ABCA4 and severe early-childhood-onset retinal dystrophy: Dysfunction of ABCA4 leads to the accumulation of cytotoxic products (lipofuscin) in the photoreceptors and retinal pigment epithelium and can manifest in different phenotypes such as Stargardt disease type 1 (STGD1), fundus flavimaculatus, cone–rod dystrophy (CRD), and pan-retinal CRD (Allikmets et al., 1997; Cremers et al., 1998; Rozet et al., 1999; Maugeri et al., 2000; Cremers et al., 2020).