下垂体腺腫に極めて類似したMRI像を呈したリンパ球性下垂体炎の1症例

A Case of Lymphocytic Hypophysitis Mimicking Pituitary Macroadenoma

Ⅰ．はじめに

　リンパ球性下垂体炎は，下垂体組織にリンパ球が浸潤し腫瘤を形成する疾患で，MRI上，しばしば下垂体腺腫との鑑別が非常に困難である^{1,3,10,11,13,16,22,27)}．今回われわれは，妊娠後期に視野障害で発症し，MRIにて非機能性下垂体腺腫と術前診断したリンパ球性下垂体炎の1例を経験した．本症例を提示し，本疾患を念頭に置くべき状況や治療方針について考察を加えたので報告する．

Lymphocytic hypophysitis is a rare autoimmune disease of the pituitary gland mimicking pituitary macroadenoma on magnetic resonance imaging (MRI).

　We encountered a 32-year-old female who presented with a typical pituitary macroadenoma causing sudden onset of visual disturbance during her second pregnancy. She underwent an endonasal-transsphenoidal resection of the mass diagnosed as a non-secreting pituitary macroadenoma after a cesarean operation. Intraoperatively,the lesion was found to be extremely tough and mucinous,and apparently differed from pituitary adenoma. The frozen section revealed hypophysitis and we performed only a biopsy of the mass. Histopathological examination showed diffuse infiltrate of non-specific lymphocytes. Postoperatively,prednisolone was given for two weeks,her visual disturbance improved with radiologically marked shrinking of the lesion.

　This case illustrates the difficulty of differentiation of lymphocytic hypophysitis from pituitary macroadenoma,and we discuss the clinical features and the management of this disease.