Association of HLA type with pseudoexfoliation of the lens capsule

Pseudoexfoliation syndrome, a systemic disorder with ocular manifestations

Pseudoexfoliation syndrome (PXS) is a systemic condition with eye manifestations. In the eye, pseudoexfoliation material deposits on various structures of the anterior segment. The nature of this material is mostly fibrillar with fibers made up of microfibrils and coated with amorphous material. The composition of these fibrils is diverse and includes basement membrane components as well as enzymes involved in extracellular matrix maintenance. Pseudoexfoliation is the most common cause of secondary open-angle glaucoma (pseudoexfoliation glaucoma, PXG) worldwide. The goal of this review is to summarize our knowledge on the genetics of this systemic disorder and its resultant ocular manifestations. PXS familial aggregation suggests genetic inheritance. PXS has been strongly associated with single nucleotide polymorphisms (SNPs) of the lysyl oxidase-like 1 (LOXL1) gene on chromosome 15q24.1. Two of these SNPs confer a higher than 99% population attributable risk for PXS and PXG in the Nordic population; however, they carry different risks in different populations. The high risk haplotypes also vary among different populations. LOXL1 is one of group of the enzymes involved in the cross-linking of collagen and elastin in the extracellular matrix. Its function in connective tissue maintenance has been confirmed in mice; however, its actual role in PXS remains unclear. Contactin-associated protein-like 2 also has a strong genetic association with PXS in a German cohort and is an attractive candidate molecule. It encodes for a protein involved in potassium channel trafficking. Other candidate genes linked to PXS include lysosomal trafficking regulator, clusterin, adenosine receptors, matrix metalloproteinase-1 (MMP1), and glutathione transferase. These genes may be modifying genes for development of PXS and PXG.

A possible link between the pseudoexfoliation syndrome and coronary artery disease

PURPOSE

This is a collaborative case-control study from Ophthalmology and Cardiology departments of a tertiary care hospital, designed to explore the relationship between coronary artery disease (CAD) and pseudoexfoliation syndrome (PEX).

METHOD

In all, 50 patients with CAD proven by coronary angiography, and 50 controls with normal coronary angiographic findings were compared in terms of PEX, other vascular diseases, and retinal vascular findings. chi2-test and Student's t-test were used for statistical analysis.

RESULTS

The number of patients with PEX among CAD (+) patients was substantially larger than controls. In all, 28 of 50 CAD (+) patients and only 12 of 50 CAD (-) patients had PEX. PEX was significantly associated with CAD (P=0.001). When all patients were regrouped according to the presence of PEX, patients with PEX did not differ from patients without PEX in terms of age (P=0.360) and sex (P=0.507), but the prevalence of CAD was higher (P=0.001) and fundoscopic findings of vascular diseases were significantly more prominent (P=0.0001) in PEX (+) patients.

DISCUSSION

We demonstrated statistically significant difference in the prevalence of PEX in CAD patients, and also in the prevalence of CAD in PEX (+) individuals. These were striking differences. We should consider the possibility of the presence of PEX in CAD patients; and the predisposition of PEX (+) persons for CAD, which necessitates a fundus examination for findings of systemic vascular diseases.

Differentiation between retrocorneal pseudoexfoliative material and keratic precipitates

A 62-year-old female presented with unilateral pseudoexfoliation syndrome. Apart from the classic pseudoexfoliation of the lens capsule, she also manifested conspicuous endothelial deposits of pseudoexfoliation material (PXM). The potential exists to misdiagnose endothelial deposits of PXM as keratic precipitates (KP). This patient was subsequently erroneously diagnosed with Fuchs' heterochromic cyclitis. Close inspection of the endothelial deposits should allow for appropriate differentiation between PXM and KP, particularly when one examines them in the context of the presenting symptoms and other ocular findings. It is incumbent on the practitioner to make the appropriate diagnosis to prevent the patient undergoing unnecessary clinical investigations or therapies.

Exfoliation syndrome

Exfoliation syndrome (XFS) is an age-related disease in which abnormal fibrillar extracellular material is produced and accumulates in many ocular tissues. Its ocular manifestations involve all of the structures of the anterior segment, as well as conjunctiva and orbital structures. Glaucoma occurs more commonly in eyes with XFS than in those without it; in fact, XFS has recently been recognized as the most common identifiable cause of glaucoma. Patients with XFS are also predisposed to develop angle-closure glaucoma, and glaucoma in XFS has a more serious clinical course and worse prognosis than primary open-angle glaucoma. There is increasing evidence for an etiological association of XFS with cataract formation, and possibly with retinal vein occlusion. XFS is now suspected to be a systemic disorder and has been associated preliminarily with transient ischemic attacks, stroke, systemic hypertension, and myocardial infarction. Further ramifications await discovery. Deposits of white material on the anterior lens surface are the most consistent and important diagnostic feature of XFS. The classic pattern consists of three distinct zones that become visible when the pupil is fully dilated. Whereas the classic picture of manifest XFS has been often described, the early stages of beginning exfoliation have not been well defined. Next to the lens, exfoliation material is most prominent at the pupillary border. Pigment loss from the iris sphincter region and its deposition on anterior chamber structures is a hallmark of XFS. Despite extensive research, the exact chemical composition of exfoliation material (XFM) remains unknown. An overproduction and abnormal metabolism of glycosaminoglycans have been suggested as one of the key changes in XFS. The protein components of XFM include both noncollagenous basement membrane components and epitopes of the elastic fiber system such as fibrillium. Regardless of etiology, typical exfoliation fibers have been demonstrated electron microscopically in close association with the pre-equatorial lens epithelium, the nonpigmented ciliary epithelium, the iris pigment epithelium, the corneal endothelium, the trabecular endothelium, and with almost all cell types of the iris stroma, such as fibrocytes, melanocytes, vascular endothelial cells, pericytes, and smooth muscle cells. The presence of XFS should alert the physician to the increased risks of intraocular surgery, most commonly zonular dehiscence, capsular rupture, and vitreous loss during cataract extraction. Heightened awareness of this condition and its associated clinical signs are important in the detection and management of glaucoma, and preoperative determination of those patients at increased risk for surgical complications.

Pseudoexfoliation syndrome in Australian adults

PURPOSE

To describe the prevalence and correlates of pseudoexfoliation syndrome in Australians aged 40 years and older.

METHODS

Cluster, stratified sampling was employed to identify a cohort representative of the population of the state of Victoria aged 40 years and older that included urban, rural, and nursing home residents. A standardized personal interview and clinical eye examination, including intraocular pressure, were performed at locally established test sites. The presence of any pseudoexfoliation material on the iris or lens capsule was noted on dilated slit-lamp examination. Participants were classified as having pseudoexfoliation syndrome if any pseudoexfoliation material was present in either eye. Univariate analyses with t tests and chi-square were first employed to evaluate risk factors for pseudoexfoliation. Any factors with P <.10 were then fitted in a backward stepwise logistic regression model. For the final multivariate models, P <.05 was considered statistically significant.

RESULTS

A total of 3,271 of the urban residents (83% of eligible), 403 nursing home residents (90% of eligible), and 1473 rural residents (92%) participated. The urban residents ranged in age from 40 to 98 years (mean = 59), and 1,511 (46%) were men. The nursing home residents ranged in age from 46 to 101 years (mean 82), and 85 (21%) were men. The rural residents ranged in age from 40 to 103 years (mean 60), and 701 (47.5%) were men. Participants with bilateral cataract extraction were excluded from further analyses. The overall rate of pseudoexfoliation syndrome in this population was 0.98% (95% confidence limit = 0.57, 1.28). The prevalence of pseudoexfoliation material in either eye increased significantly with age. No cases of pseudoexfoliation syndrome were observed in people aged 90 years and older. However, people with bilateral cataract surgery had been excluded from these analyses. After adjusting for age and cataract, only glaucoma remained significantly related to pseudoexfoliation (odds ratio = 3.80, 95% confidence limit = 1.73, 8.33).

DISCUSSION

In conclusion, we found only two strong correlates of pseudoexfoliation in our population-based sample of Victorians aged 40 years and older: age and glaucoma.

Is pseudoexfoliation syndrome inherited? A review of genetic and nongenetic factors and a new observation

Pseudoexfoliation (PEX) syndrome is the commonest identifiable cause of open-angle glaucoma worldwide. PEX is characterized clinically by small whitish deposits of fibrillar-granular material in the anterior segment of the eye. Despite its prevalence and potential for ophthalmic morbidity, surprisingly little is known about the etiology and pathogenesis of PEX. This article reviews the literature and presents evidence regarding genetic and nongenetic arguments for the etiology of pseudoexfoliation. Lines of evidence that support a genetic basis for PEX include transmission in two-generation families, twin studies, an increased risk of PEX in relatives of affected patients, and HLA studies. Nearly all pedigrees in the literature, and our own experience with PEX families in Iceland and Canada, suggest maternal transmission, raising the possibilities of mitochondrial inheritance, X-linked inheritance, and autosomal inheritance with genomic imprinting. A number of nongenetic factors have also been evaluated for their possible implication in the development of PEX. These include ultraviolet light, autoimmunity, slow virus infection, and trauma. It is possible that a combination of genetic and nongenetic factors may be involved in the etiology and pathogenesis of PEX, i.e. it may be a multifactorial disorder. Further studies with larger numbers of patients are needed to delineate more clearly the contribution of genetic (nuclear DNA, mitochondrial DNA or both) and nongenetic factors to the development of pseudoexfoliation syndrome and pseudoexfoliation glaucoma.