[Anemia with low serum cobalamin concentration. Problems of differential diagnosis]

We reviewed the records of seven patients with low serum cobalamin levels that were difficult to interpret in relation to haemoglobin concentrations and clinical symptoms. Myelodysplastic syndrome was diagnosed in four out of five anaemic patients. Three of them had a true vitamin B12 deficiency at the same time. The fifth patient had a non-Hodgkin lymphoma with Coombs-negative autoimmune haemolytic anaemia. Two patients had low cobalamin levels without anaemia. Measurements of plasma homocysteine and serum methylmalonic acid may be useful for diagnosing true vitamin B12 deficiency.