Myelodysplastic syndromes: a study of 101 cases according to the FAB classification

The myelodysplastic syndromes (MDS) are a group of closely related disorders characterized by chronic cytopenias with cellular marrow, poor prognosis and refractoriness to treatment. We studied 101 consecutive cases of MDS diagnosed over a 7-year period. Peripheral blood (PB) and bone marrow (BM) samples were reviewed and classified according to the proposals of the French-American-British (FAB) cooperative group for MDS. The combined analysis of the initial laboratory features and qualitative haematological abnormalities readily allowed the distinction between the different subgroups. Thirty-two of 79 cases (40.5%) evolved towards other diseases, frequently acute leukaemia (24/79, 30%), or transformed into other MDS (7/79, 9%). In five cases, initially classified as refractory anaemia (RA) or refractory anaemia with ring sideroblasts (RAS), a transitory change to another type of MDS--two chronic myelomonocytic leukaemias (CMML), two refractory anaemias with excess of blasts (RAEB) and one refractory anaemia with excess of blasts 'in transformation' (RAEB-t)--was observed before the evolution towards acute leukaemia. This provides a new link between all these syndromes and increases the number of transitions to other MDS. Overall prognosis was very poor, with differences between subgroups. RA had the best prognosis whereas RAEB-t had the worst one. This study shows that the FAB classification is readily usable and defines well-characterized subgroups of MDS, although there are frequent transitional forms, and as the natural history of the MDS unfolds they may convert into another. The actual poor prognosis and the frequent evolution towards acute leukaemia makes necessary to investigate new methods of treatment for these disorders.