2)透析アミロイドーシス

Dialysis-related Amyloidosis

　透析アミロイドーシスの進行例では，β₂-ミクログロブリンアミロイドの沈着により消化管障害を来すことが報告されている．今回，筆者らは初めて52例(剖検例42例，生検・切除例10例)という多数例を用いて，透析アミロイドーシスにおける消化管病変を検討した．剖検例での消化管アミロイド沈着は 81％(34例)にみられ，その程度と透析期間との間には，有意な相関が認められた．アミロイド沈着の頻度は，胃74％，小腸74％，大腸76％ で各臓器間で差がなかった．アミロイド沈着は，初期では粘膜下層の主に中小動脈の血管壁にみられた．進行期では固有筋層，特に結腸紐の筋細胞間に沈着が高度で，漿膜下層の血管壁(主に中型静脈壁)にも沈着が認められた．しかし，粘膜内のアミロイド沈着は12％ と低率で，粘膜筋板に限局し巣状で軽度のことが多く，内視鏡的に粘膜異常は捉えられなかった．経過中に，麻痺性腸閉塞を3例、低栄養状態を2例，虚血性大腸病変を3例に認め，これらのうち虚血性病変の 2例を除く6例では，固有筋層のアミロイド沈着が高度であった．

　Dialysis-related amyloidosis affects predominantly the osteoarticular system, but subsequently, gastrointestinal involvement also occurs. We studied 52 patients with dialysis-related amyloidosis to evaluate the prevalence and the clinicopathological characteristics of gastrointestinal amyloidosis. Of 42 autopsy cases, 34(81 ％)had amyloid deposits in the gastrointestinal tract. The degree of amyloid deposition tended to increase significantly with time on dialysis. We found no difference in the prevalence of amyloid deposition in the stomach, small intestine, and large intestine. Thirty-two(76％)cases showed mild to severe amyloid deposition in the submucosal vessel walls. Because only 5(12％)cases revealed subtle amyloid deposition in the muscularis mucosa, we were unable to identify gastrointestinal amyloidosis endoscopically. In 5 cases with gastrointestinal complication of the paralytic ileus or malnutrition, massive amyloid deposition in the proper muscle, especially the teniae coli was observed extensively. Three patients underwent emergency colectomy due to necrotic ischemic colitis with moderate vascular amyloid deposition.