Department of Ophthalmology, Faculty of Medicine, Kindai University, Osaka-Sayama, Japan.
Department of Ophthalmology, The Jikei University School of Medicine, Tokyo, Japan.
Doc Ophthalmol. 2024 Jun;148(3):173-182. doi: 10.1007/s10633-024-09971-0. Epub 2024 Apr 17.
KCNV2-associated retinopathy causes a phenotype reported as "cone dystrophy with nyctalopia and supernormal rod responses (CDSRR; OMIM# 610356)," featuring pathognomonic findings on electroretinography (ERG). Here, we report the clinical courses of two siblings with CDSRR.
Patient 1: A 3-year-old boy with intermittent exophoria was referred to our hospital. The patient's decimal best-corrected visual acuity (BCVA) at age 6 was 0.7 and 0.7 in the right and left eyes, respectively. Photophobia and night blindness were also observed. Because the ERG showed a delayed and supernormal b-wave with a "squaring (trough-flattened)" a-wave in the DA-30 ERG, and CDSRR was diagnosed. The patient's vision gradually worsened, and faint bilateral bull's eye maculopathy was observed at the age of 27 years, although the fundi were initially unremarkable. Genetic examination revealed a homozygous missense variant, c.529T > C (p.Cys177Arg), in the KCNV2 gene. Patient 2: The second patient was Patient 1's younger sister, who was brought to our hospital at 3 years of age. The patient presented with exotropia, mild nystagmus, photophobia, night blindness, and color vision abnormalities. The patients' decimal BCVA at age 13 was 0.6 and 0.4 in the right and left eyes, respectively, and BCVA gradually decreased until the age of 24 years. The fundi were unremarkable. The siblings had similar ERG findings and the same homozygous missense variant in the KCNV2 gene.
The siblings had clinical findings typical of CDSRR. High-intense flash ERG is recommended for identifying pathognomonic "squaring" a-waves in patients with CDSRR.
KCNV2 相关的视网膜病变导致了一种表现为“伴有暗适应和超敏杆反应的 cones 营养不良（CDSRR；OMIM#610356）”的表型，在视网膜电图（ERG）上具有特征性的发现。在这里，我们报告了两位患有 CDSRR 的兄弟姐妹的临床过程。
患者 1：一名 3 岁男孩间歇性外斜视，被转介到我们医院。患者 6 岁时的十进制最佳矫正视力（BCVA）分别为右眼 0.7 和左眼 0.7。还观察到畏光和夜盲。由于 ERG 在 DA-30 ERG 中显示出延迟和超敏 b 波以及“方形（波谷平坦）”a 波，因此诊断为 CDSRR。患者的视力逐渐恶化，27 岁时观察到双侧微弱的牛眼黄斑病变，尽管眼底最初无明显异常。基因检查显示 KCNV2 基因的纯合错义变体 c.529T>C（p.Cys177Arg）。患者 2：第二位患者是患者 1 的妹妹，她在 3 岁时被带到我们医院。该患者表现为外斜视、轻度眼球震颤、畏光、夜盲和色觉异常。患者 13 岁时的十进制 BCVA 分别为右眼 0.6 和左眼 0.4，直到 24 岁时 BCVA 逐渐下降。眼底无明显异常。这对兄弟姐妹的 ERG 发现相似，并且在 KCNV2 基因中具有相同的纯合错义变体。
这对兄弟姐妹具有典型的 CDSRR 临床特征。建议使用高强度闪光 ERG 来识别 CDSRR 患者的特征性“方形”a 波。
