Coexistence of pernicious anaemia and chronic myeloid leukaemia: an experiment of nature involving vitamin B12 metabolism.

Abstract

Summary. Chronic myeloid leukaemia (CML) and pernicious anaemia (PA) coexisted in a 51‐yr‐old man (who also had myasthenia gravis). His serum vitamin B12 level was normal instead of the high value expected in CML, or the low value expected in PA. Short‐term culture of his peripheral blood cells showed deranged DNA synthesis of the type observed in vitamin B12 deficiency, indicating that his ‘normal’ serum vitamin B12 level was not associated with normal amounts of vitamin B12 available to his CML cells. A tracer dose of 0.45 μg of[57 Co]vitamin B12 disappeared abnormally slowly from his serum over 24 hr (as previously observed by others in patients with either CML or PA). A therapeutic injection of vitamin B12 appeared to disappear abnormally slowly from his serum over a period of 2 yr. His serum showed a markedly elevated unsaturated vitamin B12 binding capacity, with a less sharp increase in percentage of vitamin B12 binding α as compared to β globulin than usually expected in CML.Withholding therapeutic vitamin B12 for 2 yr has been associated with stabilization of his WBC at the 40 000‐50 ooo/μl range. Although this association could be chance rather than cause and effect, the patient does represent an ‘experiment of nature’ involving vitamin B12 metabolism and does raise the question as to whether his leukaemia is retarded by his deficiency of vitamin B12, which results from inadequate absorption of vitamin B12 and possibly from elevated serum vitamin B12 binding a globulin rendering his circulating vitamin B12 metabolically inert.