Various mutations within a single gene can result in different diseases, as exemplified by the case of ABCA4. This gene is implicated in several disorders, including autosomal-recessive Stargardt disease 1; RP 19; Retinal dystrophy, early-onset severe; Fundus flavimaculatus; Cone-rod dystrophy 3; and autosomal-dominant Macular degeneration, age-related, 2 (MIM 601691). The gene discussed is ABCA4; the disease is retinitis pigmentosa 19.