Myelodysplastic syndromes are relatively frequent, with a distinct predominance in elderly subjects. They are characterized by a disorder of myeloid precursor cell maturation, which explains the presence of blood cytopenia responsible for clinical manifestations (anaemia, infection, haemorrhage). Beside cytopenia, the main risk is transformation into acute myeloid leukaemia. As a rule, these diseases are easily recognized by the conjunction of blood count and bone marrow aspirate. Apart from the intensive therapy prescribed for myelodysplastic syndromes in young subjects, treatments seldom have beneficial effects and are still symptomatic in most cases.