トシリズマブが有効と考えられた動脈炎型前部虚血性視神経症の1例

Tocilizumab, an IL-6 blocker, may be useful for arteritic anterior ischemic optic neuropa- thy when tapering a dosage of steroids: A case report

要約　目的：動脈炎型前部虚血性視神経症（aAION）の発症率は10万人あたり1.3人とされ，比較的稀な疾患である。予後不良で僚眼発症の危険性も高い。今回，ステロイドパルス療法後，トシリズマブ（TCZ）を使用し，僚眼発症を抑制できたと考えられた1例を経験したので報告する。

症例：78歳，女性。左眼の急激な視力低下で紹介され受診となった。視力は右（0.6），左（手動弁）で，左眼に相対的瞳孔求心路障害を認めた。動的視野検査では，左眼視野は耳側に島状に残存するのみで，右眼も耳側視野に楔状欠損を認めた。眼底は，左眼で視神経乳頭の蒼白腫脹と線状出血を，右眼で乳頭周囲に白斑を認めた。蛍光眼底造影検査では，左眼の視神経乳頭と脈絡膜の充盈遅延を認めた。血液検査ではCRP 14.25mg/dl，赤沈（1時間値）110mmと高値であった。側頭動脈生検で多核巨細胞を認めたため，aAIONと確定診断できた。ステロイドパルス療法で左眼視神経乳頭腫脹は軽減したが，視力と視野の改善は乏しく，視力は手動弁にとどまった。発症から4か月を経過したが，ステロイド漸減時のTCZ皮下注射併用で，僚眼の右視力は（0.7）を維持できている。

結論：aAIONの予後はきわめて不良で，本症例でも患眼の視機能はほとんど回復しなかった。しかし，初診時にsub-clinicalな異常を認めた僚眼の発症を抑制できた。TCZはIL-6阻害薬で，aAIONにおいてステロイド減量時に有用であると考えられた。

Abstract　Purpose：Arteritic anterior ischemic optic neuropathy（aAION）is a relatively rare disease, with an incidence rate of 1.3 per 100,000 people^1）. It has a poor prognosis and a high risk of incidence in the fellow eye. We report a case wherein tocilizumab（TCZ）, an interleukin-6（IL-6）blocker, proved to be useful when tapering a dosage of steroids after steroid pulse therapies.

Case：A 78-year-old female presented with the primary complaint of sudden visual loss in her left eye. Her visual acuities were 0.6 OD and hand motion OS, respectively, and relative afferent pupillary defect（RAPD）was positive in the left. Goldmann perimetry（GP）showed a residual islet of visual area in the temporal visual field of the left eye, and a wedge-shaped defect in the temporal visual field of the right eye. The left optic disc was swollen, with a chalky white color, and splinter disc hemorrhage was present. Soft exudates were present around the right optic disc. Fluorescein angiography（FA）showed a filling delay in the optic disc and choroid in the left eye. A blood test showed that the CRP level was as high as 14.25 mg/dl and erythrocyte sedimentation rate after 1-hour was 110 mm. Temporal artery biopsy showed a presence of multinuclear giant cells collectively, we diagnosed the patient's condition as aAION. The left optic disc swelling was decreased by steroid pulse therapies but there was no improvement in the left visual function.

Conclusion：We tapered the dose of steroids with a usage of TCZ；this helped suppress the onset of aAION in the fellow eye, which had subclinical abnormalities on the fundus at the initial examination. TCZ may be useful when tapering off a dosage of steroids.