Although RP is a genetically heterogeneous disease, most cases of RP are monogenic, and mutations in the rhodopsin gene (rho), Usher syndrome 2A gene (ush2a), and retinitis pigmentosa GTPase regulator gene (rpgr) engage in about 30% of all cases of retinitis pigmentosa. The gene discussed is RHO; the disease is retinitis pigmentosa.