アミロイドーシスの十二指腸病変

Characteristic Duodenal Lesions in Patients with Amyloidosis

要旨　消化管はアミロイド沈着の好発臓器であり，なかでも十二指腸・小腸は最も沈着の高度な部位である．また，アミロイドーシスの沈着様式はアミロイド蛋白別に特異性がみられ，蛋白ごとに形態学的変化と臨床徴候の差異が認められる．すなわちAAでは粘膜固有層と粘膜下層血管壁が沈着の主体となり，十二指腸に微細顆粒状の粗糙な粘膜が観察される．ALでは粘膜筋板と粘膜下層，固有筋層への塊状沈着がみられ，粘膜下腫瘤様隆起の多発とKerckringひだの肥厚が認められる．Aβ₂Mでは固有筋層への多量沈着が，ATTRでは自律神経節への沈着が強く，両者とも粘膜の形態学的変化は乏しい．これらの所見と鑑別を要する疾患には，糞線虫症，イソスポーラ症，immunoproliferative small intestinal disease，リンパ管拡張症などが挙げられるが，各疾患の十二指腸の組織像には差異が認められる．アミロイド蛋白別の十二指腸における形態学的特徴を知るとともに，鑑別すべき疾患との組織像の違いを考慮することが，診断を行う上で重要と考えられた．

　Clinicopathologic findings of duodenal lesions were investigated in patients with amyloidosis according to the chemical type of amyloid proteins. Radiographic and endoscopic examination of the duodenum revealed considerable differences between amyloid proteins. In case of amyloid A protein (AA), there was a coarse mucosal pattern with innumerable fine granular elevations, which reflected expansion of the lamina propria by amyloid deposits. Polypoid protrusions and invariable thickening of the folds were evident in cases of light chain protein (AL), correlating with massive amyloid deposits in the muscularis mucosa, submucosa and muscularis propria. In cases of β₂-microglobulin (Aβ₂M), marked dilatation of the duodenum was seen, indicating extensive amyloid deposits in the muscularis propria. In cases of Atypical transthyretin (ATTR), there was marked delay in transit time because of the significant amount of amyloid deposits in the nerves of the gastrointestinal tract. Characteristic radiographic and endoscopic changes due to the amyloid deposits of each chemical type can be detected easily in the duodenum.

　In addition, to the above comparisons, we demonstrated the morphological differences in the duodenum between amyloidosis and other intestinal diseases such as strogyloidiasis, isosporiasis, immunoproliferative small intestinal disease and intestinal lymphangiectasia.