Association between genotype and disease progression in Italian stargardt patients: A retrospective natural history study

Purpose:To investigate the natural history of Stargardt disease over a multiyear follow-up.Methods:We reviewed medical records of Stargardt disease patients, with clinical diagnosis of Stargardt disease at a single institution, which was also supported by molecular diagnosis. All patients underwent best-corrected visual acuity, fundus photography, optical coherence tomography, and full-field electroretinography.Results:The study cohort consisted of 157 Stargardt disease patients aged 30.4 ± 1.1 years. Longitudinal analysis (mean follow-up: 3 years) showed a significant worsening of best-corrected visual acuity at an average rate of 1.5 Early Treatment Diabetic Retinopathy Study letters/year (P < 0.001), an enlargement of retinal pigment epithelium lesion area by optical coherence tomography at an average linear rate of 0.10 mm2/year (P < 0.001), and a thinning of central macular thickness at a mean rate of-1.42 m/year (P < 0.001). Survival analysis showed that patients with 2 alleles harboring likely-null variants, on average, reached most severe disease stage, i.e., legal blindness, alteration in both dark-adapted and light-adapted electroretinographic responses, and retinal pigment epithelium lesion area larger than 2.5 mm2 significantly earlier than patients with at least one allele harboring a missense variant.Conclusion:The current longitudinal study showed a significant genotype-phenotype correlation characterization, because patients harboring 2 likely-null alleles reach a severe disease stage about 10 years earlier than patients with at least one missense allele.