,2,3,4 In the case of two ABCA4 null-alleles, disease progression is rapid and clinically recognized as autosomal recessive cone-rod dystrophy, whereas the involvement of alleles with residual ABCA4 function gives rise to Stargardt disease type 1 (STGD1).5 Here, ABCA4 is linked to autosomal recessive cone rod dystrophy.