For that reason, this study aimed to initiate preclinical testing for the ultrarare deep-intronic ABCA4 variant c.6817-713A>G, found in one early-onset STGD1 patient, which promotes the insertion of a 122-nt PE between exons 49 and 50 in the final transcript. This evidence concerns the gene ABCA4 and severe early-childhood-onset retinal dystrophy.