Abstract
Abstract: :
Purpose: To report ERG findings from a big Chinese family of ad CSNB that is unlike those reported previously. Method: Six patients were from an adCSNB of Chinese family, now the pedigree has been 12 generations. The patients were aged between 25 and 73 years. They are four male and two female. The dark adaptation curves and the full field ERGs following protocols of ISCEV were recorded. Results: Dark–adapted curves: Three patients with adCSNB show normal or elevated cone threshold and no rod function. Under scotopic ERGs, the rod–system b wave was not disappeared, but much lower amplitude for all six subjects. Moreover, their maximum response was neither Schubert–Bornschein, nor Riggs. There were two types of maximum response. The photopic ERGs were normal. Conclusion: The rod–system responses to dim flash stimuli, all of the patients described in this article, showed a significantly reduction of ERG b–wave amplitude, not unrecorded, had about 20% of normal amplitude in scotopic condition. The maximum ERGs had normal ERG a–wave amplitude, and reduced ERG b–wave amplitude(four cases), so the b/a ratio were changed. There were two types of ERGs from two sub–families: one b/a ratio > 1.6 (2 patients), another one b/a ratio <1.2 (4 patients). The cone–system responses to single bright flash stimulus and responses to 30Hz stimuli showed similarities to those of normal controls in the photopic condition. That means the recordings of our patients were not similarities to those of Schubert–Bornschein, not to those of Riggs as well. The rod–system responses to dim flash stimuli were not completely lost; we may call it an atypical of adCSNB or incomplete ERGs. In addition, five miss’s mutations have been identified to be responsible for adCSNB. Three of them were within exons 1 and 4 of rhodopsin gene, one was in exon 4 of rod cGMP phosphodiesterase (PDE) ß–subunit gene and one in exon 2 of the gene encoding for the α–subunit of rod transducin. Three gene mutations were found in Riggs type CSNB. They were RHO gene, GNAT1 gene and PDE6B gene. For this Chinese family, we have sequenced 4 exons covering the five known mutations for adCSNB. There is no mutation found in any of the exons, including the codon 90, codon 94, codon 292 of rhodopsin gene, codon 258 of ßPDE gene and codon 38 of rod transducin α–subunit gene. Therefore, it showed the machnism of our reported adCSNB was differed from those of ad CSNB in ERGs and gene mutations.
Keywords: electroretinography: clinical