Runhart EH, Khan M, Cornelis SS, et al. - Since the mechanisms behind the phenotypic variability and reduced penetrance in autosomal recessive Stargardt disease (STGD1), often a blinding disease, are incompletely defined, researchers sought to evaluate the correlation of incompletely penetrant ABCA4 alleles with sex in STGD1. Participants in the study were 550 patients, mean (SD) age 45.7 (18.0) years. The authors discovered an imbalance in the sex ratio observed among patients harboring a mild ABCA4 allele, affecting nearly 25% of all STGD1 patients, indicating that STGD1 should be considered a polygenic or multifactorial disease rather than an ABCA4 gene mutation disease alone. The results indicate that both basic research and clinical trials on STGD1 should regard sex as a possible disease-modifying variable.