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

Background-The common but incompletely understood entity of malabsorption o f food bound cobalamin is generally presumed to arise from gastritis and/or achlorhydria. Aim-To conduct a systematic comparative examination of gastric histology an d function. Subjects-Nineteen volunteers, either healthy or with low cobalamin levels, were prospectively studied without prior knowledge of their absorption or g astric status. Methods-All subjects underwent prospective assessment of food cobalamin abs orption by the egg yolk cobalamin absorption test, endoscopy, histological grading of biopsies from six gastric sites, measurement of gastric secretor y function, assay for serum gastrin and antiparietal cell antibodies, and d irect tests for Helicobacter pylori infection. Results-The six subjects with severe malabsorption (group I) had worse hist ological 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 peps in secretion overlapped considerably between individual subjects in group I and group III. Two distinct subgroups of three subjects each emerged withi n group I. One subgroup (IA) had severe gastric atrophy and achlorhydria. T he other subgroup (IB) had little atrophy and only mild hypochlorhydria; th e gastric findings were indistinguishable from those in many subjects with normal absorption, Absorption improved in the two subjects in subgroup IB a nd 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 ant ibiotics. Conclusions-Food cobalamin malabsorption arises in at least two different g astric settings, one of which involves neither gastric atrophy nor achlorhy dria. Malabsorption can respond to antibiotics, but only in some patients. Food cobalamin malabsorption is not always synonymous with atrophic gastrit is and achlorhydria, and hypochlorhydria does not always guarantee food cob alamin malabsorption.