The population was compartmentalized according to three factors: age (child [4 years old], youth [5 to 14 years old], and adult [[is greater than or equal to] 15 years old]); infection state (uninfected and infected); and clinical state (normal stomach, antrum-predominant gastritis, corpus-predominant gastritis, DU, chronic atrophic gastritis
[CAG], and GC) (Appendix).
A number of risk factors have been identified and include familial adenomatous polyposis, gastric adenomas or high grade dysplasia, chronic atrophic gastritis
, Helicobacter pylori infection, pernicious anemia and tobacco smoking.
Chronic atrophic gastritis
may have pathologic characteristics such as gland dropout and precancerous changes.
Composite gastric carcinoma and precursor lesions with amphicrine features in chronic atrophic gastritis
However, in the majority of cases, chronic atrophic gastritis
is not the result of an autoimmune disease, but is caused by a Helicobacter pylori infection, which has a more uncertain relation to cobalamin deficiency (11-13).