The phenotypes of RP1-related inherited retinal dystrophies (RP1-IRD), causing autosomal dominant (AD) and autosomal recessive (AR) diseases, vary depending on specific RP1 variants. A common nonsense mutation near the C-terminus, c.5797 C > T (p.Arg1933*), is associated with RP1-IRD, but the exact role of this mutation in genotype-phenotype correlation remains unclear. In this study, we retrospectively analyzed patients with RP1-IRD (N = 42) from a single center in Japan. AR RP1-IRD patients with the c.5797 C > T mutation (N = 14) mostly displayed macular dystrophy but rarely retinitis pigmentosa or cone-rod dystrophy. Conversely, AR RP1-IRD patients without the c.5797 C > T mutation, including those with other pathogenic RP1 variants, were mostly diagnosed with severe retinitis pigmentosa. Full-field electroretinograms were significantly better in patients homozygous or compound heterozygous for the c.5797 C > T mutation than in those without this mutation, corresponding to their milder phenotypes. Clinical tests also revealed a slower onset of age and a better mean deviation value with the static visual field in AR RP1-IRD patients with the c.5797 C > T mutation compared to those without. Therefore, the presence of c.5797 C > T may partly account for the phenotypic variety of RP1-IRD and may yield milder phenotypes. These findings may be useful for predicting the prognosis of RP1-IRD patients.
