Diagnostic and biological significance of sideroblastic erythropoiesis in the myelodysplastic syndromes.

We retrospectively reviewed clinical and hematologic features of nine patients with acquired idiopathic sideroblastic anemia (AISA). Seven of them had ringed sideroblasts (RS) more than 15% of marrow nucleated cells. RS persisted in the marrow even in the remaining two patients who had a relatively low marrow erythroblasts despite RS ranging from 1/4 to half of the marrow erythroid series. However, RS declined in proportion in another two patients of the nine whose disease progressed to refractory anemia with excess of blasts (RAEB), although a high proportion of RS reappeared in one patient at the time of relapse following allogeneic marrow transplantation. A similar decline of RS concomitant with disease progression was also seen in seven additional patients with RAEB or RAEB in transformation (RAEB-t) with sideroblastic erythropoiesis. Cytogenetic abnormalities, although rare initially, became detectable either at the time of disease progression or at the worsening of anemia in AISA. These observations suggest that the majority of AISA fall in the category of myelodysplasia, and that a progressive decline in RS is part of the natural history of myelodysplasia. Closer follow-up of the proportion of RS in patients with AISA is warranted to better understand its biologic significance.