亜急性小脳変性症，Lambert-Eaton筋無力様症候群および脳幹脳炎を合併した抗P/Q型VGCC抗体陽性肺小細胞癌の1例

A Case of Anti P/Q Type VGCC Antibody Positive Small Lung Cell Carcinoma that Occured with Subacute Cerebellar Degeneration,Lambert-Eaton Myasthenic Syndrome,and Brainstem Encephalitis

はじめに

　近年，傍腫瘍性神経症候群の診断基準が提唱された^1）が，いまだに診断困難例は多く，またLambert-Eaton症候群（Lambert-Eaton myasthenic syndrome：LEMS）を含め免疫療法・抗腫瘍療法に反応しない例も多く，治療反応例の維持療法についても一定の方針はない。今回われわれは，18F-fluorodeoxyglucose-positron emission tomography（［¹⁸F］-FDG-PET）で診断した肺小細胞癌に伴う傍腫瘍性小脳変性症（paraneoplastic cerebellar degeneration：PCD）とLEMSの合併例（PCD-LEMS）を経験した。本症例は，いったんは免疫療法に反応したが脳幹脳炎として再発した。本症例の病態について若干の考察を加え報告する。

Abstract

　A 62-year-old man was admitted to our hospital because of rapidly progressive dysarthria, truncal ataxia, and gait disturbance.　High titers of the ProGRP and anti-P/Q-type VGCC antibody were detected in the serum.　High accumulation of ［¹⁸F］ was detected at the hilus of the left lung on ［¹⁸F］-FDG-PET scan.　A high-frequency repetitive stimulation test of the median nerve yielded an incremental response.　On the basis of these findings, a diagnosis of paraneoplastic cerebellar degeneration (PCD) and Lambert-Eaton myasthenic syndrome (LEMS) associated with small cell lung carcinoma (SCLC) was diagnosed.　After intravenous immunoglobulin therapy (IVIg), methylprednisolone (m-PSL) pulse therapy, and other multidisciplinary concurrent treatments, a partial regression of the SCLC and a significant improvement in neurological symptoms were observed.　However, ataxia relapsed and brainstem encephalitis developed 6 months later.　A marginal improvement in neurological symptoms was observed with IVIg, m-PSL pulse therapy, and intravenous cyclophosphamide pulse therapy (IVCY).　SCLC also recurred later.　We hypothesized that VGCC of the brainstem was damaged by anti-P/Q-type VGCC antibody.

(Received: March 9,2007,Accepted: July 29,2008)