Overall, the pathogenic RP1 nonsense variant c.2219C>G (p.Ser740*) was identified in the heterozygous state in 28 patients with RP1-related RCD, i.e., 26 with AD pedigrees and 2 sporadic, representing 33.3% of all the examined probands, in contrast with the expected 5–10%. This evidence concerns the gene RP1 and Alzheimer disease.