This might be the case for patient LH22, who had homozygous c.164C>T mutations, but it may not cause LCA in patient QT453 since QT453 had homozygous nonsense mutations (G1226X) in CRB1. Even though both mutations themselves could be pathogenic, digenic mutations may not necessarily cause disease, since one of the phenotypically normal parents in families LH16, QT479, QT453, QT509, and RP208 presumably carry digenic mutations. This evidence concerns the gene CRB1 and Leber congenital amaurosis.