両側視床病変が遅発性に出現した悪性リンパ腫関連傍腫瘍性辺縁系脳炎の1例

A Case of Paraneoplastic Limbic Encephalitis Associated with Malignant Lymphoma Presenting with a Late-onset Bilateral Thalamic Lesion

はじめに

　傍腫瘍性辺縁系脳炎（paraneoplastic limbic encephalitis：PLE）は悪性腫瘍の免疫介在性機序による遠隔効果のため，主に大脳辺縁系が障害される病態と考えられている。悪性リンパ腫関連PLEでは抗神経抗体との関連が示唆される報告がいくつかある。しかし，その病態発症に関する機序や抗体の意義については不明な点が多い。また，悪性リンパ腫関連PLEは画像的特徴として，発症時に海馬や扁桃体など側頭葉内側にMRIで異常信号がしばしば認められる。

　われわれは，び漫性大細胞型B細胞リンパ腫（diffuse large B-cell lymphoma）関連PLEの62歳男性症例を経験した。悪性リンパ腫寛解後も神経症状は進行性であり，免疫療法にも反応は得られなかった。また，治療経過中に側頭葉内側の病変に遅れて両側視床に病変が出現した。本例は，悪性リンパ腫関連PLEとしてはこれまでの報告に比べ治療抵抗性であり，画像所見の経過が特徴的で貴重な症例と考えられたため，ここに報告する。

Abstract

　A 63-year-old man presented with cognitive impairment including disturbance of memory functions and character change. Fluid-attenuated inversion recovery (FLAIR) magnetic resonance (MR) imaging revealed signal hyperintensities in the bilateral medial temporal lobes. Cerebrospinal fluid analysis revealed high protein concentrations, positive results for the oligoclonal band, and a slightly positive result for glutamate receptor ε2 (GluRε2) antibody. Voltage-gated potassium channel (VGKC) antibody was slightly positive in serum. Computed tomography showed enlargement of the left supraclavicular, left axillary, and renal hilar lymph nodes, and ¹⁸F-fluoro-2-deoxy-D-glucose positron emission tomography revealed increased uptake at the same sites. Lymph node biopsy findings were consistent with diffuse large B-cell lymphoma. Based on these findings, the patient was diagnosed with paraneoplastic limbic encephalitis (PLE) associated with malignant lymphoma. The patient received intravenous injection of immunoglobulin and R-CHOP chemotherapy, but his neurological condition deteriorated. MR imaging showed atrophic changes in the medial temporal lobes during immunotherapy and chemotherapy. FLAIR/T2-weighted imaging revealed signal hyperintensities in the bilateral thalami after the first course of R-CHOP chemotherapy. This is the first report of PLE associated with diffuse large B-cell lymphoma presenting with late-onset bilateral thalamic lesions.

（Received: March 14,2011,Accepted: June 8,2011)