Heterogeneity of gastric histology and function in food cobalamin malabsorption: absence of atrophic gastritis and achlorhydria in some patients with severe malabsorption

Background-The common but incompletely understood entity of malabsorption of food bound cobalamin is generally presumed to arise from gastritis and/or achlorhydria. Aim-To conduct a systematic comparative examination of gastric histology and function. Subjects-Nineteen volunteers, either healthy or with low cobalamin levels, were prospectively studied without prior knowledge of their absorption or gastric status. Methods-All subjects underwent prospective assessment of food cobalamin absorption by the egg yolk cobalamin absorption test, endoscopy, histological grading of biopsies from six gastric sites, measurement of gastric secretory function, assay for serum gastrin and antiparietal cell antibodies, and direct tests for Helicobacter pylori infection. Results-The six subjects with severe malabsorption (group I) had worse histological scores overall and lower acid and pepsin secretion than the eight subjects with normal absorption (group III) or the five subjects with mild malabsorption (group II). However, histological findings, and acid and pepsin secretion overlapped considerably between individual subjects in group I and group III. Two distinct subgroups of three subjects each emerged within group I. One subgroup (IA) had severe gastric atrophy and achlorhydria. The other subgroup (IB) had little atrophy and only mild hypochlorhydria; the gastric findings were indistinguishable from those in many subjects with normal absorption, Absorption improved in the two subjects in subgroup IB and in one subject in group II who received antibiotics, along with evidence of clearing of H pylori. None of the subjects in group IA responded to antibiotics. Conclusions-Food cobalamin malabsorption arises in at least two different gastric settings, one of which involves neither gastric atrophy nor achlorhydria. Malabsorption can respond to antibiotics, but only in some patients. Food cobalamin malabsorption is not always synonymous with atrophic gastritis and achlorhydria, and hypochlorhydria does not always guarantee food cobalamin malabsorption.