一卵性品胎の1女児にみられた第二色覚異常について

Congenital deuteranomaly in one of monozygotic female triplets

　女児の品胎うち1児に第二色弱様異常を認めた。この品胎が一卵性である確率は血液型検査，唾液型検査等の結果99.99％であった。

　仮性同色表，Panel D-15テスト，100 hueテスト，アノマロスコープの結果は定型的な先天性第二色弱で，左右差を認めなかった。視力，視野，フリッカー値，眼底検査を含む眼科一般検査では異常はみられなかった。染色体検査は46XXと正常であった。家系調査では，3胎の他の2児，兄，父親，母親に色覚異常はなく，母方の祖父に第二色盲を認めた。検査の結果によりこの女児は先天性第二色弱と考えられたが，いかなる機序により一卵性品胎のうち1人に先天性色覚異常が出現したかは不明である。

We diagnosed an 8-year-old girl as congenital deuteranomaly, based on examinations with pseudoisochromatic plates, panel D-15, 100-hue test and anomaloscope. Findings were essentially simi-lar for right and left eyes. There were no abnormal-ities in visual acuity, visual field, critical fusion frequency or fundus findings. Her chromosome typing was 46XX.

She was a member of female triplets. They were monozygotic at the probability of 99.99% through examinations of blood and salivary types among others.

No color anomaly was detected in the other two members of the triplet, their elder brother, or their parents. Thier grandfather on the maternal side manifested deuteranopia. The affected girl was thus supposed to suffer from congenital deuter-anomaly. It is not clear why the condition appeared in only one member of the triplet.