SLC6A6 and retinal disorder: In family 4, trio genome sequencing identified the cause of the proband’s severe retinopathy by detecting a homozygous pathogenic truncating variant—NM_003043.6: c.338G>A, p.(Trp113Ter)—in the SLC6A6 gene, with parents being heterozygous carriers (Figure 1A; eFigure 2D in Supplement 1).