Corneal changes in Fabry's disease: a clinico-pathologic case report of a heterozygote

Assessment of Retinal Vessel Tortuosity Index in Patients with Fabry Disease Using Optical Coherence Tomography Angiography (OCTA)

Vessel tortuosity (VT) is a parameter used to assess retinal involvement in patients affected by systemic diseases such as Fabry disease (FD). In this study, we assessed a retinal VT index (VTI) using optical coherence tomography angiography (OCTA) in a group of patients with FD (FD cohort) compared to a healthy control group (HC cohort). This is a single-center, retrospective study analysis of all consecutive patients with genetically tested and confirmed FD who underwent regular ophthalmological visits from December 2017 to January 2020 at the Department of Ophthalmology at the University Hospital of Zurich, Switzerland. VTI was calculated for each OCTA image and the results were compared between FD and HC cohort. A total of 56 participants, 32 (male:female ratio 12:20) in the FD cohort and 24 (male:female ratio 13:11) in the HC cohort. Classic onset was determined in 18 patients. Overall, mean VTI (±SD) was 0.21 (±0.07). Male patients with classic-onset FD had a significantly higher mean VTI (0.33, SD ± 0.35) compared to all other subgroups (p-value < 0.05). Further investigations of retinal VTI in patients with FD could be helpful to use OCTA as a noninvasive screening and follow-up modality to assess disease progression in affected patients.

Ophthalmic Manifestations in Fabry Disease: Updated Review

Fabry disease (FD) is an X-linked lysosomal storage disorder, causing Gb-3 (globotriaosylceramide) buildup in cellular lysosomes throughout the body, in particular in blood vessel walls, neuronal cells, and smooth muscle. The gradual accumulation of this glycosphingolipid in numerous eye tissues causes conjunctival vascular abnormalities, corneal epithelial opacities (cornea verticillata), lens opacities, and retinal vascular abnormalities. Although a severe vision impairment is rare, these abnormalities are diagnostic indicators and prognostics for severity. Cornea verticillata is the most common ophthalmic feature in both hemizygous men and heterozygous females. Vessel tortuosity has been linked to a faster disease progression and may be useful in predicting systemic involvement. New technologies such as optical coherence tomography angiography (OCTA) are useful for monitoring retinal microvasculature alterations in FD patients. Along with OCTA, corneal topographic analysis, confocal microscopy, and electro-functional examinations, contributed to the recognition of ocular abnormalities and have been correlated with systemic involvement. We offer an update regarding FD ocular manifestations, focusing on findings derived from the most recent imaging modalities, to optimize the management of this pathology.

Relationship of Vessel Density to Vessel Length Density in Patients with Treated Fabry Disease

BACKGROUND

Fabry disease (FD) is a potentially lethal lysosomal disorder with systemic vascular changes. Previous studies demonstrated retinal vascular involvement using optical coherence tomography angiography (OCTA) in affected patients; Aim: To analyze and quantify the retinal vasculature measuring vessel density (VD), vessel length density (VLD), and the ratio of VD to VLD (VD/VLD) in superficial capillary plexuses (SCP) and deep capillary plexuses (DCP) using OCTA in patients with FD and to show whether they differ from healthy controls (HC); Patients and methods: Single-center, retrospective, consecutive cohort study of patients with genetically proven FD. Patients underwent an ophthalmological examination including OCTA. VD, VLD, foveal avascular zone (FAZ), and the VD/VLD were compared to an HC group using a linear mixed model; Results: A statistically significant difference in the VLD and VD/VLD of DCP was observed between the two groups (p < 0.001). Using ROC curves with AUC and Youden's Index, a cut-off value for differentiating both groups using VD/VLD in DCP FD with high specificity and high sensitivity was established; Conclusions: FD and HC groups seem to be separable using the VD/VLD ratio in DCP. This new biomarker might differentiate changes in the retinal microvasculature that are not detectable by VD or VLD alone.

Autophagy-lysosome pathway alteration in ocular surface manifestations in Fabry disease patients

Background

Fabry disease (FD) is a rare X-linked, lysosomal storage disorder caused by mutations in the alpha-galactosidase gene and characterized by neurological, cutaneous, renal, cardiovascular, cochleo-vestibular and ocular manifestations. The aim of this study is to characterize morphological, functional and autophagy-lysosome pathway alterations of the ocular surface in FD patients.

Methods

Eleven subjects with a diagnosis of FD and fifteen healthy control subjects were examined. All patients underwent ocular surface slit lamp examination, corneal aesthesiometry and in vivo confocal laser-scanning microscopy (CCM). Conjunctival impression cytology was performed in six FD patients and six controls, to assess for expression of two markers of the autophagy-lysosome pathway: the microtubule-associated protein light chain 3 (LC3) and lysosome-associated membrane protein 2 (LAMP2).

Results

Cornea verticillata and increased conjunctival vessel tortuosity were detected respectively in 67% and 33% of patients with FD. Compared with healthy subjects, patients affected by FD showed a significant reduction in corneal nerve fiber length, density and nerve branching on CCM and a significantly increased expression of LC3 on conjunctival impression cytology (p < 0.001). No changes were observed in the conjunctival expression of LAMP2 between the two groups.

Conclusions

This study shows that FD is associated with ocular surface alterations including corneal and conjunctival morphology, innervation and vascularization changes. Our data demonstrate an increased expression of LC3 protein in patients with FD, suggesting that alteration of the autophagy-lysosome pathway may play a role in the occurrence of ocular manifestations.

Globotrioasylsphingosine Levels and Optical Coherence Tomography Angiography in Fabry Disease Patients

Background: To date, there are no studies associating the dried blood spot (DBS) levels of globotrioasylsphingosine (lysoGb3) with quantitative optical coherence tomography angiography (OCTA) parameters in Fabry disease (FD) patients. Here, we aimed to investigate the association between OCTA vessel density (VD), vessel length density (VLD) with DBS lysoGb3. Methods: A retrospective, single center analysis of all consecutive FD patients enrolled at the Department of Ophthalmology of the University Hospital of Zurich from 1 December 2017 to 9 September 2020. An association between VD and VLD detected by OCTA and lysoGb3 was investigated using a linear mixed model. Results: A total of 57 FD patients (23 male, 34 female; 109 eyes) were included. Forty-one patients suffered from the classic phenotype and 16 from the later-onset phenotype. LysoGb3 inversely correlated with VD and VLD in both the superficial (VD: p = 0.034; VLD: p = 0.02) and deep capillary plexus (VD: p = 0.017; VLD: p = 0.018) in the overall FD cohort. Conclusions: Our study shows an association between lysoGb3 and OCTA VD and VLD. This supports the hypothesis that quantitative OCTA parameters might be useful as diagnostic biomarkers for evaluating systemic involvement in FD, and possibly other diseases.

Fabry Disease: A Disorder of Childhood Onset

BACKGROUND

Fabry disease, an X-linked disorder of glycosphingolipids, markedly increases the risk of systemic vasculopathy, ischemic stroke, small-fiber peripheral neuropathy, cardiac dysfunction, and chronic kidney disease.

METHODS

We performed an extensive PubMed search on the topic of Fabry disease and drew from our cumulative 43 years of experience.

RESULTS

Most of these complications are nonspecific in nature and clinically indistinguishable from similar abnormalities that occur in the context of more common disorders in the general population. This disease is caused by variants of the GLA gene, and its incidence may have been underestimated. However, one must also guard against overdiagnosis of Fabry disease and unjustified enzyme replacement therapy, because some of the gene variants are benign. Specific therapy for Fabry disease has been developed in the last few years, but its clinical effect has been modest. Novel therapeutic agents are being developed. Standard "nonspecific" medical and surgical therapy is necessary and effective in slowing deterioration or compensating for organ failure in patients with Fabry disease.

CONCLUSIONS

Fabry disease is a treatable and modifiable genetic risk factor for a myriad of clinical organ complications. Fabry disease may be frequently overlooked but on occasion overdiagnosed.

Corneal confocal microscopy: a novel noninvasive means to diagnose neuropathy in patients with Fabry disease

Neuropathy is a cause of significant disability in patients with Fabry disease, yet its diagnosis is difficult. In this study we compared the novel noninvasive techniques of corneal confocal microscopy (CCM) to quantify small-fiber pathology, and non-contact corneal aesthesiometry (NCCA) to quantify loss of corneal sensation, with established tests of neuropathy in patients with Fabry disease. Ten heterozygous females with Fabry disease not on enzyme replacement therapy (ERT), 6 heterozygous females, 6 hemizygous males on ERT, and 14 age-matched, healthy volunteers underwent detailed quantification of neuropathic symptoms, neurological deficits, neurophysiology, quantitative sensory testing (QST), NCCA, and CCM. All patients with Fabry disease had significant neuropathic symptoms and an elevated Mainz score. Peroneal nerve amplitude was reduced in all patients and vibration perception threshold was elevated in both male and female patients on ERT. Cold sensation (CS) threshold was significantly reduced in both male and female patients on ERT (P < 0.02), but warm sensation (WS) and heat-induced pain (HIP) were only significantly increased in males on ERT (P < 0.01). However, corneal sensation assessed with NCCA was significantly reduced in female (P < 0.02) and male (P < 0.04) patients on ERT compared with control subjects. According to CCM, corneal nerve fiber and branch density was significantly reduced in female (P < 0.03) and male (P < 0.02) patients on ERT compared with control subjects. Furthermore, the severity of neuropathic symptoms and the neurological component of the Mainz Severity Score Index correlated significantly with QST and CCM. This study shows that CCM and NCCA provide a novel means to detect early nerve fiber damage and dysfunction, respectively, in patients with Fabry disease.

Fabry disease

Fabry disease, an X-linked disorder of glycosphingolipids that is caused by the deficiency of alpha-galactosidase A, is associated with dysfunction of many cell types and includes a systemic vasculopathy. As a result, patients have a markedly increased risk of developing small-fiber peripheral neuropathy, stroke, myriad cardiac manifestations and chronic renal disease. Virtually all complications of Fabry disease are non-specific in nature and clinically indistinguishable from similar abnormalities that occur in the context of more common disorders in the general population. Although Fabry disease was originally thought to be very rare, recent studies have found a much higher incidence of mutations of the GLA gene, suggesting that this disorder is under-diagnosed. Although the etiology of Fabry disease has been known for many years, the mechanism by which the accumulating alpha-D-galactosyl moieties cause this multi-organ disorder has only recently been studied and is yet to be completely elucidated. Specific therapy for Fabry disease has been developed in the last few years but its role in the management of the disorder is still being investigated. Fortunately, standard 'non-specific' medical and surgical therapy is effective in slowing deterioration or compensating for organ failure in patients with Fabry disease. All these aspects are discussed in detail in the present review.

The microstructure of cornea verticillata in Fabry disease and amiodarone-induced keratopathy: a confocal laser-scanning microscopy study

PURPOSE

The purpose of this study is to describe cornea verticillata in Fabry disease and in amiodarone-induced keratopathy and to compare the corneal microstructure of both types.

PATIENTS AND METHODS

Ten eyes from ten normal subjects, 28 eyes from 22 patients with Fabry disease confirmed by molecular genetic studies, and 16 eyes from 11 patients receiving amiodarone were examined by slit-lamp microscopy and in-vivo confocal laser-scanning microscopy (CLSM) with following three-dimensional reconstruction of the individual corneal layers. Five patients with Fabry disease were monitored during the course of enzyme replacement therapy (ERT).

RESULTS

Evidence of cornea verticillata was found by slit-lamp microscopy both in patients with Fabry disease and in those with amiodarone-induced keratopathy; CLSM revealed the same pattern of hyper-reflective deposits in the basal cell layer of corneal epithelium in both sets of patients. Microdot changes in the anterior stroma were more prevalent in patients receiving amiodarone but do not presuppose the simultaneous presence of cornea verticillata. The bulbar conjunctiva was found to be normal in all patients. The tarsal conjunctival epithelium contained round hyper-reflective structures, which are also encountered physiologically, but these were more common in patients with Fabry disease. In one out of the five patients examined, monitoring of corneal changes over time during ERT disclosed a regressive tendency of the deposits in the epithelial basal cell layer documented by CLSM.

CONCLUSIONS

The microstructural corneal changes typically seen in cornea verticillata in both Fabry disease and in amiodarone-induced keratopathy can be successfully visualized by confocal in-vivo microscopy at the level of the basal cell layer. By analogy, with the grading system for cornea verticillata based on slit-lamp microscopy, staging of these deposits in the basal cell layer can also be performed following in-vivo CLSM. The microdots in the anterior stroma as well as the changes observed in the tarsal conjunctiva should be regarded as having less diagnostic value because such changes may also occur in normal subjects. The utility of CLSM as a tool for monitoring ERT in Fabry disease over time needs to be confirmed in studies with larger sample sizes conducted over a longer period.

Ocular features of Fabry disease: diagnosis of a treatable life-threatening disorder

Fabry disease is a rare, life-threatening, and under-diagnosed disease, with distinctive ocular manifestations identifiable during a routine eye examination. The disease is caused by an inherited deficiency of the lysosomal enzyme alpha-galactosidase A, resulting in progressive accumulation of glycosphingolipids throughout the body. Long-term clinical manifestations include renal failure, early stroke, and cardiomyopathy. Recently, enzyme-replacement treatment has become available, heightening the importance of early diagnosis so that treatment can be initiated before irreversible organ damage. Ocular manifestations of Fabry disease include cornea verticillata (whorl-like radial lines emanating from a single vortex, visible on slit-lamp examination), distinctive lenticular opacities, and vascular tortuosity of the conjunctiva and retina. A heightened awareness of Fabry disease among ocular professionals could greatly reduce diagnostic delays and thus reduce the morbidity and mortality of the disease.

Ocular manifestations of Fabry's disease: data from the Fabry Outcome Survey

BACKGROUND

Fabry's disease is an X-linked lysosomal storage disorder characterised by deficient activity of the enzyme alpha-galactosidase A.

AIM

To study eye abnormalities in patients with Fabry's disease in the Fabry Outcome Survey (FOS).

METHODS

This is the largest study of ocular manifestations in patients with Fabry's disease. In all, 173 of the 688 patients enrolled in FOS underwent a detailed ophthalmic examination, with a special focus on abnormalities of the cornea, lens, conjunctival and retinal vessels.

RESULTS

Cornea verticillata was reported in 76.9% of females and 73.1% of males; vessel tortuosity was observed in 21.9% of females and in 48.7% of males. Fabry cataract was recorded in 9.8% of females and in 23.1% of males. Cornea verticillata was therefore the most frequently reported ophthalmic abnormality in Fabry's disease in both hemizygotic males and heterozygotic females. Tortuous conjunctival and retinal vessels and Fabry cataract were more frequently found in males than in females. Vessel tortuosity was more frequently observed in patients with a higher severity score and greater impairment of renal and cardiac function, suggesting that it may be associated with a more severe disease. The youngest patient with ocular changes was 3 years old. The prevalence of tortuous vessels in males increased with age.

CONCLUSION

The presence of cornea verticillata is a useful aid in the diagnosis of Fabry's disease, as it is often present at the time of diagnosis. Vessel tortuosity may have some predictive value for systemic involvement.

Immunofluorescence detection of globotriaosylceramide deposits in conjunctival biopsies of Fabry disease patients

BACKGROUND

Fabry disease is an X-linked disorder due to a deficiency of alpha-galactosidase A and leads to the accumulation of globotriaosylceramide (Gb3) in various cells. The detection of Gb3 deposits may help in the diagnosis. To date, no immunofluorescence-specific detection of Gb3 in conjunctival biopsies has been reported. The aim of this work was to detect Gb3 accumulation in conjunctival biopsies from Fabry patients by immunofluorescence.

METHODS

Conjunctival biopsies taken from Fabry males and females, before and after enzyme replacement therapy, and normal controls were processed for immunofluorescence with a monoclonal antibody specific for Gb3.

RESULTS

Positive green immunofluorescence was observed in all biopsies from Fabry patients before enzyme replacement therapy. After 6 months of treatment, immunofluorescence in blood vessels was not observed.

CONCLUSIONS

Immunofluorescence detection of Gb3 in conjunctival biopsies may be a reliable method for the diagnosis of Fabry disease in family members, and to evaluate effectiveness of enzyme replacement therapy.

Corneal and conjunctival manifestations in Fabry disease: in vivo confocal microscopy study

PURPOSE

To describe the microscopic corneal and conjunctival findings in patients with Fabry disease (FD) related keratopathy by using in vivo confocal microscopy.

DESIGN

Prospective observational case series.

METHODS

Twelve eyes of six patients affected by Fabry disease, belonging to two different families, underwent in vivo confocal microscopic examination. Corneal and conjunctival morphology were assessed by means of a scanning slit corneal confocal white-light microscopy and confocal laser-scanning microscope.

RESULTS

Confocal microscopy examination evidenced two different types of corneal epithelial changes. The three hemizygous patients presented bright hyper-reflective intracellular inclusions located within the basal epithelial cells, while the three heterozygous patients showed fine diffusion of reflective substance at the level of superficial, basal epithelial cells and basal membrane, in all eyes. The complex basal-Bowman's membrane appeared irregular, distorted, and nonhomogeneous in all subjects. Stromal increased reflectivity attributable to haze and epithelial ingrowth with bright intracellular inclusions was noticed in one hemizygous patient. In all patients, conjunctival epithelial involvement represented by bright roundish intracellular inclusions was evidenced, appearing more pronounced in tarsal than in bulbar conjunctiva.

CONCLUSIONS

Although FD-related cornea verticillata attributable to glycosphingolipids accumulation is considered to be primarily a corneal disease, in vivo confocal microscopy demonstrated structural alterations throughout the entire ocular surface epithelia. It is still unclear whether the different type of corneal epithelial lesions observed for hemizygous and heterozygous patients is related to different physiopathological mechanisms. Confocal microscopy may assist ophthalmologists in the diagnosis of FD-related ocular surface and corneal manifestations.

Ophthalmological manifestations of Fabry disease: a survey of patients at the Royal Melbourne Fabry Disease Treatment Centre

BACKGROUND

Fabry disease is a rare X-linked inborn error of glycosphingolipid metabolism. The aim of this study was to document the ophthalmological manifestations of patients attending the Royal Melbourne Hospital Fabry disease treatment centre.

METHODS

Patients at the treatment centre had full ophthalmological examination performed. This included best corrected visual acuity, ocular motility examination and examination of the adnexae. Patients also underwent slit-lamp examination looking for the presence of features of Fabry disease, particularly examining the bulbar conjunctiva, cornea, lens and fundus.

RESULTS

Thirty-four hemizygous male and 32 heterozygous female patients were recruited. The mean age of the hemizygous male patients was 37.7 years (range 18-57 years). The mean age of the heterozygous female patients was 34.6 years (range 1-78 years). Visual acuity was not affected. 97.1% of the hemizygotes and 78.1% of the heterozygotes had vascular abnormalities of the bulbar conjunctiva. Cornea verticillata was noted in 94.1% of the hemizygotes and 71.9% of the heterozygotes. 41.2% of the hemizygotes and 9.4% of the heterozygotes had anterior cataract formation. Posterior lens opacities were observed in 11.8% of the hemizygotes and none of the heterozygotes. Retinal vascular tortuosity was observed in 76.5% of the hemizygotes and 18.8% of the heterozygotes.

CONCLUSION

Conjunctival vascular tortuosity was the most common manifestation in this series. Conjunctival and retinal vessel tortuosity, and corneal verticillata are frequently observed in Fabry disease. The incidence of lenticular changes is not consistently reported, but in this series and many others, it is much less common than that of corneal, conjunctival and retinal changes.