メトトレキサートによる中枢神経障害が原因で視覚障害を生じた1例

A case of visual impairment caused by damage in the brain following methotrexate

要約　目的：メトトレキサート（MTX）による中枢神経障害が原因で視覚障害を生じた症例の報告。

症例：45歳，男性。2か月前から視力と中心フリッカ値が低下し，ゴールドマン動的視野検査では中心暗点とマリオット盲点の拡大があった。検眼鏡上は異常なく，MRIでT2WI/STIR/FLAIR像で両側視神経から視交叉，さらには視索，外側膝状体にかけて高信号を認め，脳梁の著明な腫大とともに大脳半球白質に左右対称性に広範囲に同シーケンスで高信号を認めた。血液検査，髄液検査，遺伝子検査などで原因は特定できなかった。関節リウマチの既往があり，MTX 8mg/週内服していたことから薬剤性による可能性も考え休薬したところ，自覚検査，画像所見ともに徐々に改善した。

結論：さまざまな薬剤が中枢神経障害を引き起こすとされており，薬剤歴の聴取は重要であると考えられる。

Abstract　Background：Methotrexate（MTX）is regarded as beneficial in cases of malignancy and autoimmunological diseases including rheumatoid arthritis.

Purpose：To report a case who developoed impaired vision supposedly due to damage in the brain following prolonged treatment with methotrexate.

Case：A 45-year-old male presented with impaired vision in both eyes since 2 months before. He had been treated with MTX for rheumatoid arthritis since 2 years before.

Findings and Clinical Course：Corrected visual acuity was 0.4 in either eye. Perimetry showed central scotoma and enlarged blind spot. Magnetic resonance imaging（MRI）showed enhanced response in the optic nerve, optic tract, corpus callosum, and white matter in the cerebral cortex. The pathological findings were bilateral and symmetrical. Routine laboratory and cerebrospinal fluid tests gave equivocal findings. Withdrawal of MTX was followed by improved visual acuity, visual field and MRI findings 10 months later.

Conclusion：The present case illustrates that the central nervous system, including the optic nerve and tract, may be pathologically affected by prolonged treatment with MTX.