Several other studies have reported various codon mutations associated with retinitis pigmentosa, including Thr58Arg, Pro347Leu, Pro347Ser, as well as deletion of Ile-255. In 2000, a rare mutation in codon 23 was reported causing autosomal dominant retinitis pigmentosa, in which proline changed to alanine. However, this study showed that the retinal dystrophy associated with this mutation was characteristically mild in presentation and course. Furthermore, there was greater preservation in electroretinography amplitudes than the more prevalent Pro23His mutation.Autosomal recessive inheritance patterns of RP have been identified in at least 45 genes. This means that two unaffected individuals who are carriers of the same RP-inducing gene mutation in diallelic form can produce offspring with the RP phenotype. A mutation on the USH2A gene is known to cause 10-15% of a syndromic form of RP known as Ushers Syndrome when inherited in an autosomal recessive fashion.Mutations in four pre-mRNA splicing factors are known to cause autosomal dominant retinitis pigmentosa. These are PRPF3 (human PRPF3 is HPRPF3; also PRP3), PRPF8, PRPF31 and PAP1.
Pre-existing or emerging mutations that contribute to rod photoreceptor degeneration in retinitis pigmentosa are passed down through familial lines; thus, allowing certain RP cases to be concentrated to specific geographical regions with an ancestral history of the disease. Several hereditary studies have been performed to determine the varying prevalence rates in Maine (USA), Birmingham (England), Switzerland (affects 1/7000), Denmark (affects 1/2500), and Norway. Navajo Indians display an elevated rate of RP inheritance as well, which is estimated as affecting 1 in 1878 individuals. Despite the increased frequency of RP within specific familial lines, the disease is considered non-discriminatory and tends to equally affect all world populations. Research
Future treatments may involve retinal transplants, artificial retinal implants, gene therapy, stem cells, nutritional supplements, and/or drug therapies. 2012: Scientists at the University of Miami Bascom Palmer Eye Institute presented data showing protection of photoreceptors in an animal model when eyes were injected with mesencephalic astrocyte-derived neurotrophic factor (MANF). Researchers at the University of California, Berkeley were able to restore vision to blind mice by exploiting a "photoswitch" that activates retinal ganglion cells in animals with damaged rod and cone cells.2015: A study by Bakondi et al. at Cedars-Sinai Medical Center showed that CRISPR/Cas9 can be used to treat rats with the autosomal dominant form of retinitis pigmentosa.