaloid membrane exhibited a uniform cellular component, most densely populated around the Weiss’ ring. The cells were characterised by oval or round nuclei, indistinct cytoplasm and were only seen within, or abutting, the weakly eosinophilic posterior hyaloid membrane. The posterior aspect of the posterior hyaloid membrane showed a convoluted appearance staining lightly with haematoxylin and eosin. The detached posterior hyaloid membrane exhibited focal positivity for GFAP and type IV collagen. Electron microscopy demonstrates both fibres and basement membrane associated with the cellular component including hemi-desmosome attachment plaques between the cells and basement membrane.Conclusions This study illustrates some of the structural differences between the posterior hyaloid membrane and the cortical vitreous gel it envelopes and demonstrates the presence of cells intimately associated with the posterior hyaloid membrane in its naturally separated state. We propose the cellular population integral to the PHM to be designated as laminocytes in order to emphasise their type IV collagen/basement membrane association and planar array within the membrane which separates at posterior vitreous detachment.

Prevalence of mitral valve prolapse in Stickler syndrome

The prevalence of mitral valve prolapse in Stickler syndrome has been reported to be much higher than in the general population. As a result, it has been recommended that all patients with Stickler syndrome undergo routine echocardiography and have antibiotic prophylaxis prior to surgery. The purpose of this study was to evaluate the prevalence of mitral valve prolapse in a large cohort of UK patients with Stickler syndrome in whom the clinical diagnosis has been confirmed by molecular genetic analysis. Probands and pedigrees were identified from the Vitreoretinal Service database according to previously published criteria. Ophthalmic, skeletal, audiometric, and orofacial features were assessed. Affected individuals underwent a full cardiological examination including auscultation and two‐dimensional echocardiography. Mutation analysis of the COL2A1 and COL11A1 genes was carried out. Seventy‐eight patients from 25 pedigrees were studied. Mutation analysis confirmed the clinical diagnosis in every pedigree. No patient was found to have clinical evidence of cardiovascular disease and no patient had significant mitral or other valvular prolapse on echocardiography. These data from a large cohort of UK patients with proven Stickler syndrome do not suggest an increased incidence of mitral valve prolapse over and above that found in the general population. Routine echocardiography screening and use of preoperative antibiotics are unnecessary and should be reserved for those individual cases where there is clear clinical indication.

Clinical features of type 2 Stickler syndrome

The Stickler syndromes1–8 (hereditary arthro-ophthalmopathy; McKusick nos. 108300 and 604841) are one of the more frequently occurring groups of chondrodysplasias and are the commonest inherited cause of rhegmatogenous retinal detachment.9 The majority of patients and pedigrees exhibit the type 1 or “membranous” vitreous phenotype10,11 and harbour mutations in the gene for type II collagen ( COL2A1 ).12–21 While not all mutations in type II collagen result in the membranous vitreous anomaly,22,23 when it is exhibited it appears to be congenital and provides a useful basis for mutant locus assignment. This is particularly helpful for sporadic cases where linkage is impossible, and especially in those individuals with mild or minimal systemic involvement where the diagnosis might otherwise be overlooked.19,24–26 Other pedigrees exhibit a different “beaded” vitreous phenotype and are linked to a different locus.11,27 We reported the first mutation in the gene encoding the α1 chain of type XI collagen ( COL11A1 ) in one of these pedigrees28 and this locus was confirmed in other pedigrees,29,30 and is now known as type 2 Stickler syndrome (McKusick no. 604841). The intimate post-translational molecular associations between types II and XI collagen form the foundation of the close clinical overlap between these two sub-groups of Stickler syndrome, but the extent of this clinical overlap and variation remains to be defined. Whilst type 1 Stickler syndrome pedigrees have a particularly high risk of blindness through giant retinal tear and retinal detachment, Annunen et al suggest that patients with COL11A1 mutations are at a low risk of retinal detachment and have a higher incidence of midfacial hypoplasia.29 This would be an important prognostic difference if confirmed. Here we wish to report the first description of the ophthalmic, oro-facial, audiologial, skeletal, and …