Transient Selective Vitamin B_12 Malabsorption in an Adult

Abstract

An elderly Puerto Rican male presented with megaloblastic anemia. The only abnormality found was an isolated inability to absorb cyanocobalamin. The absorption defect was not corrected by addition of human or hog intrinsic factor or human small bowel juice. Intrinsic factor production, intestinal flora and a variety of absorption tests were normal, as were repeated small bowel biopsies and X-rays of the intestinal tract. There was no evidence for the presence of tropical sprue now or in the past. Transient remission occurred during corticosteroid therapy and, spontaneously, after 18 months of observation. An acquired derangement of ileal mucosal receptor sites for vitamin B-12-intrinsic factor complex is postulated, similar to the congenital vitamin B-12 absorption defect described in children.