免疫グロブリン大量静注療法が奏効した抗アクアポリン4抗体陽性視神経炎の1例

Intravenous immunoglobulin was effective for corticosteroid refractory anti-aquaporin 4 antibody positive optic neuritis

要約　目的：抗アクアポリン4（AQP4）抗体陽性視神経炎に対して免疫グロブリン大量静注療法（IVIG）を実施し，副作用なく視機能の改善が得られた1例を経験したので報告する。

症例：54歳，女性。7日前からの右視力低下で，当科を紹介され受診となった。初診時の視力は右（0.01），左（1.2）。対光反射は右遅鈍で，相対的瞳孔求心路障害は右陽性。限界フリッカ値は右12.8Hz，左41.8Hz。視神経乳頭に異常はなく，ゴールドマン動的視野検査では，右眼は耳側に一部視野が残存するのみで著明な視野狭窄を認めた。造影MRIでは右視神経に造影効果を認めた。視神経炎に対してステロイドパルス療法を1クール施行するも，改善が乏しかった。経過中に抗AQP4抗体陽性であることが判明した。抗AQP4抗体陽性視神経炎と診断し，ステロイド内服を併用しIVIGを5日間施行した。IVIG開始後，視野狭窄は著明に改善し，視力は右（0.8）まで回復した。IVIG開始から8か月後の現在まで明らかな再発や副作用はない。

結論：IVIGは血漿交換療法と比較して非侵襲的であり，治療の選択肢として有用な一手である。患者の臨床所見，全身状況を鑑みて治療選択を行うことが望ましい。

Abstract　Purpose：We report a case of anti-aquaporin 4（AQP4）antibody-positive optic neuritis that responded well to intravenous immunoglobulin（IVIG）treatment in an acute stage.

Case：A 54-year-old woman presented with blurring of vision in the right eye since the past seven days. At the first visit, corrected visual acuity was 0.01 in the right eye and 1.2 in the left eye. Pupillary light reflex is slow and relative afferent pupillary defect was positive in the right eye. Critical fusion frequency was 12.8 Hz in the right and 42.8 Hz in the left eye. No abnormality of the optic disc was found and severe constriction of visual field was presented in the right eye with only a partial visual field remaining on the ear side. Contrast-enhanced magnetic resonance imaging showed enhanced signal in the right optic nerve. During the course, the blood test was positive for anti-AQP4 antibody, leading to the diagnosis of anti-AQP4 antibody positive optic neuritis. As one course of steroid pulse therapy was ineffective, she received IVIG treatment for five days with oral steroid treatment. After IVIG treatment the narrowing of the visual field was significantly improved, and corrected visual acuity recovered to 0.8 in the right eye without side effects. There was no recurrence until 8 months later.

Conclusion：IVIG treatment is non-invasive and useful treatment option for corticosteroid refractory anti-AQP4 antibody positive optic neuritis. It is desirable to select treatment based on the patient's clinical findings and general condition.