Acute myelogenous leukaemia modulated by B12 deficiency: a case with bone marrow blast cell assay corroboration.

A patient is described who appeared to demonstrate modulation of acute myelogenous leukaemia with vitamin B12 deprivation. Support for this observation was obtained via an in vitro bone marrow blast cell assay. The addition of B12 to this patient's bone marrow in vitro significantly stimulated the colony forming ability of the blast cells. Patients with B12 deficiency have an increased incidence of haematopoietic malignancies and excessive replacement of B12 may in some cases have the potential of accelerating such disorders. Intensive B12 replacement in refractory megaloblastic anaemias should be done with caution.