先天網膜分離症の兄弟例

X-linked juvenile retinoschisis in a pair of mail siblings

　6歳の男児が視力障害で受診した。矯正視力は左右とも0.4で，両眼に銀箔様の網膜反射と車軸状黄斑変性があった。周辺網膜に分離症はなかった。フラッシュERG （網膜電図）のb／a比は，右1.40，左1.17であった。7歳の兄の矯正視力は右0.5，左0.3で，両眼に銀箔様の網膜反射と車軸状黄斑変性と，下耳側に網膜分離症があった。フラッシュERGのb／a比は右0.96，左0.89であった。X染色体劣性遺伝の網膜分離症ではMüller細胞の異常があるとされ，フラッシュERGのb／a比が減弱することがあるが，これが1以上を示す症例がありうる。

A 6-year-old boy presented with visual acuity of 0.4 in either eye. Funduscopy showed silver-gray retinal reflex and cartwheel-like macular degeneration in both eyes. Peripheral retinoschisis was absent. Single-flash electroretinogram (ERG) showed b/a amplitude ratio of 1.40 in the right eye and 1.17 in the left. His 7-year-old brother had correctd visual acuity of 0.5 right and 0.3 left. Funduscopy showed similar findings with additional peripheral retinoschisis in both eyes. The b/a ratio was 0.96 right and 0.89 left. It is claimed that abnormality in the Müller cells is involved in X-linked retinoschisis and that the b/a ratio is decreased. The first case illustrates that the b/a ratio may be over 1.0 in this disease.