多彩な神経症状を呈した小細胞肺癌に伴う傍腫瘍性神経症候群の1例

背景．傍腫瘍性神経症候群は担癌患者に生じる神経障害であり，腫瘍の転移や浸潤・圧排，代謝異常や栄養障害によるものではなく，自己免疫学的機序による神経系の障害により生じる．傍腫瘍性神経症候群を合併する腫瘍は小細胞肺癌が最も多いとされている．症例．77歳男性．従来自立した生活を送っていたがX年10月頃より倦怠感が出現した．その後歩行障害が進行し排尿障害も出現したため，X＋1年5月中旬に当院紹介となった．構音・嚥下障害や両下肢の運動・感覚障害，自律神経失調など多彩な神経症状を認め，精査によりLambert-Eaton症候群と診断された．自己抗体検査では，抗amphiphysin抗体，抗ガングリオシド（GM1，GT1b）抗体が陽性であった．精査にて小細胞肺癌cTXN2M1b（Stage IV）と診断した．PS 4のため化学療法の適応はないと判断した．免疫グロブリン大量療法を施行するも神経所見は改善しなかった．緩和医療目的に近医に転院し，X＋1年10月下旬に死亡した．結論．複数の自己抗体が検出され多彩な神経症状を呈した小細胞肺癌に伴う傍腫瘍性神経症候群の1例を経験した．

Background. Paraneoplastic neurological syndrome is a neurological disorder associated with various malignancies and is considered to be caused by autoimmune mechanisms, but not by symptoms due to tumor progression itself. Small cell lung cancer is the most common type of malignancy accompanied with paraneoplastic neurological syndrome. Case. A 77-year-old male was referred to our hospital for further examination of general fatigue, gait disturbance and dysuria. On admission, diverse neurological symptoms, such as dysarthria, dysphagia, motor and sensory disturbance in lower extremities and autonomic dysregulation, were observed. Further examination yielded the diagnosis of Lambert-Eaton myasthenic syndrome with positive results for anti-amphiphysin and anti-ganglioside antibodies. Swelling of the mediastinal lymph nodes and elevated ProGRP were detected, and a definitive diagnosis of small cell lung cancer (cTXN2M1b: Stage IV) was made. As the administration of intravenous immunoglobulin failed to ameliorate his neurological symptoms and general condition (PS 4), we determined that there were no indications for chemotherapy. He was subsequently transferred to a palliative care hospital and died nearly one year after the development of his initial symptoms. Conclusion. We experienced a case of small cell lung cancer with diverse neurological symptoms due to the presence of paraneoplastic neurological syndrome.