Ocular characteristics and complications in patients with osteogenesis imperfecta: a systematic review

Skeletal pathology in mouse models of Gould syndrome is partially alleviated by genetically reducing TGFβ signaling

Skeletal defects are hallmark features of many extracellular matrix (ECM) and collagen-related disorders. However, a biological function in bone has never been defined for the highly evolutionarily conserved type IV collagen. Collagen type IV alpha 1 (COL4A1) and alpha 2 (COL4A2) form α1α1α2 (IV) heterotrimers that represent a fundamental basement membrane constituent present in every organ of the body, including the skeleton. COL4A1 and COL4A2 mutations cause Gould syndrome, a variable and clinically heterogenous multisystem disorder generally characterized by the presence of cerebrovascular disease with ocular, renal, and muscular manifestations. We have previously identified elevated TGFβ signaling as a pathological insult resulting from Col4a1 mutations and demonstrated that reducing TGFβ signaling ameliorate ocular and cerebrovascular phenotypes in Col4a1 mutant mouse models of Gould syndrome. In this study, we describe the first characterization of skeletal defects in Col4a1 mutant mice that include a developmental delay in osteogenesis and structural, biomechanical and vascular alterations of mature bones. Using distinct mouse models, we show that allelic heterogeneity influences the presentation of skeletal pathology resulting from Col4a1 mutations. Importantly, we found that TGFβ target gene expression is elevated in developing bones from Col4a1 mutant mice and show that genetically reducing TGFβ signaling partially ameliorates skeletal manifestations. Collectively, these findings identify a novel and unsuspected role for type IV collagen in bone biology, expand the spectrum of manifestations associated with Gould syndrome to include skeletal abnormalities, and implicate elevated TGFβ signaling in skeletal pathogenesis in Col4a1 mutant mice.

Polarization-sensitive optical coherence tomography and scleral collagen fiber orientation in osteogenesis imperfecta

Osteogenesis imperfecta (OI), a rare genetic connective tissue disorder, primarily arises from pathogenic variants affecting the production or structure of collagen type I. In addition to skeletal fragility, individuals with OI may face an increased risk of developing ophthalmic diseases. This association is believed to stem from the widespread presence of collagen type I throughout various parts of the eye. However, the precise consequences of abnormal collagen type I on different ocular tissues remain unknown. Of particular significance is the sclera, where collagen type I is abundant and crucial for maintaining the structural integrity of the eye. Recent research on healthy individuals has uncovered a unique organizational pattern of collagen fibers within the sclera, characterized by fiber arrangement in both circular and radial layers around the optic nerve head. While the precise function of this organizational pattern remains unclear, it is hypothesized to play a role in providing mechanical support to the optic nerve. The objective of this study is to investigate the impact of abnormal collagen type I on the sclera by assessing the fiber organization near the optic nerve head in individuals with OI and comparing them to healthy individuals. Collagen fiber orientation of the sclera was measured using polarization-sensitive optical coherence tomography (PS-OCT), an extension of the conventional OCT that is sensitive to materials that exhibit birefringence (axial changes in light refraction). Birefringence was quantified and used as imaging contrast to extract collagen fiber orientation as well as the thickness of the radially oriented scleral layer. Three individuals with OI, exhibiting different degrees of disease severity, were assessed and analyzed, along with seventeen healthy individuals. Mean values obtained from individuals with OI were descriptively compared to those of the healthy participant group. PS-OCT revealed a similar orientation pattern of scleral collagen fibers around the optic nerve head between OI individuals and healthy individuals. However, two OI participants exhibited reduced mean birefringence of the radially oriented scleral layer compared to the healthy participant group (OI participant 1 oculus dexter et sinister (ODS): 0.34°/μm, OI participant 2: ODS 0.26°/μm, OI participant 3: OD: 0.29°/μm, OS: 0.28°/μm, healthy participants: ODS 0.38 ± 0.05°/μm). The radially oriented scleral layer was thinner in all OI participants although within ±2 standard deviations of the mean observed in healthy individuals (OI participant 1 OD: 101 μm, OS 104 μm, OI participant 2: OD 97 μm, OS 98 μm, OI participant 3: OD: 94 μm, OS 120 μm, healthy participants: OD 122.8 ± 13.6 μm, OS 120.8 ± 15.1 μm). These findings imply abnormalities in collagen organization or composition, underscoring the necessity for additional research to comprehend the ocular phenotype in OI.

Ophthalmological screening guidelines for individuals with Osteogenesis Imperfecta: a scoping review

BACKGROUND

Osteogenesis imperfecta (OI) is a connective tissue disorder in which the Type 1 collagen is defective. The eye is a structure rich in collagen Type 1 and is heavily impacted by the disease. Many vision-threatening eye diseases have been associated with OI. The onset of these diseases also tend to occur at an earlier age in individuals with OI. Despite the research on these risks, appropriate ophthalmological screening or care guidelines for individuals with OI remain unknown. As such, the purpose of this scoping review was to explore and describe existing ophthalmological screening and care guidelines to orient OI patient care.

MAIN BODY

A scoping review based on the Joanna Briggs Institute (JBI) methodology was conducted. A search of databases (PubMed and Medline) was completed in consultation with a research librarian. A total of 256 studies were imported for screening. Primary sources matching the inclusion and exclusion criteria were screened, extracted, and analyzed using Covidence.

CONCLUSION

A total of 12 primary articles met inclusion and exclusion criteria, containing case reports, case series and cohort studies. Despite the risk of blindness associated with the consequences of OI on the eye, the primary literature fails to provide detailed screening and care guidelines aimed at identifying disease early. We provide general recommendations based on the review findings to guide the ophthalmological care of patients with OI and call upon the experts to convene globally to create screening guidelines. Further investigations of ophthalmological screening are warranted to limit these vision-threatening risks with early detection and treatment. Standardized ophthalmological screening guidelines for OI remain an area for research.

Childhood glaucoma: Implications for genetic counselling

Childhood glaucoma is a heterogeneous group of ocular disorders defined by an age of onset from birth to 18 years. These vision-threatening disorders require early diagnosis, timely treatment, and lifelong management to maintain vision and minimise irreversible blindness. The genetics of childhood glaucoma is complex with both phenotypic and genetic heterogeneity. The purpose of this review is to summarise the different types of childhood glaucoma and their genetic architecture to aid in the genetic counselling process with patients and their families. We provide an overview of associated syndromes and discuss implications for genetic counselling, including genetic testing strategies, cascade genetic testing, and reproductive options.

'BLUES' procedure for assessing the blue level of the sclera in Osteogenesis Imperfecta

PURPOSE

Blue sclera is a characteristic and common clinical sign of Osteogenesis Imperfecta (OI). However, there is currently no widely accepted, objective method for assessing and grading blue sclera in individuals with OI. To address this medical need, this study is aimed to design and validate a new method called 'BLUES' (BLUe Eye Sclera) to objectively identify and quantify the blue color in the sclera of patients affected by OI.

METHODS

Sixty-two patients affected by OI and 35 healthy controls were enrolled in the present prospective study, for a total of 194 eyes analyzed. In the 'BLUES' procedure, eye images from patients with OI and control subjects were analyzed to assess and grade the blue level of the sclera using Adobe Photoshop Software. The validation process then involved comparing the results obtained with the 'BLUES' procedure to the judgement of experienced ophthalmologists (JEO). A receiver-operating characteristic (ROC) curve analysis was used to examine the overall discriminatory power. The sensitivity and specificity levels and the Cohen's Kappa (K) indexes of 'BLUES' and 'JEO' were estimated versus the standard OI diagnosis. The K indexes of 'BLUES' versus 'JEO' were also evaluated.

RESULTS

The optimal cut-off point of the scleral blue peak was calculated at 17%. Our findings demonstrated a sensitivity of 89% (CI95%: 0.835-0.945) and specificity of 87% (CI95%: 0.791-0.949) for the 'BLUES' procedure with an agreement versus the diagnosis of OI of 0.747. In comparison, the sensitivity and specificity of 'JEO' ranged from 89 to 94% and 77% to 100%, respectively, with an agreement ranging from 0.663 to 0.871 with the diagnosis of OI. The agreement between 'BLUES 'and 'JEO' evaluations ranged from 0.613 to 0.734.

CONCLUSIONS

Our findings demonstrated an 89% sensitivity and an impressive 87% specificity of our method to analyze the blue sclera in OI. The results indicated high agreement with disease diagnosis and were consistent with evaluations by experienced ophthalmologists. The 'BLUES' procedure appears to be a simple, reliable and objective method for effectively identify and quantify the blue color of the sclera in OI.

Rodent genetically modified models of glaucoma

Glaucoma, one of the leading causes of irreversible blindness worldwide, is a complex and heterogenous disease. While environmental factors are important, it is well-recognized that the disease has a strong heritable component. With the advent of large-cohort genome wide association studies, a myriad of genetic risk loci has been linked to different forms of glaucoma. Animal models have been an indispensable tool in characterizing these loci, especially if they lie within coding regions in the genome. Not only do these models connect genotype to phenotype, advancing our understanding of glaucoma pathogenesis in the process, they also have valuable utility as a platform for the pre-clinical testing of potential therapies. In this review, we will outline genetic models used for studying the major forms of glaucoma, including primary open angle glaucoma, normal tension glaucoma, primary angle closure glaucoma, pigmentary glaucoma, pseudoexfoliation glaucoma, and early onset glaucoma, including congenital and developmental glaucoma, and how studying these models have helped shed light on human glaucoma.

Emerging Landscape of Osteogenesis Imperfecta Pathogenesis and Therapeutic Approaches

Osteogenesis imperfecta (OI) is an uncommon genetic disorder characterized by shortness of stature, hearing loss, poor bone mass, recurrent fractures, and skeletal abnormalities. Pathogenic variations have been found in over 20 distinct genes that are involved in the pathophysiology of OI, contributing to the disorder's clinical and genetic variability. Although medications, surgical procedures, and other interventions can partially alleviate certain symptoms, there is still no known cure for OI. In this Review, we provide a comprehensive overview of genetic pathogenesis, existing treatment modalities, and new developments in biotechnologies such as gene editing, stem cell reprogramming, functional differentiation, and transplantation for potential future OI therapy.

Keratoconus tomographic indices in osteogenesis imperfecta

PURPOSE

Osteogenesis imperfecta (OI) is a rare inherited disease affecting collagen-rich tissues. Ocular complications have been reported such as thin corneas, low ocular rigidity, keratoconus, among others. The purpose of this study is to characterize corneal tomographic features in OI patients compared to unaffected patients, with particular focus on commonly studied keratoconus indices.

METHODS

Cross-sectional case-control study including 37 OI patients and 37 age-matched controls. Patients and controls underwent comprehensive ophthalmological examination including corneal Scheimpflug tomography with a Pentacam HR device (Oculus Optikgeräte GmbH, Wetzlar, Germany) to analyse and compare topometric, tomographic, pachymetric and Belin-Ambrósio Enhanced Ectasia Display III (BAD-D) data of both eyes of each patient.

RESULTS

Most OI patients had type I disease (n = 24; 65%) but type III-VII patients were also included. Two patients had clinically overt bilateral keratoconus. OI patients had significantly higher maximum keratometry (45.2 ± 2.1 vs. 43.7 ± 1.2; p = 0.0416), front and back elevation (3.0 ± 3.3 vs. 2.1 ± 1.3, p = 0.0201; 11.1 ± 8.2 vs. 5.0 ± 3.7, p < 0.0001), index of surface variance (25.5 ± 13 vs. 17.4 ± 8.3; p = 0.0016), index of vertical asymmetry (0.21 ± 0.14 vs. 0.15 ± 0.06; p = 0.0215), index of height asymmetry (9.2 ± 14 vs. 6.0 ± 4.5; p = 0.0421), index of height decentration (0.02 ± 0.01 vs. 0.01 ± 0.01; p < 0.0001) and average pachymetric progression (1.01 ± 0.19 vs. 0.88 ± 0.14; p < 0.0001) readings. Thinnest corneal thickness and maximum Ambrósio relational thickness were significantly lower (477 ± 52 vs. 543 ± 26; 387 ± 95 vs. 509 ± 49; p < 0.0001). Two-thirds of OI patients had corneas with a minimum thickness < 500 µm. BAD-D value was significantly higher in OI patients (2.1 ± 1.4 vs. 0.9 ± 0.2; p < 0.0001).

CONCLUSION

OI patients showed significant changes in corneal profiles compared with healthy subjects. A high proportion of patients had tomographically suspect corneas when using keratoconus diagnostic indices. Further studies are warranted to assess the true risk of corneal ectasia in OI patients.

Blue Sclerae and Differential Diagnosis in Chest Pain: A Case Report

Osteogenesis imperfecta (OI) constitutes a complex connective tissue disorder extending beyond its hallmark bone fragility. This case report explores the intricate diagnostic journey involving an elderly patient with acute chest pain, blue sclerae, and multiple fractures. Despite a thorough cardiac evaluation yielding normal results, the complex medical history and phenotypic markers directed attention toward musculoskeletal factors, underlining the importance of comprehensive diagnostic approaches in hereditary conditions like OI.

The intricate mechanism of PLS3 in bone homeostasis and disease

Since our discovery in 2013 that genetic defects in PLS3 lead to bone fragility, the mechanistic details of this process have remained obscure. It has been established that PLS3 variants cause syndromic and nonsyndromic osteoporosis as well as osteoarthritis. PLS3 codes for an actin-bundling protein with a broad pattern of expression. As such, it is puzzling how PLS3 specifically leads to bone-related disease presentation. Our review aims to summarize the current state of knowledge regarding the function of PLS3 in the predominant cell types in the bone tissue, the osteocytes, osteoblasts and osteoclasts. This is related to the role of PLS3 in regulating mechanotransduction, calcium regulation, vesicle trafficking, cell differentiation and mineralization as part of the complex bone pathology presented by PLS3 defects. Considering the consequences of PLS3 defects on multiple aspects of bone tissue metabolism, our review motivates the study of its mechanism in bone diseases which can potentially help in the design of suitable therapy.

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.

From Genetics to Clinical Implications: A Study of 675 Dutch Osteogenesis Imperfecta Patients

Osteogenesis imperfecta (OI) is a heritable connective tissue disorder that causes bone fragility due to pathogenic variants in genes responsible for the synthesis of type I collagen. Efforts to classify the high clinical variability in OI led to the Sillence classification. However, this classification only partially takes into account extraskeletal manifestations and the high genetic variability. Little is known about the relation between genetic variants and phenotype as of yet. The aim of the study was to create a clinically relevant genetic stratification of a cohort of 675 Dutch OI patients based on their pathogenic variant types and to provide an overview of their respective medical care demands. The clinical records of 675 OI patients were extracted from the Amsterdam UMC Genome Database and matched with the records from Statistics Netherlands (CBS). The patients were categorized based on their harbored pathogenic variant. The information on hospital admissions, outpatient clinic visits, medication, and diagnosis-treatment combinations (DTCs) was compared between the variant groups. OI patients in the Netherlands appear to have a higher number of DTCs, outpatient clinic visits, and hospital admissions when compared to the general Dutch population. Furthermore, medication usage seems higher in the OI cohort in comparison to the general population. The patients with a COL1A1 or COL1A2 dominant negative missense non-glycine substitution appear to have a lower health care need compared to the other groups, and even lower than patients with COL1A1 or COL1A2 haploinsufficiency. It would be useful to include the variant type in addition to the Sillence classification when categorizing a patient's phenotype.

High risk and low prevalence diseases: Open globe injury

INTRODUCTION

Open globe injury (OGI) is a rare but serious condition that carries with it a high rate of morbidity.

OBJECTIVE

This review highlights the pearls and pitfalls of OGI, including presentation, diagnosis, and management in the emergency department (ED) based on current evidence.

DISCUSSION

OGI refers to full-thickness injury to the layers of the eye. OGI can be caused by blunt or sharp trauma, and subtypes include penetration, perforation, intraocular foreign body (IOFB), globe rupture, or mixed types. OGI is more common in males and usually secondary to work-related injury, but in women it is most commonly associated with falls. Emergency clinicians should first assess for and manage other critical, life-threatening injuries. Following this assessment, a thorough eye examination is necessary. Computed tomography (CT) may suggest the disease, but it cannot definitively exclude the diagnosis. While point-of-care ultrasound (POCUS) is highly sensitive and specific for some findings in OGI, its use is controversial due to potential globe content extrusion. Management includes protecting the affected eye from further injury, preventing Valsalva maneuvers that could extrude ocular contents, updating tetanus vaccination status, administering broad-spectrum antibiotics, and ophthalmology consultation for surgical intervention to prevent the sequelae of blindness and endophthalmitis.

CONCLUSION

An understanding of OGI can assist emergency clinicians in diagnosing and managing this sight-threatening traumatic process.

Assessment of the Retinal Nerve Fibre Layer, Retina, and Choroid in Osteogenesis Imperfecta

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic disorder in which there are problems in tissues containing type I collagen, predominantly the cornea and sclera in the eye. Although there are many studies on problems with the anterior segment of the eye in patients with OI, studies on posterior structures are limited. Involvement of the sclera may affect the retinal nerve fibre layer (RNFL), which is indirectly related to intraocular pressure. In addition, the retina and choroid containing type I collagen may be affected. The aim of the study was to compare the posterior segment structures of the eye, including the RNFL, retina, and choroid, in patients with OI to those of healthy control subjects.

METHODS

This cross-sectional study recruited 19 patients with OI, as well as 22 age- and gender-similar healthy control subjects. Measurements of the RNFL, retina, and choroid were obtained with optical coherence tomography (Spectralis SD-OCT, Heidelberg Engineering, Heidelberg, Germany).

RESULTS

Patients with OI (mean age 14.32 ± 5.08 years) and the control group (mean age 13.73 ± 3.56 years) had similar age, refractive error, and intraocular pressure values (p > 0.05). There was no difference between groups in terms of RNFL thickness, including the superonasal, nasal, inferonasal, inferotemporal, temporal, and superotemporal sectors, retinal thickness, and choroidal thickness from five different locations (p > 0.05, for all).

CONCLUSION

According to these results, OI does not clinically affect the RNFL, retina, and choroid in childhood.

Risk of eye diseases in osteogenesis imperfecta - A nationwide, register-based cohort study

BACKGROUND

Osteogenesis imperfecta (OI) is a hereditary disease caused by affected collagen type 1. Collagen type 1 is an important structural component of the eye. Ocular manifestations in OI are described in literature, but little is known about the risk of eye diseases in OI.

OBJECTIVE

To investigate the risk of eye diseases in OI.

DESIGN

A Danish nationwide register-based cohort study based on data from the Danish National Patient Register.

PARTICIPANTS

All patients registered with an OI diagnosis between January 1977 and December 2018 matched 1:5 with a reference population on gender and birth month and birth year.

MEASUREMENTS

Incidence rates (IR) per 1000 patient years and sub-hazard ratio (SHR) for any eye disease, corneal diseases, cataract, refraction disorders, vitreous haemorrhage, retinal detachment, retinopathy, angiopathy, retinal haemorrhage, retinal degeneration, retinal changes, optic nerve disorders, and traumatic eye lesions.

RESULTS

We identified 907 OI patients (493 women) and 4535 persons (2465 women) in the reference population. The IR for any eye disease was 4.07 [95% CI 3.41-4.85] in the OI cohort and 1.96 [95% CI 1.89-2.12] in the reference cohort. The two diseases with highest incidence was cataract (2.41 [95%CI 1.93-3.03] vs 1.29 [95% CI 1.12-1.47], SHR 1.76 [95% CI 1.34-2.33]) and glaucoma (1.08 [95% CI 0.77-1.51] vs 0.42 [95% CI 0.33-0.54], SHR 2.33 [95% CI 1.55-3.53]). The absolute risk of most other eye diseases was low, but the SHR indicated a higher risk in the OI cohort compared to the reference group showing statistically increased risk of refractive disorders, vitreous haemorrhage, retinal detachment or ruptures, other retinal diseases (i.e., retinopathy, angiopathy, retinal haemorrhage, degeneration, retinal changes), and optic nerve disorders. Corneal diseases and traumatic eye lesions were not statistically significantly increased in OI-patients.

CONCLUSION

Patients with OI have a higher risk of cataract, refractive disorders, glaucoma, vitreous haemorrhages, retinal detachment/ruptures, retinal diseases, and optic nerve disorders.

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.

Controversy and Consideration of Refractive Surgery in Patients with Heritable Disorders of Connective Tissue

Heritable Disorders of Connective Tissue (HDCTs) are syndromes that disrupt connective tissue integrity. They include Osteogenesis Imperfecta (OI), Ehlers Danlos Syndrome (EDS), Marfan Syndrome (MFS), Loeys-Dietz Syndrome (LDS), Epidermolysis Bullosa (EB), Stickler Syndrome (STL), Wagner Syndrome, and Pseudoxanthoma Elasticum (PXE). Because many patients with HDCTs have ocular symptoms, commonly myopia, they will often present to the clinic seeking refractive surgery. Currently, corrective measures are limited, as the FDA contraindicates laser-assisted in-situ keratomileusis (LASIK) in EDS and discourages the procedure in OI and MFS due to a theoretically increased risk of post-LASIK ectasia, poor wound healing, poor refractive predictability, underlying keratoconus, and globe rupture. While these disorders present with a wide range of ocular manifestations that are associated with an increased risk of post-LASIK complications (e.g., thinned corneas, ocular fragility, keratoconus, glaucoma, ectopia lentis, retinal detachment, angioid streaks, and ocular surface disease), their occurrence and severity are highly variable among patients. Therefore, an HDCT diagnosis should not warrant an immediate disqualification for refractive surgery. Patients with minimal ocular manifestations can consider LASIK. In contrast, those with preoperative signs of corneal thinning and ocular fragility may find the combination of collagen cross-linking (CXL) with either photorefractive keratotomy (PRK), small incision lenticule extraction (SMILE) or a phakic intraocular lens (pIOL) implant to be more suitable options. However, evidence of refractive surgery performed on patients with HDCTs is limited, and surgeons must fully inform patients of the unknown risks and complications before proceeding. This paper serves as a guideline for future studies to evaluate refractive surgery outcomes in patients with HDCTs.