漏斗下垂体炎による中枢性尿崩症と後腹膜線維症を合併した，IgG4関連疾患と考えられる1例

A Case of Possible Immunoglobulin G4-related Disease (IgG4-RD) with Retroperitoneal Fibrosis and Central Diabetes Insipidus due to Infundibulohypophysitis

Ⅰ．緒　　言

　IgG4関連疾患とは，病理組織学的にリンパ球とIgG4陽性形質細胞の著しい浸潤と線維化を特徴とし，臨床的には高IgG4血症や抗核抗体などを認めるとともに，同時性あるいは異時的に全身諸臓器の腫大や結節・肥厚性病変を認める原因不明の疾患である⁴⁾．この疾患の概念が確立されたのはごく最近であり，現在もその病態・治療などについて活発に議論が重ねられている．中枢神経系においても下垂体炎⁹⁾，肥厚性硬膜炎^2,5,6)などの報告があり，われわれ脳神経外科医にとっても無縁の疾患ではない．今回われわれは後腹膜線維症および中枢性尿崩症を伴う漏斗下垂体炎を合併した，IgG4関連疾患と考えられる1例を経験したので，文献的考察を加え報告する．

　We report a case of possible immunoglobulin G4-related disease（IgG4-RD）that resulted in complications such as retroperitoneal fibrosis and infundibulohypophysitis. The patient was a 72-year-old male who presented with polyuria and polydipsia. Magnetic resonance imaging（MRI）revealed a thickened pituitary stalk and contrast enhancement with gadolinium. T1-weighted imaging revealed that the posterior pituitary high-signal zone had disappeared. Central diabetes insipidus was diagnosed on the basis of results of the hypertonic saline test. In addition, pressure due to retroperitoneal fibrosis resulted in hydronephrosis and elevated serum IgG4 levels.

　Because it was determined that the patient could have IgG4-RD, he was administered prednisolone, following which a decrease in the size of the pituitary stalk and retroperitoneal fibrosis was observed.

　IgG4-RD is characterized by elevated serum IgG4 levels and the infiltration of IgG4-positive plasma cells into various organs, including the central nervous system. Recently, IgG4-RD research teams organized by the Ministry of Health, Labour and Welfare established guidelines for the diagnosis of IgG4-RD. According to these guidelines, this case would fall under the category of “possible IgG4-RD.”

　This case suggested that when infundibulohypophysitis is detected by neuroradiology, further investigation into the possibility of IgG4-RD should be recommended.