ABCA4 and severe early-childhood-onset retinal dystrophy: Deletion of the ABC subfamily A (ABC1), member four (ABCA4, alternatively ABCR) gene [43,44], which encodes for the rod OS protein Rim (RmP) [45,46], functions in the transmembrane transport of vitamin A derivatives to the RPE and accounts for 60% of STGD cases [47].