Purpose: To identify possible correlations between the putative mutations and the clinical characteristics in X-linked retinitis pigmentosa, RP2.
Design: A retrospective, descriptive clinical study.
Material: The ophthalmological files on affected persons from three Danish families with identified pathogenic mutations in the RP2 gene.
Results: Mutation analysis in 14 Danish families with X-linked retinitis pigmentosa revealed disease-associated sequence alterations in eight of them. Five mutations were detected in the RP3 gene (RPGR) and three in the RP2 gene. Genotype-phenotype comparison in the three RP2 families revealed striking interfamilial phenotypic differences. Severe phenotypes were associated with a null mutation Gln26stop and a missense mutation Arg118His. These families differed mutually with respect to retinal appearance. Affected carriers had a delayed onset by three decades. Tapetal reflexes were not observed in the carriers. An in-frame deletion DeltaSer6 was associated with a milder phenotype.
Conclusions: Interfamilial differences in RP2 phenotype might be related to the type and location of the mutational event. Due to a considerable overlap between RP2 and RP3 phenotypes, the genotype cannot safely be deduced from conventional clinical examination methods.