[Selective vitamin B 12 malabsorption in a 19-year-old patient].

Selective malabsorption of vitamin B12, or Imerslund-Gräsbeck disease, is a rare congenital condition. The normal ileal uptake of intrinsic-factor-bound vitamin B12 is deficient. Inheritance is autosomal recessive. Megaloblastic anemia generally appears in infancy and is usually accompanied by mild proteinuria. The case is presented of a 19-year-old woman with megaloblastic anemia due to selective vitamin B12 malabsorption. As far as we know this is the only patient in whom the disease appeared so late. Of special interest are also the marginally low Schilling tests of the patient's parents. Further conditions which may lead to vitamin B12 deficiency are also discussed. A hypothesis is put forward concerning the late appearance of the disease in this particular case. Pathophysiologic, nephrologic and genetic aspects of selective vitamin B12 malabsorption are briefly reviewed.