Small-Intestinal Function in Vitamin B₁₂ Deficiency

Intestinal function was studied in 28 patients with untreated pernicious anemia and no clinically apparent intestinal disease. The absorption of xylose was impaired in 29% of these patients; fat, in 9%; and vitamin B12 given with intrinsic factor, in 75%. Xylose malabsorption was more common in patients with severe hematologic depression; it was generally reversible within 2 to 3 weeks of beginning vitamin B12 therapy. In most patients cyanocobalamin absorption returned to normal within 1 to 8 weeks. In four patients cyanocobalamin absorption remained subnormal after 4 to 41 months of vitamin repletion. In two of these patients tetracycline therapy rapidly reversed the vitamin B12 malabsorption. The remaining two patients had high titers of serum antibodies to intrinsic factor. Reversible impairment of intestinal absorptive capacity is commonly associated with vitamin B12 deficiency. Abnormalities shown in absorption tests done within 2 months of initiating therapy in patients with pernicious anemia do not necessarily reflect primary small-intestinal disease.