Abstract
Purpose:
To describe clinical and molecular characteristics of four Japanese patients with "Cone Dystrophy with Supernormal Rod Electroretinogram (ERG)."
Methods:
Four individuals form three families with clinical diagnosis of cone dystrophy with supernormal rod ERG were recruited; two siblings from one family {Patient 1 (24 yrs), Patient 2 (17 yrs)} and two simplex cases {Patient 3 (17 yrs), Patient 4 (21 yrs)}. Full clinical examinations were undertaken, including fundus photography, fundus autofluorescence (AF) imaging, spectral-domain optical coherence tomography (OCT) imaging and full-field ERG incorporating to international standard. Mutational screening of KCNV2 was performed by direct sequencing.
Results:
All patients had central visual disturbances and night blindness. Two patients (Patients 2, 3) complained of photophobia and one (Patient 3) had nystagmus. The best corrected visual acuity at the latest examination was variable ranging from 0.08 to 0.7. Fundus imaging identified RPE mottling at the macula, which was well-defined in AF imaging. ERGs showed identical features with a decreased rod response, a square-shaped a-wave and a high-amplitude b-wave in bright flash response, and decreased cone-derived responses. OCT imaging detected absence of cone outer segment tip (COST) line in the macula in all patients, with discontinuous inner and outer segment (IS/OS) junction line in 2 subjects (Patient 3, 4). Molecular analysis revealed compound heterozygosity for two alleles (p.C177R and p.G461R) in three individuals (Patient 1, 2, 4) and homozygosity for complex alleles (p.R27H and p.R206P) in Patient 3; three were putative novel (p.R27H, p.C177R, p.R206P).
Conclusions:
The clinical features of Japanese patients with KCNV2-retionpathy, including ERG, OCT and AF findings, were similar to those reported in previous studies. Three putative novel variants were identified in four subjects and there may be a distinct spectrum of KCNV2 alleles in Japanese population.
Keywords: 696 retinal degenerations: hereditary •
539 genetics •
509 electroretinography: clinical