Cytogenetic and cytochemical studies on progenitor cells of primary acquired sideroblastic anemia (PASA): involvement of multipotent myeloid stem cells in PASA clone and mosaicism with normal clone.

By cytogenetic and cytochemical analyses of individual hematopoietic colonies, we investigated clonality in progenitor compartments of primary acquired sideroblastic anemia (PASA). Two of our four subjects had reduced but countable numbers of CFU-E, BFU-E, and GFU-GM in methylcellulose culture. In one patient with cytogenetic abnormality of 47, XX, +8 in 67% of the bone marrow cells, cytogenetic analysis of individual erythroid bursts and granulocyte/macrophage colonies demonstrated two populations with and without 8 trisomy, the trisomy clone being 38% in BFU-E and 50% in CFU-GM. These findings indicate involvement of multipotent stem cells in PASA clone and mosaicism of two distinct populations in erythroid as well as granulocyte/macrophage progenitor compartments, the abnormal PASA clone and probably the normal clones. In another case with no cytogenetic abnormality, repeated iron staining showed that 31% to 40% of CFU-E and 25% to 54% of BFU-E had erythroblasts with heavy iron deposits. An ultrastructural analysis of 25 individual erythroid bursts revealed that 32% had highly dysplastic erythroblasts with marked ferruginous iron accumulation in the mitochondria. The other 68% and 15 normal bursts from a healthy control did not have noticeable dysplastic changes and iron deposits in the mitochondria. This cytochemical/ultrastructural mosaicism seems to be compatible with the cytogenetic mosaicism. However, whether the BFU-E derived from abnormal PASA clone selectively manifest iron accumulation in the mitochondria or whether the PASA clone itself shows variable degrees of abnormal iron metabolism remains to be determined by simultaneous performance of ultrastructural and cytogenetic analysis for single bursts.