PRPH2 and inherited retinal dystrophy: Mutation spectrum in ad cases (Tables 1 and 2, Fig. 2) Taking all gene defects into account, among the 17 patients with 1 pathogenic or likely pathogenic allele in genes involved in ad retinal dystrophy (12 ad and 5 sporadic cases), GUCY2D (5/17 patients, 29.4 %), CRX (4/17 patients, 23.5 %), PROM1 (2/17 patients, 11.8 %) and PRPH2 (2/17 patients, 11.8 %) were the most prevalent.