Clonal karyotype abnormalities in erythroid and granulocyte-monocyte precursors in polycythaemia vera and myelofibrosis.

To determine whether clonal karyotype abnormalities seen in myeloproliferative disorders originate in cells of only one or of more blood cell lines, committed erythroid and granulocyte-monocyte progenitor cells were cultured in vitro by the methyl cellulose assay, and chromosome studies were carried out on the colonies. 3 patients were studied, 1 with polycythaemia vera and 2 with myelofibrosis, which was preceded by polycythaemia vera in 1 of the cases. All analysable karyotypes from both erythroid and granulocyte-monocyte colonies in every patient showed the clonal karyotype aberration which had been demonstrated in the bone marrow or blood of the patient. This finding is evidence of the involvement of a multipotent stem cell in the clonal proliferation of these diseases.