網膜電図に著明な左右差を認めた両側色素性傍静脈網脈絡膜萎縮症の1例

A case of bilateral pigmented paravalvular retinal choroidal atrophy（PPRCA） with prominent left-right difference in ERG

要約　目的：網膜電図（ERG）に著明な左右差を認めた両側色素性傍静脈網脈絡膜萎縮症（PPRCA）の症例を経験したため報告する。

症例：33歳，女性。左眼の視力低下を自覚したため受診した。初診時，両眼の網膜静脈に沿った色素沈着を認め，網膜色素上皮の萎縮も認めていた。ERGでは右眼に軽度減弱型，左眼に消失型を示していた。視野検査では両眼ともに色素沈着部位にほぼ一致した視野欠損を認めていた。臨床的にPPRCAと診断した。

結論：両眼に典型的なPPRCAの眼底所見が観察されたにもかかわらず，ERG所見において右眼は軽度減弱型，左眼は網膜色素変性症（RP）様の消失型を示し，顕著な左右差を認める症例を経験した。片眼のみRP様のERGパターンを呈するPPRCAについて遺伝学的背景を精査することにより，PPRCAがRPの前駆病変であることを明らかにする可能性や，その病態のメカニズム解明に寄与する可能性がある。

Abstract　Purpose：We report a case of bilateral pigmented paravenous retinochoroidal atrophy（PPRCA） with marked bilateral differences in electroretinography（ERG）.

Case：33-year-old female.

Findings：The patient came to the clinic because she was aware of vision loss in her left eye. At the time of initial examination, pigmentation along the retinal veins and atrophy of the retinal pigment epithelium were observed in both eyes. Electroretinography showed a mildly attenuated form in the right eye and a negative form in the left eye. Visual field testing showed visual field defects in both eyes that were almost consistent with the areas of atrophy. The diagnosis of PPRCA was made clinically.

Conclusion：Despite typical fundus findings of PPRCA in both eyes, we have experienced a case with a marked left-right difference in ERG findings, with the right eye showing a mildly attenuated type and the left eye showing a negative retinitis pigmentosa（RP）-like type. A close investigation of the genetic background of PPRCA with RP-like ERG pattern in only one eye may contribute to the possibility that PPRCA is a precursor lesion of RP and to the elucidation of its pathogenetic mechanism.