High risk myelodysplastic syndrome coexistent with chronic lymphocytic leukemia for more than 9 years: inhibition of the myeloid clone by the lymphoid clone?

We describe a patient in whom the concomitant diagnosis of refractory anemia with excess of blasts (16% on initial marrow examination) and chronic lymphocytic leukemia was made more than 9 years ago. The myeloid clone showed a complex karyotypic abnormality. Evolution has so far been remarkably stable, without transformation into acute leukemia. Clonogenic assays showed that patient's serum inhibited the patient's own granulocyte-macrophage colony-forming units (CFU-GM). This inhibition was also present for a control subject's CFU-GM and acute myeloid leukemia clonogenic cells. This raises the problem of a down-regulation of the myeloid clone by the malignant lymphoid clone in this patient, and the possible mechanisms for this are discussed.