ABCA4 and severe early-childhood-onset retinal dystrophy: The importance of ABCA4 is highlighted by the finding that mutations in the gene encoding ABCA4 are responsible for autosomal recessive Stargardt disease (STGD1:MIM 248200) as well as some recessive forms of cone-rod dystrophy and retinitis pigmentosa [1,7,8,9,10,11,12].