PRA rcd4 is one of a number of late-onset PRAs (sometimes called LOPRA) Unlike other forms of PRA, such as rcd1, the age at which dogs with the rcd4 mutation develop PRA varies with reports as young as 2-3 up to 10-11 yo. The most common age of diagnosis and possible onset seems to be around 9 years. It is unknown if this is due to delays in clinical diagnosis, a manifestation of the disease, or some other variable. Owners and breeders should be aware that some breeds, such as the Irish Setter, have at least 3 identified different forms of PRA mutations, and that any tests for rcd4 identify the risks for that specific mutation only.