難治性視神経炎に単純血漿交換が著効した1例

Simple plasma exchange was effective in a patient with refractory optic neuritis

要約　目的：ステロイド抵抗性の難治性視神経炎に単純血漿交換が著効した症例の報告。

症例：既往に糖尿病のある47歳，女性。4日前からの右眼視力低下，眼痛を主訴に当院を受診した。視力は右手動弁，左（1.5），限界フリッカ値（CFF）は右測定不能，左39Hzで，RAPDx^®によるRAPD amplitude scoreは10.55と右相対的瞳孔求心路障害（RAPD）陽性であった。右視神経乳頭は軽度の発赤・腫脹を認め，左眼に異常所見はなかった。造影MRIでは右視神経全長の造影効果を認め，重篤な右球後視神経炎と診断した。髄液検査では蛋白増加を認め，視神経炎初発の多発性硬化症・視神経脊髄炎の可能性が示されたが，頭部・脊髄MRIで異常所見はなく，抗アクアポリン4抗体などの自己抗体は陰性であった。第7病日からステロイドパルス療法を2クール施行したが，視機能・造影MRI所見に変化なく，ステロイド抵抗性であった。光干渉断層計（OCT）で右網膜内層の明らかな菲薄化がなかったため，血漿浄化療法が有効ではないかと考え，第19病日より合計6回の単純血漿交換を実施した。第30病日の造影MRIの造影効果は消失し，第88病日には右視力（1.5），右CFF 27Hz，RAPD amplitude score 2.27と著明な視機能の改善を認めたが，OCTによる網膜内層は進行性に菲薄化した。発症から10か月間，再発や脊髄炎の発症はない。

結論：眼窩MRIで造影効果のあるステロイド抵抗性視神経炎に対し，単純血漿交換が有用であった。

Abstract　Purpose：To report a case of refractory optic neuritis that subsided after simple plasma exchange.

Case：A 47-year-old woman with diabetes presented with impaired vision and ocular pain in the right eye beginning 4 days before. Corrected visual acuity was hand motion in the right eye and 1.5 left. Critical flicker fusion frequency（CFF）was unrecordable in the right eye and 39 Hz left. The right eye showed relative afferent pupillary defect as the sole objective finding. Contrast MRI showed contrast enhancement of the right optic nerve in full length, resulting in the diagnosis of right refractory retrobulbar neuritis. Right optic disc showed mild redness and swelling, while left optic disc was normal. Head and spinal cord MRI showed no abnormal findings, but spinal fluid examination showed an increase in protein, suggesting the possibility of optic neuritis as part of optic neuromyelitis. Autoantibodies such as anti-aquaporin-4 autoantibody were negative. Two series of pulsed corticosteroid therapy were administered from day 7, but there were no changes in visual function and contrast MRI findings. Because there was no obvious thinning of the right retinal inner layer with optical coherence tomography（OCT）, we considered that plasma purification therapy might be effective. Therefore, we performed a total of 6 simple plasma exchanges from day 19. The contrast enhancement on MRI disappeared on day 30. Right visual function improved to visual acuity of 1.5, CFF of 27 Hz, and RAPD amplitude score of 2.27 on day 88. The retinal inner layer showed progressive thinning on OCT. There has been no recurrence during 10 months of follow-up observation.

Conclusion：Simple plasma exchange was effective in a patient with refractory optic neuritis showing contrast enhancement on MRI.