Sideroblastic anaemia with reactive thrombocytosis versus myelodysplastic/myeloproliferative disease.

The reported incidence of thrombocytosis among cases of refractory anaemia with ring sideroblasts (RARS) may be as high as 15%. We report four additional cases of this association, which appear to be hematologically heterogeneous. One patient clearly represents a case of RARS with reactive thrombocytosis. Two cases have features suggestive of the coincidental occurrence of essential thrombocythemia and RARS. The fourth case could be best classified as a subtype of myelodysplastic/myeloproliferative disease unclassifiable (MDS/MPD U). Only new biological or molecular markers will allow better differentiation between these disorders.