ABCA4 and Abnormal retinal morphology: ABCA4 is mainly expressed in the retina with very little presence in other tissues of the CNS.190ABCA4 mutation causes Stargardt disease, characterized by macular dystrophy, retinal alterations, and lipofuscin accumulation.60,61,190,191 Other retinal diseases, such as fundus flavimaculatus, retinitis pigmentosa, or cone-rod dystrophy, have also been associated with mutations of ABCA4.