Clinical-electroretinography mismatch in a patient with non-syndromic BBS1-associated retinal degeneration

BMJ Case Rep. 2025 May 26;18(5):e264886. doi: 10.1136/bcr-2025-264886.

Abstract

A male patient in his late thirties, homozygous for the M390R Bardet-Biedl Syndrome-1 (BBS1) variant, began follow-up in early adulthood, due to decreased visual acuity and photophobia. Fundus examination showed bilateral temporal wedge-shaped pallor of the optic disc and atrophic maculopathy, translating into central hypoautofluorescence on fundus autofluorescence. Even though clinical and multimodal imaging features suggested cone-dominant degeneration, electroretinography (ERG) showed reduced scotopic and photopic responses, with greater scotopic impairment. Despite a thorough systemic evaluation and long-term follow-up, no other features of BBS were found. To our knowledge, this is the first documented case of non-syndromic BBS1-associated disease with a rod-cone dystrophy phenotype on ERG and a clinical presentation (symptoms and imaging features) of cone-dominant disease. The discrepancy between clinical/imaging and ERG findings reflects the complexity of BBS1-related disease and highlights the crucial role of genetic testing and comprehensive phenotyping in inherited retinal disorders.

Keywords: Genetic screening / counselling; Retina.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Bardet-Biedl Syndrome* / diagnosis
  • Bardet-Biedl Syndrome* / genetics
  • Electroretinography
  • Humans
  • Male
  • Microtubule-Associated Proteins* / genetics
  • Phenotype
  • Retinal Degeneration* / diagnosis
  • Retinal Degeneration* / genetics
  • Visual Acuity

Substances

  • Bbs1 protein, human
  • Microtubule-Associated Proteins