Vitamin B12 metabolism in myelomatosis

In 38 patients with myelomatosis the serum cobalamin varied from 34 pmol/1 to 404 pmol/1, median 181.5 pmol/1, which is significantly lower than the levels in 22 control persons with range 173-535 pmol/1, median 265 pmol/1. In spite of low serum cobalamin no symptoms of vitamin B12 deficiency could be demonstrated in any of the patients, except for the one patient who had a serum cobalamin of 34 pmol/1. Mean values for Hb, MCV, PCV, serum lactate-dehydrogenase, adjested red cell folate and nucleated neutrophil count were similar in a group of patients with a serum cobalamin below 160 pmol/1 and a group of patients with higher serum cobalamin values. The decrease in serum cobalamin is due in part to a reduction in the major cobalamin binder (TC-I) in serum. Measuring serum cobalamin in relationship to gastric acis secretion, we found a significantly higher frequency of hypo- and achlorhydria in patients with serum cobalamin below 160 pmol/1 although the intestinal absorption of vitamin B12 was normal by a Schilling test. Although our finding of low saturation of TC-I in serum seems to demonstrate decreased vitamin B12 content in the body in myelomatosis, the lack of evidence for a functional vitamin B12 deficiency speaks against giving a supplement to patients with myelomatosis.