WT1 expression in myelodysplastic syndrome (MDS) was repeatedly tested with unequivocal results. In our study we concentrated to the determination of WT1 expression using quantitative RT-PCR in the diagnostic samples of paediatric patients with acute leukaemia (n=113), myelodysplastic syndrome (n=14) and aplastic anaemia (n=25). We used normal bone marrow samples and cord blood samples (n=35) with very low or undetectable expression as the negative controls. The expression levels in both the blasts of acute myeloid (n=62) and lymphoblastic (n=51) leukaemia widely varied. High expression was linked to the presence of MLL/AF4 fusion gene in contrast to BCR/ABL and TEL/AML1 fusion. T-cell leukaemias expressed WT1 in a wide range. In AML, high WT1 expression was linked to less mature subtypes (particularly M3), in contrast M5 subtype expressed significantly less WT1. Aplastic anaemia patients had very low or undetectable WT1 transcript levels, whereas myelodysplastic syndrome patients expressed WT1 on a higher level. Comparison of patients with aplastic anaemia to the refractory anaemia subtype of myelodysplastic syndrome revealed statistically significant difference (P=0,0079). However, the significance of WT1 expression estimation is limited due to the overlap of measured values. Lower WT1 expression in blasts of some of the acute leukaemia subtypes clearly demonstrates that WT1 hyperexpression is not a „panleukaemic” marker.

        Key words: aplastic anaemia, myelodysplastic syndrome, acute leukaemia, qRT-PCR, WT1 gene expression