A 2 year old girl with a megaloblastic anemia secondary to B12 deficiency was presented. The mechanism appeared to be a specific inability to absorb vitamin B12 from the small bowel in the absence of any other functional disability.
Evidence of absorption of vitamin B12 was obtained when intestinal juice from a normal patient was administered with the test dose of vitamin B12. This evidence consisted of (1) an increased urinary excretion of the test dose (positive Schilling test), (2) a decreased fecal excretion of the labelled B12 and (3) the presence of significant counts over the liver (positive Glass test).
A generalized malabsorption can only be totally and absolutely disproven by testing over many years. It is considered more probable, however, that this patient lacks an intestinal factor required for the absorption of vitamin B12.