Cytogenetic evidence for partially committed myeloid progenitor cell origin of chronic myelomonocytic leukaemia and juvenile chronic myeloid leukaemia: both granulocyte-macrophage precursors and erythroid precursors carry identical marker chromosome.

We used a micromethod for cytogenetic analysis from single haematopoietic colonies to study two adults with chronic myelomonocytic leukaemia (CMML) and a boy with juvenile chronic myeloid leukaemia (JCML) carrying distinct chromosome abnormalities, 7q-, der(21), and trisomy 21. We wanted to know if both granulocyte-macrophage (GM) and erythroid precursors are involved in the abnormal clone. In all three patients, their chromosome abnormality was seen in almost all metaphases obtained from GM-colonies and erythroid bursts. Peripheral blood leucocytes stimulated with phytohaemagglutinin exhibited only normal karyotypes. Clones of B-cell produced by Epstein-Barr virus had only normal karyotypes in the CMML patients. These findings indicate that CMML and JCML are clonal haemopathies that originate in a partially committed myeloid progenitor cell.