Preleukaemia and myelodysplastic syndromes today.

The clinical picture of myelodysplastic syndromes (MDS) results from the expansion of an abnormal clone of haemopoietic stem cells that has undergone premalignant transformation. Different types of "oncogene" may be involved in this process, some of which code for growth factors and their receptors, some for membrane or cytoplasmic proteins and some for nuclear binding proteins. The insults causing gene mutations are not known, though chemical, viral or radiation damage could be important. The most striking feature of MDS is the inadequate production of dysplastic, poorly functional cells as a result of impaired differentiation and premature cell death in the bone marrow. Treatment is currently directed to supportive therapy with blood components and antibiotics, attempts to stimulate proliferation and differentiation with recombinant human growth factors, and, in a few cases, bone marrow transplantation. Chemotherapy alone has met with little success.