Paediatric myelodysplastic syndrome (MDS) and juvenile chronic myelogenous leukaemia (JCML) detected by cytogenetic and FISH techniques.

This report presents two rare cases, one of paediatric myelodysplastic syndrome (MDS) and the other juvenile chronic myeloid leukaemia (jCML). In the first case, there were clinical and biological features of MDS-refractory anaemia with excess blasts (RAEB). The bone marrow (BM) karyotype demonstrated a monosomy 7 which was confirmed by fluorescence in situ hybridization (FISH). In addition, FISH analysis showed that an alpha-satellite DNA sequence had been transferred from chromosomes 13/21 to one homologue of chromosomes 22. The BCR-ABL rearrangement was negative. In the second case, at diagnosis, the karyotype was 46,XX. FISH analysis with the simultaneous and individual application of abl and bcr probes for chromosome 9 and 22, respectively, revealed the presence of the BCR-ABL rearrangement in addition to an extra ABL sequence locating chromosome 20. A clone that was BCR-ABL gene rearrangement negative but with an extra ABL DNA sequence on chromsome 20, and another clone that was BCR-ABL gene rearrangement negative were detected by DC-FISH and uni-colour (UC-) FISH analysis. No monosomy 7 was detected by conventional cytogenetic or FISH analyses.