8;21 translocation in myelodysplasia secondary to essential thrombocythemia.

A case is presented of a 73-year-old woman who received busulphan for essential thrombocythemia and subsequently developed a myelodysplastic syndrome (MDS), which transformed to acute nonlymphoblastic leukaemia within 1 month. Cytogenetic studies showed a 46,XX,t(8;21) (q22;q22) karyotype in all metaphases examined at diagnosis. The karyotypic abnormality is previously unreported in secondary myelodysplasia and may have specific clinical implications in this setting, such as early transformation to acute leukaemia and short survival. This finding contrasts with the generally favourable prognosis of the 8;21 translocation in patients with de novo acute nonlymphoblastic leukemia. A possible explanation for this difference may be the involvement of a committed progenitor in acute nonlymphoblastic leukaemia, while in myelodysplasia the more primitive multipotent stem cell may be affected.