ABSTRACT
Serum vitamin B12 and vitamin B12 binding proteins (Transcobalamin, TC) were determined in 11 patients with polycythemia vera (PV) and each patient with PV asso ciated with multiple myloma (PV/MM) and acute myelomonocytic leukemia (PV/AMML). The study was also performed on 60 normal subjects for comparison Serum vitamin B12 level and total vitamin B12 binding capacity (TBBC) were found to be significantly increased while serum unsaturated vitamin B12 binding capacity (UBBC) was slightly but not significantly higher than that of normal subjects. Both TCI and TCIII in creased 2 and 4 fold, respectively, while TCII decreased to haft the value of the normal level. This resulted in the alteration of the ratio of TCI/TCIII from 1.34 in normal subjects to 0.75 in these patients. This finding is quite specific for PV, because another 2 patients with PV associated with MM and AMML also showed a similar TCI/TCIII ratio. Although increased serum vitamin B12 UBBC, TCI and TCIII are also found in some patients with myeloproliferative disorders and leucocytosis, in no situation is it characterized by a predominantly increased TCIII with a reverse ration of TCIII/TCI as in PV. Therefore, the assay of serum vitamin B12 UBBC and TC should be a useful tool in the confirmed diagnosis of PV.