Genotypic and phenotypic factors influencing the rate of progression in ABCA-4-related Stargardt disease

ABSTRACT

Introduction: Stargardt disease (STGD) is heterogeneous in terms of severity and rate of progression. New advancements in genetic testing and retinal imaging have improved prognostication in the disease.

Areas covered: A PubMed-based search was carried out using the terms ‘Stargardt dystrophy’, ‘Stargardt disease’, ‘Fundus flavimaculatus’, and ‘ABCA4’. All studies published in English up to August 2020 were reviewed. Data from international multicenter trials were also considered in the discussion.

Expert opinion: Genotype-phenotype correlations represent a challenge in STGD, as other epigenetic and environment modifiers participate in defining the clinical outcome and the long-term prognosis. Earlier age of onset and deleterious ABCA4 variants are the main determinants of severe progression. Quantitative imaging approaches are potentially useful for following-up STGD patients. Non-invasive biomarkers are needed to predict the natural history of the disease or drug effectiveness in future therapeutic trials.

KEYWORDS:

• Stargardt dystrophy
• stargardt disease
• fundus flavimaculatus
• abca4
• retinal pigment epithelium
• flecks

Article highlights

• Stargardt disease (STGD) is the most common inherited macular dystrophy, with a prevalence of 8–10 per 100,000 persons.

• Flecks and retinal pigment epithelium (RPE) atrophy are the most prominent features.

• STGD is clinically heterogeneous: patients’ characteristics, ABCA4 variants, genetic modifiers, and environment contribute to disease severity and rate of progression.

• More than 600 variants in the ABCA4 gene have been identified. Missense mutations are associated with a milder form of STGD, while non-sense or null mutations bear the worst prognosis.

• Early-onset disease bears more deleterious genetic variants as compared with adult-onset STGD and has a higher risk of severe photoreceptor loss and lower electro-functional responses.

• Earlier age of onset, larger RPE atrophy at baseline, and multifocal disease are determinants of faster progression.

• Whole-genome sequencing techniques and larger genetic databases are pivotal to reach a complete understanding of STGD pathogenesis and guide future therapeutic multicenter trials.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Declaration of interest

The authors have no proprietary, funding, or conflicts of interest to disclose

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Additional information

Funding

This manuscript was not funded.