title: Pathognomonic (diagnostic) ERGs. A review and update.
abstract: OBJECTIVE
  To review three inherited retinal disorders associated with diagnostic or pathognomonic electroretinogram (ERG) abnormalities: cone dystrophy with supernormal rod ERG (KCNV2), enhanced S-cone syndrome (NR2E3), and bradyopsia (RGS9/R9AP).
  
  
  METHODS
  A review of clinical details, genetic basis, and electrophysiological features in these disorders and a brief summary of the standard and nonstandard ERG techniques required to identify the disorders.
  
  
  RESULTS
  The electrophysiological features in each of these three disorders are pathognomonic such that the responsible gene can be specified. The results from nonstandard electrophysiological testing in excess of international standards are necessary to describe the pathognomonic changes in cone dystrophy with supernormal rod ERG and bradyopsia. The clinical phenotype in the disorders can be variable. Mutations in NR2E3 may additionally be associated with phenotypes other than enhanced S-cone syndrome.
  
  
  CONCLUSIONS
  : Characteristic ERG changes enable the diagnosis of cone dystrophy with supernormal rod ERG, enhanced S-cone syndrome, and bradyopsia and accurate genetic screening. This review highlights the need for additional nonstandard ERGs to make the diagnosis in two of these disorders.
authors.affiliation: Department of Ophthalmology, Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Ajoy
authors.initials: A
authors.lastname: Vincent
authors.forename: Anthony G
authors.initials: AG
authors.lastname: Robson
authors.forename: Graham E
authors.initials: GE
authors.lastname: Holder
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D003937:Diagnosis, Differential; D004594:Electrophysiology; D004596:Electroretinography; D015785:Eye Diseases, Hereditary / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D057093:Orphan Nuclear Receptors / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics; D012162:Retinal Degeneration / Q000175:diagnosis* / Q000235:genetics; D012174:Retinitis Pigmentosa / Q000175:diagnosis* / Q000235:genetics; D014786:Vision Disorders / Q000175:diagnosis* / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C489610:KCNV2 protein, human; D008565:Membrane Proteins; C403073:NR2E3 protein, human; D057093:Orphan Nuclear Receptors; D024642:Potassium Channels, Voltage-Gated; C464657:RGS9BP protein, human