Failure to thrive, generalized malabsorption, and pernicious anemia caused by cyanocobalamin deficiency occurred in a child. There was a beneficial hematologic response and improvement in the malabsorption phenomena following parenteral administered cyanocobalamin. However, a selective defect in cyanocobalamin absorption persisted. Studies related to intrinsic factor activity included abnormal results of Schilling tests which were not corrected by the administration of exogenous intrinsic factor or small intestinal juice. However, intrinsic factor activity was present in the patient's gastric juice as demonstrated by in vitro and in vivo assays. These findings suggest that patients with the Imerslund-Gräsbeck syndrome have a cyanocobalamin deficiency caused by a specific defect in the small intestinal mucosa metabolism of the intrinsic factor-cyanocobalamin complex. Cyanocobalamin deficiency may occasionally be associated with generalized malabsorption.
Walters TR, Koch HF. Generalized Malabsorption, Failure to Thrive, and Megaloblastic Anemia. Am J Dis Child. 1972;124(5):766-768. doi:10.1001/archpedi.1972.02110170144025