20.粘膜脱症候群とcap polyposis

Mucosal Prolapse Syndrome and Cap Polyposis

要旨　粘膜脱症候群は消化管粘膜の逸脱による慢性的な機械的刺激によって生じる疾患で，直腸や人工肛門近傍に認められる．直腸粘膜脱症候群ではいきみの習慣を認めることが多く，直腸下部前壁に隆起性病変や潰瘍形成がみられる．一方，cappoly posisの成因は不明で，粘血便や粘液下痢を訴えることが多く，しばしば低蛋白血症を認める．直腸からS状結腸が好発部位で，典型例では表面に粘液が付着した多発性広基性病変が半月ひだにそって認められる．従来，両者は類縁疾患と考えられてきたが，臨床症状，内視鏡所見，病理組織所見，治療経過に相違がみられることから，成因が異なる別の疾患である可能性が高い．

　Mucosal prolapse syndrome is thought to occur because of chronic mechanical stimulation, and is often recognized in prolapsing colostomies, prolapsing hemorrhoid, and at the site of the rectum. Patients with mucosal prolapse syndrome of the rectum usually have a habit of straining at defecation, and have polypoid lesions and/or ulcerations at the anterior wall of the lower rectum. On the other hand, the etiology of cap polyposis is still unknown, and patients with cap polyposis usually complain of mucous bloody stool and/or mucoid diarrhea. Hypoproteinemia is often recognized in such cases. In typical cases, multiple sessile polyps are recognized on the apices of the transverse mucosal fold in the rectum and the sigmoid colon. Formerly, both of these diseases have been thought to have similar etiology, but there are many different points between mucosal prolapse syndrome and cap polyposis not only in clinical, endoscopic, and pathological features, but also in clinical responses to certain treatments.

　On the basis of these findings, we consider that cap polyposis is not a manifectation of mucosal prolapse syndrome, but is one of certain new clinical entities and may have a different pathogenesis.