Cornea verticillata in Fabry disease: a comparative study between slit-lamp examination and in vivo corneal confocal microscopy

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.

[Corneal confocal microscopy in Fabry patients with cornea verticillata]

PURPOSE

To study the changes in corneal microstructure and nerve fibers in patients with cornea verticillata in Fabry disease.

MATERIAL AND METHODS

The study included patients with a confirmed diagnosis of Fabry disease. All patients underwent standard ophthalmological examination. Corneal confocal microscopy was performed when slit-lamp examination revealed cornea verticillata.

RESULTS

Cornea verticillata was found in 64.5% of patients. Corneal microscopy revealed hyperreflective deposits in the basal cell layer of corneal epithelium in all patients with cornea verticillata. Characteristic features were desquamation of epithelial cells with islands of epithelial cells deficiency, as well as hyperreflective intracellular deposits in the basal layer. Changes in keratocytes in the form of perinuclear white microdots were found in the stroma of 25.8% of patients. Endothelial layer was not changed and had normal cell density, reflectivity and morphology in all patients with cornea verticillata.

CONCLUSION

Corneal confocal microscopy is a valuable diagnostic tool in patients with Fabry disease and may be important in evaluation of disease progression and monitoring of treatment efficacy.

Corneal densitometry: a potential indicator for early diagnosis of Fabry disease

Purpose

To assess corneal densitometry in patients with Fabry disease (FD) and to compare corneal densitometry differences in FD patients to different corneal manifestations.

Methods

Ten participants (20 eyes) with FD and 10 age-matched healthy volunteers (20 eyes) were recruited. All participants were assessed by standardized ophthalmic examinations and the corneal densitometry analysis by Pentacam HR. Densitometry measurements were analyzed in standardized grayscale units.

Results

Seven patients developed conjunctival vessel tortuosity, cornea verticillata appeared in 6 patients, and two patients had Fabry cataract. Retinal vessel tortuosity occurred in 4 patients, and dilation of retinal vessels appeared in 3 patients, all symptoms occurred in both eyes. The first diagnosis of FD up to examination was 4.7 ± 3.23 years, and first ERT up to examination was 2.6 ± 2.27 years. The initial time to diagnosis was negatively related to the corneal densitometry value of the 0–2-mm (r = − 0.556, p = 0.011) and 2–6-mm (r = − 0.482, p = 0.032) zones in the posterior layer. FD group have significantly higher corneal densitometry in anterior 0–2-mm zone and 2–10-mm zone anterior and posterior layer than the control group (p ≤ 0.035, respectively). When divided into two groups by the existence of cornea verticillata, there was a statistically significant difference in the anterior layer, 6–10-mm zone (p = 0.031); in the central layer, 0–2 mm (p = 0.012), 2–6 mm (p = 0.001), 6–10 mm (p = 0.002), and total (p = 0.002); and in the posterior layer, 6–10 mm (p = 0.004) and total (p = 0.002).

Conclusions

FD patients show higher corneal densitometry, and corneal densitometry may have potential for early diagnosis and reminding progress of FD.

[Fabry disease: A review]

Fabry disease is the second most frequent lysosomal storage disorder. It is a X-linked genetic disease secondary to alpha-galactosidase A enzyme deficiency. This is a progressive and systemic disease that affects both males and females. Classical symptoms and organ involvements are acral pain crisis, cornea verticillata, hypertrophic cardiomyopathy, stroke and chronic kidney disease with proteinuria. Nevertheless, organ damages can be missing or pauci-symptomatic and other common symptoms are poorly recognised, such as gastrointestinal or ear involvement. In classical Fabry disease, symptoms first appear during childhood or teenage in males, but later in females. Patients may have non-classical or late-onset Fabry disease with delayed manifestations or with single-organ involvement. Recognition of Fabry disease is important because treatments are available, but it may be challenging. Diagnosis is easy in males, with dosage of alpha-galactosidase A enzyme activity into leukocytes, but more difficult in females who can express normal residual activity. Other plasmatic biomarkers, such as lyso-globotriaosylceramide (lyso-Gb3), are interesting in females, but need to be associated with GLA gene analysis. In this review, we aimed at summarize the main clinical manifestations of Fabry disease and propose a practical algorithm to know how to diagnose this complex disease.

Fabry disease due to G171S GLA mutation: An atypical small nerve fiber sparing variant?

INTRODUCTION

To describe the ocular manifestations and in vivo confocal microscopic findings in a patient carrying the recently described hemizygous G171S GLA gene mutation.

CASE DESCRIPTION

A 63-year-old Albanian male patient was evaluated for cataract surgery. Anamnesis showed pacemaker implantation in left ventricular hypertrophy, chronic kidney disease, family history for kidney transplantation, and late onset of sporadic acroparesthesias. Bilateral cornea verticillata, and increased tortuosity in conjunctival and retinal vessels were present. In vivo confocal microscopy revealed clusters of hyper-reflective corneal epithelial cells centripetally extending from the limbus. Interestingly, the nerve fiber number, density, and length in the corneal sub-basal nerve plexus were preserved. Alpha-galactosidase A activity was almost absent and hemizygous c.511G>A mutation (G171S - p.Gly171Ser) of the GLA gene was identified. The patient was referred for initiation of enzyme replacement therapy, and genetic counseling was recommended for at-risk family members.

CONCLUSION

This is the third reported case of Fabry disease due to GLA G171S mutation. All patients are of Albanian descent. Cornea verticillata and vascular anomalies remain common ocular manifestations, as well as cardiac and renal involvement. Confirming its pathogenicity, this mutation results in a "classic" Fabry disease phenotype, but it seems to be associated with a relative small nerve fiber sparing that may delay a correct diagnosis. The diagnosis of Fabry disease still remains challenging due to its clinical heterogeneity, but a thorough ophthalmological examination can promote early detection and, consequently, early initiation of enzyme replacement therapy.

Cornea verticillata and acroparesthesia efficiently discriminate clusters of severity in Fabry disease

BACKGROUD

Fabry disease (OMIM #301 500), the most prevalent lysosomal storage disease, is caused by enzymatic defects in alpha-galactosidase A (GLA gene; Xq22.1). Fabry disease has historically been characterized by progressive renal failure, early stroke and hypertrophic cardiomyopathy, with a diminished life expectancy. A nonclassical phenotype has been described with an almost exclusive cardiac involvement. Specific therapies with enzyme substitution or chaperone molecules are now available depending on the mutation carried. Numerous clinical and fundamental studies have been conducted without stratifying patients by phenotype or severity, despite different prognoses and possible different pathophysiologies. We aimed to identify a simple and clinically relevant way to classify and stratify patients according to their disease severity.

METHODS

Based on data from the French Fabry Biobank and Registry (FFABRY; n = 104; 54 males), we applied unsupervised multivariate statistics to determine clusters of patients and identify clinical criteria that would allow an effective classification of adult patients. Thanks to these criteria and empirical clinical considerations we secondly elaborate a new score that allow the severity stratification of patients.

RESULTS

We observed that the absence of acroparesthesia or cornea verticillata is sufficient to classify males as having the nonclassical phenotype. We did not identify criteria that significantly cluster female patients. The classical phenotype was associated with a higher risk of severe renal (HR = 35.1; p <10-3) and cardiac events (HR = 4.8; p = 0.008) and a trend toward a higher risk of severe neurological events (HR = 7.7; p = 0.08) compared to nonclassical males. Our simple, rapid and clinically-relevant FFABRY score gave concordant results with the validated MSSI.

CONCLUSION

Acroparesthesia and cornea verticillata are simple clinical criteria that efficiently stratify Fabry patients, defining 3 different groups: females and males with nonclassical and classical phenotypes of significantly different severity. The FFABRY score allows severity stratification of Fabry patients.