Multiple myeloma involving the stomach with vitamin B12 deficiency

Involvement of the gastrointestinal tract by plasmocytoma is rare. In a 78-year-old man with IgA lambda multiple myeloma stage IIIB, the evaluation of a megaloblastic anaemia revealed a subnormal vitamin B12 level. Urinary excretion of isotope-labelled vitamin B12 was reduced. Tests for gastric parietal cell and intrinsic factor antibodies were negative. There were no clinical signs of an insufficient absorption in the ileum. Biopsy specimens of the stomach showed a dense, diffuse infiltrate of malignant plasma cells in the lamina propria of fundus and corpus. A urease test for Helicobacter pylori was positive. There was a minor haematological improvement when vitamin B12 was given parenterally. Several combinations of cytostatic drugs had no effect on the manifestations of the multiple myeloma. In our patient the vitamin B12 deficiency may be related to a displacement or destruction of parietal cells by malignant plasma cells.