TCN1 and chronic myelogenous leukemia, BCR-ABL1 positive: Elevated serum vitamin B12 levels can be caused by underlying clinical conditions such as liver disease, where hepatocyte damage leads to release of stored B12 into circulation, or myeloproliferative disorders such as chronic myeloid leukemia, where increased levels of haptocorrin-bound B12 are observed (23, 44).