Sequential karyotypic evolutions and bone marrow aplasia preceding acute myelomonocytic transformation from myelodysplastic syndrome

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Abstract
Serial hematopathological and cytogenetic studies disclosed 3 distinct clinical phases in a case of refractory anemia (RA), a subtype of myelodysplastic syndrome (MDS): chronic MDS phase (1 yr 10 mo.) with karyotypic abnormality (45, XY, -7) (Clone I); hypo-aplastic phase concurrent with 1st clonal evolution (45, XY, -7, 12p-) (Clone II) and acute myelomonocytic leukemia phase (6 mo.) with 2nd clonal evolution (45, XY, -7, t(1q-; Bq+), Bq-, 12p-) (Clone III). In the 2nd phase the bone marrow became almost aplastic as Clone II expanded progressively, indicatig simultaneous occurrence in Clone II stem cells of growth advantage for self-renewal function over Clone I and normal stem cells, and arrest of differentiation. Leukemic changes in MDS, at least in RA, occurs by stepwise clonal evolution(s), not by progressive arrest of differentiation in original MDS clone.