十二指腸偽メラノーシスの1例

Pseudomelanosis Duodeni, Report of a Case

要旨　患者は71歳，女性．高血圧症と糖尿病，蛋白尿にて外来通院中，体重減少とCEAの軽度上昇を来し，精査施行．上部消化管透視，注腸透視ともに異常なく，内視鏡検査にても食道・胃には特記すべき所見はなかったが，十二指腸球部に限局して褐色の小粒状色素沈着をびまん性に認めた．粘膜自体には異常なく，生検では粘膜固有層に散在する色素沈着がみられ，H・E染色で黒褐色に染まる集塊を形成，Fontana-Masson染色では黒色陽性に染色された．これらの点から十二指腸偽メラノーシスと診断した．文献上本邦での報告例はなく，海外での報告例を検討すると，女性に多く，降圧剤服用中の高血圧症や腎疾患の合併例が多いなどの特徴がみられ，興味深い．

　A 71-year-old woman with hypertension, diabetes mellitus, and proteinuria underwent several examinations of the gastrointestinal tract because of her body weight loss and elevated CEA titer. Findings of physical examinations were almost normal except for systolic hypertension (160/70). The color of skin and oral cavity seemed normal. Laboratory data (Table 1) revealed hyperglycemia, hypoproteinemia, proteinuria and hypercholesterolemia. All of these were explained by her concomitant medical problems. Both upper gastrointestinal fluoroscopy and barium enema showed normal findings. By endoscopy, no significant lesion was found on the mucosa of the esophagus and stomach (Fig. 1). However, numerous spots, pigmented brown, were seen on the mucosa of the bulbus duodeni (Fig. 2). The pigmetation was restricted to the bulbus, and the descending part of the duodenum was intact (Fig. 3 a).

　A biopsy specimen, obtained from the bulbus, showed pigment depositions in the lamina propria, forming a few focuses (Figs. 4, 5). The pigmented area was stained dark brown by routine hematoxylin-eosin method. The histochemical characteristics were; nega-tive for iron staining, for PAS staining, and positive (black) for Fontana-Masson method (Fig. 6).

　These endoscopic appearances and histological characteristics suggest that this pigmentation is a manifestation of so-called “pseudomelanosis duodeni”.

　As far as we know, 9 cases of this disease have been reported abroad (Table 2), but no report has been published in Japan. According to these foreign reports, this disease is usually found in middle- or high-aged women with complications of renal diseases or hypertension treated with antihypertensive drugs. The backgrounds of such patients are interesting, and may give us clues to clarify the pathogenesis of this disease.