Absence of Genotype/Phenotype Correlations Requires Molecular Diagnostic to Ascertain Stargardt and Stargardt-Like Swiss Patients.

We genetically characterized 22 Swiss patients who had been diagnosed with Stargardt disease after clinical examination. We identified in 11 patients (50%) pathogenic bi-allelic variants, c.1760+2T>C and c.4496T>C being novel. The dominantly inherited pathogenic c.810C>G p.(Tyr270*) and -c.422A>G p.(Tyr141Cys) variants were identified in eight (36%) and three patients (14%), respectively. All patients harboring the c.810C>G p.(Tyr270*) variant originated from the same small Swiss area, identifying a founder mutation. In the and cohorts, the clinical phenotypes of "flecks", "atrophy", and "bull"s eye like" were observed by fundus examination. In the small number of patients harboring the pathogenic variant, we could observe both "flecks" and "atrophy" clinical phenotypes. The onset of disease, progression of visual acuity and clinical symptoms, inheritance patterns, fundus autofluorescence, and optical coherence tomography did not allow discrimination between the genetically heterogeneous Stargardt patients. The genetic heterogeneity observed in the relatively small Swiss population should prompt systematic genetic testing of clinically diagnosed Stargardt patients. The resulting molecular diagnostic is required to prevent potentially harmful vitamin A supplementation, to provide genetic counseling with respect to inheritance, and to schedule appropriate follow-up visits in the presence of increased risk of choroidal neovascularization.