2) アミロイドーシス

Characteristic Small Intestinal Lesions in Patients with Amyloidosis

要旨　全身性アミロイドーシスのうち消化管への親和性が高く臨床上遭遇する機会が多いのはAL型とAA型アミロイドである．小腸は最も高頻度かつ高度にアミロイドが沈着する部位であるが，両者は沈着様式の相違により形態学的に異なる特徴的な所見を呈する．すなわち，AL型では粘膜筋板と粘膜下層，固有筋層に塊状沈着を生じるため，Kerckringひだの肥厚と粘膜下腫瘤様の小隆起の多発が特徴的である．一方，AA型では粘膜固有層と粘膜下層の血管壁に沈着するため，絨毛構造に変化を生じ典型例では微細顆粒状隆起が多発する特徴的な粗ぞうな粘膜像を呈してくる．近年，カプセル内視鏡とダブルバルーン小腸内視鏡の登場による小腸疾患診断学の向上は目覚しいが，びまん性小腸疾患の診断に際しては，全体像が見渡せるX線検査はいまだ簡便かつ有用であり，消化器医としてはそのX線学的特徴を知っておくことは重要と思われる．

　Radiographic and endoscopic findings of the small intestine concerning which lesion is most frequently the site of amyloid deposit, have revealed considerable differences between amyloid protein type AA and AL. In patients with primary amyloidosis (type AL), there are polypoid protrusions and invariable thickening of the folds, which reflect massive amyloid deposits in the muscularis mucosa, submucosa and muscularis propria. On the other hand, in cases of secondary amyloidosis(type AA), a mucosal pattern with innumerable fine granular elevations is evident, which correlates with expansion of the amyloid deposits in the lamina propria.

　Recently, progression and wider use of double balloon endoscopy and capsule endoscopy enable the diagnosis and treatment of various kinds of small intestine diseases. However, small bowel radiography has been more useful and necessary in cases of diffuse inflammatory diseases in the small intestine such as amyloidosis.