RPGRIP1 and retinal degeneration: Although some genotype-phenotype discrepancies could be reduced by reconsidering the phenotype, and by functionally demonstrating the involvement of the RPGRIP1 insertion in retinal degeneration in MLHDs, substantial discordances remain: the extensive range of onset among RPGRIP1−/− PRA cases; and the 20.3% of PRA cases that are non-RPGRIP1−/−.