CRB1 and retinitis pigmentosa: The Crumbs homolog-1 (CRB1) gene is one of the human homologs of the Crumbs gene in Drosophila. Mapped to chromosome 1q31.3, CRB1 mutations have been associated with a variety of retinal degenerations, including Leber congenital amaurosis (LCA), early-onset rod–cone dystrophy (EORCD), retinitis pigmentosa (RP), and cone–rod dystrophy (CRD) (1).