ELOVL4 and severe early-childhood-onset retinal dystrophy: Stargardt disease (STGD) is the most common single-gene heritable disease of the retina, with three genetic bases: STGD1 caused by autosomal recessive ATP-binding cassette, sub-family A, member 4 (ABCA4) mutations (166); STGD3 caused by autosomal dominant mutations in “elongation of very long chain fatty acid protein 4” (ELOVL4) (167); STGD4 caused by autosomal dominant mutations in prominin 1 (PROM1) (168).