Association Between Genotype and Phenotype Severity in ABCA4-Associated Retinopathy

Area of Science:

• Ophthalmology
• Genetics
• Retinal Diseases

Background:

• ABCA4-associated retinopathy is a common inherited retinal disease with a wide range of clinical presentations.
• Over 2000 disease-causing variants in the ABCA4 gene have been identified, complicating genotype-phenotype correlation.

Purpose of the Study:

• To investigate the relationship between different genotypes and the clinical phenotype in patients with ABCA4-associated retinopathy.
• To establish genotype-phenotype correlations for improved prognostication and clinical trial design.

Main Methods:

• A cohort of 71 patients with inherited retinal disease due to biallelic ABCA4 variants was studied at a single Italian referral center.
• Genotypes were classified into four groups: p.Gly1961Glu allele, hypomorphic allele, moderate variants, and severe variants.
• Key outcomes included total decreased autofluorescence (TDAF) and definitely decreased autofluorescence (DDAF) areas, retinal volumes, and their progression rates.

Main Results:

• Patients with the p.Gly1961Glu allele showed significantly smaller TDAF and DDAF lesions and slower progression rates compared to moderate genotypes.
• Hypomorphic alleles were associated with thicker inner and outer retinal volumes and slower TDAF progression.
• Severe genotypes exhibited substantially larger TDAF and DDAF areas and faster progression rates than moderate genotypes.

Conclusions:

• A four-tier genotype classification system effectively captures significant variations in disease severity for ABCA4-associated retinopathy.
• These findings are valuable for predicting patient outcomes and informing the design of future clinical trials for this inherited retinal disease.