ABCA4 and retinal degeneration: The toxic activity of A2E and bisretinoids cause an inflammatory effect that activates the complement system and the inflammasomes, leading to the death of photoreceptor cells (Sparrow et al. 2008). Pathogenic variants in ABCA4 results in a group of retinal phenotypes, collectively referred as ABCA4-associated retinal degenerations (ABCA4R) which are characterized by a notable clinical and allelic heterogeneity (Molday and Zhang 2010).