Distinctive cataract in the Stickler syndrome

Multiocular defect in the Old English Sheepdog: A canine form of Stickler syndrome type II associated with a missense variant in the collagen-type gene COL11A1

Multiocular defect has been described in different canine breeds, including the Old English Sheepdog. Affected dogs typically present with multiple and various ocular abnormalities. We carried out whole genome sequencing on an Old English Sheepdog that had been diagnosed with hereditary cataracts at the age of five and then referred to a board-certified veterinary ophthalmologist due to owner-reported visual deterioration. An ophthalmic assessment revealed that there was bilateral vitreal degeneration, macrophthalmos, and spherophakia in addition to cataracts. Follow-up consultations revealed cataract progression, retinal detachment, uveitis and secondary glaucoma. Whole genome sequence filtered variants private to the case, shared with another Old English Sheepdog genome and predicted to be deleterious were genotyped in an initial cohort of six Old English Sheepdogs (three affected by multiocular defect and three control dogs without evidence of inherited eye disease). Only one of the twenty-two variants segregated correctly with multiocular defect. The variant is a single nucleotide substitution, located in the collagen-type gene COL11A1, c.1775T>C, that causes an amino acid change, p.Phe1592Ser. Genotyping of an additional 14 Old English Sheepdogs affected by multiocular defect revealed a dominant mode of inheritance with four cases heterozygous for the variant. Further genotyping of hereditary cataract-affected Old English Sheepdogs revealed segregation of the variant in eight out of nine dogs. In humans, variants in the COL11A1 gene are associated with Stickler syndrome type II, also dominantly inherited.

The genetics and disease mechanisms of rhegmatogenous retinal detachment

Rhegmatogenous retinal detachment (RRD) is a sight threatening condition that warrants immediate surgical intervention. To date, 29 genes have been associated with monogenic disorders involving RRD. In addition, RRD can occur as a multifactorial disease through a combined effect of multiple genetic variants and non-genetic risk factors. In this review, we provide a comprehensive overview of the spectrum of hereditary disorders involving RRD. We discuss genotype-phenotype correlations of these monogenic disorders, and describe genetic variants associated with RRD through multifactorial inheritance. Furthermore, we evaluate our current understanding of the molecular disease mechanisms of RRD-associated genetic variants on collagen proteins, proteoglycan versican, and the TGF-β pathway. Finally, we review the role of genetics in patient management and prevention of RRD. We provide recommendations for genetic testing and prophylaxis of at-risk patients, and hypothesize on novel therapeutic approaches beyond surgical intervention.

Inherited causes of combined vision and hearing loss: clinical features and molecular genetics

Combined vision and hearing loss, also known as dual sensory impairment, can occur in several genetic conditions, including ciliopathies such as Usher and Bardet-Biedl syndrome, mitochondrial DNA disorders and systemic diseases, such as CHARGE, Stickler, Waardenburg, Alport and Alstrom syndrome. The retinal phenotype may point to the diagnosis of such disorders. Herein, we aim to provide a comprehensive review of the molecular genetics and clinical features of the most common non-chromosomal inherited disorders to cause dual sensory impairment.

Connective tissue disorders and eye: A review and recent updates

Collagen vascular disorders (CVDs), also known as connective tissue diseases (CTDs), are a heterogeneous group of entities that affect the connective tissues and are capable of causing end-organ damage to multiple systems, primarily cardiopulmonary and musculoskeletal. However, the occurrence and severity are highly variable among patients. Ocular involvement occurs in a significant number of these disorders and may precede the onset of other extraocular features, thereby serving as an important marker in the diagnosis of these diseases. A timely and accurate diagnosis enables the management of complications. CTDs are primarily immune-mediated inflammatory diseases; however, classifications have encompassed heritable disorders affecting collagen-containing structures and disorders of vascular development. A review of literature published until 25 January 2022 and collected from various databases using the relevant keywords was conducted. All publications (original articles, review articles, as well as case reports) describing the ocular features in CTDs were studied in detail. The objective of this review is to recognize the common ophthalmic presentations of various autoimmune and heritable CTDs, distinguish them from overlapping diseases, elaborate on the prognosis and management of these varied eye presentations, and deliberate on their impact on other ophthalmic surgeries.

LEPREL1 -RELATED GIANT RETINAL TEAR DETACHMENTS MIMIC THE PHENOTYPE OF OCULAR STICKLER SYNDROME

PURPOSE

To describe the features of retinal detachments and high myopia in patients with novel pathogenic variants in LEPREL1 and report a possible association with nephropathy.

METHODS

Retrospective study of 10 children with biallelic LEPREL1 pathogenic variants. Data included ophthalmic features, surgical interventions, and genetic and laboratory findings.

RESULTS

10 patients (8 females) from three families with homozygous (2) or compound heterozygous (1) variants in LEPREL1 were included. At presentation, mean age was 9.9 ± 2.6 years. Mean axial length was 28.9 ± 1.9 mm and mean refraction was -13.9 ± 2.8 diopters. Bilateral posterior subcapsular cataracts were present in eight patients (80%), with lens subluxation in five eyes of three patients (30%). Rhegmatogenous retinal detachments (RRD), associated with giant retinal tears (GRT), developed in seven eyes of five patients (50%) at a mean age of 14.14 ± 5.9 years. Six were successfully reattached with mean Snellen best-corrected visual acuity improving from 20/120 preoperatively to 20/60 at last follow-up. Urinalysis in nine patients revealed microhematuria and/or mild proteinuria in six patients (67%).

CONCLUSION

LEPREL1 -related high myopia confers a high risk of early-onset GRT-related RRD. The ocular phenotype may be confused with that of ocular Stickler syndrome if genetic testing is not performed. Further investigations into a potential association with renal dysfunction are warranted.

Glaucoma Syndromes: Insights into Glaucoma Genetics and Pathogenesis from Monogenic Syndromic Disorders

Monogenic syndromic disorders frequently feature ocular manifestations, one of which is glaucoma. In many cases, glaucoma in children may go undetected, especially in those that have other severe systemic conditions that affect other parts of the eye and the body. Similarly, glaucoma may be the first presenting sign of a systemic syndrome. Awareness of syndromes associated with glaucoma is thus critical both for medical geneticists and ophthalmologists. In this review, we highlight six categories of disorders that feature glaucoma and other ocular or systemic manifestations: anterior segment dysgenesis syndromes, aniridia, metabolic disorders, collagen/vascular disorders, immunogenetic disorders, and nanophthalmos. The genetics, ocular and systemic features, and current and future treatment strategies are discussed. Findings from rare diseases also uncover important genes and pathways that may be involved in more common forms of glaucoma, and potential novel therapeutic strategies to target these pathways.

Long-Term Follow-Up of Retinal Detachment Repair in Patients With Stickler Syndrome

BACKGROUND AND OBJECTIVE

To report the long-term anatomic and visual outcomes of patients with Stickler syndrome undergoing retinal detachment (RD) surgery.

PATIENTS AND METHODS

Retrospective, interventional, consecutive case series of patients with Stickler syndrome undergoing RD repair from 1999 to 2017 at the Long Island Vitreoretinal Consultants, New York. Retinal attachment status and visual acuity (VA) at 1-year and last follow-up were assessed.

RESULTS

Successful reattachment was achieved in 28 of 29 eyes (97%) with an average of 2.3 surgeries (including silicone oil removal surgeries). Redetachment after the first surgery occurred in 13 eyes (45%). Mean Snellen VA at initial presentation, 1-year follow-up, and last follow-up were 20/289, 20/118 (P = .012), and 20/103 (P = .022), respectively.

CONCLUSIONS

Anatomic success can be achieved in most eyes. However, redetachments are common, and multiple surgeries are often required. Reasonable visual recovery is possible in many eyes. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:612-616.].

Stickler Syndrome: A Review of Clinical Manifestations and the Genetics Evaluation

Stickler Syndrome (SS) is a multisystem collagenopathy frequently encountered by ophthalmologists due to the high rate of ocular complications. Affected individuals are at significantly increased risk for retinal detachment and blindness, and early detection and diagnosis are critical in improving visual outcomes for these patients. Systemic findings are also common, with craniofacial, skeletal, and auditory systems often involved. SS is genotypically and phenotypically heterogenous, which can make recognizing and correctly diagnosing individuals difficult. Molecular genetic testing should be considered in all individuals with suspected SS, as diagnosis not only assists in treatment and management of the patient but may also help identify other at-risk family members. Here we review common clinical manifestation of SS and genetic tests frequently ordered as part of the SS evaluation.

Ocular complications and prophylactic strategies in Stickler syndrome: a systematic literature review

BACKGROUND

Stickler syndrome is a collagenopathy caused by mutations in the genes COL2A1 (STL1) or COL11A1 (STL2). Affected patients manifest ocular, auditory, articular, and craniofacial manifestations in varying degrees. Ocular symptoms include myopia, retinal detachment, cataract, and glaucoma. The aim of this systematic review was to evaluate the prevalence of ocular manifestations and the outcome of prophylactic treatment on reducing the risk of retinal detachment.

METHOD

A systematic literature search was performed in the PubMed database. Information on the cross-study prevalence of myopia, retinal detachment, cataract, glaucoma, visual impairment, severity and age of onset of myopia and retinal detachments. Studies that reported on the outcome of prophylactic treatment against a control group were explored.

RESULTS

37 articles with 2324 individual patients were included. Myopia was found in 83% of patients, mostly of a moderate to severe degree. Retinal detachments occurred in 45% of patients. Generally, the first detachment occurred in the second decade of life in STL1 patients and later in STL2. Cataracts were more common in STL2 patients, 59% versus 36% in STL1. Glaucoma (10%) and visual impairment (blind: 6%; vision loss in one eye: 10%) were rare. Three studies reported on the effect of prophylactic treatment being protective.

CONCLUSION

Ocular manifestations are common in Stickler patients, but the comparison between studies was difficult because of inconsistencies in diagnostic and inclusion criteria by different studies. Sight-threatening complications such as retinal detachments are common but although prophylactic therapy is reported to be effective in retrospective studies, evidence from randomized trials is missing.

Stickler syndrome: exploring prophylaxis for retinal detachment

PURPOSE OF REVIEW

The literature regarding prophylactic treatment of rhegmatogenous retinal detachment in Stickler syndrome remains controversial. We review major published clinical studies and offer a critical analysis of this subject.

SUMMARY

Stickler syndrome is a systemic collagenopathy affecting multiple organ systems including the eye, ear, and skeleton. Stickler syndrome is probably the most common cause of genetically determined pediatric rhegmatogenous retinal detachment. Congenital developmental anomalies constitute over half rhegmatogenous detachments (RRD) in patients less than 10 years. The majority are caused by hereditary vitreoretinopathies associated with Stickler syndrome. Sixty percent of patients with Stickler syndrome develop RRD's over their lifetime with possible severe visual loss and subsequent lifelong morbidity. In view of these complications, some have emphasized the importance of prophylactic laser treatment to the retina of patients with Stickler syndrome to reduce the occurrence of and/or prevent future rhegmatogenous retinal detachment, but there appears to be insufficient data to support the absolute benefit of such prophylactic treatment. Guidelines regarding the age at prophylactic treatment as well as type and frequency of intervention are scarce and would benefit from additional clinical investigations.

Reduced penetrance in a large Caucasian pedigree with Stickler syndrome

BACKGROUND

In a four-generation Caucasian family variably diagnosed with autosomal dominant (AD) Stickler or Wagner disease, commercial gene screening failed to identify a mutation in COL2A1 or VCAN. We utilized linkage mapping and exome sequencing to identify the causal variant.

MATERIALS AND METHODS

Genomic DNA samples collected from 40 family members were analyzed. A whole-genome linkage scan was performed using Illumina HumanLinkage-24 BeadChip followed by two-point and multipoint linkage analyses using FASTLINK and MERLIN. Exome sequencing was performed on two affected individuals, followed by co-segregation analysis.

RESULTS

Parametric multipoint linkage analysis using an AD inheritance model demonstrated HLOD scores > 2.00 at chromosomes 1p36.13-1p36.11 and 12q12-12q14.1. SIMWALK multipoint analysis replicated the peak in chromosome 12q (peak LOD = 1.975). FASTLINK two-point analysis highlighted several clustered chromosome 12q SNPs with HLOD > 1.0. Exome sequencing revealed a novel nonsense mutation (c.115C>T, p.Gln39*) in exon 2 of COL2A1 that is expected to result in nonsense-mediated decay of the RNA transcript. This mutation co-segregated with all clinically affected individuals and seven individuals who were clinically unaffected.

CONCLUSIONS

The utility of combining traditional linkage mapping and exome sequencing is highlighted to identify gene mutations in large families displaying a Mendelian inheritance of disease. Historically, nonsense mutations in exon 2 of COL2A1 have been reported to cause a fully penetrant ocular-only Stickler phenotype with few or no systemic manifestations. We report a novel nonsense mutation in exon 2 of COL2A1 that displays incomplete penetrance and/or variable age of onset with extraocular manifestations.

Stickler syndrome. Epidemiology of retinal detachment

OBJECTIVE

A review was performed on all patients with Stickler syndrome that had been treated in our Centre since it was diagnosed, in order to evaluate the risk of suffering a retinal detachment (RD).

METHODS

A total of 14 patients, diagnosed by clinical criteria, were included. The following variables were evaluated: age, gender, ocular background, follow-up, initial and final visual acuity (VA), optical prescription, prophylactic treatment, surgery and techniques performed. The risk age to suffer a RD, as well as cataracts, was determined by using the Kaplan-Meier survival curve analysis.

RESULTS

From a total of 5 men and 9 women, the median initial VA was 0.35, which was the same as the final VA. The median optical prescription was -9.5 D myopia. The median of follow-up was 7 years. Ocular background was 4 RD cases and 2 Lasik surgeries. The operations performed were 8 RD, 12 cataract, 2 glaucoma, 2 macular hole, and one endotropia. The median age of RD was 20 years and cataract 34 years. As regards surgical tecnique, 4 scleral buckle cases, and 4 scleral buckle+pars plana vitrectomy cases were formed. The prophylactic treatments performed were: one scleral buckle case, 4 endolaser photocoagulation, and one cryotherapy. Two of which presented with RD.

CONCLUSION

In the series presented, retinal detachment in Stickler syndrome mainly occurs in the second decade of life, with cataracts mainly developing in the fourth decade.

Pediatric cataract: challenges and future directions

Cataract is a significant cause of visual disability in the pediatric population worldwide and can significantly impact the neurobiological development of a child. Early diagnosis and prompt surgical intervention is critical to prevent irreversible amblyopia. Thorough ocular evaluation, including the onset, duration, and morphology of a cataract, is essential to determine the timing for surgical intervention. Detailed assessment of the general health of the child, preferably in conjunction with a pediatrician, is helpful to rule out any associated systemic condition. Although pediatric cataracts have a diverse etiology, with the majority being idiopathic, genetic counseling and molecular testing should be undertaken with the help of a genetic counselor and/or geneticist in cases of hereditary cataracts. Advancement in surgical techniques and methods of optical rehabilitation has substantially improved the functional and anatomic outcomes of pediatric cataract surgeries in recent years. However, the phenomenon of refractive growth and the process of emmetropization have continued to puzzle pediatric ophthalmologists and highlight the need for future prospective studies. Posterior capsule opacification and secondary glaucoma are still the major postoperative complications necessitating long-term surveillance in children undergoing cataract surgery early in life. Successful management of pediatric cataracts depends on individualized care and experienced teamwork. We reviewed the etiology, preoperative evaluation including biometry, choice of intraocular lens, surgical techniques, and recent developments in the field of childhood cataract.

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.

Abnormal expression of collagen IV in lens activates unfolded protein response resulting in cataract

Human diseases caused by mutations in extracellular matrix genes are often associated with an increased risk of cataract and lens capsular rupture. However, the underlying mechanisms of cataract pathogenesis in these conditions are still unknown. Using two different mouse models, we show that the accumulation of collagen chains in the secretory pathway activates the stress signaling pathway termed unfolded protein response (UPR). Transgenic mice expressing ectopic Col4a3 and Col4a4 genes in the lens exhibited activation of IRE1, ATF6, and PERK associated with expansion of the endoplasmic reticulum and attenuation of general protein translation. The expression of the transgenes had adverse effects on lens fiber cell differentiation and eventually induced cell death in a group of transgenic fiber cells. In Col4a1(+/Deltaex40) mutant mice, the accumulation of mutant chains also caused low levels of UPR activation. However, cell death was not induced in mutant lenses, suggesting that low levels of UPR activation are not proapoptotic. Collectively, the results provide in vivo evidence for a role of UPR in cataract formation in response to accumulation of terminally unfolded proteins in the endoplasmic reticulum.

Focus on the physical assessment of the infant with Stickler syndrome

Stickler syndrome is an autosomal dominant, genetic connective tissue disorder characterized by ocular, orofacial, auditory, and skeletal anomalies. The diagnosis of Stickler syndrome is often missed in the newborn period and diagnosed as simply Pierre Robin sequence. For these patients, complications and disabilities could be lessened by further analysis of the family history.Neonatal caregivers are responsible for the immediate care of the newborn with Pierre Robin sequence. The prudent healthcare profession will explore the origin of the condition to provide optimal comprehensive care to the infant and family. This article reviews the physical findings of Stickler syndrome including differentiation between similar syndromes. A systematic review of physical findings is included along with treatment options.

Type 1 Stickler syndrome: a histological and ultrastructural study of an untreated globe

AIMS

To present a histological and ultrastructural study of an untreated globe in a patient with genetically confirmed type 1 Stickler syndrome.

METHODS

Histological and electron microscopic examinations were performed on the enucleated globe from the proband of a pedigree with type 1 Stickler syndrome. Linkage analysis was carried out using polymorphic markers flanking the COL2A1 gene and the mutation was identified by direct sequencing.

RESULTS

The significant retinal abnormality was incarceration of vitreous collagen within glial strands on the inner surface of an atrophic and gliotic detached retina. The incarcerated collagenous layers contained glial cells and extended from the retina to form strands, some of which contributed to a retrolental membrane. Mutation screening detected a C to T mutation in exon 47 that inserted a premature termination codon into the reading frame of the mRNA. Sequence analysis of three of the four affected children confirmed that they were also heterozygous for the base change. The youngest child's DNA was not analysed.

CONCLUSIONS

The study represents the first evidence of abnormal interactions between pathological vitreous collagen and the inner retina in a patient with type 1 Stickler syndrome with a confirmed mutation in the COL2A1 gene.

Lens opacity and photoreceptor degeneration in the zebrafish lens opaque mutant

The zebrafish lens opaque (lop) mutant was identified in a chemical mutagenesis screen. The lop mutant, which develops normally through 4 days postfertilization (dpf), exhibits several signs of lens and retinal degeneration at 7 dpf. Histology revealed disrupted lens fibers and increased numbers of nucleated cells within the mutant lens and anterior chamber. The mutant lens also exhibited aberrant epithelial cell morphologies and lacked a definitive transition zone, which suggests that secondary fiber differentiation was interrupted. In addition, the mutant exhibits severely reduced photoreceptors and a reduction in the number of horizontal cells at 7 dpf. Other retinal cell classes appeared unaffected in the mutant. Transmission electron microscopy and opsin immunohistochemistry showed that the different photoreceptor types were generated at the retinal margin, but the rods and cones failed to mature and disappeared. The mutant lens and retina also displayed increased cell proliferation based on proliferating cell nuclear antigen immunolabeling, suggesting that the lens opacity was due to unregulated cell proliferation and undifferentiated cell accumulation within the mutant lens. The lop mutant phenotype supports recent studies showing the lens has a role in regulating teleost retinal development.

Vitrectomy surgery increases oxygen exposure to the lens: a possible mechanism for nuclear cataract formation

PURPOSE

To report vitreous oxygen tension before, immediately after, and at longer times after vitrectomy.

DESIGN

A prospective, interventional consecutive case series.

METHODS

Oxygen was measured using an optical oxygen sensor in patients undergoing vitrectomy. Intraoperatively, oxygen measurements were taken before and after vitrectomy in two intraocular locations: adjacent to the lens and in the mid-vitreous.

RESULTS

Sixty-nine eyes underwent oxygen tension measurements at the time of vitrectomy. In baseline eyes, oxygen tension in the vitreous was low, measuring 8.7 +/- 0.6 mm Hg adjacent to the lens and 7.1 +/- 0.5 mm Hg in the mid-vitreous. The difference between the two locations was statistically significant (P < .003), indicating that vitreous gel maintains an intraocular oxygen gradient. Immediately after vitrectomy, oxygen tension in the fluid-filled eye was higher, measuring 69.6 +/-4.8 mm Hg adjacent to the lens and 75.6 +/- 4.1 mm Hg in the mid-vitreous. There was no statistically significant oxygen gradient between the two locations. The difference in oxygen tension pre- and postvitrectomy is highly statistically significant (P < .0001 lens, P < .0001 mid-vitreous). In eyes with a history of vitrectomy and previous removal of the vitreous gel, the intraocular oxygen tension was significantly higher than in eyes with a formed vitreous gel undergoing a first vitrectomy (P < .02 lens, P < .003 mid-vitreous).

CONCLUSION

Vitrectomy surgery significantly increases intraocular oxygen tension during and for prolonged periods after surgery. This exposes the crystalline lens to abnormally high oxygen and may lead to nuclear cataract formation.

Stickler syndrome: Clinical characteristics and diagnostic criteria

The purpose of this study was to establish diagnostic criteria for Stickler syndrome. Ninety patients from 38 families had complete evaluations for possible Stickler syndrome. Molecular confirmation of COL2A1 mutation status (type I Stickler syndrome) was available on 25 patients from six families. In the remaining 65 patients, 47 from 25 families were affected with Stickler syndrome and 18 from seven families were unaffected with Stickler syndrome. A diagnostic nosology based on type I Stickler patients with known COL2A1 mutations was applied to clinically affected and unaffected patients. A diagnostic scale of 9 points evaluated molecular data or family history data and characteristic ocular, orofacial, auditory, and musculoskeletal findings. A score of > or =5 was diagnostic of Stickler syndrome. These criteria demonstrate 100% sensitivity when applied to type I Stickler syndrome patients with known COL2A1 mutations, 98% sensitivity when applied to clinically affected Stickler patients, and 86% specificity when applied to patients unaffected based on clinical and/or molecular analysis. We conclude that diagnostic criteria based on type I Stickler patients with molecularly confirmed COL2A1 mutations appear to be sensitive and specific for the diagnosis of this syndrome and should be helpful to clinicians when making the diagnosis.

Spondylo-ocular syndrome: a new entity with crystalline lens malformation, cataract, retinal detachment, osteoporosis, and platyspondyly

PURPOSE

To define a new clinical entity in a consanguineous family with six children affected by a spondylo-ocular syndrome, including cataract, crystalline lens malformation, retinal detachment, osteoporosis, and platyspondyly. To analyze candidate genes of connective tissue disorders as a possible underlying disorder and to demonstrate especially the ocular phenotype.

DESIGN

Observational case series.

METHODS

Consanguineous parents, one unaffected sibling and five affected children with clinical features of spondylo-ocular syndrome, were demonstrated. Clinical examination, radiologic, laboratory, and cytogenetic as well as moleculargenetic analyses were performed. The segregation of flanking marker alleles of three collagen genes and the interval for osteoporosis-pseudoglioma syndrome were analyzed. Two microsatellite markers located within Pax6CA/GT region were tested for homozygosity.

RESULTS

On laboratory investigation a normal excretion of amino acids, mucopolysaccharides, and oligosaccharides could be found. The karyotype was normal. Complete radiologic examination in one index patient revealed a generalized moderate osteoporosis, platyspondyly with fish bone appearance, and greatly enlarged intervertebral spaces. The candidate genes known to be in Stickler syndrome as well as linkage to the osteoporosis-pseudoglioma syndrome candidate region could be excluded. None of the affected showed homozygosity for the Pax6 microsatellite markers.

CONCLUSIONS

We conclude that the phenotype and the clinical features in this family defines a new Mendelian disorder. It remains to be seen what kind of molecule shared by eye and bone is involved.

The morphology and natural history of childhood cataracts

The morphology of congenital cataract reflects a combination of the timing and nature of the cause, the anatomy of the lens including its capsule, its development, and changes that take place with time. Morphology may variably affect prognosis, give a clue to the etiology and the age of onset and, in an isolated case, sometimes suggest heritability. The spectrum of morphological variations is enormous and can be complex. A comprehensive approach is to classify the variations according to the area of the lens involved, and sub-dividing them by a detailed description of the shape and appearance. Each specific morphological type is then analyzed determining the etiology, visual prognosis, and management. The use of gene markers has allowed many of these variations to be identified and categorized. Cataracts in childhood can involve the whole lens, in which case they are called total, Morgagnian, or disk-like. They can affect only the center of the lens: lamellar, nuclear, oil droplet, cortical, or coronary. They can be anterior: anterior polar, anterior subcapsular, or anterior lenticonus. The posterior aspect of the lens can also be affected in different fashions: Mittendorf's dot, posterior lenticonus, posterior cortical cataracts, or posterior subcapsular. There are five more forms that must be described separately: punctuate lens opacities, sutural cataracts, coralliform or crystalline, wedge-shaped, and persistent hyperplastic primary vitreous.

The Stickler syndrome: genotype/phenotype correlation in 10 families with Stickler syndrome resulting from seven mutations in the type II collagen gene locus COL2A1

PURPOSE

To evaluate a cohort of clinically diagnosed Stickler patients in which the causative mutation has been identified, determine the prevalence of clinical features in this group as a whole and as a function of age, and look for genotype/phenotype correlations.

METHODS

Review of medical records, clinical evaluations, and mutational analyses of clinically diagnosed Stickler patients.

RESULTS

Patients with seven defined mutations had similar phenotypes, though both inter- and intrafamilial variability were apparent and extensive. The prevalence of certain clinical features was a function of age.

CONCLUSION

Although the molecular determination of a mutation can predict the occurrence of Stickler syndrome, the variability observed in the families described here makes it difficult to predict the severity of the phenotype on the basis of genotype.

Ocular changes in heredo-oto-ophthalmo-encephalopathy

BACKGROUND

Heredo-oto-ophthalmo-encephalopathy (HOOE) is a dominantly inherited disease characterised by gradual loss of vision from the age of 20, progressive hearing loss from the late 20s, cerebellar ataxia in the 30s, and death in dementia in the fourth or fifth decade. Currently, no detailed description has been given of the ocular changes seen in HOOE. Therefore, the ocular changes of HOOE were described on the basis of clinical and histological data from six affected family members.

METHODS

Three members of the family affected by HOOE were subjected to a full ophthalmological re-examination, and postmortem examination was done on three eyes from two affected family members.

RESULTS

Visual loss in HOOE was caused by posterior subcapsular cataract and retinal neovascularizations leading to vitreous haemorrhages and neovascular glaucoma. In the retina there was extensive accumulation of an amyloid material, both diffusely and in the walls of the retinal vessels. The retinal glial cells showed extensive pathological changes and retinal Müller cells were seen to occlude the lumen of retinal vessels.

CONCLUSION

Heredo-oto-ophthalmo-encephalopathy is a familial amyloidosis of the central nervous system which is different from previously reported cases of amyloidosis by including cataract and retinal neovascularizations. The disease is accompanied by extensive changes in retinal glial cells that may play a part in the pathophysiology of the ocular complications of the disease.

Variation in the vitreous phenotype of Stickler syndrome can be caused by different amino acid substitutions in the X position of the type II collagen Gly-X-Y triple helix

Stickler syndrome is a dominantly inherited disorder characterized by arthropathy, midline clefting, hearing loss, midfacial hypoplasia, myopia, and retinal detachment. These features are highly variable both between and within families. Mutations causing the disorder have been found in the COL2A1 and COL11A1 genes. Premature termination codons in COL2A1 that result in haploinsufficiency of type II collagen are a common finding. These produce a characteristic congenital "membranous" anomaly of the vitreous of all affected individuals. Experience has shown that vitreous slit-lamp biomicroscopy can distinguish between patients with COL2A1 mutations and those with dominant negative mutations in COL11A1, who produce a different "beaded" vitreous phenotype. Here we characterize novel dominant negative mutations in COL2A1 that result in Stickler syndrome. Both alter amino acids in the X position of the Gly-X-Y triple-helical region. A recurrent R365C mutation occurred in two unrelated sporadic cases and resulted in the membranous vitreous anomaly associated with haploinsufficiency. In a large family with linkage to COL2A1, with a LOD score of 2.8, a unique L467F mutation produced a novel "afibrillar" vitreous gel devoid of all normal lamella structure. These data extend the mutation spectrum of the COL2A1 gene and help explain the basis for the different vitreous phenotypes seen in Stickler syndrome.

A novel hereditary developmental vitreoretinopathy with multiple ocular abnormalities localizing to a 5-cM region of chromosome 5q13-q14

BACKGROUND

To undertake a clinical and molecular analysis of a previously unpublished kindred with a phenotypically distinct vitreoretinopathy characterized by associated ocular developmental abnormalities.

DESIGN

Family genetic study.

PARTICIPANTS

A total of 23 members, both affected and unaffected, of 1 kindred with vitreoretinopathy.

METHOD

Individuals within the kindred were examined clinically and blood samples taken for DNA analysis. Genetic analysis was performed for the proximal region of chromosome 5q by means of polymerase chain reaction (PCR).

MAIN OUTCOME MEASURES

Detection of vitreoretinopathy and associated abnormalities.

RESULTS

This novel, hereditary vitreoretinopathy, showing the classic features of vitreous pathology and early-onset retinal detachments, was associated with a variety of ocular developmental abnormalities, including posterior embryotoxon, congenital glaucoma, iris hypoplasia, congenital cataract, ectopia lentis, microphthalmia, and persistent hyperplastic primary vitreous. There were no associated systemic features. Genetic mapping with markers from the proximal region of 5q13-q14 showed linkage to a 5-cM region between the markers D5S626 and D5S2103.

CONCLUSIONS

The 5-cM region is within that implicated in the etiology of both Wagner and erosive vitreoretinopathies. This suggests that this novel condition may be allelic, refines the genetic mapping for vitreoretinopathies that map to 5q13-q14, and implicates a gene important not only in vitreous production but also in early ocular development.

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.

Cataract mutations and lens development

The lens plays an essential role for proper eye development. Mouse mutants affecting lens development are excellent models for corresponding human disorders. Moreover, using mutations in particular genes the process of eye and lens development can be dissected into distinct steps. Therefore, three mouse mutants will be described in detail and discussed affecting three essential stages: formation of the lens vesicle, initiation of secondary lens fiber cell formation, and terminal differentiation of the secondary fiber cells. The mutant aphakia (ak) has been characterized by bilaterally apakic eyes [Varnum and Stevens (1968) J. Hered. 59, 147-150], and the corresponding gene was mapped to chromosome 19 [Varnum and Stevens (1975) Mouse News Letters 53, 35]. Recent investigations in our laboratory refined the linkage 0.6 +/- 0.3 N cm proximal to the microsatellite marker D19Mit10. The linked gene Pax2, responsible for proper development of the posterior part of the eye and the optic nerve, was excluded as candidate gene by sequence analysis. Histological analysis of the homozygous ak mutants revealed a persisting lens stalk and subsequently the formation of lens rudiments. The lens defects led to irregular iris development and retinal folding. Congenital aphakia is known as a rare human anomaly. Besides a corneal dystrophy (CDTB), no corresponding disease is localized at the homologous region of human chromosome 10q23. The Cat3 mutations are characterized by vacuolated lenses caused by alterations in the beginning of secondary lens fiber cell differentiation at embryonic day 12.5. Secondary malformations develop at the cornea and the iris, but the retina remains unaffected. Two mutant alleles of the Cat3 locus have been mapped to mouse chromosome 10 very close to the microsatellite markers D10Mit41 and D10Mit95 (less than 0.3 cM). Since Cat3 is mapped to a position, which is homologous to human chromosome 12q21-24, the disorder cornea plana congenita can be considered as a candidate disease. The series of Cat2 mutations have been mapped close to the locus encoding the gamma-crystallin gene cluster Cryg [Löster et al. (1994) Genomics 23, 240-242]. The Cat2nop mutation is characterized by a deletion of 11 bp and an insertion of 4 bp in the 3rd exon of Crygh leading to a truncated gamma B-crystallin. The defect in the Crygh gene is causative for the stop of lens fiber cell differentiation from embryonic day 15.5 onward. Besides the lens, no further ocular tissue is affected. The Cat2 mouse mutants are interesting models for human cataracts caused by mutations in the gamma-crystallin genes at human chromosome 2q32-35. The ak, Cat3 and Cat2 mutants are discussed in the context of other mutants affecting early eye and lens development. Additionally, human congenital cataracts are discussed, which have been characterized similar to the mouse models. The overview of the three types of mutants demonstrates that genes, which affect the early eye development, e.g. at the lens vesicle stage, have consequences for the development of the whole eye. In contrast, if the mutation influences later steps of lens differentiation, the consequences are restricted to the lens only. These data indicate a decreasing effect of the lens for the regulation of eye development during embryogenesis.

Genetics and hearing loss: a review of Stickler syndrome

Stickler syndrome is an autosomal dominant multisystem disease. The four most affected systems are craniofacial, skeletal, ocular, and auditory. The manifestations of Stickler syndrome vary considerably among affected individuals. Audiologists and speech-language pathologists should be familiar with the characteristics associated with Stickler syndrome to facilitate early identification and appropriate management.

Hereditary vitreopathy

Heterogeneity has long been recognised within the spectrum of inherited vitreo-retinal disease but the extent of the variation has been less easy to quantify. This has been compounded by the small size and numbers of pedigrees available for the study, and the phenotypic variation both within and between pedigrees. Formation abnormalities in the vitreous architecture have, in the past, been eclipsed by classifications based on general skeletal and morphological differences. Stickler syndrome is the commonest disorder within the spectrum of hereditary vitreous abnormalities and many of the recent published advances relate to this. Stickler syndrome has been subclassified on the basis of vitreo-retinal phenotype: type 1 families with a characteristic congenital vitreous anomaly show linkage without recombination to markers at the COL2A1 locus; type 2 families with different congenital vitreo-retinal phenotypes are not linked to COL2A1. A recent report identifies the COL11A2 mutation in a Dutch pedigree with systemic features of Stickler syndrome but without ocular involvement. Others have implicated COL11A1 in a type 2 Stickler syndrome pedigree with ocular abnormalities. Both COL11A1 and COL11A2 are expressed in cartilage, but on the basis of studies of bovine vitreous it is likely that only the alpha 1(XI) chain encoded by COL11A1 is present in vitreous. This would be consistent with the hypothesis that mutations in the genes encoding collagen XI can give rise to manifestations of Stickler syndrome, but of these, only mutations in COL11A1 will give the full syndrome including the vitreo-retinal features.

Erosive vitreoretinopathy. A new clinical entity

PURPOSE

Vitreoretinopathies are disorders characterized by an abnormal vitreous gel structure and associated retinal changes. The authors report a pedigree with vitreous changes characteristic of the vitreoretinopathies, but with retinal pigment epithelial changes, electroretinographic abnormalities, and a clinical course distinct from previously described entities.

METHODS

Twenty-six family members were examined. Complete ophthalmologic examinations, electroretinography, and perimetry were performed on patients who were at genetic risk for the disease. Particular attention was given to vitreous morphology and examination of the retinal and retinal pigment epithelium (RPE).

RESULTS

Fifteen individuals affected with an autosomal dominant vitreoretinal degeneration were identified. The disease is characterized by nyctalopia, progressive visual field loss, marked vitreous syneresis, progressive RPE atrophy, and combined traction-rhegmatogenous retinal detachments (11 patients). Thinning or "erosion" of the RPE in younger patients permits increased visualization of the choroidal vessels. In advanced conditions, equatorial areas are seen that appear clinically devoid of RPE, with extensive posterior atrophy in older patients. Diffuse rod-cone dysfunction is demonstrated by electroretinography. High myopia, epiphyseal dysplasia, orofacial anomalies, and systemic manifestations characteristic of other vitreoretinopathies are not present.

CONCLUSION

The authors describe an entity clinically distinct from other vitreoretinopathies. The disease is characterized by pronounced vitreous abnormalities, complicated retinal detachments, and a progressive pigmentary retinopathy. The most unusual and constant feature is the progressive change in RPE with concurrent visual field constriction and electroretinographic abnormalities. Because the RPE initially seems normal and progressively thins or "erodes" in the equatorial periphery, the descriptive name "erosive" vitreoretinopathy is proposed.