高安動脈炎に視神経脊髄炎関連疾患を併発した1例

A case of neuromyelitis optica spectrum disorder with Takayasu arteritis

要約　目的：高安動脈炎に動脈炎性前部虚血性視神経症（aAION）様臨床所見を併発し，視神経脊髄炎スペクトラム障害（NMOSD）と診断された1例を経験したので報告する。

症例：66歳，男性。10年前に高安動脈炎と診断され投薬治療されていたが，右優位の両眼窩部痛と左側頭部痛を主訴に前医を受診した。経過中に左視力低下と両視神経乳頭腫脹が出現し，豊橋市民病院（当院）眼科を紹介され受診となった。初診時の矯正視力は右1.0，左0.01，限界フリッカ値は右29.2Hz，左は測定不能であった。両視神経乳頭に左優位の蒼白浮腫を認めた。フルオレセイン蛍光眼底造影では右視神経乳頭に初期からの過蛍光を認め，左視神経乳頭に初期の著明な充盈遅延と，後期からの過蛍光を認めた。光干渉断層計では左眼に漿液性網膜剝離（SRD）を認めた。Goldmann視野検査では右眼に異常を認めず，左眼に中心を含む広範な視野欠損を認めた。aAIONを疑い，翌日に当院総合診療科へ紹介した。同日ステロイドパルス療法が施行された。1週間後に初診時の抗アクアポリン4抗体陽性が判明し，NMOSDの診断に至った。ステロイドパルス療法後，両視神経乳頭浮腫とSRDは徐々に消退し，左眼の矯正視力は0.4まで改善した。

結論：高安動脈炎にaAION様の臨床症状を併発した際に，aAIONだけでなくNMOSDも鑑別に挙げ検査を行うことで診断に至った稀な症例を経験した。

Abstract　Purpose：This report describes the case of a patient with neuromyelitis optica spectrum disorder（NMOSD）with coexisting Takayasu arteritis who presented with clinical features resembling those of arteritic anterior ischemic optic neuropathy（aAION）.

Case Presentation：A 66-year-old man with a 10-year history of Takayasu arteritis presented with right-dominant bilateral orbital pain and a left-sided headache. Loss of visual acuity in the left eye and swelling of both optic discs prompted referral to our department. The best-corrected visual acuity（BCVA）at baseline was 1.0 and 0.01 in the right and left eyes, respectively. The critical flicker fusion frequency was 29.2 Hz and unmeasurable in the right and left eyes, respectively. Fundus examination revealed pallor and edema, which was prominent in the left optic disc. Fluorescein angiography revealed early hyperfluorescence and a marked early-filling defect with late hyperfluorescence in the right and left optic discs, respectively. Optical coherence tomography revealed serous retinal detachment（SRD）in the left eye. The Goldmann perimeter revealed no abnormalities in the right eye；however, extensive visual field defects were observed in the left eye.

　Steroid pulse therapy for the suspected diagnosis of aAION was initiated by the General Medicine Department. However, the patient tested positive for anti-aquaporin-4（AQP4）antibody one week later, confirming the diagnosis of NMOSD. The optic disc swelling and SRD resolved gradually following steroid pulse therapy；the BCVA of the left eye improved to 0.4.

Conclusion：We reported a rare case of NMOSD coexisting with Takayasu arteritis, presenting with clinical features resembling aAION. The diagnosis was achieved through a thorough differential evaluation that considered not only aAION but also NMOSD.