多発胃神経内分泌腫瘍を契機に診断された壁細胞機能不全症の1例

Parietal Cell Dysfunction in a Patient with Multiple Gastric Neuroendocrine Tumors：Report of a Case

要旨●患者は40歳代，男性．検診の上部消化管X線造影検査で異常を指摘され，近医で上部消化管内視鏡検査（EGD）を施行し，多発胃隆起性病変を指摘された．当科でのEGDでは，背景胃粘膜に萎縮はなく，胃底腺領域に多発するWGA（white globe appearance）を認めた．胃底腺領域に多発する上皮下病変があり，生検で胃神経内分泌腫瘍（NET）の診断を得た．血液検査で高ガストリン血症を認めたが，腹部造影CTでは胃NET以外に腫瘍性病変の指摘はなく，24時間胃内pHモニタリングで胃酸分泌不全が証明された．背景粘膜組織のH^＋/K^＋-ATPaseの免疫組織化学染色ではα-subunit陰性であったことを合わせて，壁細胞機能不全症に合併した多発胃NETの診断に至った．

　We present a patient with parietal cell dysfunction（PCD）and multiple gastric neuroendocrine tumors（NETs）found during a routine health checkup to highlight that PCD should be considered in the differential diagnosis of multiple gastric NETs with unknown etiology. A 40-year-old man was referred to our hospital for the assessment of multiple gastric polyps found by esophagogastroduodenoscopy during a health checkup. He was negative for anti-Helicobacter pylori antibodies and had no history of eradication therapy. Esophagogastroduodenoscopy revealed multiple reddish subepithelial tumors, and the biopsy examination led to the definitive diagnosis of NETs. No atrophy was observed in the background gastric mucosa, whereas white globe appearance was noted in the gastric fundus. Additional testing performed to determine the NET etiology revealed a serum gastrin level of 5992pg/mL, whereas he was negative for antiparietal cell and anti-intrinsic factor antibodies. Moreover, 24-h intragastric pH monitoring revealed achlorhydria despite a negative history of proton pump inhibitor use. Immunohistochemical staining of the background mucosa demonstrated parietal cells to be negative for α-subunit and weakly positive for the β-subunit of H^＋/K^＋-ATPase expression. These findings strongly suggested PCD. Distal gastrectomy was performed due to presence of a NET larger than 10mm in diameter.