Intrinsic factor deficiency in adults with normal hydrochloric acid production

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.