LATE-APPEARING PHILADELPHIA-CHROMOSOME IN A PATIENT WITH ACUTE NONLYMPHOCYTIC LEUKEMIA-DERIVED FROM MYELODYSPLASTIC SYNDROME - DETECTION OF P210-TYPE AND P190-TYPE BCR/ABL FUSION GENE TRANSCRIPTS AT THE LEUKEMIC STAGE

We describe a patient with acute nonlymphocytic leukaemia (ANLL) derived from myelodysplastic syndrome in whom the Philadelphia chromosome (Ph(1)) first emerged at the late stage of ANLL transformation. Cytogenetically, the Ph(1) chromosome was not detected until the late stage of ANLL, transformation, 14 months after the transformation following a 3-month history of refractory anaemia with excess of blasts. The cells with and without the Ph(1) chromosome had a common abnormal chromosome, t(3;3) (q21;q26). The reverse transcription-polymerase chain reaction analysis showed no bcr/abl message at diagnosis. However, the mRNA encoding P210(bcr/abl) was detected in the early stage of ANLL transformation. Furthermore, the mRNAs encoding both P210(bcr/abl) and P190(bcr/abl) were detected in the late stage of ANLL transformation when the Ph(1) chromosome was detected by cytogenetic analysis. These evidences support a multistep pathogenesis of leukaemias, and the products of bcr/abl fusion gene may influence the course of disease.