Purpose: To describe the phenotypic and genotypic features in patients with PRPH2 mutations and negative electroretinograms.
Methods: Retrospective observational case series. Records of patients with a confirmed molecular diagnosis of PRPH2 mutation, and an electronegative electroretinogram (reduced b-wave to a-wave amplitude ratio) under either photopic or scotopic conditions, were identified. Data examined included clinical history and retinal images, electrophysiology, and mutational analysis.
Results: Six patients were ascertained. All had presented with clinically evident maculopathy and Snellen visual acuities in the range of 6/6 to 1/60. All had negative electroretinograms in scotopic or photopic electroretinograms or both. Four patients were heterozygous for a previously reported missense mutation c.514C>T, p.R172W; 2 were heterozygous for the frame-shifting mutations c.259_266del8, p.D87fs and c.394delC, p.Q132fs. No other cause of electronegative electroretinogram was identified in any patient. Photopic On- and Off-response recording was useful in identifying On-pathway dysfunction.
Conclusion: PRPH2 mutation can be associated with negative electroretinograms. This novel finding is not mutation specific and does not relate to the severity of the disease. The data add to the documented phenotypical variability of PRPH2 mutations and represent a further cause of negative electroretinogram.