Heterogeneity of acquired idiopathic sideroblastic anaemia (AISA)

Clinical, haematological and outcome data were studied in 84 patients with acquired idiopathic sideroblastic anaemia (AISA) from a registry of 613 consecutive myelodysplastic syndromes (MDS) recorded by five institutions in western France. Two groups could be identified and compared: 'pure' erythroblastic AISA (AISA-E: 59 pts), and AISA with myelodysplastic features, i.e. dysgranulo and/or dysmegakaryopoiesis (AISA-M: 25 pts). Results were also compared to those of a series of 71 cases of refractory anaemia without sideroblastosis (RA) carried out from the same registry. Dyserythropoiesis was present in 90% of all AISA subtypes, dysgranulopoiesis in 88% of the AISA-M cases; dysmegakaryopoiesis was observed in 44% of AISA-M. Ten patients with both forms of AISA showed high platelet counts. These cases appeared particular in that four of them were associated with a splenomegaly and/or a hyperleucocytosis. They had to be distinguished from myeloproliferative syndromes. Outcome comparison of AISA-E with AISA-M showed a significant discrepancy of survival duration (60 vs 38 months respectively). Progression towards refractory anaemia with excess of blasts or acute leukaemia, was significantly higher for AISA-M than for AISA-E. The risk of transformation increased to 24% for the AISA-M group similarly to those of RA patients (17%). We conclude that AISA must be divided into two categories, 'pure' AISA and AISA-M, because survival duration and risk of transformation are different.