ABCA4 is a photoreceptor-specific ATP-binding cassette transporter localized to rod and cone outer segment disc membranes 1. Its primary function is to actively transport N-retinylidene-phosphatidylethanolamine (N-Ret-PE) conjugates across disc membranes in an ATP-dependent manner, functioning as a flippase that moves retinoid-phospholipid adducts from the lumen to the cytoplasmic leaflet 1. This transport mechanism efficiently clears all-trans-retinal and excess 11-cis-retinal from photoreceptors, preventing accumulation of toxic bisretinoid compounds and lipofuscin 1. ABCA4 exhibits intrinsic ATPase activity and may display GTPase activity influenced by lipid environment and retinoid presence 1. Loss-of-function mutations cause Stargardt disease (STGD1), the most common juvenile macular dystrophy, with prevalence of approximately 1 in 8,000-10,000 2. ABCA4 is the most frequently mutated gene in inherited retinal diseases, accounting for 26.3% of solved cases in a large cohort 3. Over 1,200 pathogenic variants have been identified with variable penetrance and geographical distribution 4. Patients with STGD1 present with progressive central vision loss, lipofuscin accumulation, and macular degeneration, with disease severity influenced by variant classification (null versus non-null), onset age, and genetic modifiers 5. No approved treatment currently exists, though multiple therapeutic strategies targeting retinoid metabolism, oxidative stress, and genetic repair are under investigation 4.