无法产生胃酸。最常由胃萎缩引起。胃萎缩（伴有或不伴有自身免疫性胃炎）存在于约 15% 的老年人中，且被认为是由幽门螺杆菌感染引发。
Professor of Medicine and Physiology
Virginia Commonwealth University Health System
Chief of Gastroenterology
MLS is an author of several studies referenced in this monograph.
Dr Mitchell L. Schubert would like to gratefully acknowledge Dr Juan Diego Baltodano, a previous contributor to this monograph. JDB declares that he has no competing interests.
Professor of Medicine
David Geffen School of Medicine at UCLA
JP declares that he has no competing interests.
Associate Professor of Gastroenterology and Internal Medicine
Medical University of Graz
University Hospitals Graz
HFH has been reimbursed by Astra Zeneca, Nycomed, and Janssen, the manufacturers of proton-pump inhibitors, for attending several conferences and speaking, and has been paid by Astra Zeneca for running educational programs.