Clinical and genetic characterization of patients with eye diseases included in the Spanish Rare Diseases Patient Registry

Abstract

Background: The low prevalence of rare diseases poses a significant challenge in advancing their understanding. This study aims to delineate the clinical and genetic characteristics of patients with rare eye diseases (RED) enrolled in the Spanish Rare Diseases Patient Registry.

Methods: A total of 864 patients from the registry database were included. Diseases were categorized into inherited retinal dystrophies (n=688); anterior segment diseases (n=48); congenital malformations (n=27); and syndromic diseases with ocular involvement including muscular (n=46), neurological (n=34), or metabolic (n=13); inflammatory diseases (n=4); and tumors (n=4). Data on visual acuity (VA) and/or visual field (VF), symptoms and signs, concurrent diseases in syndromic cases, age of onset and at diagnosis, affected genes, disability rating, inability to work and dependency grade recognition were collected.

Results: A mean diagnostic delay of 7 years from symptom onset was observed. Commonly reported symptoms included photophobia, night blindness, and progressive vision loss (≥57% of patients). Cataract was the most prevalent secondary disease (46%), with pseudophakia being the most common ocular surgery (26%). Hearing loss and cardiovascular diseases were the most prevalent concurrent systemic diseases (≥13%). Certificates of disability, incapacity for work, and dependency were held by 87%, 42%, and 19% of patients, respectively. Among the 719 patients with available VA data, 193 (27%) were blind, and 188 (26%) had moderate to severe visual impairment. Over half of the patients (54%) exhibited VF defects, and 216 (25%) had concentric contraction ≤5° or abolished VF. Most had genetic diseases with autosomal recessive (55%), autosomal dominant (30%), X-linked (9%), and mitochondrial (6%) patterns. One patient had mutations in both recessive USH2A and dominant RHO genes simultaneously. Of the 656 patients (75.7%) who underwent genetic testing, only 461 (70.3%) received a positive result (pathogenic or likely pathogenic mutations explaining the phenotype). We found 62 new gene variants related to RED not previously reported in databases of genetic variants related to specific phenotypes.

Conclusions: This study delineates the clinical and genotypic profiles of RED in Spain. Genetic diseases, particularly retinal disorders, predominate, but a significant proportion of affected patients remain genetically undiagnosed, hindering potential gene therapy endeavors. Despite notable improvements in reducing diagnosis delays, it is still remarkable. RED frequently lead to disability and blindness among young populations.

Keywords: Clinical; Eye; Genetic; Ocular; Rare diseases; Registry; Spain.

Fig. 1

Geographic location of patients included. The color range indicates the percentage (with darker colors representing higher percentages) of the number subjects included (S) as a proportion of the population (P) in each Spanish Autonomous Community, including the two Autonomous Cities of Ceuta and Melilla. Population data was obtained from the Spanish National Statistics Institute (INE), as of January 1, 2021

Fig. 2

Classification of rare eye diseases and the number of patients included. The number of subjects with a syndromic disease with possible eye involvement but without ocular affectation is indicated as a negative number between brackets

Fig. 3

Distributions of type of incapacity for work (top, left), level of dependence degree (top, right), visual impairment and blindness (bottom, left), and inheritance pattern (bottom, right) per disease group. The number in the bars indicate the number of subjects