Mielodysplastic syndromes (MDS) are clonal disorders of the hemopoietic stem cell. About one third of the cases terminate in an acute leukemia, usually acute myeloblastic leukemia. However, few cases of transformation into acute lymphoblastic leukemia (ALL) have been described. We present a case of refractory anemia that transformed into ALL two months after diagnosis and was successfully treated with conventional chemotherapy. Two years later a hyperfibrotic form of MDS was detected in the patient, that soon after terminated in acute megakaryoblastic leukemia. The course of MDS in the present case provides evidence that MDS can involve a pluripotent stem cell, presenting clonal evolution, documented by successive changes in its clinical and hematological features.