Another patient with a homozygous truncation mutation in USH2A and a heterozygous frameshift mutation in PDZD7 was observed to have earlier onset and more severe RP compared to her sister who carried the homozygous USH2A mutation but not the PDZD7 mutation (Ebermann et al., 2010). This evidence concerns the gene USH2A and retinitis pigmentosa 1.