CHILDHOOD MYELODYSPLASTIC SYNDROME WITH CLONAL EVOLUTION PROGRESSING TO ACUTE MEGAKARYOBLASTIC LEUKEMIA (ANLL-M7)

We treated a 16-month-old girl with myelodysplastic syndrome (MDS; refractory anemia with excess of blasts subtype, RAEB by FAB classification) that developed into acute megakaryoblastic leukemia (ANLL-M7). The blast cells were positive for CD41 shown by flow cytometry and for platelet peroxidase by electron microscopy. Cytogenetically, five kinds of abnormal karyotypes were apparent at the initial visit and karyotypic progression (clonal evolution) was also evident. These karyotypes were considered to be derived from the putative original clone, 48,XX, + 6, + 21. The observed karyotypes were 50,XX, + 4,add(4)(q31), + 6,add(7)(p22),add(10)(q24),add(12)(q11), + 20, + 21, + mar [karyotype A];48,XX,add(4)(q31), + 6,add(10)(q24),add(12)(q11), + 21 [karyotype B];48,XX, + 6,t(6;13)(p23;q14), + 21 [karyotype C];51,XX, + X, t(6;13)(p23;q14), + der(6)t(6;13)(p23;q14), + 21, + 21, + mar [karyotype D]; and 49,XX, + X, - 3,t(6;13)(p23;q14), + der(6)t(6;13)(p23;q14), - 12, + 21, + 21, + mar [karyotype E]. It seems karyotypes B and C were derived from the putative clone; karyotype B developed into karyotype A; and karyotype C developed into karyotype E through karyotype D. After development of ANLL-M7, the cytogenetic study showed a karyotype with further karyotypic progression. The patient was treated with high-dose cytosine arabinoside (HD AraC) followed by allogeneic bone marrow transplantation. Despite intensive care, she died 3 months after the transplantation.