Ellipsoid zoneの不整からacute syphilitic posterior placoid chorioretinitisの診断に至った2例

Two cases of acute syphilitic posterior placoid chorioretinitis diagnosed by irregularities in the ellipsoid zone

要約　目的：Acute syphilitic posterior placoid chorioretinitis（ASPPC）は梅毒性ぶどう膜炎の稀な病型で後極に特徴的な黄白色の円盤状病変を呈する。今回，ellipsoid zone（EZ）の不整からASPPCの診断に至った2例を報告する。

症例1：53歳，男性。4か月前からの右眼視力低下を主訴に当科を受診。矯正視力は右0.8，左0.9で，両眼に微塵様角膜後面沈着物，前房細胞1＋，硝子体混濁を認めた。後極に黄白色の色調変化を認め，光干渉断層計（OCT）でEZは不整であった。血清学的検査と画像所見よりASPPCと診断した。アモキシシリンによる治療で4か月後の矯正視力は右1.2，左1.2に改善，後極の色調変化は消失し，OCTでEZは正常となった。

症例2：43歳，男性。1週間前からの左眼視力低下，視野異常を主訴に当科を受診。矯正視力は左1.0で，黄斑下方を中心に黄白色の色調変化を認め，OCTでEZは不整であった。血清学的検査と画像所見よりASPPCと診断した。アモキシシリンによる治療で5か月後の矯正視力は左1.5に改善，後極の色調変化は消失し，OCTでEZは正常となった。

結論：OCTでEZの不整を認め，ASPPCを疑う契機となった。ぶどう膜炎にEZの不整が合併していれば，鑑別にASPPCを加える必要があると考えられる。

Abstract　Purpose：Acute syphilitic posterior placoid chorioretinitis（ASPPC）is a rare manifestation of syphilitic uveitis that is characterized by a yellowish-white discoid lesion on the posterior pole. This report presents two cases of ASPPC that were diagnosed by irregularities in the ellipsoid zone（EZ）.

Case 1：A 53-year-old man visited our hospital, complaining of vision loss in his right eye for the past four months. His corrected visual acuity measured 0.8 on the right eye and 0.9 on the left. Both eyes exhibited dust-like keratic precipitates, 1＋ anterior chamber cells, and vitreous opacities. He had a yellowish-white color-change area in the posterior pole, and optical coherence tomography（OCT）showed irregularities in the EZ. A blood test and these imaging findings led to a diagnosis of ASPPC. The corrected visual acuity improved to 1.2 in both eyes within 4 months after a course of treatment with amoxicillin. The color-change area disappeared, and OCT showed a return to a normal EZ.

Case 2：A 43-year-old man visited our department, complaining of vision loss in his left eye and visual field abnormalities for one week. The corrected visual acuity measured 1.0 on the left eye. The left eye exhibited a yellowish-white color-change area mainly inferior to the macula. OCT showed irregularities in the EZ. A blood test and these imaging findings led to a diagnosis of ASPPC. The corrected visual acuity improved to 1.5 in the left eye within 5 months after a course of treatment with amoxicillin. The color-change area disappeared, and OCT showed a return to a normal EZ.

Conclusion：The irregularity in the EZ on OCT led us to suspect ASPPC. ASPPC should be considered in the differential diagnosis, when uveitis presents irregularities in the EZ.