Ocular signs correlate well with disease severity and genotype in Fabry disease

Abstract

Ocular signs in Fabry disease have generally been regarded to be primarily of diagnostic value. We explored whether ocular findings, alone or in particular in combination with the α-galactosidase A gene mutation, have predictive value for disease severity. Data from the Fabry Outcome Survey (FOS), a large, global database sponsored by Shire, were selected for adult patients who had undergone ophthalmological examination. Three ocular signs were assessed: cornea verticillata, tortuous conjunctival and/or retinal vessels, and cataract. Fabry disease severity was measured using FOS Mainz Severity Score Index and modifications thereof. Ophthalmological data were available for 1203 (699 female, 504 male) adult patients with eye findings characteristic of Fabry disease in 55.1%. Cornea verticillata had a similar distribution in women (51.1%) and men (50.8%), whereas tortuous vessels and Fabry cataract were somewhat more frequent in men than in women. Patients with cornea verticillata, selected as the principal ocular sign for this study, had more severe disease (median score, 20.0) versus those without ocular signs (11.0; P<0.001). This finding could be confirmed by applying age adjusted severity scores. Moreover, the prevalence of cornea verticillata was significantly higher in patients with null (male, 76.9%; female, 64.5%) and missense (male, 79.2%; female, 67.4%) mutations versus mild missense (male, 17.1%; female, 23.1%) and the p.N215S (male, 15.0%; female, 15.6%) mutations (P<0.01). Our analyses show a correlation between the prevalence of ocular changes in Fabry disease and disease severity. Consequently, information on ocular findings and α-galactosidase A gene mutation may help assess the risk for more severe Fabry disease. These observed findings are of notable clinical importance, as Fabry disease is characterized by high clinical course variability and only weak genotype-phenotype correlation at the individual patient level. Further confirmatory studies are needed.

Fig 1. Representative ocular changes seen in patients with Fabry disease.

Representative ocular changes include (A) cornea verticillata, (B) increased tortuosity of conjunctival vessels, and (C) increased tortuosity of retinal vessels.

Fig 2. FOS-MSSI and ariFOS-MSSI score, and eye changes.

Median (A) FOS-MSSI and (B) ariFOS-MSSI scores in male and female adult patients with and without eye findings. ariFOS-MSSI = age-related individual Fabry Outcome Survey Mainz severity score index; FOS-MSSI = Fabry Outcome Survey Mainz severity score index. The median FOS-MSSI and ariFOS-MSSI scores represent the medians after removing cornea verticillata from the calculation of the FOS-MSSI score.

Fig 3. Relationship between disease severity and age in children with and without any eye findings.

Scatter plot of FOS-MSSI score versus age (in years) at last FOS-MSSI score assessment, showing regression (trend) lines* for children with and without any eye findings. Children with eye findings (solid grey dots) had more severe disease across all ages than children without any eye findings (open black circles). Disease severity increased with age in both children with and without eye findings. CV = cornea verticillata; FOS-MSSI = Fabry Outcome Survey Mainz severity score index. *Regression lines were determined by the following equations: 1. With any eye findings: FOS-MSSI (removing cornea verticillata) = 3.638976 + 0.613467 × age at FOS-MSSI assessment. 2. Without any eye findings: FOS-MSSI (removing cornea verticillata) = 1.646037 + 0.497238 × age at FOS-MSSI assessment.

Fig 4. Prevalence of eye findings by type of mutation.

Prevalence of eye findings overall (among those patients with mutation information available) and by type of mutation in adult (A) male and (B) female patients.

Fig 5. Disease severity score by type of mutation and presence of cornea verticillata.

Median ariFOS-MSSI score by type of mutation and presence of cornea verticillata in adult (A) male and (B) female patients. ariFOS-MSSI = age-related individual Fabry Outcome Survey Mainz severity score index.