Two cases of intrinsic factor deficiency with normal hydrochloric acid production are presented. Both patients had markedly reduced intrinsic factor secretion and substantial titers of type I (blocking) intrinsic factor antibodies. No parietal cell antibodies were recognized by immunofluorescence in either case. Three hypotheses are offered to explain these findings: (a) These patients have congenital intrinsic factor deficiency that remained in the preanemic phase until adulthood; (b) they have pernicious anemia detected at a stage before gastric mucosal atrophy and achlorhydria have occurred; or (c) they represent cases of a new syndrome characterized by isolated intrinsic factor deficiency.
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