ニボルマブまたはイピリムマブによる薬剤性視神経症が疑われた1例

A case suspected of drug-induced optic neuropathy due to nivolumab or ipilimumab

要約　目的：ニボルマブまたはイピリムマブが被疑薬と考えられた薬剤性視神経症の1例を経験したので報告する。

症例：52歳，女性。悪性胸膜中皮腫に対し，当院産婦人科でX年Y月13日よりニボルマブとイピリムマブが投与された。Y＋2月1日に左眼の視野障害を訴え，同月9日に当科を受診した。

所見：初診時の視力は右（1.2），左（0.9）で，左眼に相対的瞳孔求心路障害を認めた。両眼の視神経乳頭は腫脹し，フルオレセイン蛍光眼底造影では視神経乳頭の過蛍光を認めた。視野検査では，左眼優位に周辺部の視野欠損がみられた。頭部造影MRIは特記所見なく，ニボルマブまたはイピリムマブの薬剤性視神経症が疑われた。Y＋2月22日から被疑薬を中断したところ，自覚症状の改善はみられたが視野欠損がやや進行したため，Y＋2月29日よりステロイドパルス療法を3日間施行した。その後，視野の悪化はなく，矯正視力は両眼とも（1.2）に向上した。産婦人科医と患者との相談で，Y＋3月26日からニボルマブとイピリムマブの投与が再開されたが，発症から1年時点で視機能の悪化はみられていない。

結論：経過から，総合的に薬剤性視神経症と判断した。被疑薬の早期中断とステロイドパルス療法により，視野障害の進行を抑えられた可能性がある。被疑薬は再開されているため，今後も注意深い経過観察が必要である。

Abstract　Purpose：We report a case of drug-induced optic neuritis, which was suspected to be secondary to nivolumab and ipilimumab administration.

Case：A 52-year-old woman received nivolumab and ipilimumab for treatment of malignant pleural mesothelioma at our obstetrics and gynecology department since Y 13, X. She developed visual field disturbance in her left eye on Y＋2 1st and visited our department on Y＋2 9th. Her decimal best-corrected visual acuity was 1.2 in the right eye and 0.9 in the left eye, and we observed a relative afferent pupillary defect in the left eye. Both optic nerve heads were edematous and showed hyperfluorescence on fluorescein angiography. Visual field examination revealed peripheral field defects in the left eye. Magnetic resonance imaging and blood test results revealed no significant findings, and we suspected nivolumab or ipilimumab-induced optic neuritis. These drugs were discontinued on Y＋2 22nd, after which the patient's subjective symptoms improved, although the visual field defect progressed slightly. Therefore, a 3-day steroid pulse therapy was initiated on Y＋2 29th. Subsequently, we observed no further deterioration in the visual field, and the patient's visual acuity improved to 1.2 in both eyes. After consultation with her obstetrician, nivolumab and ipilimumab therapy was resumed on Y＋3 26th. No decline in visual function was observed at the 1-year follow-up.

Conclusion：Based on the course of events, we diagnosed the patient with drug-induced optic neuritis. Early discontinuation of the suspected drugs and steroid pulse therapy may have prevented progression of the visual field impairment in this case. Careful monitoring of the patient's condition is warranted in the future, following resumption of administration of the suspected drugs.