Ambispective study on the phenotypic progression of patients with Stargardt disease associated with ABCA4 gene mutations

Objective

This study aims to describe the phenotypic progression of patients with Stargardt disease caused by mutations in the ABCA4 gene and reports on the mutated allelic variants.

Method

We conducted an observational, ambispective, and descriptive study. Patients who had Stargardt disease by the ABCA4 gene mutation were included. The study used the genetic report and the baseline examinations appearing on health records. To evaluate the phenotypic variation, a new ophthalmological evaluation was conducted using macular OCT, retinography, autofluorescence, and electroretinogram.

Results

The study identified a total of 32 cases with a mean follow-up of 6 years. The mean age of onset was 16 years. The mean initial and final VA were 0.79 and 0.95 logMAR, respectively. The mean initial and final CMT were 142.5 and 135 microns, respectively. The predominant degree of fundus involvement and autofluorescence pattern at the beginning and end was macular atrophy with flecks and the low signal of macular autofluorescence surrounded by a heterogeneous background, respectively. Initial electroretinography showed predominantly preserved function of rods and cones, while in the end most cases presented rod and cone system dysfunction. A total of 9 cases were homozygous, and 31 different mutant allelic variants were identified. The most common variant was p.Trp1618Cys, followed by p.Ala1773Val. Two new allelic variants, p.Leu634Pro, and p.Tyr665Serfs*5, were also discovered.

Conclusions

The study found that patients experienced structural and functional deterioration at the follow-up. The study also identified 2 predominant variants and 2 new variants. Homozygotes had an earlier onset of the disease.