血漿交換療法を要した抗アクアポリン4抗体陽性視神経炎の1例

A case of anti-aquaporin 4 antibody positive optic neuritis treated by plasma exchange therapy

要約　目的：視交叉視索炎として発症した抗アクアポリン4（AQP4）抗体陽性視神経炎に対し，早期血漿交換療法により視機能の回復を認めたので報告する。

症例：65歳，女性。2018年4月より原因不明の吃逆，嘔吐が持続し6月中旬に自然治癒した。7月下旬より急激な両眼視力低下を自覚し当科を紹介され受診となった。初診時，視力は右（0.1），左（0.09），中心フリッカ（CFF）値は右35Hz，左25Hz，視神経乳頭に異常はなく，動的視野検査にて両耳側暗点と左眼鼻下側の視野狭窄を認めた。MRIにて両側視交叉および左視索に造影効果，および第4脳室周囲にFLAIRで高信号を認めた。視交叉視索炎に対してステロイドパルスを1クール施行するも，CFF値の低下と視野の悪化を認めたためステロイド内服併用血漿交換療法（PE）に切り替えた。入院中に抗AQP4抗体陽性が確認され，抗AQP4抗体陽性視交叉視索炎と診断した。2回目のPE後から視野とCFF値の改善，4回目のPE後には視力の改善を認めた。計7回のPEの後，ステロイド内服単独療法へ移行し，以後視神経炎の再燃はない。

結語：急性期治療としてのステロイドパルスへの反応が乏しく，臨床症状およびMRI所見から抗AQP4抗体陽性が強く疑われる視神経炎においては早期に血漿交換療法への移行を検討することが望ましい。

Abstract　Purpose：We report a case of anti-aquaporin 4（AQP4）antibody positive optic neuritis in the optic chiasma and tract that responded well to additional plasma exchange therapy（PE）in early stage.

Case：A 65-year-old woman had frequent hiccups and vomiting of undetermined cause since 3 months before for 2 months. She visited our hospital with acute impaired vision since late July. Corrected visual acuity was 0.1 in the right eye and 0.09 in the left. Central critical fusion frequency（CFF）was 35 Hz in the right and 25 Hz in the left. Optic disc swelling was not observed. Bitemporal hemianopia and nasal lower visual field defect in the left eye was present by Goldmann perimetry. Magnetic resonance imaging（MRI）showed contrast enhancing lesion in the chiasm and left side tract. On FLAIR MRI imaging, high intensity lesion was observed around fourth ventricle. After one course of steroid pulse therapy proved invalid, she received PE with oral steroid treatment. Serological test was positive for anti-AQP4 antibody, leading to the diagnosis of anti-AQP4 antibody positive optic neuritis. Visual field and CFF started to improve after the second PE, visual acuity after the fourth PE. There has been no recurrence of disease after seven sessions of PE followed by oral steroid treatment.

Conclusion：For optic neuritis that is resistant to steroid pulse therapy and is suspected as anti-AQP4 antibody seropositive by clinical and MRI findings, we recommend additional plasma exchange in early stage.