低ナトリウム血症による眼症状を初発症状とした肺癌の1例

A case of lung carcinoma with eye symptoms due to hyponatremia as the initial manifestation

要約　目的：近方視力低下を初発症状とした肺癌症例の報告。症例：68歳男性が16日前からの両眼の近方視力低下で受診した。高血圧の既往があり，1週間前に低ナトリム血症が発見された。所見：矯正視力は左右とも1.2で，約＋4Dの遠視があった。3か月前に作製した眼鏡は，約＋3Dであった。全身検査で肺腫瘍が発見され，生検で肺小細胞癌であり，多発性肝転移が認められた。初診から9か月後，新たに脳転移が発見され，放射線照射で消失した。血清Na値は正常化し，屈折は右＋1.75D，左＋1.62Dになった。結論：肺癌により異所性抗利尿ホルモンが分泌され，低ナトリウム血症が生じたことが遠視化の原因であったと推定される。

Abstract.　Purpose：To report a case who showed impaired near vision secondary to lung carcinoma. Case：A 68-year-old male presented with impaired near visual acuity since 16 days before. He had had systemic hypertension. Hyponatremia had been detected one week before. Findings：Visual acuity was 1.2 in either eye when corrected by about plus 4 diopters. He had been prescribed for eyeglasses 3 months before that had plus 3 diopters for either eye. Systemic examinations led to the detection of lung tumor what proved to be small cell carcinoma with metastasis to the liver. Brain metastasis was detected 9 months later that disappeared after radiation. After normalization of serum natrium level,the refraction was ＋1.75 diopters right and ＋1.62 diopters left. Conclusion：Acute hyperopia in this patient appears to have been induced by hyponatremia secondary to elevated inappropriate secretion of antidiuretic hormone due to lung carcinoma.